Another e85 thread.

[NGOT8R]

Timing aside, what about o2 sensors? Do they still read correctly or will you car show it is running rich on e85.. with the flex tune?

Mine read correctly and I’m sure most everyone else’s do too, unless of course someone has an exhaust leak.

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[PaddyPrix]

Timing aside, what about o2 sensors? Do they still read correctly or will you car show it is running rich on e85.. with the flex tune?

These simply report the number, but to only tenths precision. I'll sit and idle between 9.7 and 9.9 all day long with mine.

 

[NGOT8R]

This will shed some more light on the subject.

 

[LOL WUT]

Okay let’s break this down simply.

91-93 octane tune = run respective octane

Flex tune = run whatever you please from 91 all the way to straight pure E85. The tune will adjust for whatever fuel or mix of fuel you have in the tank.

Dedicated E85 tune also known as E85R tune = Run quality E85 with a verified E content of ideally 85%. Some tuners may have a safety net to allow you to run as low as E70 on these tunes. You need to verify with the respective tuner on that.

 

[fMErunnin]

Thanks and maybe we need an e85 sticky with the plethora of info?

 

[BoostN IT]

Can you mix E85 and 93 with no special tune?

No special tune = 91 or 93
Flex Tune = 91 or 93 or E85 (Doesn't Matter)
E85 tune = E85 only (You can give or take a little ethanol does not have to be right at 85%)

 

[Nuked]

These cars run in closed loop 95% of the time. What that means is the computer is always adjusting fuel to hit the desired AFR via the wideband oxygen sensors. This is shown as short term fuel trims (STFT), that is the real time adjustment. Over time that number is logged as a long term fuel trim (LTFT). The LTFT is applied based on rpm and load. When you do a KAM reset, LTFT is cleared to Zero. When you enable the flex fuel logic, it has a gas tank refill threshold that puts it into a learning mode. In the learning mode it analyzes the AFR and based off of that it infers the ethanol %. There is no timing modifier based off ethanol content. The only thing the flex fuel tune does is set the stoic point for the fuel. Every tuner is going to go about timing differently, but the most common way is to let the knock sensors add timing up to a hard cap. On the E85 tune, the stoic is set for 85% ethanol. Being that it is only to be used for E85, the tuner can add timing to the borderline (base) timing tables, while still allowing the knock sensors to add/remove as necessary.

 

[cbrtrx]

These cars run in closed loop 95% of the time. What that means is the computer is always adjusting fuel to hit the desired AFR via the wideband oxygen sensors. This is shown as short term fuel trims (STFT), that is the real time adjustment. Over time that number is logged as a long term fuel trim (LTFT). The LTFT is applied based on rpm and load. When you do a KAM reset, LTFT is cleared to Zero. When you enable the flex fuel logic, it has a gas tank refill threshold that puts it into a learning mode. In the learning mode it analyzes the AFR and based off of that it infers the ethanol %. There is no timing modifier based off ethanol content. The only thing the flex fuel tune does is set the stoic point for the fuel. Every tuner is going to go about timing differently, but the most common way is to let the knock sensors add timing up to a hard cap. On the E85 tune, the stoic is set for 85% ethanol. Being that it is only to be used for E85, the tuner can add timing to the borderline (base) timing tables, while still allowing the knock sensors to add/remove as necessary.

Gen 3 does have the ability if calibrated to add timing based off of ethanol content from the inferred value.

 

[Nuked]

Gen 3 does have the ability if calibrated to add timing based off of ethanol content from the inferred value.

Does it actually work? I know the gen 2 has timing modifiers based off of ethanol content, but last time I looked it did not appear to be working. If it does work then just run a flex with the timing multiplier and one should be golden. Really no reason for a dedicated E85 tune at that point.

 

[cbrtrx]

Does it actually work? I know the gen 2 has timing modifiers based off of ethanol content, but last time I looked it did not appear to be working. If it does work then just run a flex with the timing multiplier and one should be golden. Really no reason for a dedicated E85 tune at that point.

It works when calibrated correctly.

 

[Grimreaper]

gen2 does not have the tables for timing adjustments based on ethanol/flex fuel. few creative ways to do it but its dependent on other sections of the tune, not just ethanol.
gen3 does. very jealous of that.

not a fan of letting the knock sensors add until it hits knock with flex fuel like one of the big name tuners does. another big name tuner wont allow timing above gas mbt with flex fuel.

the concern is running pump gas that squeaks by for a pull or two then one bore gets hot and you rattle it hard at peak tq or above in timing that is past the ford set mbt on gas.

i use flex fuel to get to and from the pump when switching. a graduated cylinder/tubing/syringe and 5 minutes of time will have an accurate ethanol content within few tenths of a percent.

older threads on svt sight suggest max benefit from e-fuel ends at 60% even for boosted setups.

if ethanol is truly 113 octane, and the base gas is 84 octane:
60%=101.4 octane
70%=104.3 octane
80%=107.2 octane

all well above the 91/93 pump octane that most of us use that gets us close to mbt as is.

i suspect the biggest reason for warning to use high e content is the stoich value would cause an overly rich condition that the trims would fight none stop. and a bunch of CYA.

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