Running FiST with E85 Blends - Discussion Thread

[razorlab]

How would I know if I was running too little ethanol in my E30 blend? Would my access port show any funky readings that could be a warning to me? I feel that with how over cautious I am blending to E40 on the max side, that I should have enough safety built in. From here forward I am going to test the fuel every time I fill up so no more guessing what the ethanol % is.

In addition to what I posted above...

You can see if you are swaying away from the ethanol % you are tuned for by looking at your fuel trims. if STFT and LTFT are positive then you have more ethanol % and if they are negative you have less ethanol %.

That said, small deviations are just fine. The MED ecu in the Fiesta works VERY well at fuel adjustments VERY quickly. Example: If you put E30 in a stock Fiesta or even any of the COBB stage tunes the AFR would still be spot on at WOT, the STFT can adjust fueling at WOT very quickly.

My last Fiesta I had tuned for E40 and I wouldn't be too strict on my mixes. Sometimes I would put E30 in, sometimes E45. Logging always showed target AFR spot on with STFT adjustments.

The thing you need to be concerned about is too little ethanol when you are tuned for a certain Ethanol mix. The ignition timing and boost might be too much for less ethanol. The ECU is good about reactive timing adjustments but to be safe I would always error on the side of slightly too much ethanol than too little, unless you are at the upper limit of your fuel system...

 

[Rhinopolis]

^ That's what I was looking for. Thanks!

 

[Rhinopolis]

In addition to what I posted above...

You can see if you are swaying away from the ethanol % you are tuned for by looking at your fuel trims.if STFT and LTFT are positive then you have more ethanol % and if they are negative you have less ethanol %.

That said, small deviations are just fine. The MED ecu in the Fiesta works VERY well at fuel adjustments VERY quickly. Example: If you put E30 in a stock Fiesta or even any of the COBB stage tunes the AFR would still be spot on at WOT, the STFT can adjust fueling at WOT very quickly.

My last Fiesta I had tuned for E40 and I wouldn't be too strict on my mixes. Sometimes I would put E30 in, sometimes E45. Logging always showed target AFR spot on with STFT adjustments.

The thing you need to be concerned about is too little ethanol when you are tuned for a certain Ethanol mix. The ignition timing and boost might be too much for less ethanol. The ECU is good about reactive timing adjustments but to be safe I would always error on the side of slightly too much ethanol than too little, unless you are at the upper limit of your fuel system...

I monitored STFT and LTFT this morning, and initially my STFT was showing negative. I filled about 3 gallons of E85 (68% ethanol) and let the fuel mix in before monitoring again.

The positive or negative readings fluctuate, and the readings seem dependent on my throttle application at any given moment. If I let off the gas then LTFT is a little negative, but during part throttle they are both positive.

When WOT then STFT is a little negative (2-3%) but LTFT is positive. How should I interpret this?

Thank you,

Ryan

 

[razorlab]

I monitored STFT and LTFT this morning, and initially my STFT was showing negative. I filled about 3 gallons of E85 (68% ethanol) and let the fuel mix in before monitoring again.

The positive or negative readings fluctuate, and the readings seem dependent on my throttle application at any given moment. If I let off the gas then LTFT is a little negative, but during part throttle they are both positive.

When WOT then STFT is a little negative (2-3%) but LTFT is positive. How should I interpret this?

Thank you,

Ryan

LTFT is the long term stored fuel trim. After a certain amount of time with STFT adjustments, it gets moved to LTFT. It does this to try and keep the STFT as little as possible for efficiency reasons.

What are your LTFT and where they reset before you put the ethanol in?

I wouldn't worry about 2-3% STFT either way if the LTFT number isn't large.

 

[Pete]

Welcome back razor!

 

[socalwrxx]

Install an ethanol sensor and gauge. Then you'll never get it wrong. It takes me about 4 miles before the ethanol percentage settles at a constant number. I put in 91 octane first then the e85. I use Arco or 76. I use an android app called e85 mix calculator. Is really easy to use

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Can you explain the usage of an ethanol sensor/gauge? You try and mix to the best of your ability then use the sensor to be on the safe side? (drive a few miles) If it's too little or too much you go BACK to the gas station and try to get it as close to e30?

 

[westcoaST]

After a while, you can get the correct percentage of e85 to 91/93 octane, especially when you are adding fuel to an e30 mixture. I was a little light on my estimate of fuel remaining at first, but I sit and wait at the pump until the gauge on the access port settles down, and use the reading in the calculations to get to a solid e30.
I use an android program called "e85 mix calculator" ?t calculates the number of gallons of e85 and 91 octane needed to get an e30 mixture. You need to know how many gallons you have in the tank and the ethanol percentage. That's where you use the access port and the ethanol gage.

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[Rhinopolis]

LTFT is the long term stored fuel trim. After a certain amount of time with STFT adjustments, it gets moved to LTFT. It does this to try and keep the STFT as little as possible for efficiency reasons.

What are your LTFT and where they reset before you put the ethanol in?

I wouldn't worry about 2-3% STFT either way if the LTFT number isn't large.

I'm not sure what you mean by reset, but the car sat for a week not driven while I was out of town working and I assume that this reset the reading.

I drove it yesterday and LTFT was around +5% under WOT.

 

[jeff]

Great thread guys thanks. I'm considering an E85 tune and wanted some feedback on MPG loss. What sort of MPG drops have you seen as compared to premium grade gas in your experience?

Thanks in advance.

 

[jdubs]

Great thread guys thanks. I'm considering an E85 tune and wanted some feedback on MPG loss. What sort of MPG drops have you seen as compared to premium grade gas in your experience?

Thanks in advance.

I do all city driving and usually averaged 27-28mpg on my 93 Tune+ Tune. Just switched to E30 i'm on my second tank. My first tank I still managed 26. I'll be running to ST Fest on E30 so we'll see what highway mileage is like this weekend.

 

[Jesse]

I've been on e30 for 6-7 tanks I've been averaging 25.5 mpg city/hwy mix, 32 if its just straight highway running.

 

[Rhinopolis]

I run E30 on the X37 and most of my driving is weekend only and aggressive. 23 mpg average on E30 is what I'm seeing.

 

[jeff]

Thanks guys.

I do all city driving and usually averaged 27-28mpg on my 93 Tune+ Tune. Just switched to E30 i'm on my second tank. My first tank I still managed 26. I'll be running to ST Fest on E30 so we'll see what highway mileage is like this weekend.

jdubs, we're about at the same mod setup and both using Adam as our tuner - could you comment on the difference between his regular vs. E30 tune on your car as it is right now? That will help me....trying to decide if I want to go this route and whether the power gains are worth the MPG losses.

 

[jdubs]

Thanks guys.



jdubs, we're about at the same mod setup and both using Adam as our tuner - could you comment on the difference between his regular vs. E30 tune on your car as it is right now? That will help me....trying to decide if I want to go this route and whether the power gains are worth the MPG losses.

I will hit the dyno sometime in September. My commute to work is like 1.5miles lol so gas mileage doesn't concern me much.

If you have a lifetime tune from him I would say why not give it a try? It doesn't cost anything extra and is just loaded in a different map slot for on the fly switching. Car feels stronger. I don't get the OMG effect others have claimed but certainly noticed an increase. Soon as I get dyno'd i'll know better on whether i'll continue with it.

 

[Rhinopolis]

I test the ethanol content via the "test tube" shaker method (fill up the tube with water to the water line and then fill with E85 to the E85 line, shake it up and then set it on a flat surface and see where the ethanol content line settles at) before every fill up.

Three weeks back and when I last mixed E30, the same E85 pump tested out to 70% ethanol, and this fill up it tested out to 95%!

I trusted what the results showed and mixed to E30 accordingly, and utilizing what Razorlab mentioned with regards to monitoring STFT and LTFT the fueling is mixed correctly. Just goes to show how much the ethanol content can vary from one fill up to the next.

 

[Fiestarawpower]

We should be able to fill up with straight e85 and call it day, someone needs to make this happen.

 

[Spaceman_Spiff]

Questions:
1. Would this be something that can be switched back and forth between mixes and regular 93 octane tunes? I'd like the 93 octane tune's MPGs during the work for the commute, but the extra power on the weekends when I want to go out and have some fun.
2. Is this something that can be done on a completely stock car, or do I need supporting mods? This seems like it would be a good "bang for the buck" power-wise, and easy enough to remove the tune and have no tell-tale signs that the car was modded if warranty work was required...

 

[westcoaST]

Questions:
1. Would this be something that can be switched back and forth between mixes and regular 93 octane tunes? I'd like the 93 octane tune's MPGs during the work for the commute, but the extra power on the weekends when I want to go out and have some fun.
2. Is this something that can be done on a completely stock car, or do I need supporting mods? This seems like it would be a good "bang for the buck" power-wise, and easy enough to remove the tune and have no tell-tale signs that the car was modded if warranty work was required...

I used to switch back and Forth between e30 and 91 octane all the time. It really bells I'd you have a razor lab ethanol gauge.

As long as you have the tunes to support both e30 and 91/93 octane, you can do this on a new engine with no add ons. Talk to Adam at Tune+

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[Izzy]

We should be able to fill up with straight e85 and call it day, someone needs to make this happen.

I utterly redundantly concur with this!!

 

[TyphoonFiST]

So how does the e85 calculator work and what numbers are you looking for when calculating?