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NoDOHC · 07-01-2011, 10:26 PM

Update:

My previous test setup was not as accurate as I had hoped, so I decided to build a setup that could graphically display what the exhaust was doing.

To that end, I used two Ashcroft K1 150 psi pressure transducers in the exhaust to measure backpressure (watching the pulses on an oscilloscope). These transducers are the same ones I use for compression tests.

Unfortunately, I didn't think that the neighbors would appreciate me starting the car and reving it up right now, so I will have to wait for tomorrow to collect data.

Anyhow, what waveforms do you guys want to see?

I can tell that the headers scavenge well at higher speeds, but I can't get a good scope trace there as the engine revs too fast.

I watched the exhaust pressure at idle and was appalled by how frequently the engine misfires. About every 15th power stroke is a full and complete combustion, the rest are partial or complete misfires. I think that 14.2:1 is a bit lean after all.

I will post some traces tomorrow - what would interest you?

07-01-2011, 10:26 PM	#19
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Update: My previous test setup was not as accurate as I had hoped, so I decided to build a setup that could graphically display what the exhaust was doing. To that end, I used two Ashcroft K1 150 psi pressure transducers in the exhaust to measure backpressure (watching the pulses on an oscilloscope). These transducers are the same ones I use for compression tests. Unfortunately, I didn't think that the neighbors would appreciate me starting the car and reving it up right now, so I will have to wait for tomorrow to collect data. Anyhow, what waveforms do you guys want to see? I can tell that the headers scavenge well at higher speeds, but I can't get a good scope trace there as the engine revs too fast. I watched the exhaust pressure at idle and was appalled by how frequently the engine misfires. About every 15th power stroke is a full and complete combustion, the rest are partial or complete misfires. I think that 14.2:1 is a bit lean after all. I will post some traces tomorrow - what would interest you? __________________ 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)