Well the other day someone asked if I had any E85 left and would I sell it cause they bought a car with an e85 tune they could flash on it. Well it was an SRT4. He asked what afrs he should be looking for. I always thought you needed the tune to be richer for e85 due to 25-30% more e85 being required to create the same amount of combustion. Apparently they run around 11s or so on 93. Well they run mid 11s to low 12s on E85. How is this possible they are running leaner than on 93, let alone what my LNF was running. It was to my understanding as well that Direct Injection allowed for a leaner mixture. Someone please let me know what I'm not understanding here.

 

my bros old SRT-4 was big turbo'd on 26psi tuned at 11.7 on full E85

 

he had 1200cc injectors as well, he was tuned by one of the owners of DynoJet

 

as a fuels ethanal content goes up the stoich of the mixture goes down. we all know 93 gasoline is around 14.7:1. the stoich for E85 ideally would be around 9.8:1; 100% ethanol's stoich is 9:1 roughly

If you're using a wideband that is calibrated for gasoline(14.7:1) and cannot change the calibration of the wideband, take your gasoline AFR and divide it by 1.5 to get actual e85 AFR or use the wideband in lambda mode (THIS MODE IS WHAT WE USE AS LNFS IN TUNING!!).

Here are some common AFR conversions ROUGHLY using the 1.5 as a divider (Gas AFR on left, e85 on right):

18.0:1=12.000
17.5:1=11.666
17.0:1=11.333
16.5:1=11.000
16.0:1=10.666
15.5:1=10.333
15.0:1=10.000
14.5:1=9.666
14.0:1=9.333
13.5:1=9.000
13.0:1=8.666
12.5:1=8.333
12.0:1=8.000
11.5:1=7.666
11.0:1=7.333



basically all this is saying is that the AFR gauge your reading is calibrated for gasoline, when running E using a AFR gauge still calibrated for gasoline it will read higher (leaner) but actually be lower (richer) due to not being calibrated for E AFR measurement. lambda is much easier to work with

 

tune lambda. not afr's. you will get better results.
.85 is .85 either fuel used.

 

People tune with AFR's in there head for gasoline. He had to richen it up for E85, just his WB displays Gasoline AFR so he thinks it's the same. Very common & misleading mistake.

A WB calculates Lambda, then displays what you want it to. lol. 1.0 lambda is stoich regardless of fuel.

Area is correct, if you tune in Lambda, all is well.

 

p.s. if you go off that conversion for gasoline to e85. you're over fueling the engine and leaving power on the table.

 

So does this mean that my RPD AFR readings are inaccurate when using 93/E10?
Anybody got conversions for that?

 

Stoich of gasoline is 14.7, E10 is 14.1

14.1/14.7 ~= .96

All your factory WB knows is Lambda, it added the 4% fuel into the LTFT's for the E10.

I guess I should say the AFR readings are off 4% if you really care.

 

Interesting...good info thank u