Comp ratio on E85

[anders]

Hi!
Have someone run 9.7:1 CP on E85 or will it be to high.

 

[dank GN]

E85 loves compression ,timing and boost . I Learned the hard way and melted a piston because my EGTs where super high . With e85 you have to raise the timing to lower the EGTs . You usually want to add 5-6 degrees so 25-26 * WOT is what I'm runing

 

[dank GN]

And 9.7 isn't high FYI 10:1 would be a great compression ratio with built internals in my opinion

 

[anders]

Ok thanks !

 

[bison]

Opinions may vary but I wouldn't use the above timing recs on e85 if you plan on running it hard unless you want to have an expensive molten ball under the hood! You should be running the least amount of timing you need to get most of the power available. If you are running 18 and it picks up 3 hp going to 18.5 and loses 15 dropping to 17 then you know you are close at 18. Timing is the biggest timing obstacle in most engines. I see so much damage due to poor timing schedules I don't even want to think about it. Without knowing the drive pressure, cam data and having some experience I wouldn't be increasing the CR too much either. Run a larger hot side on the turbo. Cylinder pressure will get you in trouble. Fill the cylinder before you worry about increasing the pressure in it.


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[Nick Micale]

From our experience from a few e-85 GN's and my race car, 9.7:1 will do fine, but we keep timing low around 19-21 degrees.

You do not need or want high timing especially at WOT with that compression ratio. Works well for me as I can run high 9's with 16-18 PSI using a 70mm turbo.

 

[anders]

Ok,i will start safe on the dyno ,i just wanted to now if the CR was way off,i have the 224/224 cam

 

[dank GN]

I'm just curious guy maybe it's my motor but when I was runing 19 degrees and 20 lbs my EGTs where around 1600-1650 when I started to add more timing 24-26.* @ the same boost level my EGTs came down around 1500-1550*F ?

 

[Nick Micale]

We set up my basic tune of the race car on the dyno, and dialed it in with many passes at the track.

The EGT is not what we use for tuning? Since we want to optimize WOT, actual and target air/fuel ratio are very important data points we use.

At the track the MPH number is telling us the HP, and using the same procedure which Bison stated, we increased timing to see if it helped or not in the range I was dialing in the car.

It took 3 or 4 track sessions with many passes to optimize the tune. A tuner friend out of state is the lead we followed as he has done many 800 HP street tunes on e-85, and we followed his advise to the letter.

The results with my car is that I can run faster with e-85 vs.116 octane race fuel, and actually with less boost!

 

[forcefed3.8's]

25°timing on accident and 28psi on a high 9 sec car popped a headgasket.
I run 10.25:1 compression and 32psi with 18° timing on e85.

 

[dank GN]

What else is strange is with the SD2 chip he is adding about 5* of timing at WOT with the flexfuel option If you look at the spark adder table srait from Eric or at least mine came like that

 

[BEATAV8]

What else is strange is with the SD2 chip he is adding about 5* of timing at WOT with the flexfuel option If you look at the spark adder table srait from Eric or at least mine came like that

yep gotta zero that guy out unless you want to go full flex fuel capable.

 

[forcefed3.8's]

What else is strange is with the SD2 chip he is adding about 5* of timing at WOT with the flexfuel option If you look at the spark adder table srait from Eric or at least mine came like that

That is what screwed me. I had the timing I wanted in the table, then after going over the log, saw 25°. By then the cooling system was pressurized and the gasket was done.

 

[dank GN]

I am using that table and have had no problem using those numbers . If those numbers where super high and could do damage I don't get why he would load such high numbers in there . I know ERIC has more tuning skills then the average bear

 

[forcefed3.8's]

That is way too much timing for any fuel at 28lbs. I have more tuning skills than the average bear too. I overlooked that this table was active and didnt realize it was adding timing until it was too late. You might be able to get away with it with a high 10, low 11 sec car, but a high 9 sec car isnt going to tolerate it.

 

[Eric Stage I]

The default flexfuel timing table is just an average starting point for most cars. It needs to be evaluated for each individual car when creating the tune. Like forcefed said, the default is more for a mid 10 and slower car (and typical compression ). Bob and I have talked about zeroing out that table as the default.
Sorry about your head gasket forcefed!
Eric

 

[dank GN]

Copy that I can see where u r coming from guys as every motor is different . So where would you guys set your timing to with 85% ethonal to start tuning 17-18*? And sorry Anders for jacking your thread up but all these guys know a lot more about tuning these motors then myself so disregard my statements .

 

[forcefed3.8's]

This was on a 8.5:1 engine.

 

[forcefed3.8's]

It depends on boost level. I would run in the 20s at lower boost.

 

[bison]

Copy that I can see where u r coming from guys as every motor is different . So where would you guys set your timing to with 85% ethonal to start tuning 17-18*? And sorry Anders for jacking your thread up but all these guys know a lot more about tuning these motors then myself so disregard my statements .

Believe it or not I start even lower than that when over 80lbs/min and on pump e85. If it's e85 out of a sealed can that is mixed with high octane I have other strategies I use. I'd rather be chasing timing rather than pulling it. The cylinder pressure is the problem. Timing equals cylinder pressure. I agree with you based on your high egt though id want 100% verification of base timing and to know exactly what fuel i was in the car before I was questioning my timing strategy. I had an engine that wouldn't run for crap with low timing. It was 7.5:1 with a crappy set of iron heads. It needed 22-24* of timing or it lost a bunch of power. I had about 200 dyno pulls on it so I know I had the timing dialed in over the entire map. The quickest it ever went was 10.60.