Flex Fuel Tune - Questions

[txpat3]

Hello! I recently upgraded to a flex fuel and E85 tune on my 2019 GT. I’ve had trouble so far locating consistent E85 that actually measures a high enough percentage to run the dedicated E85 tune. As such, I’ve been using the flex fuel tune. Lund has advised to swap to the E85 tune if I find 75% or better. Specifically, they say the flex fuel tune is just meant to be used as a transition tune and not to rely on it consistently.

I’ve read lots of forums posts about people running the flex fuel tune all the time whether they fill up on 93 or E85.

Looking for opinions on those that have run into this issue or just may be more knowledgeable than me about this topic. Is it safe to use the flex fuel tune all the time?

Additionally, my car seems to take forever to “learn” the % after filling up. I’m using the “alch learn” PID and on my current tank I’ve gone 90 miles and it’s still sitting at “0” (not learned). The % constantly fluctuates from 60-75% on this tank.

Thanks!

Sponsored

 

[NGOT8R]

Mine has lived on the Flex tune for about 5K miles. During that time, I’ve filled up on 93 about 5 times. My car doesn’t like it either when I put it on 93, while on the Flex. It pops occasionally, doesn’t sound as crisp as when it’s on E85 and it feels down on power.

 

[kz]

Additionally, my car seems to take forever to “learn” the % after filling up. I’m using the “alch learn” PID and on my current tank I’ve gone 90 miles and it’s still sitting at “0” (not learned). The % constantly fluctuates from 60-75% on this tank.
Thanks!

What's your AFR ? I don't think that PID is used anymore - at least by Lund.

I think reason they say Flex is for transition is to dial back people's expectations about power / torque out of it - since it more conservative than full E85 tune.

 

[txpat3]

What's your AFR ? I don't think that PID is used anymore - at least by Lund.

I think reason they say Flex is for transition is to dial back people's expectations about power / torque out of it - since it more conservative than full E85 tune.

AFR hangs around 14.6-15 while driving.

I’m hoping that’s the reason for the whole “transition tune” terminology. Since I haven’t tried the dedicated E85 tune I can’t say which is stronger but the flex fuel tune feels good. I just want to ensure I’m not doing any damage if I decide to keep that tune and switch between E85 & 93 as I see fit.

 

[PaddyPrix]

What's your AFR ? I don't think that PID is used anymore - at least by Lund.

I think reason they say Flex is for transition is to dial back people's expectations about power / torque out of it - since it more conservative than full E85 tune.

Not really. I don't work for Lund or anything, but regular gas has an Air Fuel Ratio 14.7:1 stoich, e85 has a 9.85:1 stoich. If you ran your regular gas tank down to say, the last gallon, and filled up with a quality e85, you'd have 1 gallon of 91, and 15 gallons of e85, which (15/16) * (0.85) would be e80 which is above the e70 or e75 requirement that most tuners want. If you had 3 gallons, and again, assuming quality e85 then you'd have (13/16) * (0.85) would be e69, below what the tune is looking for, granted, you could probably go real easy and then top back off or something. Because the two fuels act so differently, you would do really bad things if you leaned out your engine, because while a 12:1 AFR is super rich for gas, it's super lean for e85, right? Flex is for all those times inbetween when you're trying to burn off the last of the old fuel type, so you can then fill up and switch to the other type.

 

[txpat3]

The AFR question got me thinking..

What’s a normal reading on 93 versus E85? I filled up from almost empty with E85 and am seeing about 70% content according to my Nguage. AFR is 14.6-15 at idle.

 

[PaddyPrix]

The AFR question got me thinking..

What’s a normal reading on 93 versus E85? I filled up from almost empty with E85 and am seeing about 70% content according to my Nguage. AFR is 14.6-15 at idle.

Generally (blanket statement!) around 14.7 (:1) is what it aims for on Gasoline, e85 stoich is 9.85:1.

The lower the number gets, the less air to fuel, or rather, the more fuel to air, which you'll hear people call "rich", and opposite of it, less fuel or more air is called "lean." Going too lean, or having not enough fuel is potentially bad, and if you've driven an older automatic and gone up a hill with a heavy car, you might have heard pinging noises, and then it'll drop a gear and back to normal. Would not recommend pinging at a higher RPM with much more power, but as I'm not your accountant or engine builder, I'll patiently wait for the pictures and aftermath story Going too rich is just wasting fuel away, but for supercharged cars and response times, some tuners might go lower/richer as a safety measure to prevent terrible things from happening. When some people are getting dyno tuned, and they're trying to make max numbers/power runs at the end, they're leaning out the mixture and walking very carefully through a minefield.

 

[onlyturbo]

Running flex tune will not hurt your car, it was designed to switch between 91/93 and e85 mid stream. You will not get as much aggressive timing like in dedicated e85, but will work well .

After filling tank with e85, and switching to flex tune, did you wait and idle car for 10 minutes revving before driving? If not this may be the reason the car computer is not learning that fast. You need to do that for the learning procedure, everytime you switch to flex tune.

This is what I used to do when I had my 2015 GT.

 

[txpat3]

Generally (blanket statement!) around 14.7 (:1) is what it aims for on Gasoline, e85 stoich is 9.85:1.

With my gas being mostly E85 (2 fill-ups in a row even if content is closer to 70%), should my AFR not be lower than 14.8ish like I'm seeing?

Running flex tune will not hurt your car, it was designed to switch between 91/93 and e85 mid stream. You will not get as much aggressive timing like in dedicated e85, but will work well .

After filling tank with e85, and switching to flex tune, did you wait and idle car for 10 minutes revving before driving? If not this may be the reason the car computer is not learning that fast. You need to do that for the learning procedure, everytime you switch to flex tune.

This is what I used to do when I had my 2015 GT.

The first time I filled up with E85 I let the car idle for 10-15 minutes with some slow revs and then drove it around for about 20 minutes until it "learned". However, with the latest fill-up (~15 gallons of E85), I didn't follow the same procedure because it was the second tank in a row of E85. I'm at 200 miles on the tank and it still hasn't "learned" according to the PID and content is sitting around 67% but fluctuates. I really don't like the idea of having to waste 10 minutes idling/revving if that's what's required on each and every trip to the tank.

 

[PaddyPrix]

The first time I filled up with E85 I let the car idle for 10-15 minutes with some slow revs and then drove it around for about 20 minutes until it "learned". However, with the latest fill-up (~15 gallons of E85), I didn't follow the same procedure because it was the second tank in a row of E85. I'm at 200 miles on the tank and it still hasn't "learned" according to the PID and content is sitting around 67% but fluctuates. I really don't like the idea of having to waste 10 minutes idling/revving if that's what's required on each and every trip to the tank.

I used my Flex tune just once, 2 years ago to finish off the tiny bit of whatever gas it had in there, and never looked back, putting on the e85 race tune and going full-time e85 since. Now I just pour in a 5g jug and hurt people's ears and feelings. Do you test your fuel before/as it's going in? There's no guarantee that your e85 is actually 85% ethanol. There are glass bottle testers (boost monkey makes one) where you've got a little pipette, squeeze in a little bit of e85, and then pour in some water, shake it up, and wait a few seconds for it to settle. The alcohol and water separate because of their different densities, and you're left with a solid line, and against some hash mark lines should show what you're then about to add in. If you're in SoCal, you're likely spoiled by Pearson and Propel who are consistently 86-88% for the 2 years and 10k track miles I've put on them, to the point where I've stopped checking, because I hit the same exact gas stations on the way to the track.

I've heard horror stories from other people where it can be as low as 55-60% at times depending on the season, quality, etc... so yeah, you put in 15 gallons, but what a shitty 15 gallons they were, and if that's the case, your EtOH% might be correct.

 

[Kennysum1]

Mapcos around me have great E85. Tested them multiple times and always around above E80. Most of the time right in the middle of E80 and E85

 

[txpat3]

I used my Flex tune just once, 2 years ago to finish off the tiny bit of whatever gas it had in there, and never looked back, putting on the e85 race tune and going full-time e85 since. Now I just pour in a 5g jug and hurt people's ears and feelings. Do you test your fuel before/as it's going in? There's no guarantee that your e85 is actually 85% ethanol. There are glass bottle testers (boost monkey makes one) where you've got a little pipette, squeeze in a little bit of e85, and then pour in some water, shake it up, and wait a few seconds for it to settle. The alcohol and water separate because of their different densities, and you're left with a solid line, and against some hash mark lines should show what you're then about to add in. If you're in SoCal, you're likely spoiled by Pearson and Propel who are consistently 86-88% for the 2 years and 10k track miles I've put on them, to the point where I've stopped checking, because I hit the same exact gas stations on the way to the track.

I've heard horror stories from other people where it can be as low as 55-60% at times depending on the season, quality, etc... so yeah, you put in 15 gallons, but what a shitty 15 gallons they were, and if that's the case, your EtOH% might be correct.

Judging by the gas station I’ve used for E85 the last 2 fill-ups, I’d say it’s closer to 75% which is what worries me about swapping to the dedicated E85 race tune. To answer your question though, no I have not tested it myself - going off what the Nguage says.

Just seems to be a disconnect out there in regards to the “safety” of using the flex tune every day. With my lower quality E85, I’d prefer to keep it on the flex tune but if it’s only meant as a transition tune as Lund states, I may need to go back to the 91-93 tune. I’ve got the authority on one hand telling me to only utilize the flex tune for transitioning between gas and others that seem to run the flex tune 100% of the time.

 

[onlyturbo]

You only have to do the 10 minutes idle/rev wait learn the first time you switch to a different gas blend and tune, and back to flex, as long as you use the same fuel afterwards.

Not sure why they are telling you this is only a transition tune, as far as I understand and know you an run flex indefinitely this way.

Did you call the tuner directly to speak with them? Maybe you should do that so you can put this to bed.

E85 is fun, but a pain because you burn 30% more fuel, so you visit the gas station more often.

 

[txpat3]

Tuner said it may not “learn” the ethanol percentage but suggested going forward with the e85 tune. My AFR at idle is 10.8. I believe the tune is still ok to use as long as ethanol content is 70-75% or greater. Is my AFR indicative of a high enough ethanol content since the nguage doesn’t want to complete the learning process?

 

[PaddyPrix]

Tuner said it may not “learn” the ethanol percentage but suggested going forward with the e85 tune. My AFR at idle is 10.8. I believe the tune is still ok to use as long as ethanol content is 70-75% or greater. Is my AFR indicative of a high enough ethanol content since the nguage doesn’t want to complete the learning process?

That's probably something to ask him, perhaps it's by design (I'd hope not). I'm idling between 9.6-9.9, and when I go full ham I sit low 9's, that being a point higher makes me wonder why they'd want you running so lean... similar to a 16:1 in a regular gas car.

Sponsored