racingdragracer

If I have a good tune on 93 octane, What all has to be changed to run E85 on this computer. Is it just changing the Stoich value in the computer to 9.77 to run e85? Or does it get more complicated. I run 30# injectors in a 355 motor. I think I should be ok with 39 to 40# injectors.

Saar

well, you'll need to change stoich ratio, PE target AFR, any stuff that is measured/adjusted in mSec(cranking fuel is a big one), maybe a few others.

racingdragracer

I have tunerpro and what is PE target AFR listed as?

Saar

depends, what mask are you running? if i had to guess, i'd say 8D, in which case it could be listed as quite a few different names dependong on who made the XDF.

Fast355

iTrader: (2)

In my experienc you won't have to touch the PE Target AFR as it is based off of stoich I didn't even have to touch the crank pulse width. Just set the stoich afr and tweek the timing in the low-midrange. Might have to add a touch of additional AE.

Saar

in 8D, yes, the PE AFR is based on stoich, but again, depends on the mask. i would think it would want quite a bit more fuel when cranking though.... unless that's done differently in 8D than compared to masks i'm more familiar with.

Fast355

iTrader: (2)

I was running larger than stock injectors and never touched the factory cranking fuel tables. Never failed to fire right up with a touch of the key.

I assumed 8D due to the fact the OP said he was running a 355 with it.

Jaxom

Fast 355: I'm guessing you bumped up the injector size but left the flow rate constant unchanged in the tune....effectively richening it across the board by whatever factor you increased the actual injector size. It's a workable way to go, but not technically correct, and could cause problems with future mods/tuning (sort of like how some guys adjust fuel pressure to get BLMs close on the stock calibration instead of actually tuning their cars.) I'm sure Saar is assuming that when the OP swaps injectors he'll change the constant in the tune to match...in which case the car will be approx 30% lean under nearly all conditions.

For the orignial poster: E85 has some other characteristics that differ from straight gasoline, in addition to producing less power than gas for a given volume. I suspect you'll end up having to do quite a bit of tuning to both the fuel control AND the ignition timing to get the cars performance and driveability back up to par on E85, and you're going to lose at LEAST 20% of your fuel mileage no matter HOW you tune it. That's just the nature of ethanol.

Fast355

iTrader: (2)

I changed the injector constant, stoichiometric air/fuel ratio, and tweaked the VE tables and timing. BOTH the injector constant and command stoichiometirc air/fuel ratio constants affect the pulsewidth substantially. By adjusting the stoichiometric air/fuel ratio you are adding the proportional amount of pulsewidth automatically. Same goes for the injector constant, when you increase the value the pulsewidth decreases. Both are global changes in fuel delivery, which means small tweaks to the VE tables.

With little more than the injector constant and stoichiometric air/fuel ratio changed it ran absolutely GREAT. One thing about E85 over Gasoline is the Ethanol blend makes a substantial gain in mid-range torque. Steady state highway driving fuel economy is hurt somewhat, but I found my city mileage dropped less than 1 mpg. Just more torque to get the heavy Van rolling.

racingdragracer

Ok, I will say this,

This car is ran on 8D and aujp code. It is a drag car. The main issues would be idle and wide open throttle. The tune I have is good. I just would like to change to E85 for less expense and highr octane ratings. Would just changing Stoich and injector constant get me close?

Saar

according to Fast355, it sounds like it should.