4.2 Running E85

[justin99]

Can someone give me some insight on what tuning needs to be done to run E85 in my envoy? I do not plan on running it alone and all the time but would like to substitute it with the price of fuel now.

[Mep_q8]

try getting some flex fuel V8 files and compare them to the stock V8 ones.

From what I've heard, spark control needs to be played around with the most.

[Baldturbofreak.com]

If it's not flex fuel you'll have to dedicate a tune for E85 and flash it in when you wanna use it. In addition, you can t really ever count on the alky% in the fuel so your tune will almst never be spot on.

[justin99]

I would like to have a dedicated E85 tune. It doesnt have to be a tune that is only 100% E85. I would just like to be able to run in like 50/50 or even 75% E85. I just have no idea what to change. I know that the Stoich has to be changed.

[Baldturbofreak.com]

Thats the thing bud- it does. You need to be able to count on alky% to be able to create the right stoich #. Winter E85 is actually E70 to help with the vaporization. It all makes a difference.
The flex fuel vehicles either have a realtime % content sensor in the return line or use sophisticated algorithmns to predict alky%
Stoich for E85 is like 9.12:1. Gasoline-14.7:1

Maybe you could get a flex fuel patch from another op system. I think you;d be the first though. Start by downloading a flex fuel cal from any GM vehicle from the repository.
View it and see what the general has done to get the motor to run right under varying amounts of alky. Stoich is obvioisly a big part of the fueling, but alky has a significantly different burn rate/temp so there are seperate Ignition tables written for alky.
The reid vapor pressure for alcohol also requires separate cold start tables.

To be honest justin, unless your going forced induction or something IMO it's alotta work for not too much reward.

[justin99]

Thats the answer I was looking for.

[MinusG40]

Not excatly right, i have work on a project (Frenc car sell in Brazil) with the E100 fuel yhe correct need to be 9:1 (gasoline ratio = 14.7:1)

edit :
You need to know that to run with a lot of ethanol in your fuel, you need to change :

your valves
injectors
fuel hose
fuel tank
and the fuel pump

Regard

[tahoe]

You need to know that to run with a lot of ethanol in your fuel, you need to change :

your valves
injectors
fuel hose
fuel tank
and the fuel pump

Not correct.
The fuel systems on cars that fulfill OBDII has materials that are compatible with Ethanol, as opesed to Methanol.
In Sweden there is wast eperience with this kind of conversions,
there are no problems in practical use.

As for the stoich, no problems there either, set your stoich on 9,5:1 to run
E70-E85, the variation in fuel blend is taken care of the STF/LTF in closed loop. Tune cold start with E85, then you will be running rich in winter with E70, just what you want to do.

I have now 40k miles on E85 converted gas Tahoe.

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