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NoDOHC · 06-03-2011, 10:45 PM

Good post Vex!

I especially like the way you tied Barry's theory to other's experience.

I can tell from my last dyno session that the more the timing was advanced, the more quickly the engine overheated. The closer I ran to max power AFR, the more quickly the engine overheated.

In my previous dyno session, I ran all the way to 9,000 RPM without severe overheating at 11.2:1 AFR and 22 degrees of ignition timing (I also only made 175 WHp).

I was making 175 WHp by 5,000 RPM on my next run, but the significantly more optimum AFR and 28 degree ignition timing proved too much for the engine.

Last time I ran for hours at optimum AFR with no issues, but I couldn't advance the timing enough to make much power as the engine would overheat immediately.

Basically, there was no difference in the engine internals between the dyno pulls, but keeping the engine from overheating was key in keeping the engine intact. There are those who would claim that the advanced ignition killed the apex seals, but I think it was more a temperature thing, as I ran 38 degrees of total advance at my last session, but I couldn't get past 4,000 RPM without overheating. As long as I stopped when the coolant temp hit about 115C I saw no problems with seal failure.

Interestingly enough, the only time I ever got to 9,000 RPM in 3rd gear on the dyno without overheating was when I was running 17:1 AFR.

06-03-2011, 10:45 PM	#35
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Good post Vex! I especially like the way you tied Barry's theory to other's experience. I can tell from my last dyno session that the more the timing was advanced, the more quickly the engine overheated. The closer I ran to max power AFR, the more quickly the engine overheated. In my previous dyno session, I ran all the way to 9,000 RPM without severe overheating at 11.2:1 AFR and 22 degrees of ignition timing (I also only made 175 WHp). I was making 175 WHp by 5,000 RPM on my next run, but the significantly more optimum AFR and 28 degree ignition timing proved too much for the engine. Last time I ran for hours at optimum AFR with no issues, but I couldn't advance the timing enough to make much power as the engine would overheat immediately. Basically, there was no difference in the engine internals between the dyno pulls, but keeping the engine from overheating was key in keeping the engine intact. There are those who would claim that the advanced ignition killed the apex seals, but I think it was more a temperature thing, as I ran 38 degrees of total advance at my last session, but I couldn't get past 4,000 RPM without overheating. As long as I stopped when the coolant temp hit about 115C I saw no problems with seal failure. Interestingly enough, the only time I ever got to 9,000 RPM in 3rd gear on the dyno without overheating was when I was running 17:1 AFR. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)