Maximum Brake Torque (MBT) timing for E85?

[JayRolla]

Just wondering what the e85 users out there have found to be the best MBT. I have know a few people at a local shop that has tuned a lot of cars on dynos finding mbt on race fuel to be around an average of 22*, give or take a few depending on the car.

Now e85 burns slower so it can handle a higher timing to get the same burn from what Ive researched. On the link forums people are running as high as 28*.

So people that have actually dynoed what have you found to be mbt running e85?

Thanks.

 

[Black_Bullet]

Its going to be different from car to car, especially with different mods/ altitudes etc.
Rule of thumb, just go to the dyno and in your case, start with your base timing at like 0*, then do a dyno pull, then advance your base timing 1* and log how much ign timing increases, while also factoring in the gains on paper. Keep advancing base timing until you are no longer gaining 9-10ish awhp per deg of timing.
Once you've advanced far enough to were your only getting 2-3awhp per timing deg then you've found point of dimishment and going any further will begin to lose power while amplifying motor stress.

What other people run for timing will only give you a general ball park figure but doesnt mean it will work for your application even if the comparisons are similar.

I have heard that E85 burns slower and that more timing is needed, but at the same time, there are other variables that affect how it burns also, consider your 2g compression ratio and what AFR your running as well.

FWIW, personally Id imagen an ideal tune on your e316g car would be say 28-24 psi
12.1 afr, 18deg timing around 4k-ish advancing to around 21degs around 5500 ish, then peaking at 24 degs by redline with dsmlink to do the tuning and a pair of 272 camshafts for the cherry on top! You should reach very decent numbers like that long as theres no boost leaks or other factors hurting your power production!

 

[JayRolla]

I do know if verys from car to car. But most of the time it will be pretty close. Most people will make power up too 22*. MBT on our cars is a lot more consistent than you think when running high octane fuel. I dont know about doing that at the dyno, since my CAS is a pain to move and I only will have an hour at the dyno. Dont want to pay more money bye running out of time. With my 3.5" gm maf, I have to pretty much remove the UICP just to get the CAS loose. Takes a lot more time than you think to adjust it. Ohh and 12.1 is way to lean, I dont care what anyone says. Jack has seen burnt valves at lean afr's like that.

Again still want to know what people have found to be mbt on e85.

 

[Black_Bullet]

If your saying how slow e85 burns why would 12.1 be too lean. Good C16 tunes are leaner than that..
Cant be as harmful as the cylinder pressures of running over 30psi with over 26 degs of timing at WOT.

 

[JayRolla]

that is true. Ive burnt a valve before so I'm scared of lean afr's. I guess once I blow a HG then I will be scared of the timing.

 

[Chiefsublime]

E-85 Has a stoichiometric A/F ratio of 9.8526:1. So I'd say that's pretty lean.

 

[99dsmer4g63]

This thread is from 2008 my guy.

-Daniel

 

[Chiefsublime]

Yeah, I realized that after typing my reply and figured I'd post it anyway in case someone came across it and wanted the correct info.