About 2-3 months ago I added many new parts and got a dual map tune. I've been driving it mostly on e85 up until recently. Lately I've noticed that under WOT above roughly 5500rpm the air/fuel ratio will climb to 13-14:1. Did a visual check to make sure nothing stupid happened, car doesn't have anything obviously out of place. I decided to swap to the 93 tune and see what happened. Once I hit my second tank of 93, at WOT the ratio is solid between 11.2-11.5.

I am wondering if it is a fuel pump/flow issue. The car is making 500whp on e85 with an AEM 320 pump and pte 1200cc injectors. The pump is 2-3 months old, and been in e85 95% of the time. The car pulls fine through the power band, nothing feels funny or unusual as it gets lean. My tune is pretty conservative so that's a good reason why.

Contemplating going with a double pumper so I will know I have more than enough fuel available. I am posting this to see if anyone has had a similar issue and what they found? Due to some unfortunate events I have been daily driving the evo and haven't been in a situation to dig into the issue. I'm leaning strongly towards the pump, but wanted some other opinions.

 

You might just need a touch up on your tune for winter. In a lot of places the combination of temperature change and E-85 seasonal blend changes have led people to have a winter and a summer tune. There is also the chance of "gunk" build up on your injectors. Running gasoline usually clears the gunk out, so after a few tanks of gas you can try switching back to E-85 and see if the problem has corrected itself.

 

Alright, that is good advice. I have read online about the differences of e85 by season, I figured if I always went to the same place maybe the fuel wouldn't vary too much. Makes since though since it has gotten significantly cooler since my initial tune. Definitely going to run 93 for a while to let any possible build up clean itself out.

 

Winter mix would make the car run richer, not leaner, as it would have less Ethanol in it.

How many tanks of E85 did you go through since the dual map tune?

What are your logged IDCs?

 

Probably 7-8 tanks. Just guessing though. I haven't taken any logs, but when the car was tuned I believed the duty cycle was between 85-90%. It was within the 80's just don't remember exactly what percentage.

 

Was this the first time running E85 in the car for an extended period of time?

 

Not trying to thread jack but this particular situation has gotten me thinking about how the ECU would behave. So in the short term I would totally expect what you said to happen. You would see it run rich, but after the LTFT's have started to adjust to the different fuel and go negative that would have an effect on the fuel map. So if say the trims went negative like 10% (number pulled out of my ***) and you where already pushing say 90% IDC at lets assume close to 0 LTFT , could that result in an actual lean condition setting in? Or should the Trims basically do their job under most circumstances and get you close to the original targets you where tuned for? Another way of asking the question would be, would you expect the effects of the trims as far as actual measured AFR to be linear across the entire MAP or non-linear towards the top with a bit of a magnified effect?

Also , yah i didn't mean to suggest that a winter blend alone would be the cause of OP's problem, just that more generally a retune for winter might be what is needed.

 

I would lean towards gunk build-up on the injector tips, and gasoline would definitely cure this issue quickly... I would throw another tank of E85 in and see if the issue is still present or not...

 

Most tuners worth their beans turn off fuel trims affecting WOT so fuel trims wouldn't affect WOT.

I experimented awhile back on my Evo 10 with keeping fuel trims affecting WOT to see if I could do a "poor mans flex fuel" tune but it was too inconsistent for me.

 

Oh nice, i didn't know you could do that without disabling closed loop. Thanks! you just gave me something new to research

 

Yes this is the first time the car has seen e85 to my knowledge. If the previous owner ran it, than it has atleast been about 4 years.

I figure I will try this instead of worrying about buying any new parts. I'll go through about 3-4 tanks of 93 and try e85 again. My tuner warned me about using e85 excessively, I'm just hard headed and couldnt pass up the power and cost.

 

Make sure you check the fuel pump assembly filter. It's the big darker object molded into the white plastic fuel pump assembly.

Sometimes they clog up after using E85 for the first time on a used Evo. I went through two of them on my Evo 8.

You have to replace the whole assembly to get a new filter (aprox $140)

I'd try out Fast Freddies suggestion first though.

 

The fuel filter was the first thing I considered. After some research, I found that the filter is in the assembly and not serviceable to much disappointment. So at that point I'd just buy a double pumper anyways. We shall see within a few hundred miles. Thanks for the input!

 

Very similar issue going on with my car Josh. Me and Kasey are stomped. Ordering a set of injectors come new year and going to pray it fixes the issue.

 

Kasey told me another customer of his was having similar issues, I was wondering if it was you. He said we both have similar setups. Did you switch between e85 and 93 to see if it cleared up?