Has anybody done any adjustment to the PE table with consideration to 10% alcohol blends?
Has anybody done any adjustment to the PE table with consideration to 10% alcohol blends?
Last edited by seevi; 02-01-2011 at 04:16 PM. Reason: typo
I think you only need to change the first block (0.00) on the stoich table.
As mentioned, the proper place to adjust for a fuel spec change would be in the fuel stoichiometry table, not just the PE multiplier. If you set the fundamental ratio properly in the stoich table, PE's relative ratio will just fall in line.
why would you change the stoich ratios on a car with a blend sensor/stoich % table?
All of the newer operating systems have the table that shows stoich vs. percent ethanol concentration regardless of whether there is a physical or virtual content sensor active. If the flex fuel logic is not turned on, it always just uses the first value in the table. If your actual fuel chemistry results in a stoich point of something other than 14.68:1 then it's a good idea to make sure that the reference ratio the PCM is using matches the fuel being burned.
i figured the table meant the sensor. guess my calculations were off....
Adjusting the Stoich AFR cell works like a charm. i've tuned my car with a 14.395 stoich under the assumption that the fuel around here we get is not really E0, nor E10. Most gas pumps here in Southern Cali have the "might contain 10% ethanol" sticker, some others doesn't even display the label, so like other people have suggested, i simply halved the difference between E0 and E10 AFR (14.68 + 14.11)/2=14.395 AFR to use in the Stoich cell.
After that, just tune her as you will normally, adjusting you fuel trims to -2%+2%, and PE to where you want her to be, using MAF/VE accordingly.
As an experiment, i pumped E85 2 weeks ago, and left the tune the way it was to observe the changes, and as expected, within 2-3 min, the trims went lean to almost past 25%. My fuel trims are normally between -2 and 0% on the regular E10 stuff, and my fuel error is also about -2% at WOT.
Before getting the bank to lean codes, I simply changed the Stoich point in the AFR cell to satisfy E85 Stoich, then flashed that tune to her, and simple drove away with E85 for 2 days without any single issue, without changing anything else in the tune. trims and fuel error% went to -2% more or less as well. i tuned using Lambda so it's very easy to see you don't need to change your PE once you get use to see Lambdas.
The injectors we have in the G8's from the factory are 39lb, so with my mods,
IDC was around 83% at WOT on E85, i could run E85 if i wanted everyday, however, i'll have to modify (add timing) to optimize the tune for it.
On my way back to E10, i just waited until i was almost empty (had one gallon left in the tank), pumped Cali 91 gas, full tank, changed the stoich point back to 14.395 and that was it. my trims are still at -2% - 0% on Cali 91 gas and my WOT fueling hasn't changed.
Last edited by bluegoat06; 02-04-2011 at 11:04 PM.
Originally Posted by bluegoat06
Wow that is a great narrative, thank you. I have been planning the same thing, but have been anticipating the timing changes. I also have to deal with Michigan cold starts.
The other caveat is e70 since we are in MI, but the correct stoich should take care of that. I have a tester and will use that before putting the fuel in my vehicle. I have 60#/hr injectors so I am far from 80% duty cycle, actually more like 49% at last WOT.
My setup is a cammed LQ9 forged iron block 370, edelbrock intake manifold, 4" intake, 1 7/8" kooks with catted y-pipe. My truck has no problem starting in cold, but it likes to 'warm up' for at least 2 minutes when it's 30*F or below.
Thanks again you almost make it sound too easy. (I also have upgraded lines and fuel pump in my system as well)--I was previously supercharged.
-Mike
2007 TBSS AWD 1SS - miles of Pro Classic Hose!
~War Machine~
LEP 370 (10.74:1cr), ARP where possible
Edelbrock Pro-Flow XT intake with jeTTT Stage 4" CAI
Fast Motorsports jeTTT cam
1 7/8" Kooks w/ cats, Magnaflow catback
FLT Max Performance Level VII, Yank PTB3200, Cat power Flex Plate, LC32 Driveshaft safety loop
The most important thing would be to get as closer as you can from the real stoich of the gas, and use that number in the cal.
Your fuel trims would let you know how far/close you're from the actual stoich once you make the change in the cal.
Add some timing to account for the higher octane, and cranking fuel to account for cold starts and you're done. even better for you that you already have upgraded fuel lines and pump.
Is this also an easy way to change the AFR?
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