Some S550 Flex Fuel Questions

[doc350]

I have a friend with a 2015 S550 Mustang that currently has a Kenne Bell 2.8 with a trunk mounted ice box and American Racing long tube headers on it. We are now installing a Fore triple pump hat and complete return fuel system, along with a set of ID1050x injectors. the plan is to run a smaller pulley and e85.

It seems like the Ford Flex Fuel strategy is quite a bit different from the GM cars I've done in the past. I have read a bunch of threads on it and I think I understand most of it, but I want a little bit of clarification.

Fir the actual Flex Fuel settings, I copied the values from a F150 that had it enabled from the factory. Here is what I came up with. Is there anything I need to do to make this work correctly in the Mustang?

FF Tables.png

The main area where I'm a little fuzzy is adding ignition timing. The GM cars have an actual Flex Fuel Advance table that it adds from, but I don't see anything like that in the Mustang file. Is the timing added automaticly via the knock sensors? What does the "Flex Fuel Blending vs. Ethanol %" table blend together? I couldn't find any relevant information in regards to that.

I attached the tune I am working with for anyone to take a look at. All it is at this point is the file that comes with the Kenne Bell kit that I changed to accommodate the boost referenced return fuel system, the larger injectors, and flex fuel. It's really just something to get the car running once all the parts are done being install.

2015 GT KB_ID1000_Flex Fuel_Fore.hpt

[tbrtuning]

Not missing anything as far as spark goes. 15-17 Mustangs don't seem to have good flex fuel modifiers for spark so you basically have to free up knock sensors to add a lot and not cap it. I don't typically like letting 93 add to MBT depending on setup but if knock sensor sensitivity can be left near stock I think it's fine.

I really prefer if customers have a way to switch tunes to run different tunes on these because it can give more safety on 93 by limiting how high timing can go and let you ramp in timing quicker on E85.

[Jn2]

I normally recommend against using the flex fuel logic with boosted cars, it's inferred and the chance or engine damage is greater if it infers the incorrect ethanol percentage when boosted then when NA. Make your friend a dedicated e85 file so he can run e85 100% of the time or make him a 93 octane file. If you do decide to use the flex logic, make sure that your fuel trims are +/- 3%, this way you are more likely to infer the correct ethanol percentage. How ever due to how it's inferred it will never be 100% accurate on the first fill up since the left over fuel in the lines and tank throw it off during the learning period.

[tbrtuning]

On a 15-17 car where you aren't adding timing based on ethanol content there's not so much risk... It's essentially just a long term fuel trim with very few changes based on it. Maybe if you want to run leaner on E85.

[doc350]

Thanks guys.

I think what I'll end up doing is writing a Flex Fuel tune for his low boost pulley that he can run around on the street with, and then a dedicated e85 only tune for his 15psi pulley for when he goes racing. That seems to me like the best/safest course of action.

[tbrtuning]

That's a good idea. On the dedicated E85 tune you don't need to keep Borderline low and let it add timing so seems to be a decent bit more responsive that way.

Not sure if you've tuned one of these cars yet where the MAF is out of calibration some but they are very fast to use the widebands and correct so you don't really have to worry about being in E70s or something like that on E85 tune. It will barely go rich before STFT brings it back where you target during a pull.

[Kcc0521]

That's a good idea. On the dedicated E85 tune you don't need to keep Borderline low and let it add timing so seems to be a decent bit more responsive that way.

Not sure if you've tuned one of these cars yet where the MAF is out of calibration some but they are very fast to use the widebands and correct so you don't really have to worry about being in E70s or something like that on E85 tune. It will barely go rich before STFT brings it back where you target during a pull.

I am having a similar issue with my car right now. I am running return setup and a Paxton on e85. The AFR looked good and I flashed a new tune to update the 5th gear shift and the car is way rich now. I am on the same fuel and one run shows the LTFT at WOT to be .85 and lambda was .78 and after the tune update the LTFT is 1 and Lambda was .70-.74. Any idea why this happened or what to log or look for?

[superman07]

I am having a similar issue with my car right now. I am running return setup and a Paxton on e85. The AFR looked good and I flashed a new tune to update the 5th gear shift and the car is way rich now. I am on the same fuel and one run shows the LTFT at WOT to be .85 and lambda was .78 and after the tune update the LTFT is 1 and Lambda was .70-.74. Any idea why this happened or what to log or look for?

Flex fuel tune? After you flashed did you let the ecu relearn the alc percentage?

[Kcc0521]

It is not flex fuel tune. I heard it is not good to use flex fuel on forced induction. My LTFT on that tune were around were pulling about 15-20% of the fuel before the tune.

[Thatwhite5.0]

Every time you flash the car, the LTFTs are reset. I can't see the LTFT pulling fuel with a .7 lamda.

I'd do the dedicated e85 tune as well. Flex fuel logic does work on the s550s. The sn197s need blank spark tables populated.

I disabled my LTFT a long time ago and never looked back.