E85 PE question

[wtf777]

Hi guys I just installed a flex fuel sensor on my 2016 stingray C7 (M7). i have done all the steps to turn on the sensor and it's reading the ethanol content like it should. My car is fbo and has a 93 tune that ran great. my question is on PE (power enrich) do i leave the EQ Ratio (alcohol) tables the same as the gas eq ratio?

[5FDP]

No, I don't. I run leaner with E85.

This is my truck but I run in AFR terms 12.3-12.5 on gas and around 12.9-13.0 on E85.

[wtf777]

ok good i was thinking that. so as an example if let's say my gas PE EQ is 1.16 would i be going down under 1.00 or just go down inclemently by .05 of so? thanks for response by the way, i know this might be a simple question its been over 12 years since i tuned and i used to tune with microtech so quite a difference.

[5FDP]

I would go to like 1.135 or 1.130 on the EQ ratio. That is a little leaner.

That's basically like what I was doing. Going from in your case 12.6 to 12.9-13.0 AFR.

Obviously a dyno would be best but not everyone has that. If your fueling is on point with your wideband and there is no knock, you should be able to run around that higher 12's to right around 13.

[wtf777]

i plugged in those numbers and nothing else. i went for a drive and did a pull in 3rd gear at about 3.5k and it started breaking up so i immediately let off unfortunately i didn't have my laptop so no log. after getting home i checked the tune on vcm editor. i noticed under spark>advance>Flex fuel the table was completely empty is it suppose to populate it self after turning on flex fuel? here is the tune file. i changed only wat we discussed. from my 93 tune it had. thanks again for the help.

[ns158sl]

Ive yet to understand DI. Everyone runs them on the lean side because of the cooling affect which does make sense. Banish released an article I think on a 6 cylinder, and he was running that to almost 10:1? I think on pump gas and it kept making power.

[5FDP]

You'd have to make your own spark tables for flex fuel, they don't populate themselves.

I did notice that your stoich table is wrong, not a huge deal but it's still wrong. 0% alcohol isn't 14.1, it would be 14.68. Find a stock stoich table from a factory flex fuel vehicle and past that in there, it will fix all the rest of it so your fueling is correct for all percentages of alcohol content.

[wtf777]

wow thanks for that catch. ill plug it in tomorrow dont want to harass the neighbors

[GHuggins]

I find it varies depending on the cam or build. Most of the time the NA ones actually like richer on ethanol whereas boosted likes about .5 leaner. I think that just has to do with how the ethanol ignites between the two. I test them both ways with the customers using some sort of drag race app just to see which way their build likes it, but almost always it's richer with NA and leaner with FI.

[wtf777]

I find it varies depending on the cam or build. Most of the time the NA ones actually like richer on ethanol whereas boosted likes about .5 leaner. I think that just has to do with how the ethanol ignites between the two. I test them both ways with the customers using some sort of drag race app just to see which way their build likes it, but almost always it's richer with NA and leaner with FI.

hmmm intresting..yes mine is NA. here is a list of mods and tune. what do you think leaner or richer?
2016 c7 LT1 7speed manual
afe intake momentum pro 5r
full exhuast headers no cats. dbbl helix x pipe straight pipe.
ngk LTrIX spark plugs
taylor wire set
ATI super damper

on the 93 tune it made 459hp/473tq

[wtf777]

Img

[GHuggins]

Try them both and see which it likes. Just make sue the rest of the cal is right first.

Just a couple of notes after looking at it - actually looks like another one I recently looked at for another gentleman. Whomever set your multipliers up doesn't understand how they work. You shouldn't have 1's in the multipliers and usually it needs the inverse in the MAF side of the calibration to keep the trims right, so basically you can copy your OE alcohol multiplier in the SD section and put that into the injector or "maf" section and that'll have it really close. Also your timing is very interesting to say the least if you paste special add your ethanol timing to your main spark table...

[wtf777]

Try them both and see which it likes. Just make sue the rest of the cal is right first.

Just a couple of notes after looking at it - actually looks like another one I recently looked at for another gentleman. Whomever set your multipliers up doesn't understand how they work. You shouldn't have 1's in the multipliers and usually it needs the inverse in the MAF side of the calibration to keep the trims right, so basically you can copy your OE alcohol multiplier in the SD section and put that into the injector or "maf" section and that'll have it really close. Also your timing is very interesting to say the least if you paste special add your ethanol timing to your main spark table...

well that's concerning! the tuning was done by a reputable shop near me that for the most part only deals with corvette builds..SHit!. which multiplier am i looking for? i did notice the MAF was changed. sorry for my simplicity and lack of knowledge on some of these terms, but wat is the SD section? and the timing being interesting is it the flex fuel table or the high octane table that is problem? i copied the flex fuel table from another stock c7 file found in repository.

[GHuggins]

They may have done the boosted truck I looked at too then. A lot was screwed up the same.

This is the SD alcohol multiplier - put it back to stock

Alcohol Multiplier SD.jpg

Take that same stock SD alcohol multiplier and paste it into this table - this is the MAF one

MAF alcohol multiplier.jpg

This is your ethanol table paste special added into your main table. Some areas need to drop down, but usually not like this and I would grab one from a 16 5.3 truck file before I got one from a car.

Spark added to main.jpg

[wtf777]

They may have done the boosted truck I looked at too then. A lot was screwed up the same.

This is the SD alcohol multiplier - put it back to stock

Alcohol Multiplier SD.jpg

Take that same stock SD alcohol multiplier and paste it into this table - this is the MAF one

MAF alcohol multiplier.jpg

This is your ethanol table paste special added into your main table. Some areas need to drop down, but usually not like this and I would grab one from a 16 5.3 truck file before I got one from a car.

Spark added to main.jpg

ok so i changed the SD multiplier and copied unto MAF table. I copied the tables from the file you sent and paste on the high octane table and flex fuel spark. is this correct? just want to make sure before i upload tune and fire up tomorrow.

[GHuggins]

Your spark table looked like one from a truck. Didn't realize it was a car. Either way that should work better with that flex table. Everything looked good. If you really want to dial it in you'll need to go to full flex then work the multipliers to keep fueling the same as pump.

[wtf777]

sorry English is my 3rd language. so the 2.0 file i sent is ok to start and drive to get a log and go from there ?

[GHuggins]

Yes

[TriPinTaZ]

I run a little leaner on E60+ than I would on Pump gas but I usually set the PE tables the same and let the other alcohol tables lean out the car as Ethanol content ramps up. But my delta between pump gas and E is about .02 Lambda max.

[Alvin]

Sometimes more power is found richer.. You don't know until you dyno it.

I will tell you the window for making good power AFR wise is fairly wide. If your in the ball park and not so lean you get clobbered by knock retard occasionally.. you are doing fine.