Running Partial Mix of E85 in LT1

cmitchell17 · 02-13-2017, 12:47 PM

If I understand the way fueling is setup then it seems like it would be possible to run a partial mix of E85 in a ratio being limited to the fuel trims max rich adjustment. It seems like if you start with a small mix of E85 you should see the fuel trim percentage start to increase.

As long as you stay out of the throttle and not go into PE mode, it seems like it would be fine. Then once you see the fuel trims hit their limit (I don't know what that is) while increasing E85 percentage, you stop.

If I remember how the fueling commands work, I believe there is a PE mode AFR adjustment that will only add fuel in PE mode if fuel trims are rich? So in PE mode you would be limited to an E85 mix corresponding to the maximum rich adjustment in PE mode?

I want to eventually get the kit to convert to E85 but I only have 3000mi on my car and I'm scared to tune because of voiding the warranty.

EFI Tuning · 02-13-2017, 02:24 PM

Do not do this! Yes the LTrims will increase in a positive direction but you can't guarantee what your end AFR will be at WOT. You won't be able to add enough ethanol within the limits of the fuel trims to get the benefits of ethanol anyways. Your risk of problems is greater doing this than installing the kit and having it tuned correctly.

Tim

cmitchell17 · 02-14-2017, 07:38 AM

Yeah I didn't think PE mode would be able to be as accurate as needed without the system knowing true stoich.

I haven't really looked into the tune files for a E92 LT1 yet, but I remember on the GEN IIIs basically stock the ECM never really enabled PE mode. I could not really figure out the point though. I realize emissions may be a part of that, but without PE mode wouldn't it be running the mixture at stoich? Isnt this a potential bad thing for the components? Or is the point of PE mode entirely for more power.

It seems like if it did add that much more power with a rich mixture and a timing multiplier, wouldn't the driver notice it when enabled?

02-13-2017, 12:47 PM	#1
cmitchell17 Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016 Location: US Posts: 1,200	Running Partial Mix of E85 in LT1 If I understand the way fueling is setup then it seems like it would be possible to run a partial mix of E85 in a ratio being limited to the fuel trims max rich adjustment. It seems like if you start with a small mix of E85 you should see the fuel trim percentage start to increase. As long as you stay out of the throttle and not go into PE mode, it seems like it would be fine. Then once you see the fuel trims hit their limit (I don't know what that is) while increasing E85 percentage, you stop. If I remember how the fueling commands work, I believe there is a PE mode AFR adjustment that will only add fuel in PE mode if fuel trims are rich? So in PE mode you would be limited to an E85 mix corresponding to the maximum rich adjustment in PE mode? I want to eventually get the kit to convert to E85 but I only have 3000mi on my car and I'm scared to tune because of voiding the warranty.

02-13-2017, 02:24 PM	#2
EFI Tuning Drives: 2016 Camaro SS Join Date: Oct 2016 Location: Mount Dora, FL Posts: 792	Do not do this! Yes the LTrims will increase in a positive direction but you can't guarantee what your end AFR will be at WOT. You won't be able to add enough ethanol within the limits of the fuel trims to get the benefits of ethanol anyways. Your risk of problems is greater doing this than installing the kit and having it tuned correctly. Tim

02-14-2017, 07:38 AM	#3
cmitchell17 Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016 Location: US Posts: 1,200	Yeah I didn't think PE mode would be able to be as accurate as needed without the system knowing true stoich. I haven't really looked into the tune files for a E92 LT1 yet, but I remember on the GEN IIIs basically stock the ECM never really enabled PE mode. I could not really figure out the point though. I realize emissions may be a part of that, but without PE mode wouldn't it be running the mixture at stoich? Isnt this a potential bad thing for the components? Or is the point of PE mode entirely for more power. It seems like if it did add that much more power with a rich mixture and a timing multiplier, wouldn't the driver notice it when enabled?

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