OK guys. First off, I'm just a novice tuner, so don't bash me too bad. My 02 8.1L truck is tuned by myself with EFI Live. When looking at the tables, there is the FLEX FUEL tables everywhere. Can I setup the 8.1 to run both fuels or a mixture? Or is this just in all GM ECM's? I would like to be able to use E85 for a few off road purposes, but its only available in one place in a 120 mile range. So a constant tune would be useless. Thanks guys!

 

If you don't have the fuel composition sensor then no. I'm guessing you don't. Basically you can just change your stoich AFR value to that of the ethanol mixture and it will work fine, assuming your fueling tables are accurate.

 

Is that WITH the sensor I don't have(fuel composition) or on the current setup?

 

With the sensor you can utilize the factory tables and it will automatically select the stoich AFR. I run e85 on my 2000 but I had to manually tune for it. I could easily go fill up with gas (e10), but I'd have to flash a new cal with a stoich of 14.1. This assumes your ve table and airflow values are accurate.

 

OK I get you! Would it be worth installing a comp. sensor or just keep away from it all? I really would LOVE to utilize the e85 power gains, but its just looking like I'm going to have to do a lot of flashing, or get me another ecm.

 

Adding the comp sensor would depend on how often you would fill up with E85. If it is all the time, then I would add it. Should be pretty simple and then the computer will automatically update the stoich value.

You can look at Atomics ethanol/gasoline stoich excel sheet. That will help figure out the correct value when you mix fuels.

 

Well tested the waters yesterday. Tuned stoich to 13.6 and ran a 20% e85 mix. Left the timing the same. Did very well. Ran and idled normal. Seemed like mileage wasn't affected much, seems like it may have gotten a 1/2 or so mile better to the gallon, or it could be my imagination. Haven't calculated yet.

 

with the comp sensor it wouldn't matter. it's getting the ecm to read anything like a true FF vehicle would. thats coding that we can not see. you can wire up the sensor itself and change the stoich off a simple display gauge setup.

 

I understand that. Seems like that sensor is priced for and arm and a leg tho. Trying to find a junkyard special at the moment

 

Well yesterday was the day, guys. Had a long trip planned. Threw in 5 gallons of 93 and topped it off with E85, ran the tank nearly empty and ran moderately better than gas. Got back late and filled it COMPLETELY with E85. Never touched the tune....and it runs EXTREMELY well. Very noticeable amount of power gain. I'm sure its not optimized but its incredible. Ran 60 miles with the pure rank and no problem at all. Had a code of both bank 1 & 2 lean early in the day but I cleared it and haven't seen them again. I guess it has compensated??? I was so surprised with then outcome. And I have NOT installed the sessor we spoke of above