Terrible Fuel-Efficiency - 2003 Accord
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Re: Terrible Fuel-Efficiency - 2003 Accord
On Wed, 24 Aug 2005 20:48:13 -0700, jim beam <nospam@example.net>
wrote:
>flobert wrote:
><snip>
>>
>> Ok, i just spent the last half hour or so getting some figures to
>> match to my facts.
>
>"getting"? you didn't do them yourself?
Oh, naturally, i 'get them' in the sense that i ut them on a piece of
paper, and work them out.
>
>>
>> The difference in values for the figures for a fast emergency stop to
>> zero, and for riding the brakes was even greater than i thought. and
>> to vastly simplify the maths (so i comfortably got the entire set of
>> calculations on s single sheet of paper, i even made many assumptions
>> in your favour. Lets see them brakes burn!.
>>
>> I'm using for the vehicle, my 88 honda civic DX - partly since its
>> relevent, this being a honda group, but also because i had the figures
>> for it to hand, unlike the caravan, and its been so much longer since
>> its brake service (which plays to you)
>>
>> Mass, approximatly 1000KG (2200lb) Its about right, and makes a nice
>> easy figure for calculations. for the rapid braking, i'll use the
>> 50mph distance from yesterday, but attribute itt o a speed of 55mph -
>> eases to your argument, since its more energy dumped into the brakes,
>> and saves me calculating too many values. For the 'coasting and riding
>> your brakes' which i'll call 'coasting' now, I used the model of the
>> hill on US19 that i've previously mentioend. cresting the hill at
>> 55mph, in gear the engine braking keeps the speed at 55mph, or
>> thereabouts, unchecked it gets to about 65mph, in the distances of
>> about 1 mile. Thus, i'll call the difference in KE between 55mph and
>> 65mph (now see why i picked 55mph as the speed for the braking
>> distance above) as the amount dumped into the brakes, or engine going
>> down a hill.
>>
>> Kinetic energy: (1/2 Mv^2)
>> brake - 0.5 x 1000 x 24.5872^2 (using meters/sec)
>> = 302,265.2 J
>
>first, for this to be a safe vehicle, you have to assume max gross
>vehicle weight [mgvw]. that's ~3000lbs or 1363kg. the brakes are no
>good if they can't stop the vehicle when fully loaded.
as long as the vehicle weights are the same for both calculations,
they cancel out. using MGVW for coasting, and for braking, the 1/2MV^2
for both has the same M, and thus is equivilent. I didn't actually do
the tests at mgvw either, so the braking distances, and so on are not
empyrically correct. If you want to increase the value of m by 30%,
you are free to do that, although it becomes experimentally incorrect,
and will just raise all figures by 30%.
>
>that's KE = 0.5 x 1363 x 24.5872^2
>i.e. 412,180J from your 55mph velocity.
>
>> coast - 0.5x 1000 x 29.6576^2 - 302265.2
>> = 422172.05 - 302265.2
>> = 119,906.85 J
>
>to clarify & grossly simplify, "coast" is the _additional_ energy that
>needs to be dissipated by the brakes if it's not being dissipated by
>engine braking.
Yes, exactly. At the bottom of the hill, after a coast, i would be
travveling at 65mph. that is what the first of the 3 lines above
calculates. The secondline removes the initial starting energy (ie
that of the car at 55) o give the figure of the third line, or the
energy gain through free coasting.
>using mgvw, KE = (0.5 x 1363 x 29.6576^2) - 412,180
>i.e. 599,429 - 412,180 = 187,249J is dissipated by engine braking.
>
>>
>> Hmm, the coast energy is only just over 1/3 the brake energy. Oh dear,
>> not looking good for your argument...
>
>not sure you understand the concept, but let's continue...
the 'concept' is that quite simple one. in short, cancelling out 0.5M
we get
55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
difference in energy values. this is the crux of the argument.
3025= k (4225 - 3025)
3025 = 1200k
2.52 = k
the coast energy is 2.52x SMALLER than the emergency stop energy.
>
>>
>> Lets see about how much energy per second is put into the brakes per
>> second. I'm assuming, of course, that the vehicle only has front
>> brakes. Again, simplifies for me, and is biased towards your claims.
>>
>> assuming a linear speed decrease - it isn''t, i know, but as its a
>> quadratic decrease, divide it by your straight line assertation of
>> brake performance decrease with temp,a nd it comes to a near linear
>> line
>>
>> 55-0 mph in 100ft is a time of 2.47sec. 55mph to cover 1 mile is 65.44
>> seconds.
>> joules per second works out as
>> brake - 302265.2 / 2.47 = 122374.57 J/s
>
>ok, let's just get back to mgvw, so we have:
>412,180J / 2.47 = 166,874W
>
>> coast - 119906.85 / 65.4 = 1832.3174
>>
>> Hang on, notice something there? in one second, the emergency stop has
>> absorbed more energy than over the entire run of the coast. Odd...
>
>this is way off. the "coast" is the energy difference. you're not
>trying to calculate the energy dissipated by just drifting along, you're
>trying to calculate how much difference engine braking makes to brake
>temperature.
no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
length with a starting speed of 55mph. if the engine is left in gear,
the vehicle stays at 55mph. if it is taken out of gear, it reaches
65mph at the bottom. Thus, the energy difference between 55mph and
65mph is dissipated by the engine over that 1 mile. In one second of
braking from 55mph, the amount of energy transfered to the braking
system is greater than the ENTIRE rise in energy due to coasting over
64 secondsLater on, i even calculate for you that the change in
vehicluar energy due to the coast is equivilent to a stop from 35mph.
thats if you want to incease the figures by 30% for 'mgvw' or not,
since mass is purely a linear variable in all the calculations.
>
>per the above, if the engine is not braking the car, you need to
>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>simplification ignoring wind, friction, etc., but it'll do for first order.
an additional amount? wheres this come from? you seem to have just
gone ahead and generated some additional energy value and added it to
the emergency stop value, something to do with engine braking. Is this
the added enegery value required to stop the rotational inertia of the
engine in an emergency stop?
>
>>
>> Now, i mentioned temperature just before. how hot will it get? Again,
>> for simplicity, all the energy is going into heating the brake discs
>> only. There is NO cooling effect allowed for. This HEAVILY favours
>> your arguments, and this is where you win through, clearly. The weight
>> of each brake disc for a honda civic is 10lb, or 4.54Kg. The specific
>> heat capacity of cast iron is 460J/Kg/K - or, in other words, for
>> every 460J of energy put into it, 1Kg of cast iron will be raised 1
>> Kelvin (or 1 Centrigrade) in temperature. Lets dump those energies in,
>> shall we? Remember, 2 discs, (or rotors if you will) so 9.08kg
>>
>> lets see then
>> brake - (302265.2 / 9.08) / 460 = 72.36K rise.
>
>the running surface of the disk, the bit that gets hot, is less than
>that because the 10lbs includes the hub part, not just the rotor. that
>does not heat significantly for this first order calc, but hey...
over the 3 seconds of the emergency stop, no it wouldn't. Over the
60-seconds or so of the coast, sure it would. thats more than enough
time to transfer heat.
>
>so, with mgvw, that's 412,180J / (9.08lbs x 460) = 99K rise.
>
>> coast - (119906.85 / 9.08) / 460 = 28.70K rise.
>
>with mgvw, that's 187,249J / (9.08lbs x 460) = 45K rise.
>
>that gets /added/ to the rise in disk temp if you're coasting because no
>energy is being dissipated by the engine.
>
>>
>> Lets say the ambient temperature here in georgia was 90F, or 32.2C. We
>> add those figures, and what do we get?
>>
>> brake - 104.2C - 219F
>> coast - 60.9C - 141F
>
>make that:
>131C for normal braking, and
>176C without additional engine braking
see, this is the bit i don't get. You've taken the value for a 2.5
second emergency stop, and THEN you've added the 55mph emergency stop
figure. What i'm guessing is that you're assuming someone coasts to
the bottom of the hill riding their brakes, and THEN makes an
emergency stop.thats something completely different, but ok.
>but neither are anything too serious given that we're talking single
>application.
and we're talking front brakes only, AND we're discounting the huge
amount of cooling flow you actually get of the brakes during that 60+
second coast, dissipating all that heat in the discs.
>
>>
>> look att hat, If we used water as our brake fluid, assuming it was run
>> right onto the disc, it would have boiled.
>>
>> What are the boiling points for brake fluid?
>> acording to govt. specs, the WET boiling point of DOT3 brake fluid
>> (3.7% h2O by vol) is 284F - significantly higher than the maximum
>> possible temperature of any braking componant in these tests.
>
>that's true, for one single stop, from cold. here's where we get to the
>point, and where your water tank analogy comes in: you don't just
>operate a brake once. for example, like my descent of filbert st,
>coming to a halt at each stop sign. each time you brake, you "fill the
>tank". particularly if you're at mgvw. now we need to figure out how
>quickly is the heat "leaving the tank"? in other words, to what already
>existing disk temp are you now adding your delta T? you want to take a
>shot at the heat dissipation rate? [hint: it's /less/ than the heating
>rate.]
So, let me try and understand what you're trying to say. If you go
down a steep hill, in neutral, riding your brakes, and then make an
emergency stop, then accelerate up to a fair speed, and repeat, after
a couple of occasions, your brakes are toast? In that convoluted
situation, then yes, they would be. Is that how you drive down filbert
street, or how you expect i drive down filbert street? as in
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP argh i can't stop
what out people in lombard!!!!!
Don't be a ing idiot.
>
>>
>> in short, your claims and assertations are utter bullshit. I've given
>> the amth, worked it through. Where i've had to approximate, i've done
>> so heavily biased in your direction (front brakes only, no cooling,
>> all temperature udmped into one comonant only) and even then they were
>> a ways away from failure point. As I said, only very badly maintained
>> brakes would fail the way you claim happens, and only then if you
>> heavily ride the brakes as you coast, and if that were to happen,
>> you'd be a lot more ed if you had to do any kind of emergency
>> stop. Just as an aside, any ideas what sort of speed that coast energy
>> figure represents? just 35mph. So, a car that has the braking from
>> 35mph over a mile and still has brake failure - sounds like
>> you've got a lot of problems there.
>
>ok, let's get to the links i posted.
>
>if you'd bothered to scroll to the bottom of this page:
>http://www.whnet.com/4x4/brakepads.html
>you'd see this:
>http://www.whnet.com/4x4/pix/hot_brake.jpg
>
>that looks remarkably like a disk that's exceeded 176C to me. how could
>that possibly be? [rhetorical]. easy, multiple brake applications that
>"fill the tank", just like the one i described to you for filbert st.
filbert street, no. Nurenburgring, silverstone, any race track
application, yes. Normal road use, no. through coasting downa hill,
don't be stupid. Iron gets to around that temperature at around 750C
(1382F) maybe he was coasting down Everest
>
>and let's look at this:
>http://www.e-z.net/~ts/ts/Brakfade.htm
>that graphic shows brake fade. you try to assert it's "irrelevant"
>because it happens to mention drums, not disks. that's an
>extraordinarily incorrect statement considering that the friction
>material and the drum material in both systems is identical and their
>friction characteristics are temperature dependent in exactly the same way.
WEll, i hated to point this out before but ok...
you say just before
>131C for normal braking, and
>176C without additional engine braking"
176c is 348F. looking at that graph, for quality linings, it seems
that thats in the OPTIMUM retardation range, for a decent quality
shoe. however...
>On Sat, 20 Aug 2005 12:34:13 -0700, jim beam <nospam@example.net>
>wrote:
>you don't know what you're talking about. any brake fades as a function
>of temperature.
Which this graph CLEARLY disproves. It might be true for cheap low
quality pads+shoes, such as the ones you buy (which you stated
earlier) but *shem*
i /do/ however care if [your] willful ignorance affects /my/ safety on
the road. if [you] careens out of control onto /my/ side of the
freeway and hits /my/ car because [you've bought cheap useless
brakepads] and has lost control because his brakes are toasted, he'd
better make sure he can run faster than me, because i /will/ be upset.
Sorry, just had to change your statement from ealier to reflect my
attitudes, and yours. You buy cardboard brakepads, and then drive like
a bat out of hell down filbert, i will make you regret it.
>
>disks don't get hot? from:
>http://encyclopedia.laborlawtalk.com/disc_brake
>we have:
>http://encyclopedia.laborlawtalk.com/Image:1901.jpg
>now, that's a stretch because it's a racing car driven to the limit, but
>the disks still look warm to me. [i initially included the article for
>the carbon disk discussion, since you raised them.]
And what you didn't realise, it seems, is thats those rbakes
functioning at their ideal temperature. Go watch any high end
motorsport, and you'll see that. Cars at LeMans will do that all day
long, and have no problems. These are not running the same braking
systems as you and me on the roads
www.canadiandriver.com/articles/tw/brembo.htm
"Many racing brake systems use discs of carbon composite material
(often misnamed "ceramic") which offer long life, light weight and
exceptional braking efficiency, among various benefits. In race-car
applications, these brakes can glow red-hot under hard use. So far,
only a limited number of exotic sports models offer carbon discs, but
I wouldn't be surprised to see their use widen over the next few
years."
>
>finally, from:
>http://www-personal.engin.umich.edu/...animation.html
>we have the animated disk warming measurement where delta T is shown
>settling at 236C after peaking at 242C. this exceeds your worse case
>scenario, and still does not approach the temperatures seen in the links
>i've just posted. did you notice hot the temp rise starts at 98C?
>that's only possible if the time for heat dissipation to ambient is
>somewhat slower than the period to brake re-application, i.e. real world
>usage.
I have yet to get a reply back from the Professor, but bet you that
the disc was completely stationary, and the applied brakepads were
rotated agaisnt it. This makes experimental sense, since that way, the
wires for the temperature sensors don't end up being all twisted, and
you ahve more control over the frictional energies, plus don't require
arotation rig for the disc, and a compression rig for the pads,
Thus there is zero coling due to airflow, which is how modern brakes
are cooled. Again, i point out that it shows vastly increased heat
buildup than even your emergency stop AFTER riding the brakes can
show. at 36 seconds its still a ways hotter than after 66 seconds by
your worst calculation. I think the best way we could give a
qualitative aspect to that is a prelude at mgvw going down filbert
street, with only the front right brake from an 88 civic working.
however, lets not lose sight of what that annimation tells us, and
ONLY what it tells us. under an unspecified (but very large) braking
force, with unspecified componants, non-uniform heat buildup occured
across the face of the disc. thats ALL that says, nothing more,
nothing less. No indication of the materials used, no conditions
listed, Thus inferrence to everyday use is useless, and unwise, since
the relevence to everyday conditions is unknown. In fact, considering
he was testing the pattern of heat buildup, i wouldn't be surprised if
he took all possible efforts to reduce as far as possible the ability
of the disc to cool.
>
>>
>> thats the brake failure utterly annihilated, even for your claims that
>> you have to be riding the brakes. AS for 'full control' - the only two
>> manouvers, as i've said before now, is aceleration (which was what you
>> were trying to counter with your engine braking anyway) and to correct
>> rear wheel skids. anything else you do NOt want the application of
>> power, and thus having the engine connected to the wheels is
>> meaningless.
>>
>> hope i've enlightened you with how things actually, numerically work
>> in the real world, or even in heavily biased 'jim beam world'. If you
>> can prove any factual, or numerical problems with my figures, then go
>> ahead, if not, why not act like a man for onec, and actual admit you
>> were wrong.
>
>now, to be fair, i acknowledge that your opinion may be colored by your
>never having experienced brake fade, particularly if you live in
>flatlands that surround airfields and drive a well-braked car like a
>lotus elise, but to say fade does not happen is simply incorrect.
First time i've ever heard of northern/central georgia as flatland.
Nor are 88 civic, or 87 caravan (the two vehicles i did the brake,a nd
engine-braked stops with) elises. In fact, an elise would have
favoured you, since that cars engine is so much bigger in relation to
the vehicles overall weight, on the same hill that engine braking
keeps me at 55 in my two US vehicles, it would actually slow me down
in the elise. Of course, i don't have an elise, and my friend with one
is back in the UK. I am hankering after an atom2 myself (which, in
case you don't know, is the 3rd fastest street legal vehicle around a
track, as tested by top gear, beaten only by the Ferrari F60, and the
F60 based Masserarti MC12, from a supercharged JDM civic type-R
engine,)
Tell you what though, if you think Filbert street is bad, go south a
little to Portola vally, and try Old Spanish Trail. If your brakes
cooked in SF, you'll not make it a quarter-way down that. my friends
who live there (and with whom i sometimes stay when i work in SF)
would surely crash into a ditch, if they drove in the apprantly
reckless and careless way you do. just part of the road (vista verde,
from old spanish trail, or ramona road) is a 1 in 6.8 gradient (worse
than filbert, and its not even half way down). overall its 4.2 miles
from the interstate, averaging 1 in 19
>
>let's just re-state some facts for the record:
>
>1. fade can and does happen.
Can happen yes. Does happen, no. not in all but extreme circumstances,
or on badly maintained vehicles.
>
>2. brake heating is exacerbated by not taking advantage of engine braking.
If the 1800W (the amount engine braking dissipates) in the real-life
coast example, would make such a big difference to your vehicles
braking system, you really need to get it into a shop, and have it
overhauled by professionals. 122KW to stop from 55mph, averaged, and
engine braking is 1.8KW. Its almost 1%.
>
>3. fade is partly dependent on brake materials.
>
>4. fade is partly dependent on the rate at which a brake component can
>be cooled.
Persoanlly, i'd ahve lumped these together - 'fade is dependant mainly
on temeprature, energy dissipation, and the frictional materials
used.'
>
>i have personally seen brakes on a normal family sedan glow red after
>repeated emergency braking tests. i can personally attest to these hot
>brakes exhibiting significant fade.
My word, you must ahve a long neck, in order to see the brakes glow
red, AND feel them fade. You ahve just disproved, though, the whole
argument above, and in all other posts. REgular car brakes that glow
red hot have significant fade. Not 'gotten so hot they faiiled, which
is your entire argument about riding the brakes, but 'significant
fade'. Any ideas how hot said brakes were? I'll give you a hint - Cast
iron glows red at about 750-800C (as any machinists handbook will tell
you). That is SO far above the experimental values we have both
calculated above, its not funy, and still, they only had 'significant
fade' They didn't fail, as you claimed coasting would do. Lets see,
using our 'test' vehicle of a civic with only 2 front brakes, no
dissipation to air, 1000K (you might do your brake tests with a couple
of porkers next to you, but i don't) and we're raising 9.08KG of cast
iron from 32C to 750C, lets round off again, and call it 720C (or
Kelvin), and if you think that sort of temperature only builds up on
the surface, you're dreaming - the expansion would shatter the disc.
420j/kg/k for iron...
720*9.08*420 = 2,748,537,792 - thats a LOT of energy.
Its EQUIVILENCE is an emergency stop from well...
KE = 0.5mv^2
(KE/500)^1/2 =
5497075.584^0.5 = 2344.58m/s
about 5244.67miles/hour.Hmm, lets see about 10 runs, eh
549707.5584^0.5=741.42m/s
or 741.44miles an hour.
*thinks* Your sedan wasn't testing thrust SSC's engines was it?
100 runs is 234m/s or 523.44mph.
Either your vehicle was using carbon-based brakes, or you're talking
out of your ****. Considering all your other claims, i'm going with
the latter.
> i have cited links that evidence
>both fade and highly elevated brake temperatures. if you've never seen,
>experienced or don't care to believe, hey, good luck to you.
I've experianced fade. I've studied brake systems in length. If yoursa
are failing on you going down filbert street (which isn't that bad a
hill
http://maps.google.com/maps?q=mariet...5819&t=h&hl=en
there's a hill your vehicle will thus fail on. The hills highest point
it at the top right, just at that bend, and it goes downhlil to the
juntion of merrit road, distance is approx 0.58 mile, peak elivation
is 1261ft, 980ft at the bottom, A 1 in 16 slope, compaired to
filbart's 1 in 7.5 slope, its not very steep, but it IS long. and that
is the average grade. and Barnes mill road is overall more than 50%
greater drop. As everyone knows, potential energy is MGh. for the same
car, m and g both cancel, the 50% greater hight drop means 50% more
energy. its also a 40mph road, whilst filbart is a 10 or 15mph road,
if memory serves me. Lets go easy on you and say 20, which is half the
speed, or one quarter the energy.
In short, your maths doesn't add up, your theories show little to no
scientific basis, or enginering basis. You quibble over a weight,
increasing it wholesale by 30%, just to fit your 'worst case' then
suggest that the brakes should be ridden, then an emergency stop, AND
the enegy from riding the brakes applied again (because there was no
engine braking, you say). All this, you claim, is evidence of fade and
failure, and THEN you contradict yourself by saying you've driven a
sedan till its brakes glowed red, and then there was quite a it of
fade. thats after erm, about 688 runs stopping from 200mph, with ZERO
cooling to ambient air, or, by your argument, riding the brakes for a
mile or two down a hill at 55mph.Gee, these figures are not mathcing
up.
Don't give up your day job - good fry chefs are hard to find in SF.
wrote:
>flobert wrote:
><snip>
>>
>> Ok, i just spent the last half hour or so getting some figures to
>> match to my facts.
>
>"getting"? you didn't do them yourself?
Oh, naturally, i 'get them' in the sense that i ut them on a piece of
paper, and work them out.
>
>>
>> The difference in values for the figures for a fast emergency stop to
>> zero, and for riding the brakes was even greater than i thought. and
>> to vastly simplify the maths (so i comfortably got the entire set of
>> calculations on s single sheet of paper, i even made many assumptions
>> in your favour. Lets see them brakes burn!.
>>
>> I'm using for the vehicle, my 88 honda civic DX - partly since its
>> relevent, this being a honda group, but also because i had the figures
>> for it to hand, unlike the caravan, and its been so much longer since
>> its brake service (which plays to you)
>>
>> Mass, approximatly 1000KG (2200lb) Its about right, and makes a nice
>> easy figure for calculations. for the rapid braking, i'll use the
>> 50mph distance from yesterday, but attribute itt o a speed of 55mph -
>> eases to your argument, since its more energy dumped into the brakes,
>> and saves me calculating too many values. For the 'coasting and riding
>> your brakes' which i'll call 'coasting' now, I used the model of the
>> hill on US19 that i've previously mentioend. cresting the hill at
>> 55mph, in gear the engine braking keeps the speed at 55mph, or
>> thereabouts, unchecked it gets to about 65mph, in the distances of
>> about 1 mile. Thus, i'll call the difference in KE between 55mph and
>> 65mph (now see why i picked 55mph as the speed for the braking
>> distance above) as the amount dumped into the brakes, or engine going
>> down a hill.
>>
>> Kinetic energy: (1/2 Mv^2)
>> brake - 0.5 x 1000 x 24.5872^2 (using meters/sec)
>> = 302,265.2 J
>
>first, for this to be a safe vehicle, you have to assume max gross
>vehicle weight [mgvw]. that's ~3000lbs or 1363kg. the brakes are no
>good if they can't stop the vehicle when fully loaded.
as long as the vehicle weights are the same for both calculations,
they cancel out. using MGVW for coasting, and for braking, the 1/2MV^2
for both has the same M, and thus is equivilent. I didn't actually do
the tests at mgvw either, so the braking distances, and so on are not
empyrically correct. If you want to increase the value of m by 30%,
you are free to do that, although it becomes experimentally incorrect,
and will just raise all figures by 30%.
>
>that's KE = 0.5 x 1363 x 24.5872^2
>i.e. 412,180J from your 55mph velocity.
>
>> coast - 0.5x 1000 x 29.6576^2 - 302265.2
>> = 422172.05 - 302265.2
>> = 119,906.85 J
>
>to clarify & grossly simplify, "coast" is the _additional_ energy that
>needs to be dissipated by the brakes if it's not being dissipated by
>engine braking.
Yes, exactly. At the bottom of the hill, after a coast, i would be
travveling at 65mph. that is what the first of the 3 lines above
calculates. The secondline removes the initial starting energy (ie
that of the car at 55) o give the figure of the third line, or the
energy gain through free coasting.
>using mgvw, KE = (0.5 x 1363 x 29.6576^2) - 412,180
>i.e. 599,429 - 412,180 = 187,249J is dissipated by engine braking.
>
>>
>> Hmm, the coast energy is only just over 1/3 the brake energy. Oh dear,
>> not looking good for your argument...
>
>not sure you understand the concept, but let's continue...
the 'concept' is that quite simple one. in short, cancelling out 0.5M
we get
55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
difference in energy values. this is the crux of the argument.
3025= k (4225 - 3025)
3025 = 1200k
2.52 = k
the coast energy is 2.52x SMALLER than the emergency stop energy.
>
>>
>> Lets see about how much energy per second is put into the brakes per
>> second. I'm assuming, of course, that the vehicle only has front
>> brakes. Again, simplifies for me, and is biased towards your claims.
>>
>> assuming a linear speed decrease - it isn''t, i know, but as its a
>> quadratic decrease, divide it by your straight line assertation of
>> brake performance decrease with temp,a nd it comes to a near linear
>> line
>>
>> 55-0 mph in 100ft is a time of 2.47sec. 55mph to cover 1 mile is 65.44
>> seconds.
>> joules per second works out as
>> brake - 302265.2 / 2.47 = 122374.57 J/s
>
>ok, let's just get back to mgvw, so we have:
>412,180J / 2.47 = 166,874W
>
>> coast - 119906.85 / 65.4 = 1832.3174
>>
>> Hang on, notice something there? in one second, the emergency stop has
>> absorbed more energy than over the entire run of the coast. Odd...
>
>this is way off. the "coast" is the energy difference. you're not
>trying to calculate the energy dissipated by just drifting along, you're
>trying to calculate how much difference engine braking makes to brake
>temperature.
no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
length with a starting speed of 55mph. if the engine is left in gear,
the vehicle stays at 55mph. if it is taken out of gear, it reaches
65mph at the bottom. Thus, the energy difference between 55mph and
65mph is dissipated by the engine over that 1 mile. In one second of
braking from 55mph, the amount of energy transfered to the braking
system is greater than the ENTIRE rise in energy due to coasting over
64 secondsLater on, i even calculate for you that the change in
vehicluar energy due to the coast is equivilent to a stop from 35mph.
thats if you want to incease the figures by 30% for 'mgvw' or not,
since mass is purely a linear variable in all the calculations.
>
>per the above, if the engine is not braking the car, you need to
>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>simplification ignoring wind, friction, etc., but it'll do for first order.
an additional amount? wheres this come from? you seem to have just
gone ahead and generated some additional energy value and added it to
the emergency stop value, something to do with engine braking. Is this
the added enegery value required to stop the rotational inertia of the
engine in an emergency stop?
>
>>
>> Now, i mentioned temperature just before. how hot will it get? Again,
>> for simplicity, all the energy is going into heating the brake discs
>> only. There is NO cooling effect allowed for. This HEAVILY favours
>> your arguments, and this is where you win through, clearly. The weight
>> of each brake disc for a honda civic is 10lb, or 4.54Kg. The specific
>> heat capacity of cast iron is 460J/Kg/K - or, in other words, for
>> every 460J of energy put into it, 1Kg of cast iron will be raised 1
>> Kelvin (or 1 Centrigrade) in temperature. Lets dump those energies in,
>> shall we? Remember, 2 discs, (or rotors if you will) so 9.08kg
>>
>> lets see then
>> brake - (302265.2 / 9.08) / 460 = 72.36K rise.
>
>the running surface of the disk, the bit that gets hot, is less than
>that because the 10lbs includes the hub part, not just the rotor. that
>does not heat significantly for this first order calc, but hey...
over the 3 seconds of the emergency stop, no it wouldn't. Over the
60-seconds or so of the coast, sure it would. thats more than enough
time to transfer heat.
>
>so, with mgvw, that's 412,180J / (9.08lbs x 460) = 99K rise.
>
>> coast - (119906.85 / 9.08) / 460 = 28.70K rise.
>
>with mgvw, that's 187,249J / (9.08lbs x 460) = 45K rise.
>
>that gets /added/ to the rise in disk temp if you're coasting because no
>energy is being dissipated by the engine.
>
>>
>> Lets say the ambient temperature here in georgia was 90F, or 32.2C. We
>> add those figures, and what do we get?
>>
>> brake - 104.2C - 219F
>> coast - 60.9C - 141F
>
>make that:
>131C for normal braking, and
>176C without additional engine braking
see, this is the bit i don't get. You've taken the value for a 2.5
second emergency stop, and THEN you've added the 55mph emergency stop
figure. What i'm guessing is that you're assuming someone coasts to
the bottom of the hill riding their brakes, and THEN makes an
emergency stop.thats something completely different, but ok.
>but neither are anything too serious given that we're talking single
>application.
and we're talking front brakes only, AND we're discounting the huge
amount of cooling flow you actually get of the brakes during that 60+
second coast, dissipating all that heat in the discs.
>
>>
>> look att hat, If we used water as our brake fluid, assuming it was run
>> right onto the disc, it would have boiled.
>>
>> What are the boiling points for brake fluid?
>> acording to govt. specs, the WET boiling point of DOT3 brake fluid
>> (3.7% h2O by vol) is 284F - significantly higher than the maximum
>> possible temperature of any braking componant in these tests.
>
>that's true, for one single stop, from cold. here's where we get to the
>point, and where your water tank analogy comes in: you don't just
>operate a brake once. for example, like my descent of filbert st,
>coming to a halt at each stop sign. each time you brake, you "fill the
>tank". particularly if you're at mgvw. now we need to figure out how
>quickly is the heat "leaving the tank"? in other words, to what already
>existing disk temp are you now adding your delta T? you want to take a
>shot at the heat dissipation rate? [hint: it's /less/ than the heating
>rate.]
So, let me try and understand what you're trying to say. If you go
down a steep hill, in neutral, riding your brakes, and then make an
emergency stop, then accelerate up to a fair speed, and repeat, after
a couple of occasions, your brakes are toast? In that convoluted
situation, then yes, they would be. Is that how you drive down filbert
street, or how you expect i drive down filbert street? as in
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP!
[D] 35mph [N] brakes on, ride those brakes, and STOP argh i can't stop
what out people in lombard!!!!!
Don't be a ing idiot.
>
>>
>> in short, your claims and assertations are utter bullshit. I've given
>> the amth, worked it through. Where i've had to approximate, i've done
>> so heavily biased in your direction (front brakes only, no cooling,
>> all temperature udmped into one comonant only) and even then they were
>> a ways away from failure point. As I said, only very badly maintained
>> brakes would fail the way you claim happens, and only then if you
>> heavily ride the brakes as you coast, and if that were to happen,
>> you'd be a lot more ed if you had to do any kind of emergency
>> stop. Just as an aside, any ideas what sort of speed that coast energy
>> figure represents? just 35mph. So, a car that has the braking from
>> 35mph over a mile and still has brake failure - sounds like
>> you've got a lot of problems there.
>
>ok, let's get to the links i posted.
>
>if you'd bothered to scroll to the bottom of this page:
>http://www.whnet.com/4x4/brakepads.html
>you'd see this:
>http://www.whnet.com/4x4/pix/hot_brake.jpg
>
>that looks remarkably like a disk that's exceeded 176C to me. how could
>that possibly be? [rhetorical]. easy, multiple brake applications that
>"fill the tank", just like the one i described to you for filbert st.
filbert street, no. Nurenburgring, silverstone, any race track
application, yes. Normal road use, no. through coasting downa hill,
don't be stupid. Iron gets to around that temperature at around 750C
(1382F) maybe he was coasting down Everest
>
>and let's look at this:
>http://www.e-z.net/~ts/ts/Brakfade.htm
>that graphic shows brake fade. you try to assert it's "irrelevant"
>because it happens to mention drums, not disks. that's an
>extraordinarily incorrect statement considering that the friction
>material and the drum material in both systems is identical and their
>friction characteristics are temperature dependent in exactly the same way.
WEll, i hated to point this out before but ok...
you say just before
>131C for normal braking, and
>176C without additional engine braking"
176c is 348F. looking at that graph, for quality linings, it seems
that thats in the OPTIMUM retardation range, for a decent quality
shoe. however...
>On Sat, 20 Aug 2005 12:34:13 -0700, jim beam <nospam@example.net>
>wrote:
>you don't know what you're talking about. any brake fades as a function
>of temperature.
Which this graph CLEARLY disproves. It might be true for cheap low
quality pads+shoes, such as the ones you buy (which you stated
earlier) but *shem*
i /do/ however care if [your] willful ignorance affects /my/ safety on
the road. if [you] careens out of control onto /my/ side of the
freeway and hits /my/ car because [you've bought cheap useless
brakepads] and has lost control because his brakes are toasted, he'd
better make sure he can run faster than me, because i /will/ be upset.
Sorry, just had to change your statement from ealier to reflect my
attitudes, and yours. You buy cardboard brakepads, and then drive like
a bat out of hell down filbert, i will make you regret it.
>
>disks don't get hot? from:
>http://encyclopedia.laborlawtalk.com/disc_brake
>we have:
>http://encyclopedia.laborlawtalk.com/Image:1901.jpg
>now, that's a stretch because it's a racing car driven to the limit, but
>the disks still look warm to me. [i initially included the article for
>the carbon disk discussion, since you raised them.]
And what you didn't realise, it seems, is thats those rbakes
functioning at their ideal temperature. Go watch any high end
motorsport, and you'll see that. Cars at LeMans will do that all day
long, and have no problems. These are not running the same braking
systems as you and me on the roads
www.canadiandriver.com/articles/tw/brembo.htm
"Many racing brake systems use discs of carbon composite material
(often misnamed "ceramic") which offer long life, light weight and
exceptional braking efficiency, among various benefits. In race-car
applications, these brakes can glow red-hot under hard use. So far,
only a limited number of exotic sports models offer carbon discs, but
I wouldn't be surprised to see their use widen over the next few
years."
>
>finally, from:
>http://www-personal.engin.umich.edu/...animation.html
>we have the animated disk warming measurement where delta T is shown
>settling at 236C after peaking at 242C. this exceeds your worse case
>scenario, and still does not approach the temperatures seen in the links
>i've just posted. did you notice hot the temp rise starts at 98C?
>that's only possible if the time for heat dissipation to ambient is
>somewhat slower than the period to brake re-application, i.e. real world
>usage.
I have yet to get a reply back from the Professor, but bet you that
the disc was completely stationary, and the applied brakepads were
rotated agaisnt it. This makes experimental sense, since that way, the
wires for the temperature sensors don't end up being all twisted, and
you ahve more control over the frictional energies, plus don't require
arotation rig for the disc, and a compression rig for the pads,
Thus there is zero coling due to airflow, which is how modern brakes
are cooled. Again, i point out that it shows vastly increased heat
buildup than even your emergency stop AFTER riding the brakes can
show. at 36 seconds its still a ways hotter than after 66 seconds by
your worst calculation. I think the best way we could give a
qualitative aspect to that is a prelude at mgvw going down filbert
street, with only the front right brake from an 88 civic working.
however, lets not lose sight of what that annimation tells us, and
ONLY what it tells us. under an unspecified (but very large) braking
force, with unspecified componants, non-uniform heat buildup occured
across the face of the disc. thats ALL that says, nothing more,
nothing less. No indication of the materials used, no conditions
listed, Thus inferrence to everyday use is useless, and unwise, since
the relevence to everyday conditions is unknown. In fact, considering
he was testing the pattern of heat buildup, i wouldn't be surprised if
he took all possible efforts to reduce as far as possible the ability
of the disc to cool.
>
>>
>> thats the brake failure utterly annihilated, even for your claims that
>> you have to be riding the brakes. AS for 'full control' - the only two
>> manouvers, as i've said before now, is aceleration (which was what you
>> were trying to counter with your engine braking anyway) and to correct
>> rear wheel skids. anything else you do NOt want the application of
>> power, and thus having the engine connected to the wheels is
>> meaningless.
>>
>> hope i've enlightened you with how things actually, numerically work
>> in the real world, or even in heavily biased 'jim beam world'. If you
>> can prove any factual, or numerical problems with my figures, then go
>> ahead, if not, why not act like a man for onec, and actual admit you
>> were wrong.
>
>now, to be fair, i acknowledge that your opinion may be colored by your
>never having experienced brake fade, particularly if you live in
>flatlands that surround airfields and drive a well-braked car like a
>lotus elise, but to say fade does not happen is simply incorrect.
First time i've ever heard of northern/central georgia as flatland.
Nor are 88 civic, or 87 caravan (the two vehicles i did the brake,a nd
engine-braked stops with) elises. In fact, an elise would have
favoured you, since that cars engine is so much bigger in relation to
the vehicles overall weight, on the same hill that engine braking
keeps me at 55 in my two US vehicles, it would actually slow me down
in the elise. Of course, i don't have an elise, and my friend with one
is back in the UK. I am hankering after an atom2 myself (which, in
case you don't know, is the 3rd fastest street legal vehicle around a
track, as tested by top gear, beaten only by the Ferrari F60, and the
F60 based Masserarti MC12, from a supercharged JDM civic type-R
engine,)
Tell you what though, if you think Filbert street is bad, go south a
little to Portola vally, and try Old Spanish Trail. If your brakes
cooked in SF, you'll not make it a quarter-way down that. my friends
who live there (and with whom i sometimes stay when i work in SF)
would surely crash into a ditch, if they drove in the apprantly
reckless and careless way you do. just part of the road (vista verde,
from old spanish trail, or ramona road) is a 1 in 6.8 gradient (worse
than filbert, and its not even half way down). overall its 4.2 miles
from the interstate, averaging 1 in 19
>
>let's just re-state some facts for the record:
>
>1. fade can and does happen.
Can happen yes. Does happen, no. not in all but extreme circumstances,
or on badly maintained vehicles.
>
>2. brake heating is exacerbated by not taking advantage of engine braking.
If the 1800W (the amount engine braking dissipates) in the real-life
coast example, would make such a big difference to your vehicles
braking system, you really need to get it into a shop, and have it
overhauled by professionals. 122KW to stop from 55mph, averaged, and
engine braking is 1.8KW. Its almost 1%.
>
>3. fade is partly dependent on brake materials.
>
>4. fade is partly dependent on the rate at which a brake component can
>be cooled.
Persoanlly, i'd ahve lumped these together - 'fade is dependant mainly
on temeprature, energy dissipation, and the frictional materials
used.'
>
>i have personally seen brakes on a normal family sedan glow red after
>repeated emergency braking tests. i can personally attest to these hot
>brakes exhibiting significant fade.
My word, you must ahve a long neck, in order to see the brakes glow
red, AND feel them fade. You ahve just disproved, though, the whole
argument above, and in all other posts. REgular car brakes that glow
red hot have significant fade. Not 'gotten so hot they faiiled, which
is your entire argument about riding the brakes, but 'significant
fade'. Any ideas how hot said brakes were? I'll give you a hint - Cast
iron glows red at about 750-800C (as any machinists handbook will tell
you). That is SO far above the experimental values we have both
calculated above, its not funy, and still, they only had 'significant
fade' They didn't fail, as you claimed coasting would do. Lets see,
using our 'test' vehicle of a civic with only 2 front brakes, no
dissipation to air, 1000K (you might do your brake tests with a couple
of porkers next to you, but i don't) and we're raising 9.08KG of cast
iron from 32C to 750C, lets round off again, and call it 720C (or
Kelvin), and if you think that sort of temperature only builds up on
the surface, you're dreaming - the expansion would shatter the disc.
420j/kg/k for iron...
720*9.08*420 = 2,748,537,792 - thats a LOT of energy.
Its EQUIVILENCE is an emergency stop from well...
KE = 0.5mv^2
(KE/500)^1/2 =
5497075.584^0.5 = 2344.58m/s
about 5244.67miles/hour.Hmm, lets see about 10 runs, eh
549707.5584^0.5=741.42m/s
or 741.44miles an hour.
*thinks* Your sedan wasn't testing thrust SSC's engines was it?
100 runs is 234m/s or 523.44mph.
Either your vehicle was using carbon-based brakes, or you're talking
out of your ****. Considering all your other claims, i'm going with
the latter.
> i have cited links that evidence
>both fade and highly elevated brake temperatures. if you've never seen,
>experienced or don't care to believe, hey, good luck to you.
I've experianced fade. I've studied brake systems in length. If yoursa
are failing on you going down filbert street (which isn't that bad a
hill
http://maps.google.com/maps?q=mariet...5819&t=h&hl=en
there's a hill your vehicle will thus fail on. The hills highest point
it at the top right, just at that bend, and it goes downhlil to the
juntion of merrit road, distance is approx 0.58 mile, peak elivation
is 1261ft, 980ft at the bottom, A 1 in 16 slope, compaired to
filbart's 1 in 7.5 slope, its not very steep, but it IS long. and that
is the average grade. and Barnes mill road is overall more than 50%
greater drop. As everyone knows, potential energy is MGh. for the same
car, m and g both cancel, the 50% greater hight drop means 50% more
energy. its also a 40mph road, whilst filbart is a 10 or 15mph road,
if memory serves me. Lets go easy on you and say 20, which is half the
speed, or one quarter the energy.
In short, your maths doesn't add up, your theories show little to no
scientific basis, or enginering basis. You quibble over a weight,
increasing it wholesale by 30%, just to fit your 'worst case' then
suggest that the brakes should be ridden, then an emergency stop, AND
the enegy from riding the brakes applied again (because there was no
engine braking, you say). All this, you claim, is evidence of fade and
failure, and THEN you contradict yourself by saying you've driven a
sedan till its brakes glowed red, and then there was quite a it of
fade. thats after erm, about 688 runs stopping from 200mph, with ZERO
cooling to ambient air, or, by your argument, riding the brakes for a
mile or two down a hill at 55mph.Gee, these figures are not mathcing
up.
Don't give up your day job - good fry chefs are hard to find in SF.
#62
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
"flobert" <nomail@here.NOT> wrote in message
news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com...
Wow .. you guys are writing some long replies in this thread!
I'd like to point out two facts, which may be contrary to an extent to what
each of you are saying:
1) Modern cars do suffer from brake fade (I had a Civic as my last car and
when I drove it like I stole it, there came a point after a few *really*
heavy stops from high speed where the pedal would disappear to the floor
virtually with the pressure before doing anything much - get out of the car
and smell the wonderful baking smell of toasted brake pads!). However, with
a normal person driving it legally, there are very few situations in the
world where it's going to be a worry. OK - some of us live in the Alps and
drive for 15 mins as fast as we can down a hill ... worry! The rest of us
rarely see a hill more than 1km long!
I now have a ATR - no matter what I've done to it so far, it's coped fine.
But then it's got whopping great vented discs that are built to take a
constant heat input and dissipate it as quickly as possible and keep all of
the braking materials at an operational temperature.
2) Driving out of gear is rightly illegal in many places. This is because
you are less in control and less able to respond to any given situation.
The engine breaking is a bonus for those of us who aren't so goddam tight
that we'll do anything to save £1 a year on fuel costs. Many situations
occur where you need to take evasive action and drive out of trouble. A car
is also more stable and "drivable" in gear. If you're coasting around in
neutral, you're doing two things - concentrating less than you should on the
road because you're worrying about keeping your toboggan going fast enough
for your lazy **** not to get back into gear again and perhaps taking risks
by going faster than you should in places to keep up that precious momentum;
and two, you're probably annoying the living hell out of the driver behind
you by driving in an unexpected and erratic manner (too slow at times,
correct or too fast at others), thus increasing the likelihood of a crash
out of frustration from other road users.
Please, guys - life is too short!! There is a reason why coasting is
frowned upon - you don't know better than most driving standards across the
civilised worlds. Also, car brakes are more than able to cool themselves
adequately under normal driving conditions.
al
news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com...
Wow .. you guys are writing some long replies in this thread!
I'd like to point out two facts, which may be contrary to an extent to what
each of you are saying:
1) Modern cars do suffer from brake fade (I had a Civic as my last car and
when I drove it like I stole it, there came a point after a few *really*
heavy stops from high speed where the pedal would disappear to the floor
virtually with the pressure before doing anything much - get out of the car
and smell the wonderful baking smell of toasted brake pads!). However, with
a normal person driving it legally, there are very few situations in the
world where it's going to be a worry. OK - some of us live in the Alps and
drive for 15 mins as fast as we can down a hill ... worry! The rest of us
rarely see a hill more than 1km long!
I now have a ATR - no matter what I've done to it so far, it's coped fine.
But then it's got whopping great vented discs that are built to take a
constant heat input and dissipate it as quickly as possible and keep all of
the braking materials at an operational temperature.
2) Driving out of gear is rightly illegal in many places. This is because
you are less in control and less able to respond to any given situation.
The engine breaking is a bonus for those of us who aren't so goddam tight
that we'll do anything to save £1 a year on fuel costs. Many situations
occur where you need to take evasive action and drive out of trouble. A car
is also more stable and "drivable" in gear. If you're coasting around in
neutral, you're doing two things - concentrating less than you should on the
road because you're worrying about keeping your toboggan going fast enough
for your lazy **** not to get back into gear again and perhaps taking risks
by going faster than you should in places to keep up that precious momentum;
and two, you're probably annoying the living hell out of the driver behind
you by driving in an unexpected and erratic manner (too slow at times,
correct or too fast at others), thus increasing the likelihood of a crash
out of frustration from other road users.
Please, guys - life is too short!! There is a reason why coasting is
frowned upon - you don't know better than most driving standards across the
civilised worlds. Also, car brakes are more than able to cool themselves
adequately under normal driving conditions.
al
#63
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
flobert wrote:
<snip>
> the 'concept' is that quite simple one. in short, cancelling out 0.5M
> we get
> 55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
> difference in energy values. this is the crux of the argument.
> 3025= k (4225 - 3025)
> 3025 = 1200k
> 2.52 = k
> the coast energy is 2.52x SMALLER than the emergency stop energy.
but dude, that energy is otherwise dissipated by engine braking. if
it's /not/ being dissipated by engine braking, it's being dissipated by
the brakes.
>
>
<snip>
>
>
> no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
> length with a starting speed of 55mph. if the engine is left in gear,
> the vehicle stays at 55mph. if it is taken out of gear, it reaches
> 65mph at the bottom. Thus, the energy difference between 55mph and
> 65mph is dissipated by the engine over that 1 mile. In one second of
> braking from 55mph, the amount of energy transfered to the braking
> system is greater than the ENTIRE rise in energy due to coasting over
> 64 secondsLater on, i even calculate for you that the change in
> vehicluar energy due to the coast is equivilent to a stop from 35mph.
> thats if you want to incease the figures by 30% for 'mgvw' or not,
> since mass is purely a linear variable in all the calculations.
again, you're mission the point. you still seem having difficulty
grasping the concept that /less/ engine braking means /more/ service
braking, which means higher operating temperatures. you can't just
gloss over it with a dismissive "it's equivalent to coasting 64
seconds". same for mass - clutching at "linearity" is either a
deliberate red herring or conceptual myopia.
>
>
>>per the above, if the engine is not braking the car, you need to
>>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>>simplification ignoring wind, friction, etc., but it'll do for first order.
>
>
> an additional amount? wheres this come from? you seem to have just
> gone ahead and generated some additional energy value and added it to
> the emergency stop value, something to do with engine braking. Is this
> the added enegery value required to stop the rotational inertia of the
> engine in an emergency stop?
ok, this is where i quit arguing with you. if the engine is disengaged,
the energy that would otherwise be lost to engine braking is added to
the energy that needs to be dissipated in the braking system. this is
the 3rd time in a single response that you've fudged this point. the
math is grade school. the science is grade school. if you won't or
can't grasp that concept, sorry, i have no more time for you. have a
nice day.
<snip>
> the 'concept' is that quite simple one. in short, cancelling out 0.5M
> we get
> 55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
> difference in energy values. this is the crux of the argument.
> 3025= k (4225 - 3025)
> 3025 = 1200k
> 2.52 = k
> the coast energy is 2.52x SMALLER than the emergency stop energy.
but dude, that energy is otherwise dissipated by engine braking. if
it's /not/ being dissipated by engine braking, it's being dissipated by
the brakes.
>
>
<snip>
>
>
> no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
> length with a starting speed of 55mph. if the engine is left in gear,
> the vehicle stays at 55mph. if it is taken out of gear, it reaches
> 65mph at the bottom. Thus, the energy difference between 55mph and
> 65mph is dissipated by the engine over that 1 mile. In one second of
> braking from 55mph, the amount of energy transfered to the braking
> system is greater than the ENTIRE rise in energy due to coasting over
> 64 secondsLater on, i even calculate for you that the change in
> vehicluar energy due to the coast is equivilent to a stop from 35mph.
> thats if you want to incease the figures by 30% for 'mgvw' or not,
> since mass is purely a linear variable in all the calculations.
again, you're mission the point. you still seem having difficulty
grasping the concept that /less/ engine braking means /more/ service
braking, which means higher operating temperatures. you can't just
gloss over it with a dismissive "it's equivalent to coasting 64
seconds". same for mass - clutching at "linearity" is either a
deliberate red herring or conceptual myopia.
>
>
>>per the above, if the engine is not braking the car, you need to
>>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>>simplification ignoring wind, friction, etc., but it'll do for first order.
>
>
> an additional amount? wheres this come from? you seem to have just
> gone ahead and generated some additional energy value and added it to
> the emergency stop value, something to do with engine braking. Is this
> the added enegery value required to stop the rotational inertia of the
> engine in an emergency stop?
ok, this is where i quit arguing with you. if the engine is disengaged,
the energy that would otherwise be lost to engine braking is added to
the energy that needs to be dissipated in the braking system. this is
the 3rd time in a single response that you've fudged this point. the
math is grade school. the science is grade school. if you won't or
can't grasp that concept, sorry, i have no more time for you. have a
nice day.
#64
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
jim beam <nospam@example.net> wrote in
news:2-2dnZ2dnZ21k2DenZ2dnTDrk96dnZ2dRVn-z52dnZ0@speakeasy.net:
> ok, this is where i quit arguing with you. if the engine is
> disengaged, the energy that would otherwise be lost to engine braking
> is added to the energy that needs to be dissipated in the braking
> system. this is the 3rd time in a single response that you've fudged
> this point. the math is grade school. the science is grade school.
> if you won't or can't grasp that concept, sorry, i have no more time
> for you. have a nice day.
>
flobert was totally wrong on the rear fog light thing, too. I checked. It
seems the rear fog light in the UK is the sole exception to the "all lights
must work" general rule. The driver's side is the ONLY one that has to work
if two rear fog lights are fitted.
It further seems that there are many MoT testers who are not fully familiar
with their own rules. It is common for testers to fail cars based on their
own personal pseudo-knowledge, and not the actual law, especially when it
comes to older vehicles.
I'm damn glad Ontario has no MoT.
--
TeGGeR®
The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/
news:2-2dnZ2dnZ21k2DenZ2dnTDrk96dnZ2dRVn-z52dnZ0@speakeasy.net:
> ok, this is where i quit arguing with you. if the engine is
> disengaged, the energy that would otherwise be lost to engine braking
> is added to the energy that needs to be dissipated in the braking
> system. this is the 3rd time in a single response that you've fudged
> this point. the math is grade school. the science is grade school.
> if you won't or can't grasp that concept, sorry, i have no more time
> for you. have a nice day.
>
flobert was totally wrong on the rear fog light thing, too. I checked. It
seems the rear fog light in the UK is the sole exception to the "all lights
must work" general rule. The driver's side is the ONLY one that has to work
if two rear fog lights are fitted.
It further seems that there are many MoT testers who are not fully familiar
with their own rules. It is common for testers to fail cars based on their
own personal pseudo-knowledge, and not the actual law, especially when it
comes to older vehicles.
I'm damn glad Ontario has no MoT.
--
TeGGeR®
The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/
#65
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
On Thu, 25 Aug 2005 18:55:57 -0700, jim beam <nospam@example.net>
wrote:
>flobert wrote:
><snip>
>
>> the 'concept' is that quite simple one. in short, cancelling out 0.5M
>> we get
>> 55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
>> difference in energy values. this is the crux of the argument.
>> 3025= k (4225 - 3025)
>> 3025 = 1200k
>> 2.52 = k
>> the coast energy is 2.52x SMALLER than the emergency stop energy.
>
>but dude, that energy is otherwise dissipated by engine braking. if
>it's /not/ being dissipated by engine braking, it's being dissipated by
>the brakes.
ONLY IF THE BRAKES ARE APPLIED INSTEAD.
>
>>
>>
><snip>
>>
>>
>> no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
>> length with a starting speed of 55mph. if the engine is left in gear,
>> the vehicle stays at 55mph. if it is taken out of gear, it reaches
>> 65mph at the bottom. Thus, the energy difference between 55mph and
>> 65mph is dissipated by the engine over that 1 mile. In one second of
>> braking from 55mph, the amount of energy transfered to the braking
>> system is greater than the ENTIRE rise in energy due to coasting over
>> 64 secondsLater on, i even calculate for you that the change in
>> vehicluar energy due to the coast is equivilent to a stop from 35mph.
>> thats if you want to incease the figures by 30% for 'mgvw' or not,
>> since mass is purely a linear variable in all the calculations.
>
>again, you're mission the point. you still seem having difficulty
>grasping the concept that /less/ engine braking means /more/ service
>braking, which means higher operating temperatures. you can't just
>gloss over it with a dismissive "it's equivalent to coasting 64
>seconds". same for mass - clutching at "linearity" is either a
>deliberate red herring or conceptual myopia.
If/when you coast, you generally don't ride the brakes. If the hill is
steep enough to ride the brakes, then generally you don't coast. Very
simple, point it out like 50 posts back. (after you claimed that you
can't pick the situatiosn you coast in)
>
>>
>>
>>>per the above, if the engine is not braking the car, you need to
>>>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>>>simplification ignoring wind, friction, etc., but it'll do for first order.
>>
>>
>> an additional amount? wheres this come from? you seem to have just
>> gone ahead and generated some additional energy value and added it to
>> the emergency stop value, something to do with engine braking. Is this
>> the added enegery value required to stop the rotational inertia of the
>> engine in an emergency stop?
>
>ok, this is where i quit arguing with you. if the engine is disengaged,
>the energy that would otherwise be lost to engine braking is added to
>the energy that needs to be dissipated in the braking system. this is
>the 3rd time in a single response that you've fudged this point. the
>math is grade school. the science is grade school. if you won't or
>can't grasp that concept, sorry, i have no more time for you. have a
>nice day.
The science is grade school eh. Its very grade school. Energy
dissipated by a d15b2 (the one in my civic, which we've been using for
caculations) is 1800W. Doesn't matter how much mass you put in a car,
its 1800W, if you're stopping the car in, or out of gear, those 1800W
don't matter. in fact, if you're stopping it in gear, you end up
loading the brakes MORE since you've also got to stop the rotational
energy of said engine. It can't dissipate any more, or any less. It
dissipates by operating, the energy is used to have the engine
continue to operateat that speed. It takes 1800W to keep the engine at
that speed. If the vehicle speed is producing a load on the engine of
1800W (as the downhill segment does) then the engine dissipates that,
and keeps it at a steady speed, If you then try and suddenly reduce
the engine speed, the engine, which has this great inertia (just try
leaving it idling in netrual, then jam is straight into gear, and see
how much inertia there is transfered to vehicular momentum.
you can't ahve it both ways, you see. the engine braking you attribute
to 'saving the brakes' is loading the brakes up similarly in an
emergency stop when you're not coasting. wheels, transmission, engine,
all connected. when you try and stop, you see, the wheels have an
inertia, the transmission has an inertia, the engine has an inertia
(hell, thats the point of the damned flywheel) In gear, that has to go
somewhere. When engine braking, the momentum of the car is used to
move that, This is what engine braking is. Under REALy braking, its
stoping those same moving parts.
It all comes down to one thing, we've established that you believe
that if you've taken the car out of gear, you must automatically apply
the brakes to do the same job - fundamentally untrue, but it is the
basis of your argument. We then proved, mathematically, under a worst
case scenario, that even riding the brakes at 55mph for a mile, then
an emergency stop, does NOT casuse significant heat rise, that the
riding of the brakes doesn't impart more than a comparitively
minescule amount of energy. If you want to think about it this way,
that coast down the hill, and the sudden stop from 55, is the EXACT
same thing, using our calculation parameters, as a single stop from
the 'free' speed (or the speed of the vehicle had the brakes not been
ridden, nor the car in gear). After all, in the simplistic model we're
using, the instant before the brakes are applied, its KE is equal to
the initial KE and the Pe at the start. Work backwards through your
own figures. In practice, the airflow through the brakes wilst going
down the hill dissipates the heat over the free speed stop.
You stated it was bad, because it was illegal, but could only site the
most knee-jerk of the US states, where laws are made with more regard
to the spin, and the perception, than the actualfacts. (single
occupancy hybrids counting as carpool, the fuel additives are two
examples)
In short, and in conclusion, coasting, and then stopping, the brakes
will recieve the same amount of braking energy. Go down the hill in
gear, the engine will contribute in its momentum what it took from the
vehicles speed, minus a small amount for friction. The higher speed of
the free, will cause greater wind resistance (its a square increase,
like KE) the greater the speed, the greater the air ressitance. so
energy is lost there. increased brake wear, loss of control, you never
did respond with any manouvers or measures in which the engine being
connected was required, except the two i listed. One, the speed up,
runs counter to your argument of being unsafe because you're going
faster, and the other (power application to correct oversteer) can be
avoided by better driving practice.
I will prove this one way or another. This weekend, i will get some
more sensitive measurement devices, some friends, and we'll go and
actually measure the forces, temperatures, etc. I'm willing to put the
theories, both of ours, to the test. We will see then which one is
accurate. I will put my money where my mouth is, will you?
wrote:
>flobert wrote:
><snip>
>
>> the 'concept' is that quite simple one. in short, cancelling out 0.5M
>> we get
>> 55^2 = k (65^2 - 55^2) where k is some constant. this is the raw
>> difference in energy values. this is the crux of the argument.
>> 3025= k (4225 - 3025)
>> 3025 = 1200k
>> 2.52 = k
>> the coast energy is 2.52x SMALLER than the emergency stop energy.
>
>but dude, that energy is otherwise dissipated by engine braking. if
>it's /not/ being dissipated by engine braking, it's being dissipated by
>the brakes.
ONLY IF THE BRAKES ARE APPLIED INSTEAD.
>
>>
>>
><snip>
>>
>>
>> no, Lets reiterate what goes on, shall we? going down a hill of 1 mile
>> length with a starting speed of 55mph. if the engine is left in gear,
>> the vehicle stays at 55mph. if it is taken out of gear, it reaches
>> 65mph at the bottom. Thus, the energy difference between 55mph and
>> 65mph is dissipated by the engine over that 1 mile. In one second of
>> braking from 55mph, the amount of energy transfered to the braking
>> system is greater than the ENTIRE rise in energy due to coasting over
>> 64 secondsLater on, i even calculate for you that the change in
>> vehicluar energy due to the coast is equivilent to a stop from 35mph.
>> thats if you want to incease the figures by 30% for 'mgvw' or not,
>> since mass is purely a linear variable in all the calculations.
>
>again, you're mission the point. you still seem having difficulty
>grasping the concept that /less/ engine braking means /more/ service
>braking, which means higher operating temperatures. you can't just
>gloss over it with a dismissive "it's equivalent to coasting 64
>seconds". same for mass - clutching at "linearity" is either a
>deliberate red herring or conceptual myopia.
If/when you coast, you generally don't ride the brakes. If the hill is
steep enough to ride the brakes, then generally you don't coast. Very
simple, point it out like 50 posts back. (after you claimed that you
can't pick the situatiosn you coast in)
>
>>
>>
>>>per the above, if the engine is not braking the car, you need to
>>>dissipate an additional 187,249J / 2.47 = 75,809W. this is a GROSS
>>>simplification ignoring wind, friction, etc., but it'll do for first order.
>>
>>
>> an additional amount? wheres this come from? you seem to have just
>> gone ahead and generated some additional energy value and added it to
>> the emergency stop value, something to do with engine braking. Is this
>> the added enegery value required to stop the rotational inertia of the
>> engine in an emergency stop?
>
>ok, this is where i quit arguing with you. if the engine is disengaged,
>the energy that would otherwise be lost to engine braking is added to
>the energy that needs to be dissipated in the braking system. this is
>the 3rd time in a single response that you've fudged this point. the
>math is grade school. the science is grade school. if you won't or
>can't grasp that concept, sorry, i have no more time for you. have a
>nice day.
The science is grade school eh. Its very grade school. Energy
dissipated by a d15b2 (the one in my civic, which we've been using for
caculations) is 1800W. Doesn't matter how much mass you put in a car,
its 1800W, if you're stopping the car in, or out of gear, those 1800W
don't matter. in fact, if you're stopping it in gear, you end up
loading the brakes MORE since you've also got to stop the rotational
energy of said engine. It can't dissipate any more, or any less. It
dissipates by operating, the energy is used to have the engine
continue to operateat that speed. It takes 1800W to keep the engine at
that speed. If the vehicle speed is producing a load on the engine of
1800W (as the downhill segment does) then the engine dissipates that,
and keeps it at a steady speed, If you then try and suddenly reduce
the engine speed, the engine, which has this great inertia (just try
leaving it idling in netrual, then jam is straight into gear, and see
how much inertia there is transfered to vehicular momentum.
you can't ahve it both ways, you see. the engine braking you attribute
to 'saving the brakes' is loading the brakes up similarly in an
emergency stop when you're not coasting. wheels, transmission, engine,
all connected. when you try and stop, you see, the wheels have an
inertia, the transmission has an inertia, the engine has an inertia
(hell, thats the point of the damned flywheel) In gear, that has to go
somewhere. When engine braking, the momentum of the car is used to
move that, This is what engine braking is. Under REALy braking, its
stoping those same moving parts.
It all comes down to one thing, we've established that you believe
that if you've taken the car out of gear, you must automatically apply
the brakes to do the same job - fundamentally untrue, but it is the
basis of your argument. We then proved, mathematically, under a worst
case scenario, that even riding the brakes at 55mph for a mile, then
an emergency stop, does NOT casuse significant heat rise, that the
riding of the brakes doesn't impart more than a comparitively
minescule amount of energy. If you want to think about it this way,
that coast down the hill, and the sudden stop from 55, is the EXACT
same thing, using our calculation parameters, as a single stop from
the 'free' speed (or the speed of the vehicle had the brakes not been
ridden, nor the car in gear). After all, in the simplistic model we're
using, the instant before the brakes are applied, its KE is equal to
the initial KE and the Pe at the start. Work backwards through your
own figures. In practice, the airflow through the brakes wilst going
down the hill dissipates the heat over the free speed stop.
You stated it was bad, because it was illegal, but could only site the
most knee-jerk of the US states, where laws are made with more regard
to the spin, and the perception, than the actualfacts. (single
occupancy hybrids counting as carpool, the fuel additives are two
examples)
In short, and in conclusion, coasting, and then stopping, the brakes
will recieve the same amount of braking energy. Go down the hill in
gear, the engine will contribute in its momentum what it took from the
vehicles speed, minus a small amount for friction. The higher speed of
the free, will cause greater wind resistance (its a square increase,
like KE) the greater the speed, the greater the air ressitance. so
energy is lost there. increased brake wear, loss of control, you never
did respond with any manouvers or measures in which the engine being
connected was required, except the two i listed. One, the speed up,
runs counter to your argument of being unsafe because you're going
faster, and the other (power application to correct oversteer) can be
avoided by better driving practice.
I will prove this one way or another. This weekend, i will get some
more sensitive measurement devices, some friends, and we'll go and
actually measure the forces, temperatures, etc. I'm willing to put the
theories, both of ours, to the test. We will see then which one is
accurate. I will put my money where my mouth is, will you?
#66
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
On 26 Aug 2005 02:19:59 GMT, "TeGGeR®" <tegger@tegger.c0m> wrote:
>jim beam <nospam@example.net> wrote in
>news:2-2dnZ2dnZ21k2DenZ2dnTDrk96dnZ2dRVn-z52dnZ0@speakeasy.net:
>
>
>> ok, this is where i quit arguing with you. if the engine is
>> disengaged, the energy that would otherwise be lost to engine braking
>> is added to the energy that needs to be dissipated in the braking
>> system. this is the 3rd time in a single response that you've fudged
>> this point. the math is grade school. the science is grade school.
>> if you won't or can't grasp that concept, sorry, i have no more time
>> for you. have a nice day.
>>
>
>
>flobert was totally wrong on the rear fog light thing, too. I checked. It
>seems the rear fog light in the UK is the sole exception to the "all lights
>must work" general rule. The driver's side is the ONLY one that has to work
>if two rear fog lights are fitted.
See, i didn't know that. then again, i'm not now, nor have i ever
been, an MOT inspector. not exactly 'totally' wrong either, i was
write on the era, and many other things, just one small area i was
misinformed, by someone who should have known.
>
>It further seems that there are many MoT testers who are not fully familiar
>with their own rules. It is common for testers to fail cars based on their
>own personal pseudo-knowledge, and not the actual law, especially when it
>comes to older vehicles.
If you believe there to ahve been an error and to ahve been failed for
a reason unwarrented, you can appeal. If it had been a major rewire
job on my passenger-side fog light, and not just a blown bulb, then
who knows, i might have Then again, it isa light, and really, if you
have it, you should have it working. Where I was, Liverpool, is right
on the coast, so we often had bad fog and mist in the autumn/winter.
Better to be safe than sorry. Nor was it really a fail, more a case of
'the bulbs gone, 2 quid for a pair, and i'll slap it in for you, since
you don't have any in the car' about the same cost as halfords, did it
during the test, was the right size, and i use the same bulb elsewhere
anyway. Its only a fail when its written down on the sheet. Was
Niovember too, that i remember well, since it had missed its MOT
because i was freezing my **** off in Vegas for 2 weeks (and me, being
silly, throught vegas never got cold, and only packed summer things,
was below freezing most of the time, and i was working outside)
>
>I'm damn glad Ontario has no MoT.
>jim beam <nospam@example.net> wrote in
>news:2-2dnZ2dnZ21k2DenZ2dnTDrk96dnZ2dRVn-z52dnZ0@speakeasy.net:
>
>
>> ok, this is where i quit arguing with you. if the engine is
>> disengaged, the energy that would otherwise be lost to engine braking
>> is added to the energy that needs to be dissipated in the braking
>> system. this is the 3rd time in a single response that you've fudged
>> this point. the math is grade school. the science is grade school.
>> if you won't or can't grasp that concept, sorry, i have no more time
>> for you. have a nice day.
>>
>
>
>flobert was totally wrong on the rear fog light thing, too. I checked. It
>seems the rear fog light in the UK is the sole exception to the "all lights
>must work" general rule. The driver's side is the ONLY one that has to work
>if two rear fog lights are fitted.
See, i didn't know that. then again, i'm not now, nor have i ever
been, an MOT inspector. not exactly 'totally' wrong either, i was
write on the era, and many other things, just one small area i was
misinformed, by someone who should have known.
>
>It further seems that there are many MoT testers who are not fully familiar
>with their own rules. It is common for testers to fail cars based on their
>own personal pseudo-knowledge, and not the actual law, especially when it
>comes to older vehicles.
If you believe there to ahve been an error and to ahve been failed for
a reason unwarrented, you can appeal. If it had been a major rewire
job on my passenger-side fog light, and not just a blown bulb, then
who knows, i might have Then again, it isa light, and really, if you
have it, you should have it working. Where I was, Liverpool, is right
on the coast, so we often had bad fog and mist in the autumn/winter.
Better to be safe than sorry. Nor was it really a fail, more a case of
'the bulbs gone, 2 quid for a pair, and i'll slap it in for you, since
you don't have any in the car' about the same cost as halfords, did it
during the test, was the right size, and i use the same bulb elsewhere
anyway. Its only a fail when its written down on the sheet. Was
Niovember too, that i remember well, since it had missed its MOT
because i was freezing my **** off in Vegas for 2 weeks (and me, being
silly, throught vegas never got cold, and only packed summer things,
was below freezing most of the time, and i was working outside)
>
>I'm damn glad Ontario has no MoT.
#67
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
On Thu, 25 Aug 2005 22:35:35 GMT, "al"
<[ask_me_first]@blueyonder.co.uk> wrote:
>"flobert" <nomail@here.NOT> wrote in message
>news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
>
>Wow .. you guys are writing some long replies in this thread!
>
Yeah, i tend to get a bit frothy at the mouth when i see sloppy
thinking touted as fact. Comes from my nature i guess. and my father,
who as a rally driver, and mechanical engineer, often tried and forced
me into arguments just be sure i know my stuff. He was a hard bastard,
but he really drummed into me how to make a complete and concise
argument, which should bend to your opoonants view as much as is
reasonable, in order to prove how silly it is. This is something i do
a lot of. Since part of my job involves prototyping vehicles, for
various uses, safety systems are where my priority lies, mainly in
overestimating them - Half the time, i'm the one inside (if i won't
ride it, its not safe enough)
>I'd like to point out two facts, which may be contrary to an extent to what
>each of you are saying:
>
>1) Modern cars do suffer from brake fade (I had a Civic as my last car and
>when I drove it like I stole it, there came a point after a few *really*
>heavy stops from high speed where the pedal would disappear to the floor
>virtually with the pressure before doing anything much - get out of the car
>and smell the wonderful baking smell of toasted brake pads!). However, with
>a normal person driving it legally, there are very few situations in the
>world where it's going to be a worry. OK - some of us live in the Alps and
>drive for 15 mins as fast as we can down a hill ... worry! The rest of us
>rarely see a hill more than 1km long!
not at any kind of grade, no. one of the worst of that length that i
do quite regularly, is the 0.85mile one 9about what, 1.2km) which
averages a 1in16, just north of atlanta. We've both given examples of
a steeper one, but much shorter (some 0.3km only). You are someone
who's had real wold practical experiance with heavy braking, hills and
fade, or lackthereof.
>
>I now have a ATR - no matter what I've done to it so far, it's coped fine.
>But then it's got whopping great vented discs that are built to take a
>constant heat input and dissipate it as quickly as possible and keep all of
>the braking materials at an operational temperature.
Yep, brakes dissipate lots of heat when the vehicle is in motion -
something we deliberately removed from the calculations, primarally
because i have no way to measure, but also because it leans to Jim's
side (see above)
>
>
>2) Driving out of gear is rightly illegal in many places. This is because
>you are less in control and less able to respond to any given situation.
>The engine breaking is a bonus for those of us who aren't so goddam tight
>that we'll do anything to save £1 a year on fuel costs. Many situations
>occur where you need to take evasive action and drive out of trouble. A car
>is also more stable and "drivable" in gear. If you're coasting around in
>neutral, you're doing two things - concentrating less than you should on the
>road because you're worrying about keeping your toboggan going fast enough
>for your lazy **** not to get back into gear again and perhaps taking risks
>by going faster than you should in places to keep up that precious momentum;
>and two, you're probably annoying the living hell out of the driver behind
>you by driving in an unexpected and erratic manner (too slow at times,
>correct or too fast at others), thus increasing the likelihood of a crash
>out of frustration from other road users.
Here i'm not too sure. We agree that about the only use being in gear
has, is accelerating, or 'driving out' of a situation. Avalanches,
yes, not situations you'll see on either cost of the US though, where
we are. If it were really that important to accelerate, I'd be
changine gears anyway, for a lower one, for better acceleration, if a
tornado is comming (a more common risk over here at least, 4rth or 3rd
would be a better gear to aceclerate in, than the 5th gear i'd be in
for the cruise down the hill.
i wouldn't say its unpredictable, or 'less concentrating' though. When
keeping the momentum up, you end up glacing at the speedo, yes, (but
isn't that the point of all those speed cameras, to make you watch
your speedo!) but putting it into gear from neutral is no more
involved than just changing gear, after all, in a manual car, part of
changing gear is 'coasting'. Eratic speeds don't match either, since i
will put it into gear to keep my speed to a point i set myself at.
i'll aim to keep that speed above that minimum regardless. downhill
you'll be going faster, not slower, so you'll be leaving those brake
riders, or engine brakers behind. (assuming of course, they don't
either coast, or accelerate down the hill themselves).
>
>
>
>Please, guys - life is too short!! There is a reason why coasting is
>frowned upon - you don't know better than most driving standards across the
>civilised worlds. Also, car brakes are more than able to cool themselves
>adequately under normal driving conditions.
>
I've fuond that only a few palces actually BAN coasting, or at least
make it a ticketable offence. Many others frown on it, the same way
corsing your hands on the wheel, or changing gear ina corner is fornw
upon. Of course, there is something i've been longing to say, but have
avoided it hoping someone else would. Automatic hgearboxes, in the
main, do not offer any form of engine braking at hgiher speeds, in
higher gears. Lock them into 2, or ! and they will, but regular D,
nope.
"Many automatic transmissions use overrunning or one-way mechanical
clutches to transmit power through the transmission. These devices
make upshifts smooth because only one clutch has to apply during a
shift instead of one applying and another releasing (the overrunning
clutch releases automatically). The disadvantage of overrunning
clutches is that they can only transfer torque one way so they provide
no engine braking."
(source http://www.canadiandriver.com/articles/jk/030806.htm - the
very first link ona google search for "Automatic transmission"
"Engine braking" You'd have to manually shift an automatic box to a
non-overdrive situation, to a gear with engine braking. Maybe you
didn't understand how the civic was coasting. (lovely overdrive, which
is neutral). The van has no such lovelyness (being a crappy american
slushbox) but since i've uprated the brakes anyway, to the point
where, if needed, under normal use any one wheel will function to slow
the vehicle under normal loading on its own (since on occasion, i take
it right upto its mgvw, with all the hills and stop-starts here for
deer and such, i don't like to take chances with substandard parts,
like jim does 9after all, he uses cheap pads, and had them burn outt o
nothing ona short 1 in 7.5 grade, at low speed)
Oh dear, its gotten another long post again (sorry, i'm a windbag) but
i hope you get my intent.
>
>
>
>
>al
>
<[ask_me_first]@blueyonder.co.uk> wrote:
>"flobert" <nomail@here.NOT> wrote in message
>news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
>
>Wow .. you guys are writing some long replies in this thread!
>
Yeah, i tend to get a bit frothy at the mouth when i see sloppy
thinking touted as fact. Comes from my nature i guess. and my father,
who as a rally driver, and mechanical engineer, often tried and forced
me into arguments just be sure i know my stuff. He was a hard bastard,
but he really drummed into me how to make a complete and concise
argument, which should bend to your opoonants view as much as is
reasonable, in order to prove how silly it is. This is something i do
a lot of. Since part of my job involves prototyping vehicles, for
various uses, safety systems are where my priority lies, mainly in
overestimating them - Half the time, i'm the one inside (if i won't
ride it, its not safe enough)
>I'd like to point out two facts, which may be contrary to an extent to what
>each of you are saying:
>
>1) Modern cars do suffer from brake fade (I had a Civic as my last car and
>when I drove it like I stole it, there came a point after a few *really*
>heavy stops from high speed where the pedal would disappear to the floor
>virtually with the pressure before doing anything much - get out of the car
>and smell the wonderful baking smell of toasted brake pads!). However, with
>a normal person driving it legally, there are very few situations in the
>world where it's going to be a worry. OK - some of us live in the Alps and
>drive for 15 mins as fast as we can down a hill ... worry! The rest of us
>rarely see a hill more than 1km long!
not at any kind of grade, no. one of the worst of that length that i
do quite regularly, is the 0.85mile one 9about what, 1.2km) which
averages a 1in16, just north of atlanta. We've both given examples of
a steeper one, but much shorter (some 0.3km only). You are someone
who's had real wold practical experiance with heavy braking, hills and
fade, or lackthereof.
>
>I now have a ATR - no matter what I've done to it so far, it's coped fine.
>But then it's got whopping great vented discs that are built to take a
>constant heat input and dissipate it as quickly as possible and keep all of
>the braking materials at an operational temperature.
Yep, brakes dissipate lots of heat when the vehicle is in motion -
something we deliberately removed from the calculations, primarally
because i have no way to measure, but also because it leans to Jim's
side (see above)
>
>
>2) Driving out of gear is rightly illegal in many places. This is because
>you are less in control and less able to respond to any given situation.
>The engine breaking is a bonus for those of us who aren't so goddam tight
>that we'll do anything to save £1 a year on fuel costs. Many situations
>occur where you need to take evasive action and drive out of trouble. A car
>is also more stable and "drivable" in gear. If you're coasting around in
>neutral, you're doing two things - concentrating less than you should on the
>road because you're worrying about keeping your toboggan going fast enough
>for your lazy **** not to get back into gear again and perhaps taking risks
>by going faster than you should in places to keep up that precious momentum;
>and two, you're probably annoying the living hell out of the driver behind
>you by driving in an unexpected and erratic manner (too slow at times,
>correct or too fast at others), thus increasing the likelihood of a crash
>out of frustration from other road users.
Here i'm not too sure. We agree that about the only use being in gear
has, is accelerating, or 'driving out' of a situation. Avalanches,
yes, not situations you'll see on either cost of the US though, where
we are. If it were really that important to accelerate, I'd be
changine gears anyway, for a lower one, for better acceleration, if a
tornado is comming (a more common risk over here at least, 4rth or 3rd
would be a better gear to aceclerate in, than the 5th gear i'd be in
for the cruise down the hill.
i wouldn't say its unpredictable, or 'less concentrating' though. When
keeping the momentum up, you end up glacing at the speedo, yes, (but
isn't that the point of all those speed cameras, to make you watch
your speedo!) but putting it into gear from neutral is no more
involved than just changing gear, after all, in a manual car, part of
changing gear is 'coasting'. Eratic speeds don't match either, since i
will put it into gear to keep my speed to a point i set myself at.
i'll aim to keep that speed above that minimum regardless. downhill
you'll be going faster, not slower, so you'll be leaving those brake
riders, or engine brakers behind. (assuming of course, they don't
either coast, or accelerate down the hill themselves).
>
>
>
>Please, guys - life is too short!! There is a reason why coasting is
>frowned upon - you don't know better than most driving standards across the
>civilised worlds. Also, car brakes are more than able to cool themselves
>adequately under normal driving conditions.
>
I've fuond that only a few palces actually BAN coasting, or at least
make it a ticketable offence. Many others frown on it, the same way
corsing your hands on the wheel, or changing gear ina corner is fornw
upon. Of course, there is something i've been longing to say, but have
avoided it hoping someone else would. Automatic hgearboxes, in the
main, do not offer any form of engine braking at hgiher speeds, in
higher gears. Lock them into 2, or ! and they will, but regular D,
nope.
"Many automatic transmissions use overrunning or one-way mechanical
clutches to transmit power through the transmission. These devices
make upshifts smooth because only one clutch has to apply during a
shift instead of one applying and another releasing (the overrunning
clutch releases automatically). The disadvantage of overrunning
clutches is that they can only transfer torque one way so they provide
no engine braking."
(source http://www.canadiandriver.com/articles/jk/030806.htm - the
very first link ona google search for "Automatic transmission"
"Engine braking" You'd have to manually shift an automatic box to a
non-overdrive situation, to a gear with engine braking. Maybe you
didn't understand how the civic was coasting. (lovely overdrive, which
is neutral). The van has no such lovelyness (being a crappy american
slushbox) but since i've uprated the brakes anyway, to the point
where, if needed, under normal use any one wheel will function to slow
the vehicle under normal loading on its own (since on occasion, i take
it right upto its mgvw, with all the hills and stop-starts here for
deer and such, i don't like to take chances with substandard parts,
like jim does 9after all, he uses cheap pads, and had them burn outt o
nothing ona short 1 in 7.5 grade, at low speed)
Oh dear, its gotten another long post again (sorry, i'm a windbag) but
i hope you get my intent.
>
>
>
>
>al
>
#68
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
flobert <nomail@here.NOT> wrote in message
news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> On Thu, 25 Aug 2005 22:35:35 GMT, "al"
> <[ask_me_first]@blueyonder.co.uk> wrote:
>
> >"flobert" <nomail@here.NOT> wrote in message
> >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
>
> I've fuond that only a few palces actually BAN coasting, or at least
> make it a ticketable offence. Many others frown on it, the same way
> corsing your hands on the wheel, or changing gear ina corner is fornw
> upon. Of course, there is something i've been longing to say, but have
> avoided it hoping someone else would. Automatic hgearboxes, in the
> main, do not offer any form of engine braking at hgiher speeds, in
> higher gears. Lock them into 2, or ! and they will, but regular D,
> nope.
> "Many automatic transmissions use overrunning or one-way mechanical
> clutches to transmit power through the transmission. These devices
> make upshifts smooth because only one clutch has to apply during a
> shift instead of one applying and another releasing (the overrunning
> clutch releases automatically). The disadvantage of overrunning
> clutches is that they can only transfer torque one way so they provide
> no engine braking."
> (source http://www.canadiandriver.com/articles/jk/030806.htm - the
> very first link ona google search for "Automatic transmission"
> "Engine braking" You'd have to manually shift an automatic box to a
> non-overdrive situation, to a gear with engine braking. Maybe you
> didn't understand how the civic was coasting. (lovely overdrive, which
> is neutral). The van has no such lovelyness (being a crappy american
> slushbox) but since i've uprated the brakes anyway, to the point
> where, if needed, under normal use any one wheel will function to slow
> the vehicle under normal loading on its own (since on occasion, i take
> it right upto its mgvw, with all the hills and stop-starts here for
> deer and such, i don't like to take chances with substandard parts,
> like jim does 9after all, he uses cheap pads, and had them burn outt o
> nothing ona short 1 in 7.5 grade, at low speed)
>
> Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> i hope you get my intent.
>
Just for the record, I have an '03 Toyota Corolla that was bothering me for some
time until I finally realised that it downshifts from overdrive when the brakes
are applied (fairly hard) going downhill. I haven't determined exactly why it
does it (that, the parameters of when it happens), but it definately does
downshift.
#69
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
In article <ZMyPe.16016$Hi.5700@trnddc04>, "Doug McCrary"
<DougMcCrary@spamcop.net> wrote:
> flobert <nomail@here.NOT> wrote in message
> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
> > <[ask_me_first]@blueyonder.co.uk> wrote:
> >
> > >"flobert" <nomail@here.NOT> wrote in message
> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
> >
> > I've fuond that only a few palces actually BAN coasting, or at least
> > make it a ticketable offence. Many others frown on it, the same way
> > corsing your hands on the wheel, or changing gear ina corner is fornw
> > upon. Of course, there is something i've been longing to say, but have
> > avoided it hoping someone else would. Automatic hgearboxes, in the
> > main, do not offer any form of engine braking at hgiher speeds, in
> > higher gears. Lock them into 2, or ! and they will, but regular D,
> > nope.
> > "Many automatic transmissions use overrunning or one-way mechanical
> > clutches to transmit power through the transmission. These devices
> > make upshifts smooth because only one clutch has to apply during a
> > shift instead of one applying and another releasing (the overrunning
> > clutch releases automatically). The disadvantage of overrunning
> > clutches is that they can only transfer torque one way so they provide
> > no engine braking."
> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
> > very first link ona google search for "Automatic transmission"
> > "Engine braking" You'd have to manually shift an automatic box to a
> > non-overdrive situation, to a gear with engine braking. Maybe you
> > didn't understand how the civic was coasting. (lovely overdrive, which
> > is neutral). The van has no such lovelyness (being a crappy american
> > slushbox) but since i've uprated the brakes anyway, to the point
> > where, if needed, under normal use any one wheel will function to slow
> > the vehicle under normal loading on its own (since on occasion, i take
> > it right upto its mgvw, with all the hills and stop-starts here for
> > deer and such, i don't like to take chances with substandard parts,
> > like jim does 9after all, he uses cheap pads, and had them burn outt o
> > nothing ona short 1 in 7.5 grade, at low speed)
> >
> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> > i hope you get my intent.
> >
> Just for the record, I have an '03 Toyota Corolla that was bothering me
for some
> time until I finally realised that it downshifts from overdrive when the
brakes
> are applied (fairly hard) going downhill. I haven't determined exactly why it
> does it (that, the parameters of when it happens), but it definately does
> downshift.
Hello,
I just wanted to let people know that plan to coast their vehicles down
hill that it causes more WEAR on the transmissions. It also causes more
WEAR on the clutch. In other words, if you two people have the same type
of cars, the person that coasts down the hills is more likely to have to
have the transmission or clutch repaired or replaced than the other person
that did NOT coast down hills.
Jason
--
NEWSGROUP SUBSCRIBERS MOTTO
We respect those subscribers that ask for advice or provide advice.
We do NOT respect the subscribers that enjoy criticizing people.
<DougMcCrary@spamcop.net> wrote:
> flobert <nomail@here.NOT> wrote in message
> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
> > <[ask_me_first]@blueyonder.co.uk> wrote:
> >
> > >"flobert" <nomail@here.NOT> wrote in message
> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
> >
> > I've fuond that only a few palces actually BAN coasting, or at least
> > make it a ticketable offence. Many others frown on it, the same way
> > corsing your hands on the wheel, or changing gear ina corner is fornw
> > upon. Of course, there is something i've been longing to say, but have
> > avoided it hoping someone else would. Automatic hgearboxes, in the
> > main, do not offer any form of engine braking at hgiher speeds, in
> > higher gears. Lock them into 2, or ! and they will, but regular D,
> > nope.
> > "Many automatic transmissions use overrunning or one-way mechanical
> > clutches to transmit power through the transmission. These devices
> > make upshifts smooth because only one clutch has to apply during a
> > shift instead of one applying and another releasing (the overrunning
> > clutch releases automatically). The disadvantage of overrunning
> > clutches is that they can only transfer torque one way so they provide
> > no engine braking."
> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
> > very first link ona google search for "Automatic transmission"
> > "Engine braking" You'd have to manually shift an automatic box to a
> > non-overdrive situation, to a gear with engine braking. Maybe you
> > didn't understand how the civic was coasting. (lovely overdrive, which
> > is neutral). The van has no such lovelyness (being a crappy american
> > slushbox) but since i've uprated the brakes anyway, to the point
> > where, if needed, under normal use any one wheel will function to slow
> > the vehicle under normal loading on its own (since on occasion, i take
> > it right upto its mgvw, with all the hills and stop-starts here for
> > deer and such, i don't like to take chances with substandard parts,
> > like jim does 9after all, he uses cheap pads, and had them burn outt o
> > nothing ona short 1 in 7.5 grade, at low speed)
> >
> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> > i hope you get my intent.
> >
> Just for the record, I have an '03 Toyota Corolla that was bothering me
for some
> time until I finally realised that it downshifts from overdrive when the
brakes
> are applied (fairly hard) going downhill. I haven't determined exactly why it
> does it (that, the parameters of when it happens), but it definately does
> downshift.
Hello,
I just wanted to let people know that plan to coast their vehicles down
hill that it causes more WEAR on the transmissions. It also causes more
WEAR on the clutch. In other words, if you two people have the same type
of cars, the person that coasts down the hills is more likely to have to
have the transmission or clutch repaired or replaced than the other person
that did NOT coast down hills.
Jason
--
NEWSGROUP SUBSCRIBERS MOTTO
We respect those subscribers that ask for advice or provide advice.
We do NOT respect the subscribers that enjoy criticizing people.
#70
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
On Fri, 26 Aug 2005 10:10:39 -0700, jason@nospam.com (Jason) wrote:
>In article <ZMyPe.16016$Hi.5700@trnddc04>, "Doug McCrary"
><DougMcCrary@spamcop.net> wrote:
>
>> flobert <nomail@here.NOT> wrote in message
>> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
>> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
>> > <[ask_me_first]@blueyonder.co.uk> wrote:
>> >
>> > >"flobert" <nomail@here.NOT> wrote in message
>> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
>> >
>> > I've fuond that only a few palces actually BAN coasting, or at least
>> > make it a ticketable offence. Many others frown on it, the same way
>> > corsing your hands on the wheel, or changing gear ina corner is fornw
>> > upon. Of course, there is something i've been longing to say, but have
>> > avoided it hoping someone else would. Automatic hgearboxes, in the
>> > main, do not offer any form of engine braking at hgiher speeds, in
>> > higher gears. Lock them into 2, or ! and they will, but regular D,
>> > nope.
>> > "Many automatic transmissions use overrunning or one-way mechanical
>> > clutches to transmit power through the transmission. These devices
>> > make upshifts smooth because only one clutch has to apply during a
>> > shift instead of one applying and another releasing (the overrunning
>> > clutch releases automatically). The disadvantage of overrunning
>> > clutches is that they can only transfer torque one way so they provide
>> > no engine braking."
>> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
>> > very first link ona google search for "Automatic transmission"
>> > "Engine braking" You'd have to manually shift an automatic box to a
>> > non-overdrive situation, to a gear with engine braking. Maybe you
>> > didn't understand how the civic was coasting. (lovely overdrive, which
>> > is neutral). The van has no such lovelyness (being a crappy american
>> > slushbox) but since i've uprated the brakes anyway, to the point
>> > where, if needed, under normal use any one wheel will function to slow
>> > the vehicle under normal loading on its own (since on occasion, i take
>> > it right upto its mgvw, with all the hills and stop-starts here for
>> > deer and such, i don't like to take chances with substandard parts,
>> > like jim does 9after all, he uses cheap pads, and had them burn outt o
>> > nothing ona short 1 in 7.5 grade, at low speed)
>> >
>> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
>> > i hope you get my intent.
>> >
>> Just for the record, I have an '03 Toyota Corolla that was bothering me
>for some
>> time until I finally realised that it downshifts from overdrive when the
>brakes
>> are applied (fairly hard) going downhill. I haven't determined exactly why it
>> does it (that, the parameters of when it happens), but it definately does
>> downshift.
>
>Hello,
>I just wanted to let people know that plan to coast their vehicles down
>hill that it causes more WEAR on the transmissions. It also causes more
>WEAR on the clutch. In other words, if you two people have the same type
>of cars, the person that coasts down the hills is more likely to have to
>have the transmission or clutch repaired or replaced than the other person
>that did NOT coast down hills.
>Jason
You said this early as well, and then, as now, you gave nothing to
back it up.
>In article <ZMyPe.16016$Hi.5700@trnddc04>, "Doug McCrary"
><DougMcCrary@spamcop.net> wrote:
>
>> flobert <nomail@here.NOT> wrote in message
>> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
>> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
>> > <[ask_me_first]@blueyonder.co.uk> wrote:
>> >
>> > >"flobert" <nomail@here.NOT> wrote in message
>> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
>> >
>> > I've fuond that only a few palces actually BAN coasting, or at least
>> > make it a ticketable offence. Many others frown on it, the same way
>> > corsing your hands on the wheel, or changing gear ina corner is fornw
>> > upon. Of course, there is something i've been longing to say, but have
>> > avoided it hoping someone else would. Automatic hgearboxes, in the
>> > main, do not offer any form of engine braking at hgiher speeds, in
>> > higher gears. Lock them into 2, or ! and they will, but regular D,
>> > nope.
>> > "Many automatic transmissions use overrunning or one-way mechanical
>> > clutches to transmit power through the transmission. These devices
>> > make upshifts smooth because only one clutch has to apply during a
>> > shift instead of one applying and another releasing (the overrunning
>> > clutch releases automatically). The disadvantage of overrunning
>> > clutches is that they can only transfer torque one way so they provide
>> > no engine braking."
>> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
>> > very first link ona google search for "Automatic transmission"
>> > "Engine braking" You'd have to manually shift an automatic box to a
>> > non-overdrive situation, to a gear with engine braking. Maybe you
>> > didn't understand how the civic was coasting. (lovely overdrive, which
>> > is neutral). The van has no such lovelyness (being a crappy american
>> > slushbox) but since i've uprated the brakes anyway, to the point
>> > where, if needed, under normal use any one wheel will function to slow
>> > the vehicle under normal loading on its own (since on occasion, i take
>> > it right upto its mgvw, with all the hills and stop-starts here for
>> > deer and such, i don't like to take chances with substandard parts,
>> > like jim does 9after all, he uses cheap pads, and had them burn outt o
>> > nothing ona short 1 in 7.5 grade, at low speed)
>> >
>> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
>> > i hope you get my intent.
>> >
>> Just for the record, I have an '03 Toyota Corolla that was bothering me
>for some
>> time until I finally realised that it downshifts from overdrive when the
>brakes
>> are applied (fairly hard) going downhill. I haven't determined exactly why it
>> does it (that, the parameters of when it happens), but it definately does
>> downshift.
>
>Hello,
>I just wanted to let people know that plan to coast their vehicles down
>hill that it causes more WEAR on the transmissions. It also causes more
>WEAR on the clutch. In other words, if you two people have the same type
>of cars, the person that coasts down the hills is more likely to have to
>have the transmission or clutch repaired or replaced than the other person
>that did NOT coast down hills.
>Jason
You said this early as well, and then, as now, you gave nothing to
back it up.
#71
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
In article <6amug19l42ojvpjp5q6g56rforsaqh1ihr@4ax.com>, flobert
<nomail@here.NOT> wrote:
> On Fri, 26 Aug 2005 10:10:39 -0700, jason@nospam.com (Jason) wrote:
>
> >In article <ZMyPe.16016$Hi.5700@trnddc04>, "Doug McCrary"
> ><DougMcCrary@spamcop.net> wrote:
> >
> >> flobert <nomail@here.NOT> wrote in message
> >> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> >> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
> >> > <[ask_me_first]@blueyonder.co.uk> wrote:
> >> >
> >> > >"flobert" <nomail@here.NOT> wrote in message
> >> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
> >> >
> >> > I've fuond that only a few palces actually BAN coasting, or at least
> >> > make it a ticketable offence. Many others frown on it, the same way
> >> > corsing your hands on the wheel, or changing gear ina corner is fornw
> >> > upon. Of course, there is something i've been longing to say, but have
> >> > avoided it hoping someone else would. Automatic hgearboxes, in the
> >> > main, do not offer any form of engine braking at hgiher speeds, in
> >> > higher gears. Lock them into 2, or ! and they will, but regular D,
> >> > nope.
> >> > "Many automatic transmissions use overrunning or one-way mechanical
> >> > clutches to transmit power through the transmission. These devices
> >> > make upshifts smooth because only one clutch has to apply during a
> >> > shift instead of one applying and another releasing (the overrunning
> >> > clutch releases automatically). The disadvantage of overrunning
> >> > clutches is that they can only transfer torque one way so they provide
> >> > no engine braking."
> >> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
> >> > very first link ona google search for "Automatic transmission"
> >> > "Engine braking" You'd have to manually shift an automatic box to a
> >> > non-overdrive situation, to a gear with engine braking. Maybe you
> >> > didn't understand how the civic was coasting. (lovely overdrive, which
> >> > is neutral). The van has no such lovelyness (being a crappy american
> >> > slushbox) but since i've uprated the brakes anyway, to the point
> >> > where, if needed, under normal use any one wheel will function to slow
> >> > the vehicle under normal loading on its own (since on occasion, i take
> >> > it right upto its mgvw, with all the hills and stop-starts here for
> >> > deer and such, i don't like to take chances with substandard parts,
> >> > like jim does 9after all, he uses cheap pads, and had them burn outt o
> >> > nothing ona short 1 in 7.5 grade, at low speed)
> >> >
> >> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> >> > i hope you get my intent.
> >> >
> >> Just for the record, I have an '03 Toyota Corolla that was bothering me
> >for some
> >> time until I finally realised that it downshifts from overdrive when the
> >brakes
> >> are applied (fairly hard) going downhill. I haven't determined
exactly why it
> >> does it (that, the parameters of when it happens), but it definately does
> >> downshift.
> >
> >Hello,
> >I just wanted to let people know that plan to coast their vehicles down
> >hill that it causes more WEAR on the transmissions. It also causes more
> >WEAR on the clutch. In other words, if you two people have the same type
> >of cars, the person that coasts down the hills is more likely to have to
> >have the transmission or clutch repaired or replaced than the other person
> >that did NOT coast down hills.
> >Jason
>
> You said this early as well, and then, as now, you gave nothing to
> back it up.
Murphy's Law and common sense. The more that a transmission or clutch is
used, the more likely it is to develop problems. That's one of reasons
that most people trade in or sell their cars after they are three or four
years old.
They know that those older cars will have more problems than a new cars
will have.
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<nomail@here.NOT> wrote:
> On Fri, 26 Aug 2005 10:10:39 -0700, jason@nospam.com (Jason) wrote:
>
> >In article <ZMyPe.16016$Hi.5700@trnddc04>, "Doug McCrary"
> ><DougMcCrary@spamcop.net> wrote:
> >
> >> flobert <nomail@here.NOT> wrote in message
> >> news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> >> > On Thu, 25 Aug 2005 22:35:35 GMT, "al"
> >> > <[ask_me_first]@blueyonder.co.uk> wrote:
> >> >
> >> > >"flobert" <nomail@here.NOT> wrote in message
> >> > >news:4mmrg15k3bo1nkg8fv40t38stma68ut328@4ax.com.. .
> >> >
> >> > I've fuond that only a few palces actually BAN coasting, or at least
> >> > make it a ticketable offence. Many others frown on it, the same way
> >> > corsing your hands on the wheel, or changing gear ina corner is fornw
> >> > upon. Of course, there is something i've been longing to say, but have
> >> > avoided it hoping someone else would. Automatic hgearboxes, in the
> >> > main, do not offer any form of engine braking at hgiher speeds, in
> >> > higher gears. Lock them into 2, or ! and they will, but regular D,
> >> > nope.
> >> > "Many automatic transmissions use overrunning or one-way mechanical
> >> > clutches to transmit power through the transmission. These devices
> >> > make upshifts smooth because only one clutch has to apply during a
> >> > shift instead of one applying and another releasing (the overrunning
> >> > clutch releases automatically). The disadvantage of overrunning
> >> > clutches is that they can only transfer torque one way so they provide
> >> > no engine braking."
> >> > (source http://www.canadiandriver.com/articles/jk/030806.htm - the
> >> > very first link ona google search for "Automatic transmission"
> >> > "Engine braking" You'd have to manually shift an automatic box to a
> >> > non-overdrive situation, to a gear with engine braking. Maybe you
> >> > didn't understand how the civic was coasting. (lovely overdrive, which
> >> > is neutral). The van has no such lovelyness (being a crappy american
> >> > slushbox) but since i've uprated the brakes anyway, to the point
> >> > where, if needed, under normal use any one wheel will function to slow
> >> > the vehicle under normal loading on its own (since on occasion, i take
> >> > it right upto its mgvw, with all the hills and stop-starts here for
> >> > deer and such, i don't like to take chances with substandard parts,
> >> > like jim does 9after all, he uses cheap pads, and had them burn outt o
> >> > nothing ona short 1 in 7.5 grade, at low speed)
> >> >
> >> > Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> >> > i hope you get my intent.
> >> >
> >> Just for the record, I have an '03 Toyota Corolla that was bothering me
> >for some
> >> time until I finally realised that it downshifts from overdrive when the
> >brakes
> >> are applied (fairly hard) going downhill. I haven't determined
exactly why it
> >> does it (that, the parameters of when it happens), but it definately does
> >> downshift.
> >
> >Hello,
> >I just wanted to let people know that plan to coast their vehicles down
> >hill that it causes more WEAR on the transmissions. It also causes more
> >WEAR on the clutch. In other words, if you two people have the same type
> >of cars, the person that coasts down the hills is more likely to have to
> >have the transmission or clutch repaired or replaced than the other person
> >that did NOT coast down hills.
> >Jason
>
> You said this early as well, and then, as now, you gave nothing to
> back it up.
Murphy's Law and common sense. The more that a transmission or clutch is
used, the more likely it is to develop problems. That's one of reasons
that most people trade in or sell their cars after they are three or four
years old.
They know that those older cars will have more problems than a new cars
will have.
--
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#72
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
"flobert" <nomail@here.NOT> wrote in message
news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> Here i'm not too sure. We agree that about the only use being in gear
> has, is accelerating, or 'driving out' of a situation. Avalanches,
> yes, not situations you'll see on either cost of the US though, where
> we are. If it were really that important to accelerate, I'd be
> changine gears anyway, for a lower one, for better acceleration, if a
> tornado is comming (a more common risk over here at least, 4rth or 3rd
> would be a better gear to aceclerate in, than the 5th gear i'd be in
> for the cruise down the hill.
>
Hmm ... I still think you understate the usefullness of being in gear. A
car looses certain handling characteristics when out of gear too - hard to
explain, but from trying both, it certainly feels less surefooted without
drive.
> i wouldn't say its unpredictable, or 'less concentrating' though. When
> keeping the momentum up, you end up glacing at the speedo, yes, (but
> isn't that the point of all those speed cameras, to make you watch
> your speedo!) but putting it into gear from neutral is no more
> involved than just changing gear, after all, in a manual car, part of
> changing gear is 'coasting'. Eratic speeds don't match either, since i
> will put it into gear to keep my speed to a point i set myself at.
> i'll aim to keep that speed above that minimum regardless. downhill
> you'll be going faster, not slower, so you'll be leaving those brake
> riders, or engine brakers behind. (assuming of course, they don't
> either coast, or accelerate down the hill themselves).
>
When you change gear, you really don't coast - you momentarily interrupt
drive. If you stay out of gear, it takes time to react, grab the ****, get
it in gear (you'll probably miss if you panic) and drive away. Much better
to be in gear in the first place. Sometimes just a small bit of throttle is
needed to minimise risk - not quite the live/die evasive action scenario you
refer to.
> Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> i hope you get my intent.
I get what you're saying, and you're defending against an opinion that goes
too far the other way, but I still don't think you should coast - it's kinda
lazy driving. That in conjunction to the points above to me means you could
be slightly (not a lot, but a little) more likely to suffer misfortune than
if you didn't.
So to sum up, I agree and disagree with you both, on separate points ;p
a
news:nh3tg1d1ls3l0tqo4gh9ig75nkk0isqoho@4ax.com...
> Here i'm not too sure. We agree that about the only use being in gear
> has, is accelerating, or 'driving out' of a situation. Avalanches,
> yes, not situations you'll see on either cost of the US though, where
> we are. If it were really that important to accelerate, I'd be
> changine gears anyway, for a lower one, for better acceleration, if a
> tornado is comming (a more common risk over here at least, 4rth or 3rd
> would be a better gear to aceclerate in, than the 5th gear i'd be in
> for the cruise down the hill.
>
Hmm ... I still think you understate the usefullness of being in gear. A
car looses certain handling characteristics when out of gear too - hard to
explain, but from trying both, it certainly feels less surefooted without
drive.
> i wouldn't say its unpredictable, or 'less concentrating' though. When
> keeping the momentum up, you end up glacing at the speedo, yes, (but
> isn't that the point of all those speed cameras, to make you watch
> your speedo!) but putting it into gear from neutral is no more
> involved than just changing gear, after all, in a manual car, part of
> changing gear is 'coasting'. Eratic speeds don't match either, since i
> will put it into gear to keep my speed to a point i set myself at.
> i'll aim to keep that speed above that minimum regardless. downhill
> you'll be going faster, not slower, so you'll be leaving those brake
> riders, or engine brakers behind. (assuming of course, they don't
> either coast, or accelerate down the hill themselves).
>
When you change gear, you really don't coast - you momentarily interrupt
drive. If you stay out of gear, it takes time to react, grab the ****, get
it in gear (you'll probably miss if you panic) and drive away. Much better
to be in gear in the first place. Sometimes just a small bit of throttle is
needed to minimise risk - not quite the live/die evasive action scenario you
refer to.
> Oh dear, its gotten another long post again (sorry, i'm a windbag) but
> i hope you get my intent.
I get what you're saying, and you're defending against an opinion that goes
too far the other way, but I still don't think you should coast - it's kinda
lazy driving. That in conjunction to the points above to me means you could
be slightly (not a lot, but a little) more likely to suffer misfortune than
if you didn't.
So to sum up, I agree and disagree with you both, on separate points ;p
a
#73
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
"Jason" <jason@nospam.com> wrote in message
news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
> Murphy's Law and common sense. The more that a transmission or clutch is
> used, the more likely it is to develop problems. That's one of reasons
> that most people trade in or sell their cars after they are three or four
> years old.
> They know that those older cars will have more problems than a new cars
> will have.
>
While that is literally true, I'm not so sure it's particularly relevant.
In the scheme of things, clutches take a lot of wear. How many times you
change isn't nearly as important as how often you pull away in 1st/2nd and
how badly you change gear!
Also, new cars have problems because they're new and unproven, which can
often equal the problems of older cars - particularly on reliable models.
a
news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
> Murphy's Law and common sense. The more that a transmission or clutch is
> used, the more likely it is to develop problems. That's one of reasons
> that most people trade in or sell their cars after they are three or four
> years old.
> They know that those older cars will have more problems than a new cars
> will have.
>
While that is literally true, I'm not so sure it's particularly relevant.
In the scheme of things, clutches take a lot of wear. How many times you
change isn't nearly as important as how often you pull away in 1st/2nd and
how badly you change gear!
Also, new cars have problems because they're new and unproven, which can
often equal the problems of older cars - particularly on reliable models.
a
#74
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
In article <qLLPe.33012$jr4.27306@fe3.news.blueyonder.co.uk >, "al"
<[ask_me_first]@blueyonder.co.uk> wrote:
> "Jason" <jason@nospam.com> wrote in message
> news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
> > Murphy's Law and common sense. The more that a transmission or clutch is
> > used, the more likely it is to develop problems. That's one of reasons
> > that most people trade in or sell their cars after they are three or four
> > years old.
> > They know that those older cars will have more problems than a new cars
> > will have.
> >
>
> While that is literally true, I'm not so sure it's particularly relevant.
> In the scheme of things, clutches take a lot of wear. How many times you
> change isn't nearly as important as how often you pull away in 1st/2nd and
> how badly you change gear!
>
> Also, new cars have problems because they're new and unproven, which can
> often equal the problems of older cars - particularly on reliable models.
Hello,
Those cars don't develop problems due to WEAR. They develop problems due
to other problems. New cars are covered by warranties. The issue in this
case is the extra WEAR that is caused by over use of the clutch and
transmissions. If people want to do it--just don't be shocked when you
have to spend several thousand dollars replacing the clutch or
transmission.
Jason
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<[ask_me_first]@blueyonder.co.uk> wrote:
> "Jason" <jason@nospam.com> wrote in message
> news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
> > Murphy's Law and common sense. The more that a transmission or clutch is
> > used, the more likely it is to develop problems. That's one of reasons
> > that most people trade in or sell their cars after they are three or four
> > years old.
> > They know that those older cars will have more problems than a new cars
> > will have.
> >
>
> While that is literally true, I'm not so sure it's particularly relevant.
> In the scheme of things, clutches take a lot of wear. How many times you
> change isn't nearly as important as how often you pull away in 1st/2nd and
> how badly you change gear!
>
> Also, new cars have problems because they're new and unproven, which can
> often equal the problems of older cars - particularly on reliable models.
Hello,
Those cars don't develop problems due to WEAR. They develop problems due
to other problems. New cars are covered by warranties. The issue in this
case is the extra WEAR that is caused by over use of the clutch and
transmissions. If people want to do it--just don't be shocked when you
have to spend several thousand dollars replacing the clutch or
transmission.
Jason
--
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#75
Guest
Posts: n/a
Re: Terrible Fuel-Efficiency - 2003 Accord
On Sat, 27 Aug 2005 09:55:09 -0700, jason@nospam.com (Jason) wrote:
>In article <qLLPe.33012$jr4.27306@fe3.news.blueyonder.co.uk >, "al"
><[ask_me_first]@blueyonder.co.uk> wrote:
>
>> "Jason" <jason@nospam.com> wrote in message
>> news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
>> > Murphy's Law and common sense. The more that a transmission or clutch is
>> > used, the more likely it is to develop problems. That's one of reasons
>> > that most people trade in or sell their cars after they are three or four
>> > years old.
>> > They know that those older cars will have more problems than a new cars
>> > will have.
>> >
>>
>> While that is literally true, I'm not so sure it's particularly relevant.
>> In the scheme of things, clutches take a lot of wear. How many times you
>> change isn't nearly as important as how often you pull away in 1st/2nd and
>> how badly you change gear!
>>
>> Also, new cars have problems because they're new and unproven, which can
>> often equal the problems of older cars - particularly on reliable models.
>
>Hello,
>Those cars don't develop problems due to WEAR. They develop problems due
>to other problems. New cars are covered by warranties. The issue in this
>case is the extra WEAR that is caused by over use of the clutch and
>transmissions. If people want to do it--just don't be shocked when you
>have to spend several thousand dollars replacing the clutch or
>transmission.
Dont it for years, in mainly older cars. Only in one have i had to
replace transmissions/clutches - my 89 mg metro twin turbo, snapped
clutch cable, and once i also overfilled the engine with oil a bit -
those engines are real finicky, as the oil is also shared with the
gearbox. it seeped out and into the clutch itself. took about an hour
or twos work, to clean the oil off the plates, a few hundred miles of
driving,a nd it was good as new.
i think you minsunderstand just whats going on. In coasting, the
cluthc is used to disengage the transmission, as it would be in
changing gear. it is then left out of gear, meaning that the wheel
side is going at the road wheel speed, as is ormal, so no difference
in wear there, and the engine side is going at the engine speed, which
is lower, thus LESS wear there. Struggling to see how this increases
wear myself...
>Jason
>In article <qLLPe.33012$jr4.27306@fe3.news.blueyonder.co.uk >, "al"
><[ask_me_first]@blueyonder.co.uk> wrote:
>
>> "Jason" <jason@nospam.com> wrote in message
>> news:jason-2608051312430001@pm4-broad-41.snlo.dialup.fix.net...
>> > Murphy's Law and common sense. The more that a transmission or clutch is
>> > used, the more likely it is to develop problems. That's one of reasons
>> > that most people trade in or sell their cars after they are three or four
>> > years old.
>> > They know that those older cars will have more problems than a new cars
>> > will have.
>> >
>>
>> While that is literally true, I'm not so sure it's particularly relevant.
>> In the scheme of things, clutches take a lot of wear. How many times you
>> change isn't nearly as important as how often you pull away in 1st/2nd and
>> how badly you change gear!
>>
>> Also, new cars have problems because they're new and unproven, which can
>> often equal the problems of older cars - particularly on reliable models.
>
>Hello,
>Those cars don't develop problems due to WEAR. They develop problems due
>to other problems. New cars are covered by warranties. The issue in this
>case is the extra WEAR that is caused by over use of the clutch and
>transmissions. If people want to do it--just don't be shocked when you
>have to spend several thousand dollars replacing the clutch or
>transmission.
Dont it for years, in mainly older cars. Only in one have i had to
replace transmissions/clutches - my 89 mg metro twin turbo, snapped
clutch cable, and once i also overfilled the engine with oil a bit -
those engines are real finicky, as the oil is also shared with the
gearbox. it seeped out and into the clutch itself. took about an hour
or twos work, to clean the oil off the plates, a few hundred miles of
driving,a nd it was good as new.
i think you minsunderstand just whats going on. In coasting, the
cluthc is used to disengage the transmission, as it would be in
changing gear. it is then left out of gear, meaning that the wheel
side is going at the road wheel speed, as is ormal, so no difference
in wear there, and the engine side is going at the engine speed, which
is lower, thus LESS wear there. Struggling to see how this increases
wear myself...
>Jason