Parameters to monitor with E85 tune

[OffTheWall503]

I just switched over to an E85 tune from Stratified. I am wondering what the best things are to monitor as I go through my first couple tanks of gas. E85 mixed with 92 octane.

This is my first experience with ethanol fuel and I want to make absolutely sure I don't damage anything unintentionally if I miss something important is going ok.

 

[Hijinx]

The best parameter to monitor is none. Do your datalogs and store the AP when done; enjoy driving the car. Trust me, if its going to be catastrophic, you won't be able to get your foot out of the gas fast enough to prevent it.

But, to answer your question, monitor what you've always monitored.

 

[Rhinopolis]

I learned that my local E85 station (after using a test tube ethanol content gauge) is providing me with only 68% ethanol. This of course skewed my mixing with 93 octane.

Anyway, [MENTION=1076]razorlab[/MENTION] taught me that I could monitor LTFT and that if my ethanol was in line with my tuning then it would read a positive reading. I adjusted my E85 mix and have settled on + 4 LTFT reading which from my understanding should mean that my ethanol content is suitable for the E30 tune that I am running.

After I measure the ethanol and fuel up according to the ethanol content, I monitor LTFT for 10 miles and make sure that it is consistently reading + in the 1-5 range.

 

[OffTheWall503]

I've been keeping an eye on the LTFT, what is the good number to know my mixture is E30 or better? About 20 miles into my first tank it seems to be hovering around +5.00, and OAR is at -0.73 so far, which keeps getting more negative as time goes on. Not sure how the two are related, however.

 

[razorlab]

Anyway, [MENTION=1076]razorlab[/MENTION] taught me that I could monitor LTFT and that if my ethanol was in line with my tuning then it would read a positive reading. I adjusted my E85 mix and have settled on + 4 LTFT reading which from my understanding should mean that my ethanol content is suitable for the E30 tune that I am running.

Just to clarify, the closer your LTFT and WOT STFT are to zero, the less the fueling system is compensating for more/less ethanol content.

In general, if it's showing positive, the ecu is adding more fuel to compensate for more ethanol, if it's showing negative it's taking away fuel to compensate for less ethanol.

If the tune and ethanol percentage is truly dialed in, you shouldn't see more than approx +/- 5 or so.

 

[OffTheWall503]

So generally speaking, Stratified recommends 3 gallons of E85 and the rest with premium, while some members have recommended doing 4 gallons of E85 because it's better to have too much ethanol than not enough if you have the tune for E30. What is your take on this? I just want to make sure I'm taking full advantage of my tune.

 

[razorlab]

I'd listen to your tuner if you are running their tune.

 

[Fiestarawpower]

Doesn't 3 gallons come out to e25?

 

[razorlab]

Doesn't 3 gallons come out to e25?

Fiesta ST tank size: 12.4 gallons

Mixing chart:

It would be approx E28 but in the real world of pumps that are never exactly 85% Ethanol.... probably more like E20-E35

 

[OffTheWall503]

My LTFT at WOT was at +3.70 or so. Is that ok?

 

[Jesse]

Long Term Fuel Trim is an avg over time, Short Term Fuel Trim is more of an instant result. You should buy a digital ethanol content gauge and hook it up to your fuel line so you always know exactly what ethanol % your running... That is really the only true way to know what is going into your engine.

In AZ we only have e54, so I have to mix 50/50 to get e30...