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E85 Tuning Discussion

L

LapeerGTP

New member
So I'm running E85 in the Grand Prix.. Seems to really like it .

I've been reading up on tuning for E85 and there seems to be a couple different ways to go about doing it.

I personally just offset the IFR table the percentage between stoich of E85 and E10.
This seems to work "OK" but I'm looking at other suggestions. I've heard of adjusting the Base AF ratio to your desired FA but I wasn't sure how things Like PE enrichment are affected.
I'm basically looking for the quickest, most efficient way to go from E85 to E10 and back to E85.
Thanks in Advance.
Anyone have experience in E85 tuning??
 


IFR is the quickest.

You don't need to adjust the other AFRs in the PCM.

If the PCM used equivalence ratio instead of AFR, then adjusting stoich would be easier.

E85 stoich changes all the time anyways. New tune every time the mixture changes.
 
What are the StartUp Enrichment by Coolant Temps Values Represent as it pertains to AFR during startup.. Is it a multiplier or something
 
its adjustment to commanded afr in the form of + or -.

IFR is the easiest and most complete switch between e10 and e85.
 
So if it has a value of 1 in that table then it would run the 14.7 ratio commanded?? if it is a value of 2.5 it'll run 13.2??
 
its an AFR subtractor.

0 is stoich, 6 is stoich-6 and so on.

Then there is delay.

At least in HPT, may be different in DHP.
 


Is there an economic incentive to do this? I heard it is actually more expensive because your efficiency plummets which offsets the lower fuel price. If I'm I'm not making sense, think of it as miles per dollar.
 


Yeah it's the 105 octane.. Under power enrichment you don't have to enrich as much as gasoline either to maintain the same EGT's, that along with being able to run a lot more cruise timing you can get some of the deficiency back... As of right now I've been getting 21-23 mpg with E85.. Best tank with 93 octane was 28..
 
WTF matt werent you and I debating over this tuning method and you were saying the exact opposite? and E85 is not economical at all around here with the drought. E85 is up to 3.30 a gallon here and premium is like 3.80. How are you guys getting over 20 mpg? Ive been calculating it off of how many gallons used vs miles traveled and i can not get over 20, even going 65 on a highway the whole way. I upped my cruise timing to over 40* and lowered my part throttle shift speeds and TC lockup speeds, and even put the stock pulley size on.

The quickest way to tune it is IFR's, but i cant seem to get my fuel trims dialed in (not that i ever could before)
 
Just because its easy doesn't make it correct.

Try running open loop, then you're not at the mercy of your narrow band, but instead the mercy of your wide band.

I've seen rigs from other platforms where they measure the E85 to determine that tanks precise mixture, then adjust fuel for that setting.

IMO, E85 seems like a giant headache for a daily driven vehicle unless you're running a flex fuel system.

Before you ask: I can't see it working. Our CKP system is 3x 18x, 3500 impala (E38 pcm IIRC, flex fuel compatible) seems to only have one CKP signal, and a different firing order.
 
JoRoW99 said:
WTF matt werent you and I debating over this tuning method and you were saying the exact opposite? and E85 is not economical at all around here with the drought. E85 is up to 3.30 a gallon here and premium is like 3.80. How are you guys getting over 20 mpg? Ive been calculating it off of how many gallons used vs miles traveled and i can not get over 20, even going 65 on a highway the whole way. I upped my cruise timing to over 40* and lowered my part throttle shift speeds and TC lockup speeds, and even put the stock pulley size on.

The quickest way to tune it is IFR's, but i cant seem to get my fuel trims dialed in (not that i ever could before)
Click to expand...

Open loop.

I was seeing 29mpg @ 75 with cruise held down on E28 blend running high 30's timing.. same tune more or less ran 31.5mpg @ 75 on E0 93 -- Figure a 7-8mpg drop from E0 to E85 and low-mid 20's mpg highway is a real possibility with the right tuning scheme.
 
I checked my mileage with miles driven vs fuel used.. It's only been 2 tanks on the new motor on E85. I have headers, S1x cam, High Comp Pistons, 3.4 pulley, no cat, no egr, and vr1 10w30 oil.. I drive mostly 2 lane roads and highway to and from work..
 


You should be comparing E85 to race gas, a full size intercooler, meth setup, not 91/93 gas. It's a MINIMUM of 105 octane and gets to be about 109 full blend but has the characteristics to be very competitive with C16 when used wisely. E85 can replace a full size intercooler but comes with some drawbacks and that is it needs a bigger fuel system, gas mileage is reduced. Anyone who is running E85 and overly concerned with gas mileage shouldn't be running it all the time.

Without the 10-20% ethanol blend in regular/some premium gas the price of that fuel would go up 40-60 cents. It's used as an octane adder which would normally be toluene, trimeth and a few others. The problem is that those additives are very expensive, ethanol is less.

The main problem with ethanol is the misinformation.
 
FoSHO99 said:
You should be comparing E85 to race gas, a full size intercooler, meth setup, not 91/93 gas. It's a MINIMUM of 105 octane and gets to be about 109 full blend but has the characteristics to be very competitive with C16 when used wisely. E85 can replace a full size intercooler but comes with some drawbacks and that is it needs a bigger fuel system, gas mileage is reduced. Anyone who is running E85 and overly concerned with gas mileage shouldn't be running it all the time.

Without the 10-20% ethanol blend in regular/some premium gas the price of that fuel would go up 40-60 cents. It's used as an octane adder which would normally be toluene, trimeth and a few others. The problem is that those additives are very expensive, ethanol is less.

The main problem with ethanol is the misinformation.
Click to expand...
105 when it's E79 or higher.

E70 (E68) is less though.
 
Ok, the actual octane rating of e85 (assuming it is actual 85% ethanol) is only about 96 AKI (its 105 octane in the RON scale).... which is the scale that the US and Canada use for their octane rating (RONxMON/2)...

the reason it seems like a higher octane is because it burns a lot cooler than regular gasoline..

In regards to the mpg (or mpd in this case) you have to consider your driving habits more than anything. first off, with e85, you should really be tuning in open loop if you can. This will save you some highway (and city for that matter) mpgs. I get about 23-24 (91 premium was 28-29) mpg on the highway running 50* of timing with an average afr (gas afr that is) of ~16/1. Around town I get just under 20mpgs (91 premium was ~21) with about a 15.5/1 afr. So as long as your % mpg loss isn more than the % difference in the price of premium youre still going to be saving money but each person will have different results pending.

But in the end you dont get e85 for the economical factor anyway... and if you do most of your driving around town youre not gonna lose that much mpg anyway... just the biggest hits on the highway...
 
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