Todd H. wrote:
> I mean could they make the decision any more freakin difficult...

Toyota Sienna LE 7 passenger
What did it for me was AWD, 266 HP and 245 lb.ft. of torque @ 21/30 MPG...

a

 

Edward W. Thompson wrote:
> On Wed, 23 Jul 2008 06:00:57 -0700, jim beam
> <spamvortex@bad.example.net> wrote:
>
> snip
>>
>>> Incidentally rpm and throttle position does not indicate torque
>>> reversal (coasting) as you have implied.
>> then you need to think this situation through one more time - there's no
>> situation under which you can have high rpm's and a closed throttle
>> unless you're coasting.
>
>
> I agree I am nit picking now but a closed throttle and high rpm (plus
> 750-1500 rpm I think you said) is not quite the same as torque
> reversal although it is certainly indicative.
>
> This, for me, has been a very intertesting exchange and I thank you
> for you explanations and patience.

The point is that the ecu doesn't *need* to detect "torque reversal" to
know when to shut off fuel. All it needs is RPM and throttle position.

a

 

Dan C wrote:
> On Wed, 23 Jul 2008 06:00:57 -0700, jim beam wrote:
>
>>> As I understand it you are saying that during the period when
>>> 'coasting' to stop no fuel is being admitted to the engine. If this
>>> correct at some point fuel must be readmitted to allow the engine to
>>> idle when the vehicle is at stop. The question is how does the
>>> 'system' determine when fuel is to be readmitted during the coasting
>>> event to prevent the engine from 'stopping' when at rest?
>
>> the computer monitors rpm's and starts re-injecting below a base
>> threshold. older systems, that's about 1500rpm. according to tegger,
>> more modern systems cut it to as low as 750rpm.
>
> Let me get this straight. I think you are claiming that the engine uses
> *NO FUEL* during coasting...., right? So, let's think of an example....
> If I was coming down a large mountain, on the Interstate, at 65mph, and
> was to *COAST* for 20 miles (entirely realistic in some places), you are
> saying that I would not use ANY FUEL? Right?
>
> My take on that is that it's absolutely wrong. The engine is still
> running, even if it's not doing any real "work". It is using fuel.
>
>


Not at all. think about it - take the engine out of the car and put a
handle on the crank - you can turn it with your own hand! Why is it hard
to believe that thousands of lbs. of moving car can't do that? The
friction of moving turning the engine without fuel is what slows you down
when gearing down. It's often good practise to be in a lower gear and off
the throttle when descending a steep hill - the engine resistance will slow
you or keep you at a constant speed. If there were fuel being fed to the
engine to "keep it running" then there would be no braking effect.

NB: I know this is the case with a manual transmission, but IIRC, there are
instances where an automatic still feeds a tiny amount of fuel during
"rundown".

a