Re: Adding an O2 sensor?
 

"sharx333" <emil.santos@gmail.com> wrote in
news:1158179035.612237.136510@i42g2000cwa.googlegr oups.com:

>
> Jim Yanik wrote:
>>
>> "closed loop" is just using feedback from the O2 sensor to
>> continually adjust input fuel/air mix to optimum. Fine tuning on the
>> run.
>>
>> "open loop" is just "dump enough gas in to make it run" for a wide
>> range of conditions. There's no correctional feedback.
>>
>> Without the sensor measuring at the END of the combustion
>> process,it's not "closed loop".
>
>
> Thanks. I think I see now. That since the main output of the ECU is
> the injector duration, then the main input (to have a true feedback
> "closed" loop) is a sensor that measures the effects of combustion (O2
> sensor).
>
> So I take it you mean that based on the other sensors (MAP, TA, TPS,
> PA), the ECU does no fine tuning based on real-time combustion result,
> but rather only bases the injector duration on predefined "maps" in
> its ROM. So, the ECU does vary the injector duration and spark timing,
> but only based on what it "thinks" is best for a given situation, but
> would still not be "closed loop". You really need to somehow measure
> the exhaust. Is my understanding correct?

Excellent!
>
> This makes sense, but isn't the O2 sensor just another input for the
> ECU? Is it any different from the other sensors, that the ECU uses to
> vary timing and injection? What makes O2 so special, if the responses
> to it are also based on a ROM "map"?

Well,the desired end result is complete combustion(a clean exhaust),and
exhaust O2 content is an indication of how well that's happening.
They are real-time corrections,and measure ACTUAL exhaust output.
(if a plug misfires,or a input-condition sensor is inaccurate,this feedback
corrects for it.it also allows for individual cylinders' injectors to be
corrected,compensating for differing air flow thru the cylinders.They are
not necessarily all equal!)


I believe there may be two 'maps".
One for open-loop,and one for when everything warms to operating temp.
The 2nd map would be much simpler,and smaller in data size,or just a
refinement on (or corrections for) the primary map.
It's like the ECU first sets injector duration for the TPS,IAT,MAP and RPM
via the map,and -then- looks at O2S data and fine-tunes if needed (at op
temp) for optimal exhaust O2 content. It also minimizes the work the
catalytic has to do,-and makes it last longer.

It does take some amount of time to balance the loop once a variable is
changed.(like throttle position or intake air temp)
Loop response cannot be instant,there's always some hysteresis,but it's
inconsequential,until the O2 sensor gets "slow" in it's response(degrades).

OBD-II systems supposedly measure this O2S response time and set a trouble
code (and CEL)if it gets too long(or fails),and also uses a 2nd O2 sensor
to back up the first sensor and monitor the catalytic converter's
performance to ensure low emissions.


--
Jim Yanik
jyanik
at
kua.net

Re: Adding an O2 sensor?
 

"sharx333" <emil.santos@gmail.com> wrote in
news:1158179035.612237.136510@i42g2000cwa.googlegr oups.com:


To add more;

>
> So I take it you mean that based on the other sensors (MAP, TA, TPS,
> PA), the ECU does no fine tuning based on real-time combustion result,
> but rather only bases the injector duration on predefined "maps" in
> its ROM.

Yes.
The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
ONLY output measurement.

If I said this in the first post,apologies.
(it's then just a "senior moment"!) 8-)

--
Jim Yanik
jyanik
at
kua.net

Re: Adding an O2 sensor?
 

"sharx333" <emil.santos@gmail.com> wrote in
news:1158179035.612237.136510@i42g2000cwa.googlegr oups.com:


To add more;

>
> So I take it you mean that based on the other sensors (MAP, TA, TPS,
> PA), the ECU does no fine tuning based on real-time combustion result,
> but rather only bases the injector duration on predefined "maps" in
> its ROM.

Yes.
The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
ONLY output measurement.

If I said this in the first post,apologies.
(it's then just a "senior moment"!) 8-)

--
Jim Yanik
jyanik
at
kua.net

Re: Adding an O2 sensor?
 

"sharx333" <emil.santos@gmail.com> wrote in
news:1158179035.612237.136510@i42g2000cwa.googlegr oups.com:


To add more;

>
> So I take it you mean that based on the other sensors (MAP, TA, TPS,
> PA), the ECU does no fine tuning based on real-time combustion result,
> but rather only bases the injector duration on predefined "maps" in
> its ROM.

Yes.
The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
ONLY output measurement.

If I said this in the first post,apologies.
(it's then just a "senior moment"!) 8-)

--
Jim Yanik
jyanik
at
kua.net

Re: Adding an O2 sensor?
 

Jim Yanik wrote:
>
> To add more;
>
> The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
> ONLY output measurement.
>
> If I said this in the first post,apologies.
> (it's then just a "senior moment"!) 8-) ...


Wow, Jim, kudos on all the info, you really hit the spot. Thanks!

I'll take a look at "megasquirt", it sounds really interesting!

Re: Adding an O2 sensor?
 

Jim Yanik wrote:
>
> To add more;
>
> The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
> ONLY output measurement.
>
> If I said this in the first post,apologies.
> (it's then just a "senior moment"!) 8-) ...


Wow, Jim, kudos on all the info, you really hit the spot. Thanks!

I'll take a look at "megasquirt", it sounds really interesting!

Re: Adding an O2 sensor?
 

Jim Yanik wrote:
>
> To add more;
>
> The TPS,MAP,IAT,and RPM sensors are all input-side variables,the O2S is the
> ONLY output measurement.
>
> If I said this in the first post,apologies.
> (it's then just a "senior moment"!) 8-) ...


Wow, Jim, kudos on all the info, you really hit the spot. Thanks!

I'll take a look at "megasquirt", it sounds really interesting!

Re: Adding an O2 sensor?
 

Jim Yanik wrote:

>
> Well,the desired end result is complete combustion(a clean exhaust),and
> exhaust O2 content is an indication of how well that's happening.
> They are real-time corrections,and measure ACTUAL exhaust output.
> (if a plug misfires,or a input-condition sensor is inaccurate,this feedback
> corrects for it.it also allows for individual cylinders' injectors to be
> corrected,compensating for differing air flow thru the cylinders.They are
> not necessarily all equal!)
>

Uh, hold on there. Few if any modern fuel injection systems monitor
each cylinder and adjust them independently. At best you have one O2
sensor per bank on a multi-head engine. The ECU has no information
about individual cylinders.

I know that some years ago Saab was working on a system which used an
ionization current passed through the spark plug during the exhaust
cycle to try and do the individual cylinder optimization you talk about,
but I don't know if such a thing ever got into production. Certainly
that is not the scheme in use on the majority of vehicles today.

Closed loop fuel injection also does not correct for ignition problems
like a misfiring spark plug.

John

Re: Adding an O2 sensor?
 

Jim Yanik wrote:

>
> Well,the desired end result is complete combustion(a clean exhaust),and
> exhaust O2 content is an indication of how well that's happening.
> They are real-time corrections,and measure ACTUAL exhaust output.
> (if a plug misfires,or a input-condition sensor is inaccurate,this feedback
> corrects for it.it also allows for individual cylinders' injectors to be
> corrected,compensating for differing air flow thru the cylinders.They are
> not necessarily all equal!)
>

Uh, hold on there. Few if any modern fuel injection systems monitor
each cylinder and adjust them independently. At best you have one O2
sensor per bank on a multi-head engine. The ECU has no information
about individual cylinders.

I know that some years ago Saab was working on a system which used an
ionization current passed through the spark plug during the exhaust
cycle to try and do the individual cylinder optimization you talk about,
but I don't know if such a thing ever got into production. Certainly
that is not the scheme in use on the majority of vehicles today.

Closed loop fuel injection also does not correct for ignition problems
like a misfiring spark plug.

John

Re: Adding an O2 sensor?
 

Jim Yanik wrote:

>
> Well,the desired end result is complete combustion(a clean exhaust),and
> exhaust O2 content is an indication of how well that's happening.
> They are real-time corrections,and measure ACTUAL exhaust output.
> (if a plug misfires,or a input-condition sensor is inaccurate,this feedback
> corrects for it.it also allows for individual cylinders' injectors to be
> corrected,compensating for differing air flow thru the cylinders.They are
> not necessarily all equal!)
>

Uh, hold on there. Few if any modern fuel injection systems monitor
each cylinder and adjust them independently. At best you have one O2
sensor per bank on a multi-head engine. The ECU has no information
about individual cylinders.

I know that some years ago Saab was working on a system which used an
ionization current passed through the spark plug during the exhaust
cycle to try and do the individual cylinder optimization you talk about,
but I don't know if such a thing ever got into production. Certainly
that is not the scheme in use on the majority of vehicles today.

Closed loop fuel injection also does not correct for ignition problems
like a misfiring spark plug.

John

Re: Adding an O2 sensor?
 

John Horner wrote:
> Jim Yanik wrote:
>
>>
>> Well,the desired end result is complete combustion(a clean
>> exhaust),and exhaust O2 content is an indication of how well that's
>> happening.
>> They are real-time corrections,and measure ACTUAL exhaust output.
>> (if a plug misfires,or a input-condition sensor is inaccurate,this
>> feedback corrects for it.it also allows for individual cylinders'
>> injectors to be corrected,compensating for differing air flow thru the
>> cylinders.They are not necessarily all equal!)
>>
>
> Uh, hold on there. Few if any modern fuel injection systems monitor
> each cylinder and adjust them independently. At best you have one O2
> sensor per bank on a multi-head engine. The ECU has no information
> about individual cylinders.

Well, I can't claim to know exactly how these systems DO work, but I can
hypothesize that it wouldn't be all that difficult for the ECU to get an idea
what's going on with each cylinder individually. Given timing input, it will
know which cylinder is firing when, and a subsequent change in the O2 sensor
reading is pretty easy to correlate to that cylinder.

As O2 sensor input is split up to separate groups of cylinders, as has already
been discussed here, such calculations become even easier...

Re: Adding an O2 sensor?
 

John Horner wrote:
> Jim Yanik wrote:
>
>>
>> Well,the desired end result is complete combustion(a clean
>> exhaust),and exhaust O2 content is an indication of how well that's
>> happening.
>> They are real-time corrections,and measure ACTUAL exhaust output.
>> (if a plug misfires,or a input-condition sensor is inaccurate,this
>> feedback corrects for it.it also allows for individual cylinders'
>> injectors to be corrected,compensating for differing air flow thru the
>> cylinders.They are not necessarily all equal!)
>>
>
> Uh, hold on there. Few if any modern fuel injection systems monitor
> each cylinder and adjust them independently. At best you have one O2
> sensor per bank on a multi-head engine. The ECU has no information
> about individual cylinders.

Well, I can't claim to know exactly how these systems DO work, but I can
hypothesize that it wouldn't be all that difficult for the ECU to get an idea
what's going on with each cylinder individually. Given timing input, it will
know which cylinder is firing when, and a subsequent change in the O2 sensor
reading is pretty easy to correlate to that cylinder.

As O2 sensor input is split up to separate groups of cylinders, as has already
been discussed here, such calculations become even easier...

Re: Adding an O2 sensor?
 

John Horner wrote:
> Jim Yanik wrote:
>
>>
>> Well,the desired end result is complete combustion(a clean
>> exhaust),and exhaust O2 content is an indication of how well that's
>> happening.
>> They are real-time corrections,and measure ACTUAL exhaust output.
>> (if a plug misfires,or a input-condition sensor is inaccurate,this
>> feedback corrects for it.it also allows for individual cylinders'
>> injectors to be corrected,compensating for differing air flow thru the
>> cylinders.They are not necessarily all equal!)
>>
>
> Uh, hold on there. Few if any modern fuel injection systems monitor
> each cylinder and adjust them independently. At best you have one O2
> sensor per bank on a multi-head engine. The ECU has no information
> about individual cylinders.

Well, I can't claim to know exactly how these systems DO work, but I can
hypothesize that it wouldn't be all that difficult for the ECU to get an idea
what's going on with each cylinder individually. Given timing input, it will
know which cylinder is firing when, and a subsequent change in the O2 sensor
reading is pretty easy to correlate to that cylinder.

As O2 sensor input is split up to separate groups of cylinders, as has already
been discussed here, such calculations become even easier...

Re: Adding an O2 sensor?
 

Matt Ion wrote:
> John Horner wrote:
>> Jim Yanik wrote:
>>
>>>
>>> Well,the desired end result is complete combustion(a clean
>>> exhaust),and exhaust O2 content is an indication of how well that's
>>> happening.
>>> They are real-time corrections,and measure ACTUAL exhaust output.
>>> (if a plug misfires,or a input-condition sensor is inaccurate,this
>>> feedback corrects for it.it also allows for individual cylinders'
>>> injectors to be corrected,compensating for differing air flow thru
>>> the cylinders.They are not necessarily all equal!)
>>>
>>
>> Uh, hold on there. Few if any modern fuel injection systems monitor
>> each cylinder and adjust them independently. At best you have one
>> O2 sensor per bank on a multi-head engine. The ECU has no
>> information about individual cylinders.
>
> Well, I can't claim to know exactly how these systems DO work, but I can
> hypothesize that it wouldn't be all that difficult for the ECU to get an
> idea what's going on with each cylinder individually.

it's already done to some extent - angular velocity for each power
stroke is measured, so any cylinder not producing the same "oomph" as
the others gets individually tuned.

> Given timing
> input, it will know which cylinder is firing when, and a subsequent
> change in the O2 sensor reading is pretty easy to correlate to that
> cylinder.
>
> As O2 sensor input is split up to separate groups of cylinders, as has
> already been discussed here, such calculations become even easier...
>

Re: Adding an O2 sensor?
 

Matt Ion wrote:
> John Horner wrote:
>> Jim Yanik wrote:
>>
>>>
>>> Well,the desired end result is complete combustion(a clean
>>> exhaust),and exhaust O2 content is an indication of how well that's
>>> happening.
>>> They are real-time corrections,and measure ACTUAL exhaust output.
>>> (if a plug misfires,or a input-condition sensor is inaccurate,this
>>> feedback corrects for it.it also allows for individual cylinders'
>>> injectors to be corrected,compensating for differing air flow thru
>>> the cylinders.They are not necessarily all equal!)
>>>
>>
>> Uh, hold on there. Few if any modern fuel injection systems monitor
>> each cylinder and adjust them independently. At best you have one
>> O2 sensor per bank on a multi-head engine. The ECU has no
>> information about individual cylinders.
>
> Well, I can't claim to know exactly how these systems DO work, but I can
> hypothesize that it wouldn't be all that difficult for the ECU to get an
> idea what's going on with each cylinder individually.

it's already done to some extent - angular velocity for each power
stroke is measured, so any cylinder not producing the same "oomph" as
the others gets individually tuned.

> Given timing
> input, it will know which cylinder is firing when, and a subsequent
> change in the O2 sensor reading is pretty easy to correlate to that
> cylinder.
>
> As O2 sensor input is split up to separate groups of cylinders, as has
> already been discussed here, such calculations become even easier...
>