Adjusting ignition based on fuel composition & temperature

[grippo]

There is capability for entering a table of ignition advance vs coolant temperature and there is a spark correction vs fuel composition. So this would allow you to have a cold advance table that would add advance when cold, but the spark correction would then subtract out some of this advance for alcohol which burns faster. This would give you some control in the way you want, but there is no 2-dimensional table of spark vs coolant vs fuel composition, which would give you even more control, but would require a lot more tuning.

[S.Bretz]

Grippo, do you have any recommendations for timing retard with e85 other then the conservative -13 degrees that set when you activate the flex-fuel?

I found an article where aviation grade e85 (AGE85) was used and tested against low-lead 100 in the ame engine.
The engine made about 3% more power with the e85, but they had to pull out 5 degrees of timing. If you do a stright linear interpotation, this would be -6 degree retard with 100% ethanol.

Does 6 degrees still sound like a safe level.

[grippo]

I don't have any first hand experience with e85, but if I were using it I would find out the combustion rate of alcohol vs gas and scale the timing according to that as a first guess.

[S.Bretz]

ummm....

We..I guess I just have to find out. I found an eddy-brake dyno in my area and was just trying to save some time @ the high rates they charge.

I have been searching around and have found some interesting and varing results, but they just don't seem to logically make sense.
Some people claim that they can add 5-10 degree IN, other say to tune with 105 octane unleaded and just use the same timing numbers. I have found people claim that they lost power (well, et and mph in the drag, that not too convincing to me) by advancing or retard the timgin off of what worked great with 93 octane unleaded... but then agian I found a published paper in a database that claimed their engine needed 5 degreed retard.


The plan is to load the car up with the e10 that is availabe. I plan to load it around 4K-4.5K on low boost (10-12psi). I can adjust up the timing and fuel with the e10 until the eddy current is the max to hold it at that rpm and map bin. Then fill the tank with as much e85 as I can get in there, then back the timing off with the retard feature in the FF window, then add in timing until I get to the same power level +/-2% .