Pertains to 2004 eco cavalier. In open loop or PE modes, does the ECU adjust the fuel for the temperature it sees with the IAT sensor? Or is the fueling in these modes totally static? I ask because I'm thinking if we can tune the low RPM/low TPS fueling with a wideband in open loop, we can improve economy by leaning it out a little If there is no compensation for air temperature (and hence density provided your not changing alittude dramatically), we'd be stuck flashing a new tune for each season, or going rich/lean ans it gets warmer/colder respectively. God i cannot wait to start!
Thanks for reading.
fueling is static in open loop modes, the only thing that is constantly adjusted for temperature and MAP input is the ignition advance/retard
I wouldn't worry about tuning for gas mileage.. closed loop is best at doing that. using open loop to try and control fueling for lean conditions won't end well. Also, you'll be reflashing several times a day. Fuel density changes with temperature change, I'd imagine as little as 5 degrees ambient would be all that is necessary to throw off the accuracy of tables in the ecu.
Quote:
fueling is static in open loop modes, the only thing that is constantly adjusted for temperature and MAP input is the ignition advance/retard
Huh??
This would be a first. Although "constantly adjusted" may be the point of misunderstanding, as long as the ecm is in open loop it will be delivering fuel based on desired afr vs temp, or a desired afr times a temp based multiplier. Imagine how difficult it would be to try and drive a car with a cold engine and IAT's at -30 deg F if the AFR were 14.7:1!
-->Slow
slowolej wrote:Quote:
fueling is static in open loop modes, the only thing that is constantly adjusted for temperature and MAP input is the ignition advance/retard
Huh??
This would be a first. Although "constantly adjusted" may be the point of misunderstanding, as long as the ecm is in open loop it will be delivering fuel based on desired afr vs temp, or a desired afr times a temp based multiplier. Imagine how difficult it would be to try and drive a car with a cold engine and IAT's at -30 deg F if the AFR were 14.7:1!
-->Slow
You are mistaken, the computer only uses IAT and MAP sensors for fuel adjustment in Closed Loop mode. The car will run open loop when it is cold, which is why it will run richer and get worse fuel economy (more common during winter) It also runs in Open Loop during Power Enrich (PE) Mode.
___________________________________________________________________
Mitsu TD06-20g |3" Turbo-back Exhaust | 61mm Bored TB |
HP Tuners | Innovate WB02 | Spec Stage 3 | Team Green LSD | TurboTech Upper | Full Addco Sways | Sportlines & Yellows |
BlackEco wrote:slowolej wrote:Quote:
fueling is static in open loop modes, the only thing that is constantly adjusted for temperature and MAP input is the ignition advance/retard
Huh??
This would be a first. Although "constantly adjusted" may be the point of misunderstanding, as long as the ecm is in open loop it will be delivering fuel based on desired afr vs temp, or a desired afr times a temp based multiplier. Imagine how difficult it would be to try and drive a car with a cold engine and IAT's at -30 deg F if the AFR were 14.7:1!
-->Slow
You are mistaken, the computer only uses IAT and MAP sensors for fuel adjustment in Closed Loop mode. The car will run open loop when it is cold, which is why it will run richer and get worse fuel economy (more common during winter) It also runs in Open Loop during Power Enrich (PE) Mode.
NO you are mistaken.
IAT is calculated in to find the density of the air entering the engine.
Whether its TPS or MAP based fueling, the PCM does not know how much air is entering the engine until it also knows the temperature of the air and the barometric pressure pushing it in. The only way to avoid that is to use a MAF to accurately measure the air entering.
If it didn't factor in temp then it would go really lean in cold air.
And your statement (BlackEco) about richer in open loop in the winter is completely off base here. Open loop does not mean "rich" at all, especially not excessively. As a matter of fact, the car will switch between both at various times while it runs. Engines run richer cold because the fuel does not atomize completely so more fuel is needed to get a complete burn.
Skwirl- Just because you can't see a table for it does not mean it isn't there.
Edited 1 time(s). Last edited Wednesday, December 17, 2008 4:57 PM
sig not found
slowolej wrote:Quote:
fueling is static in open loop modes, the only thing that is constantly adjusted for temperature and MAP input is the ignition advance/retard
Huh??
This would be a first. Although "constantly adjusted" may be the point of misunderstanding, as long as the ecm is in open loop it will be delivering fuel based on desired afr vs temp, or a desired afr times a temp based multiplier. Imagine how difficult it would be to try and drive a car with a cold engine and IAT's at -30 deg F if the AFR were 14.7:1!
-->Slow
I'm sorry but I've never heard of that.
My understanding of the Jbody ecu is that In open loop, the ecu ignores other sensors, and delivers fuel based on the VE maps. It figures out the targeted AFR via the AFR vs ECT map (which is very broad in its definitions, and at op temp wants 13:1 AFR). There is a multiplier based on RPM which is all 1s, rendering it useless. There is also an injector pulsewidth multiplier that is based on MAP, which I'd imagine takes into consideration elevation and air temperature changes.
other than these tables, nothing effects fueling. There is an ECT startup vs closed loop ECT which the ecu looks at the startup ECT, and is then told what ECT it can begin to run for stoich.
Anything in relation to startup is not seen by HPT.
Anything in relation to closed loop fueling is not seen by HPT.
The only maps with IAT as a reference control spark advance.
Does that mean IAT doesn't have a multiplier attached to it that effects pulsewidth? not necessarily, but its null because it cannot be edited in HPT.
we can only really control when and if the ecu goes into closed loop. Everything we can edit (fueling wise) is open loop related.. other than multipliers.
here's the tables from my stock 2004 coupe.
thats all there is in relation to fuel control other than the VE maps under the airflow tab
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:
I'm sorry but I've never heard of that.
My understanding of the Jbody ecu is that In open loop, the ecu ignores other sensors, and delivers fuel based on the VE maps. It figures out the targeted AFR via the AFR vs ECT map (which is very broad in its definitions, and at op temp wants 13:1 AFR). There is a multiplier based on RPM which is all 1s, rendering it useless. There is also an injector pulsewidth multiplier that is based on MAP, which I'd imagine takes into consideration elevation and air temperature changes.
other than these tables, nothing effects fueling. There is an ECT startup vs closed loop ECT which the ecu looks at the startup ECT, and is then told what ECT it can begin to run for stoich.
Anything in relation to startup is not seen by HPT.
Anything in relation to closed loop fueling is not seen by HPT.
The only maps with IAT as a reference control spark advance.
Does that mean IAT doesn't have a multiplier attached to it that effects pulsewidth? not necessarily, but its null because it cannot be edited in HPT.
But if there IS a multiplier for IAT in open loop, than temperature (density) changes will be compensated for, even if running off the VE maps. Or am I misunderstanding?
Maybe it's better to look at it from an experimental point of view. What are peoples experiences? If you have a wideband and you've tuned in one season (say summer), does the readout change siginificantly in the winter?
Quote:
But if there IS a multiplier for IAT in open loop, than temperature (density) changes will be compensated for, even if running off the VE maps. Or am I misunderstanding?
no way to tell. since nobody can see them, its all speculation.
there are only two tables that have IAT in them..
the first table is somewhat confusing, but I'm fairly sure both don't modify fuel tables.
HPT is pretty limited in what we can do, and open loop stuff is about it. Tune for WOT performance under as many RPM cells as you can hit vs TPS input, call it a day, and put the car beck into normal operation mode (ie. not forced open loop).
let fuel trims do the work of running the car in closed loop, that's what they're for.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:
I'm sorry but I've never heard of that.
My understanding of the Jbody ecu is that In open loop, the ecu ignores other sensors, and delivers fuel based on the VE maps.
Actually it only ignores one sensor, the oxygen sensor. It very definitely pays close attention to all the others... exactly the same as it does all the time.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: It figures out the targeted AFR via the AFR vs ECT map (which is very broad in its definitions, and at op temp wants 13:1 AFR).
No, it reads the target AFR from the AFR vs ECT map. It figures out how much fuel to spray to achieve it by calculating the mass of the air injested for that event. It calculates the mass of the air using the VE % it looks up for that operating point and the air temperature to know the density of that air. Cold air is more dense and has a higher mass than hot air.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: There is a multiplier based on RPM which is all 1s, rendering it useless.
It means the table is not used for that application and is "zero'ed out" from a function standpoint so it does not affect that calibration. There are instances when you would want it changed. One such reason would be to not go boost rich with a large turbo that cannot spool down low where there is no reason to run 10.5:1 if no boost is possible. Sometimes engines respond very well to slightly different AFRs at different RPMs.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: There is also an injector pulsewidth multiplier that is based on MAP, which I'd imagine takes into consideration elevation and air temperature changes.
Not at all. 1st issue with that statement is how would it know temperature from a MAP reading?
The IPW function is used on cars with returnless fuel or where the fuel regulator is not referenced to intake manifold pressure.
If fuel pressure is constant, a 3ms spray into a -20inhg manifold pressure (as in idle) will spray much more fuel than the same 3ms into 0inhg (WOT). With a vacuum referenced regulator, the fuel pressure delta is constant (the pressure difference between the rain and the tip). The IPW table is like an electronic version of a vacuum referenced regulator. And for the record, as delivered from GM, ECOs are not manifold vacuum referenced.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: other than these tables, nothing effects fueling. There is an ECT startup vs closed loop ECT which the ecu looks at the startup ECT, and is then told what ECT it can begin to run for stoich.
Anything in relation to startup is not seen by HPT.
Anything in relation to closed loop fueling is not seen by HPT.
The only maps with IAT as a reference control spark advance.
Does that mean IAT doesn't have a multiplier attached to it that effects pulsewidth? not necessarily, but its null because it cannot be edited in HPT.
we can only really control when and if the ecu goes into closed loop. Everything we can edit (fueling wise) is open loop related.. other than multipliers.
Just because you can't edit it does not mean you should simply ignore its influence.
sig not found
Back on to the original question...
oldskool wrote:Pertains to 2004 eco cavalier. In open loop or PE modes, does the ECU adjust the fuel for the temperature it sees with the IAT sensor? Or is the fueling in these modes totally static?
Yes it does. The fueling is not static.
sig not found
protomec wrote:DaFlyinSkwir(LS61) /PJ/ OEM+ wrote:
I'm sorry but I've never heard of that.
My understanding of the Jbody ecu is that In open loop, the ecu ignores other sensors, and delivers fuel based on the VE maps.
Actually it only ignores one sensor, the oxygen sensor. It very definitely pays close attention to all the others... exactly the same as it does all the time.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: It figures out the targeted AFR via the AFR vs ECT map (which is very broad in its definitions, and at op temp wants 13:1 AFR).
No, it reads the target AFR from the AFR vs ECT map. It figures out how much fuel to spray to achieve it by calculating the mass of the air injested for that event. It calculates the mass of the air using the VE % it looks up for that operating point and the air temperature to know the density of that air. Cold air is more dense and has a higher mass than hot air.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: There is a multiplier based on RPM which is all 1s, rendering it useless.
It means the table is not used for that application and is "zero'ed out" from a function standpoint so it does not affect that calibration. There are instances when you would want it changed. One such reason would be to not go boost rich with a large turbo that cannot spool down low where there is no reason to run 10.5:1 if no boost is possible. Sometimes engines respond very well to slightly different AFRs at different RPMs.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: There is also an injector pulsewidth multiplier that is based on MAP, which I'd imagine takes into consideration elevation and air temperature changes.
Not at all. 1st issue with that statement is how would it know temperature from a MAP reading?
The IPW function is used on cars with returnless fuel or where the fuel regulator is not referenced to intake manifold pressure.
If fuel pressure is constant, a 3ms spray into a -20inhg manifold pressure (as in idle) will spray much more fuel than the same 3ms into 0inhg (WOT). With a vacuum referenced regulator, the fuel pressure delta is constant (the pressure difference between the rain and the tip). The IPW table is like an electronic version of a vacuum referenced regulator. And for the record, as delivered from GM, ECOs are not manifold vacuum referenced.
DaFlyinSkwir(LS61) /PJ/ OEM+ wrote: other than these tables, nothing effects fueling. There is an ECT startup vs closed loop ECT which the ecu looks at the startup ECT, and is then told what ECT it can begin to run for stoich.
Anything in relation to startup is not seen by HPT.
Anything in relation to closed loop fueling is not seen by HPT.
The only maps with IAT as a reference control spark advance.
Does that mean IAT doesn't have a multiplier attached to it that effects pulsewidth? not necessarily, but its null because it cannot be edited in HPT.
we can only really control when and if the ecu goes into closed loop. Everything we can edit (fueling wise) is open loop related.. other than multipliers.
Just because you can't edit it does not mean you should simply ignore its influence.
well that makes a lot more sense than how I *thought* things worked. Obviously I had my wires crossed. thanks for clarifying proto.
I think this confirms that there is a lot going on beyond what can be seen in HPT.
Thanks for the bitch slap Promo =) It was sorely needed.
I agree there is a lot going on we can't see with HPT. I know there has to be a hidden table influencing Commanded AFR in addition to the ones we have as with all the constants set it still deviates slightly richer.
___________________________________________________________________
Mitsu TD06-20g |3" Turbo-back Exhaust | 61mm Bored TB |
HP Tuners | Innovate WB02 | Spec Stage 3 | Team Green LSD | TurboTech Upper | Full Addco Sways | Sportlines & Yellows |
I know there are more hidden tables. I finally got Chris @ HPT to admit it. They claim they will "look into it" more but I guess will have to wait and see.... Here is a link to it... Add to it, it may help, more than likely not.
http://www.hptuners.com/forum/showthread.php?t=20255
Also PJ, the PE MULT vs RPM table can be your friend. I personally think most do not understand how it works and just simply leave it alone or lower the numbers to make it rich when they can't figure out the proper way to adjust fueling...
P&P Tuning
420.5whp / 359.8wtq
protomec wrote:Back on to the original question...
oldskool wrote:Pertains to 2004 eco cavalier. In open loop or PE modes, does the ECU adjust the fuel for the temperature it sees with the IAT sensor? Or is the fueling in these modes totally static?
Yes it does. The fueling is not static.
So just to confirm in plain English, if i tune to a certain open loop/PE AFR in the winter, all other things being equal, that AFR will be maintained in the summer?
In the most simplifed terms, Yes.
there are many seemingly unimportant things that can slightly shift things so that it isn't absolutely 100% dead on... things like an injector change.
But it will still do ok at hitting its targets in warm weather,
The way an injector change can affect it is because of injector characterization.
Injector characterization is how an injector responds to pressure, voltage and temperature changes and is different for every different size and design of injector. HP does not give you access to this stuff either, but settings are in there for it either directly or indirectly.
Things like this can make it miss its targets when temperature changes. But these settings are really similar no matter what parts are used, so it won't miss by much and it won't be anough to be dangerous.
sig not found
Well I disagree. I'm by no means a pro at tuning, and most of the ones in this post know more than I do in that field. I have seen a major difference in my AFR's between Winter and Summer.
FU Tuning
John Higgins wrote:Well I disagree. I'm by no means a pro at tuning, and most of the ones in this post know more than I do in that field. I have seen a major difference in my AFR's between Winter and Summer.
That's why I'm asking.
Is your experience on a boosted application, n/a, or both? I mean, under what conditions did you see the difference?
oldskool wrote:John Higgins wrote:Well I disagree. I'm by no means a pro at tuning, and most of the ones in this post know more than I do in that field. I have seen a major difference in my AFR's between Winter and Summer.
That's why I'm asking. Is your experience on a boosted application, n/a, or both? I mean, under what conditions did you see the difference?
Actually both. My personal 01 Z24 n/a, and a 99 z24 with GM charger. The 99 I expected it because it is a Alpa N program running boost. as the weather changes so does the boost, which then requires a new tune.
My 01 has seen the same, but not as drastic, more than liveable as well. Most would probably never know it. I'm still ok with it because I have the program and wideband to change it, and really I'm always tweaking it anyways.
FU Tuning
John Higgins wrote:oldskool wrote:John Higgins wrote:Well I disagree. I'm by no means a pro at tuning, and most of the ones in this post know more than I do in that field. I have seen a major difference in my AFR's between Winter and Summer.
That's why I'm asking. Is your experience on a boosted application, n/a, or both? I mean, under what conditions did you see the difference?
Actually both. My personal 01 Z24 n/a, and a 99 z24 with GM charger. The 99 I expected it because it is a Alpa N program running boost. as the weather changes so does the boost, which then requires a new tune.
My 01 has seen the same, but not as drastic, more than liveable as well. Most would probably never know it. I'm still ok with it because I have the program and wideband to change it, and really I'm always tweaking it anyways.
Yea, i figured it would probably be worse with boosted apps and alpha-n. So when you say "most would probably never know it" what does that mean? What differences in AFR did you notice from season to season. As long as it can maintain +/- 0.2 AFR between seasons, I'm quite happy with that.
oldskool wrote:John Higgins wrote:oldskool wrote:John Higgins wrote:Well I disagree. I'm by no means a pro at tuning, and most of the ones in this post know more than I do in that field. I have seen a major difference in my AFR's between Winter and Summer.
That's why I'm asking. Is your experience on a boosted application, n/a, or both? I mean, under what conditions did you see the difference?
Actually both. My personal 01 Z24 n/a, and a 99 z24 with GM charger. The 99 I expected it because it is a Alpa N program running boost. as the weather changes so does the boost, which then requires a new tune.
My 01 has seen the same, but not as drastic, more than liveable as well. Most would probably never know it. I'm still ok with it because I have the program and wideband to change it, and really I'm always tweaking it anyways.
Yea, i figured it would probably be worse with boosted apps and alpha-n. So when you say "most would probably never know it" what does that mean? What differences in AFR did you notice from season to season. As long as it can maintain +/- 0.2 AFR between seasons, I'm quite happy with that.
What I have seen is like a .3 difference.
FU Tuning
