LIVERNOIS FLEX TUNE

[engineermike]

@engineermike thanks again for your knowledge. Can you explain further how a flex tune works? I understand that the ramps are different on a flex tune vs a straight E85 tune, but I admittedly do not fully understand other effects of using a flex tune. I personally did not want to take the chance of using a dedicated e85 tune based on the pump variations. Was that a miscalculation on my part?
Thanks.

I was about to write a long explanation pertaining to Gen3 F150 because they have the best OS for managing flex. I see you have a GT350, which has "different" capabilities in that arena. Are you asking about the Gen1 GT350 specifically, and how does Livernois do it? Or in general?

Sponsored

 

[engineermike]

...I personally did not want to take the chance of using a dedicated e85 tune based on the pump variations. Was that a miscalculation on my part?
Thanks.

Specific to this question, pump E85 could be 51% or 85% or anything between. For NA, the borderline spark timing will be basically the same whether it's 51 or 85%, so you need not sweat minor timing differences. If an NA engine doesn't knock on 85%, it won't knock on 51% either. The fuel trims will be a bit different, but if the tune is set up to be 67% with 0 fuel trims then the trims will still be in an acceptable range whether its 51 or 85.

That said, once I figured out how flex works, I was thinking it actually makes sense to run a flex tune all the time whether on pump gas or e85. It works by adjusting stoichiometry until the STFT are near 0 in the 10 minutes or so after a refill. This could work to your advantage whether you're always on pump gas (by keeping fuel trims close to 0) or always on e85 (adjusts for minor differences and also keeps fuel trims close to 0).

 

[Mjc1241]

Yes if

I was about to write a long explanation pertaining to Gen3 F150 because they have the best OS for managing flex. I see you have a GT350, which has "different" capabilities in that arena. Are you asking about the Gen1 GT350 specifically, and how does Livernois do it? Or in general?

Thanks for the explanation. Glad that l made the decision to go flex tune based on your findings.
How does a flex tune work on a Gen 1 GT350 if there is a difference than what was outlined above.

 

[engineermike]

Yes if
Thanks for the explanation. Glad that l made the decision to go flex tune based on your findings.
How does a flex tune work on a Gen 1 GT350 if there is a difference than what was outlined above.
Thanks

Assuming your tuner used the Ford logic as best he can, it works the same way.

When you refill the fuel tank, it restarts the learning process. It locks the LTFT at their prior values until the learning is complete (matured). Then it adjusts the stoichiometric ratio until the STFT are near zero. It checks to see if they the adjustment has stabilized and locks into the learned value. However, it will delay maturing until the fuel in the fuel line is used up by the engine.

The learned stoichiometric ratio is then converted to a percent ethanol with a simple lookup table. The ethanol percent is used in many places to "weight" the normal vs FFV tables. So something like cranking fuel, only a small difference needs to happen when ethanol percent is modestly increased over gasoline. However, with something like spark timing, a little bit of ethanol goes a long way. As such, there are something like a dozen different weighting curves that are applied, depending on what aspect we are dealing with at the time. For cranking fuel, the FFV table could be weighted very mildly at 30% ethanol, but for spark timing the FFV table could be weighted heavily at the same 30% ethanol.

In the gen3 there are a huge number of tables that you can adjust as a function of Flex learned ethanol. You can change the obvious things but also a ton of not-so-obvious things like GDI pressure, min lambda, inferred EGT, etc. You can modulate boost, even, as a function of ethanol. In my Roush truck, I have it capped at 8 psi boost on gasoline and 14 on e85, all managed by the stock OS. The gen2 is a bit more limited and won't even allow you to adjust spark timing as a function of ethanol, which is a travesty. However, gen2 will allow modulation of load vs ethanol%, though it appears HPT didn't define these parameters in the mustang. The gen1 GT350 appears to be lacking ethanol timing adjustment, but does appear to have load limiting vs ethanol though it's also not defined in HPT.

This is how the Ford logic works. For something like canbus flex by PCMTec it's totally different.

 

[Mjc1241]

Thanks for breaking it down for me. Interesting that Gen 1 GT350 and Gen 2 GT350 ECMs are different and/or have different logic.

 

[engineermike]

Thanks for breaking it down for me. Interesting that Gen 1 GT350 and Gen 2 GT350 ECMs are different and/or have different logic.

Sorry, I should have been clearer. I meant gen2 coyote. However, the gen2 GT350 went to the 4 knock sensors so I have to believe they switched to some of the Bosch knock sensing and control. I haven't dug into that rabbit hole though.

Sponsored