Thread: I can add some 91 to E85 to bring my LTFT down. Confirmed.

I recently converted to E85 by swapping to 42lb injectors without a tune. Ran two full tanks through without a problem. Car loved the corn juice. Killed all my knock! LTFT settled in between 10-11. Life was good.

Until...

My last fill up. Shortly after topping up this last time, my LTFT began creeping up. To the point where I'm at 16.4 under acceleration and while cruising. Even set a MIL. (P0170 Bank 1 too lean.) I am almost certain it's fuel related because it happened right after my last fill up, and all my mechanical maintenance is up to snuff. New(ish) plugs, wires, fuel filter, and a walbro 255 pump. Rail pressure is about 45 while parked.

So here's my question:
Can I throw a couple gallons of 91 in the tank to try to bring my trims down? Would this hurt anything?

My first thought was vac leak also, so I did the propane check. Didn't yield any results. The only thing that changed between my 10.9 LTFT and 16.4 LTFT was a tank of fuel.

Definitely highest while driving. Maxed out at 16.4. Sitting at a light it comes back down to 10.9. I guess it's possibly a fuel delivery also. I have an AEM 340 LPH E85 pump on order. I though my Walbro 255 would have been enough. It just seems weird that it happened right after a new tank of fuel.

I was just thinking, if I throw some 91 in it, that might bring my LTFT down. Would't that confirm or rule out a fuel quality issue?

I did have a small leak where the front header meets the crossover, but I sealed that up. Like I say, first two tank were great. Last fill up=poopy.

I'm gonna try it. What's the worst that could happen?

It worked. 2-1/2 gallons on top of the half tank I already had, brought me back to where I was before my last fill up.

Gonna try the E85 from a different place next time. See if there's a difference.

http://www.grandprixforums.net/threa...ur-car-for-e85

Read it. Learn from your mistake. Enjoy the corn.

Using method #1 what was my mistake? What did I do wrong?

Great write-up BTW! I did read through it at least once. Although, there were some distractions in the background at the time.

I will probably rephrase #1 later to make it more clear that its a really bad way to do it. For now ill single out these quotes from #1.

This will never be 100% correct

Its just too crude to get a steady air fuel ratio at wide open and your fuel trims will always be a bit off.

Finished tweaking it. I was a little drunk when I was writing that section. Im a happy drinker so I was WHHAAAYYYY too nice. Edited it to make it a little more angry.

Originally Posted by Frosty

I will probably rephrase #1 later to make it more clear that its a really bad way to do it. For now ill single out these quotes from #1.

That's fair. I do plan on doing my own tuning in the future. I just couldn't wait to get on the corn. Still no regrets. It killed the 3° of KR I was seeing even after CAI, headers and colder plugs.

I guess I'll just have to be less surprised in the future if/when my trims go bonkers. Knowing that I can dial the LTFT down with 91 is reassuring.

Thanks for chiming in!

I still love my 2.55" and full stack you intercooler hater you.

Not gonna lie, I may own an intercooler some day also. As far as "more and more people switching to E85" I think its great too. I really enjoy reading all the E85 threads. I like all the discussion and spread of solid information!

I did change the filter. I thought the same thing. No difference. Everything went whack after that last fill up. I thought rail pressure was supposed to be like 43 psi?

I hear you. I should mention, it's not my end game. I do plan to tune, eventually. It just really threw me off because my first two tanks went through as predicted. Trims and all. I was surprised to see that much of a difference between fill ups.

Originally Posted by Frosty

Finished tweaking it. I was a little drunk when I was writing that section. Im a happy drinker so I was WHHAAAYYYY too nice. Edited it to make it a little more angry.

I didn't see any anger there. Some strong words of discouragement, sure.

I get where all the "you have to tune it" guys are coming from. If this car was my daily, and only mode of transport, there's no way I would roll the dice on some of the stuff I do. But it's a hobby/grocery getter. I'm willing to play with things a bit. It's reminiscent of the old school hot rodders who would do different things just to see what would work, and work the best.