Exhaust Experiments & Air Fuel Ratio

[ProtonXX]

Hmm Good idea.I got a spare EFIE to put on the Cat Sensor. I will boost it to make it look extra rich. However It may not solve the problem with the front and cat O2 Sensor mirroring each other causing a Cat Converter Efficiency Check Engine Code.

I went ahead and bought a Cat O2 Simulator, if it don't work Ill sell it to my friend who runs no cats at all.

Efie is made to go on the front O2 Sensor, since thats the sensor that directly detects the A/F Ratio. The Cat sensor is supposed to have slower fluctuation & read slightly leaner detecting Catalysm efficiency. Since the converter is burning more oxygen/fuel giving a more richer reading.

Im running this test on a 03 Pontiac Vibe that hate all mileage mods.

[XFi]

Originally Posted by cfg83

ZugyNA -



I think that having an EFIE on both 02 sensors would be best. In terms of dominance, everything I have read about "closed loop" operation implies (to me) that the 02 sensor in the exhaust manifold is the one that is primarily used by the ECU/PCM. The second 02 sensor (again, from what I have read), is helping to maintain the health and efficiency of the catalytic converter.

Hrmmmmmmmm ...

Hypothesis : At least one 02 sensor is needed for closed loop operation.
Test #1 : Disconnect first 02 sensor and see if car is able to go into closed loop operation. Note OBDII error codes. Reconnect sensor. Clear error codes.
Test #2 : Disconnect second 02 sensor and see if car is able to go into closed loop operation. Note OBDII error codes. Reconnect sensor. Clear error codes.

For each test, a failure to enter closed loop implies that the ECU/PCM depends on that sensor for closed-loop operation. If both tests fail to enter closed loop, then both sensors are absolutely necessary for closed loop operation.

Here is another thread by XFi on the same subject :

Just ordered an EFIE - BrightGreen FeverBuster
http://www.gassavers.org/showthread.php?t=4894

I think that someone around here (XFi?!??!) was going to install an EFIE on both 02 sensors, but I can't remember who.

CarloSW2

Originally Posted by ZugyNA

Well....if the second O2 has the final say...it's possible that using the EFIE on it would work? Using it there would tell the ECU that the mix was too rich and over ride the first O2?

I have gotten little to no results utilizing my EFIE. I believe, as you do, that the second sensor is compensating/overriding the first. I also think that results do vary from vehicle to vehicle. I have not tried a second EFIE yet and would be interested to hear the results of someone who has. If nothing else, I will remove it and try it on one of my other vehicles. (maybe the UnNamed Wagon).

[bones33]

I use an EFIE on my Mazda (Ford) pickup on the first O2 sensor in conjunction with an A/F ratio gauge and SG1. It works. The A/F gauge hovers around 1-2 bars when at light to moderate load. Only goes to rich at about LOD=85 on the SG. This engine has dual spark plugs so it has a pretty good lean limit.

I honestly see only about 5% improvement. Don't expect alot of MPG improvement from lean mixtures. I think someone said that the non lean burn California Civic VX was only a few MPG worse than the 49 state lean burn VX's.

According to eagle research, the EFIE benefit is realized when used in conjunction with other 'enhancements' like warm air intake, hydrogen, heated fuel, etc. Even in the EFIE literature it says that used alone it won't make much difference, I agree with that.

[Programmer]

Here's some food for thought. Everyone is talking about 'fooling' the sensors, etc...when I still don't believe air fuel ratio 'management' is directly going to solve things.

We've experimented a lot on our chassis dyno, the majority of our clients are HP hungry, so we're always looking for the best modifications to make power--but we get the occasional fleet looking for mileage.

I'll use a 2007 GMC 6.0 3500HD as an example as it's probably one of the worst mileage offenders out there.

Monitoring the air fuel ratio always revealed that at whatever speed -- (we tested this one at 62 MPH or 100kms/hr), the air fuel ratio was ALWAYS 14.7lbs of air to one lb of fuel at the tailpipe regardless of engine load--even wide open throttle in this model.
This is a 'closed loop' closely managed system with 2 precat and 2 post cat O2 sensors, of course.
So we're looking at the numbers here...we've actually got to reduce air entering the engine, while maintaining the same 58HP at the wheels it's requiring to maintain speed in our highway simulation...this is going to be the only way to gain mileage ? Are you still with me ?

So--we looked at air flow through the MAF sensor--average was 62-65 grams of air per second. This was easier than connecting our flow meter to the engine inlet--the MAF sensor is very accurate.

We went directly to the ----- ----- values in the ECU and modified them to gain the proper cylinder pressure required, maintaining HP, lowering throttle angle -- and reducing air entering the engine. We got as low as 47 grams per second on this specific truck !! Same 14.7 air fuel ratio at the tailpipe, remember ? This is going to be the only way to save fuel, guys--it's never by making the engine more 'air flow' efficient--its by making the engine 'cylinder pressure' efficient...by getting cylinder pressure where it needs to be. I'd think by now, most of you know what values need to be changed.

We did no physical modifications to the truck, no whizzy add-on H generators (that don't do anything), we didn't drip water into the engine, didn't do anything other than correctly set up the OEM ECU, -- didn't hack into the O2 sensor harness, either.
Besides--don't you think the GM, Ford, Dodge engineers know that you guys will try this ??

Any questions--email us directly at ecmprogrammer@canopycanada.net--I'll try posting here when time permits.

[kamesama980]

the manufacturers qualify warranties because they know people will do stuff and they design engines for paper numbers not real world performance.

Are you not posting the values you changed to not lose business? I understand but not everyone can get up to your shop... use more gas doing so than you'd save in the life of hte car thereafter. PM me more info if you don't mind, I'm interested because I'm going to be doing a full standalone ECU on my next engine.

[GasSavers_Rotareneg]

Originally Posted by kamesama980

the manufacturers qualify warranties because they know people will do stuff and they design engines for paper numbers not real world performance.

Are you not posting the values you changed to not lose business? I understand but not everyone can get up to your shop... use more gas doing so than you'd save in the life of hte car thereafter. PM me more info if you don't mind, I'm interested because I'm going to be doing a full standalone ECU on my next engine.

He's tweaking the VVT and maybe ignition timing.

[kamesama980]

Originally Posted by Rotareneg

He's tweaking the VVT and maybe ignition timing.

I didn't think the GM truck engines have VVT but that would make sense. We can play guessing games all day or wait till he responds.

[GasSavers_Rotareneg]

Originally Posted by kamesama980

I didn't think the GM truck engines have VVT but that would make sense. We can play guessing games all day or wait till he responds.

The '07 GMC Sierra 3500HD comes with a Vortec 6.0L V-8 (LY6) which has VVT. The only way to change the amount of air going into the cylinders at a fixed RPM is by changing valve timing/lift and/or the throttle position.

[ZugyNA]

Originally Posted by XFi

I have gotten little to no results utilizing my EFIE. I believe, as you do, that the second sensor is compensating/overriding the first. I also think that results do vary from vehicle to vehicle. I have not tried a second EFIE yet and would be interested to hear the results of someone who has. If nothing else, I will remove it and try it on one of my other vehicles. (maybe the UnNamed Wagon).

I've always heard that using the EFIE on the second O2 was the best bet. Try this?

[ZugyNA]

Originally Posted by Programmer

Monitoring the air fuel ratio always revealed that at whatever speed -- (we tested this one at 62 MPH or 100kms/hr), the air fuel ratio was ALWAYS 14.7lbs of air to one lb of fuel at the tailpipe regardless of engine load--even wide open throttle in this model.

This is a 'closed loop' closely managed system with 2 precat and 2 post cat O2 sensors, of course.

So we're looking at the numbers here...we've actually got to reduce air entering the engine, while maintaining the same 58HP at the wheels it's requiring to maintain speed in our highway simulation...this is going to be the only way to gain mileage ? Are you still with me ?

So--we looked at air flow through the MAF sensor--average was 62-65 grams of air per second. This was easier than connecting our flow meter to the engine inlet--the MAF sensor is very accurate.

We went directly to the ----- ----- values in the ECU and modified them to gain the proper cylinder pressure required, maintaining HP, lowering throttle angle -- and reducing air entering the engine. We got as low as 47 grams per second on this specific truck !! Same 14.7 air fuel ratio at the tailpipe, remember ?

So you are claiming a possible 25% gain in mpg from this change?