In Chamber Testing

NoDOHC · 08-08-2010, 02:45 PM

Peak pressure still at 38 degrees, if that engine were NA, I recommend that you advance the timing more. Turbo, you probably have it pretty much maxed out.

Are you sure that the exhaust port opening time on the chart is accurate? I would have expected the pressure to drop significantly more than 12 psi in 15 degrees of eccentric shaft rotation if the exhaust port were open. This is very close to the curve that would be followed with the port closed. I know that the exhaust port opens 75 degrees before BBDC = 195 ATDC, but I suspect that the trace may be inaccurate in scaling (which is weird, because the no-fire trace line looks Ok).

Can you continue the trace out to 250 ATDC? Your sensor should be able to read about that long.

08-08-2010, 02:45 PM	#34
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Peak pressure still at 38 degrees, if that engine were NA, I recommend that you advance the timing more. Turbo, you probably have it pretty much maxed out. Are you sure that the exhaust port opening time on the chart is accurate? I would have expected the pressure to drop significantly more than 12 psi in 15 degrees of eccentric shaft rotation if the exhaust port were open. This is very close to the curve that would be followed with the port closed. I know that the exhaust port opens 75 degrees before BBDC = 195 ATDC, but I suspect that the trace may be inaccurate in scaling (which is weird, because the no-fire trace line looks Ok). Can you continue the trace out to 250 ATDC? Your sensor should be able to read about that long. __________________ 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)