Spark plug issues

NoDOHC · 04-20-2011, 10:32 PM

I do not have means to monitor EGT at WOT. The headers were white hot on the dyno with the old ignition, but only over 6500 rpm, below that they were normal looking grey.

Why does advancing the timing increase the EGT? My experience would indicate that EGT goes down with advanced timing. Coolant temp and oil temp go up, but EGT goes down. (This is piston engine experience again...)

I made peak power at 38 degrees total advance last time on the dyno. There was about 4% improvement between 30 degrees and 38 degrees. This was with no hint of pre-ignition, 43 degrees lost power but did not cause any pre-ignition. I was running 8.2:1 polished rotors at that time.

I never heard any pre-ignition on the dyno with 9.4:1 non-polished rotors before the seals failed in the front rotor either (although the AFR was so rich that I really shouldn't have worried about it anyway).

I tried running a higher octane fuel (89) and have not experienced any pre-ignition since. It might just have been that batch of fuel.

04-20-2011, 10:32 PM	#3
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	I do not have means to monitor EGT at WOT. The headers were white hot on the dyno with the old ignition, but only over 6500 rpm, below that they were normal looking grey. Why does advancing the timing increase the EGT? My experience would indicate that EGT goes down with advanced timing. Coolant temp and oil temp go up, but EGT goes down. (This is piston engine experience again...) I made peak power at 38 degrees total advance last time on the dyno. There was about 4% improvement between 30 degrees and 38 degrees. This was with no hint of pre-ignition, 43 degrees lost power but did not cause any pre-ignition. I was running 8.2:1 polished rotors at that time. I never heard any pre-ignition on the dyno with 9.4:1 non-polished rotors before the seals failed in the front rotor either (although the AFR was so rich that I really shouldn't have worried about it anyway). I tried running a higher octane fuel (89) and have not experienced any pre-ignition since. It might just have been that batch of fuel. __________________ 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)