How much timing on race fuel?

[Guest Tom Scala]

I was wondering how much total timing evryone with programmable systems is running when they switch to high octane race fuel. I run a conservative timing curve of 37 total with no boost and retard approx 1 degree per lb. I can run 18psi without any traces of detonation on 94 octane pump gas @ 20 degrees total.

 

If I gassed up with 112 octane race fuel how much timing could I safely run? How much if any do you guys richen the mixture for race fuel? I've heard you should go 5-7% richer when running leaded race fuel.

[Scottie-GNZ]

Tom,

 

I think you can take better advantage of the race gas by focusing on running more boost vs more timing. You can increase the timing also but more boost will net more HP. E.g., I run 18* total (after retard) and about 16-17# boost on pump gas. At the track I run 24* total and 25# boost. I have only run my car once at the track with low boost and street timing and that was to test a fuel problem but I would venture a guess the difference is about 100hp. This is where an EGT comes in handy.

 

Not sure what you are using to retard the timing, but here is how I would approach it. Right now I am assuming you are running 19* total derived from 37* advance and 18* retard (1* for 1#). If you can, start retarding at 5# with the race gas giving you 23* total at the same 18#. With that as a base, start turning up the boost in small increments so 19#=22*, 20#=21*, etc. Of course, as you turn up the boost you also have to supply more fuel. With SDS, I can tell you how to do that as all that would be very SIMPLE

 

I hate to sound like a broken record, but when you start doing this type of tuning, you really need and EGT or WB and not have to rely on your ears. However, IMO that is a simple and safe approach. If you follow this approach with the right tuning tools, do not be afraid of boost. Just turn it up in small increments and monitor your mixture. Remember, it is detonation not boost that kills engines. Also remember there is no magic amount of boost or timing that you can run as there are too many variables. You run the max you can w/o detonation.

[240Z Turbo]

a good timing curve may retard 18deg total with 18psi of boost, but not usually in a linear fashion. For example, you may want to have retarded 2/3 to 3/4 of your total timing by 9psi and then taper off. So, if you started at 38deg by 9psi you would be at 26deg and then retard the remaining 6deg until you reach 18psi of boost. As far as AFR goes, 11.5:1 is good on pump gas and you can run as low as 12:1-12.2:1 on race gas. To answer your question, you can probably safely run 26-28deg at 18psi on 114oct race gas.

[Guest Tom Scala]

Thats just the kind of info I was looking for. Thanks guys