Flex Fuel Tune Question / pros cons

[stannypack]

Been researching e85 for my stock 22 GT (besides exhaust), and it looks like all I need is 1) tuning device 2) flex fuel tune.

There's only 1 station near me and I've never tested it, plus I don't want to get stranded somewhere. And I read it's good to clean everything out every once in a while so I can run 93 to flush the system occasionally?

Lund used to offer a flex fuel tune but doesn't anymore, anyone know why? And who should I go with now? I know about not letting it sit for a long time, but is it safe in general to run a flex fuel tune long term (corrosion etc)?

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[Joshinator99]

Been researching e85 for my stock 22 GT (besides exhaust), and it looks like all I need is 1) tuning device 2) flex fuel tune.

There's only 1 station near me and I've never tested it, plus I don't want to get stranded somewhere. And I read it's good to clean everything out every once in a while so I can run 93 to flush the system occasionally?

Lund used to offer a flex fuel tune but doesn't anymore, anyone know why? And who should I go with now? I know about not letting it sit for a long time, but is it safe in general to run a flex fuel tune long term (corrosion etc)?

Most modern vehicles are good to go with E corrosion-wise, so I wouldn’t sweat that. Juggernaut is doing flex tunes for non-boosted applications. I just ordered one up for my ‘22 as well and will let you know how it goes (if the rain ever stops in New England).

 

[CR151S]

I haven’t really found a downside with my flex tune. It’s great to jump back and forth.

I had a local reputable tuner do mine. Not sure where NOVA is but you might find someone near you?

The car is beastly on e85. Have fun!

 

[K4fxd]

At one time Lund was the go to for coyote tuning, like the Rabbit they (Lund) took a nap and all the turtles passed them by.

 

[stannypack]

So much conflicting info... I read some people mention flex should only be used when transitioning since itlearns the ethanol content too slowly and then you're too rich or too lean? or is that only an issue in the first 15 mins after you get gas you just have to take it easy while it "adapts"

 

[CR151S]

So much conflicting info... I read some people mention flex should only be used when transitioning since itlearns the ethanol content too slowly and then you're too rich or too lean? or is that only an issue in the first 15 mins after you get gas you just have to take it easy while it "adapts"

The car adapts and I don’t go WOT for about 10 min of driving after switching from e to 93

 

[engineermike]

I’ve been testing flex tuning on my 2018 Whipple setup lately. The issue with transitions isn’t necessarily that it will run lean or rich before it learns when switching fuels. The STFT will generally keep lambda where it wants it.

It works by driving the fuel trims down to zero by changing the stoichiometric a/f ratio value it uses to calculate fueling. So when e85 first hits the rail, the STFT increases to 20-30%. Then the learned inferred stoichiometry starts falling until the fuel trims are very low. When it stabilizes, it “matures” and ceases learning until you add fuel to the tank and the process starts over again. From the inferred stoichiometric lambda, it looks up an ethanol % in a table. That value is then used to change engine efficiency, cranking fuel, and a dozen other things in the calibration.

Some operating systems, such as gen3 f150 and Whipple, have a table that adds timing as a function of alcohol percent. This is really a nice feature. While flex fuel can be enabled on a gen2 coyote and ecoboost, they won’t add timing as a function of ethanol. I’ve set mine up to not add any timing until the inferred ethanol exceeds 55%. This adds some safety to the transitions.

The issue I’ve been working through is that it “matures” too soon. When I fill the tank and switch fuels, it generally takes 3.5-4 minutes of normal driving before the new fuel reaches the engine. In the right conditions, it only takes 2-3 minutes for it to “mature”, so it stops learning before the new fuel has even reached the engine. I could disable the maturing function completely but this isn’t really the right answer either.

 

[CR151S]

I’ve been testing flex tuning on my 2018 Whipple setup lately. The issue with transitions isn’t necessarily that it will run lean or rich before it learns when switching fuels. The STFT will generally keep lambda where it wants it.

It works by driving the fuel trims down to zero by changing the stoichiometric a/f ratio value it uses to calculate fueling. So when e85 first hits the rail, the STFT increases to 20-30%. Then the learned inferred stoichiometry starts falling until the fuel trims are very low. When it stabilizes, it “matures” and ceases learning until you add fuel to the tank and the process starts over again. From the inferred stoichiometric lambda, it looks up an ethanol % in a table. That value is then used to change engine efficiency, cranking fuel, and a dozen other things in the calibration.

Some operating systems, such as gen3 f150 and Whipple, have a table that adds timing as a function of alcohol percent. This is really a nice feature. While flex fuel can be enabled on a gen2 coyote and ecoboost, they won’t add timing as a function of ethanol. I’ve set mine up to not add any timing until the inferred ethanol exceeds 55%. This adds some safety to the transitions.

The issue I’ve been working through is that it “matures” too soon. When I fill the tank and switch fuels, it generally takes 3.5-4 minutes of normal driving before the new fuel reaches the engine. In the right conditions, it only takes 2-3 minutes for it to “mature”, so it stops learning before the new fuel has even reached the engine. I could disable the maturing function completely but this isn’t really the right answer either.

that’s really helpful info!

 

[Dinokill3.7]

I have been running e85 on my 2017 GT from Lund for a year and a half. I do have the Flex tune but I had only used it about 4 times total(When going on a long trip and I know there is no e85 on the way) luckily I have a e85 station between work and home and always tests 80% or more.

Pros of e85
-More power/torque down low
-Cheaper than 93

Cons
-More visits to gas stations since MPGs drops considerably
-Not many gas stations offer e85

 

[ZXMustang]

https://www.mustang6g.com/forums/th...arns-e85-with-a-flex-tune-step-inside.187945/

 

[GR8 V8]

Lund used to offer a flex fuel tune but doesn't anymore, anyone know why? And who should I go with now? I know about not letting it sit for a long time, but is it safe in general to run a flex fuel tune long term (corrosion etc)?

I recently asked Lund to update my Flex Fuel and e85 for my 18 manifold swap. They gave me the updated e85 but not the FF. They said that the FF was a free tune they offered when I first purchased the e85 tune. However, i can now purchase their PCMtech multi tune for an additional cost which has the Flex Fuel in it. Now this is the interesting part. My N gauge always learned the alcohol content which worked well. I would also test with a tester just to be safe In order to go from FF to e85. Easy process right? Sure is. I questioned Lund on how to test the amount of alcohol in the tank with their new PCMtech multi tune and was told to disconnect the fuel line in engine and use a test kit. ARE YOU KIDDING ME? Kinda sounds like we’re going the wrong direction here.

Flex fuel tune is a great tune indeed. Find a tuner that offers one. One tuner that offers this is Shaun with AED. More info at aedhp.com.

 

[stannypack]

Thanks all for the info, wish there was a dedicated/stickied guide to e85 for noobies like me lol. It looks like a flex fuel tune is fine and the biggest "issue" people talk about is the learning part. I'd only be pumping 93 occasionally to "flush" the system.

I also came across this https://www.advancedfueldynamics.co...lex-dx-for-2018-23-5-0l-mustang-gt-and-mach-1

which says no tune required and looks more "oem", any thoughts on that?

 

[Mikepol2]

I was in the same boat as you and ended up with a Livernois flex tune. Makes the car feel more lively and responsive.

The learning process took about 15-20 minutes to settle out. If your car has air/fuel ratio gage capability, display it and you can watch it gradually change during learning. Mine started out around 14 and settled out around 10.

You can go to this site to find flex stations near you (it says E85 but I think it really means flex):

https://afdc.energy.gov/fuels/ethanol_locations.html#/find/nearest?fuel=E85

My programmer is reading about E77 most of the time, pretty high considering the pump advertises something like 51-83.

 

[ChitownStang]

I’ve been running Livernois Flex tune on my 21 Mach 1 for about 9 months, 6k miles now.
Runs perfect.
Pulls hard and has much more torque down low.
I run 93 in the winter here in Chicago because I don’t need the extra power, car may sit a week sometimes, and it doesn’t start well in the cold.
My local gas station which is a mile from me tests at E70 consistently.
Another thing I love is that the tail pipes never have carbon buildup when running the clean E!

 

[K4fxd]

The issue I’ve been working through is that it “matures” too soon.

I just increased the time for it to learn parameters. The only problem so far is if set too high I need to drive on the freeway for several miles.

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