Blow-by versus compression?
04-14-2003, 11:47 AM
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Burning Brakes
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Blow-by versus compression?
Does anyone know if it's possible to have an engine that gets good compression numbers (~165psi on all 4 cylinders) but has enough blow-by to cause serious problems? Is there some quirk of engine design that allows for nearly perfect compression but tons of blow-by?
My '88 n/a 944 seems to have enough blow-by that the crankcase is getting pressurized and that pressure gets injected into the intake elbow via the crankcase ventilation system. There is so much of the oil vapor that the car won't start (since it's unmetered air).
But it repeatedly tests out at the above mentioned 165psi in compression tests (I don't have a leakdown tester and have heard conflicting information on their value).
Thoughts?
Bryan
My '88 n/a 944 seems to have enough blow-by that the crankcase is getting pressurized and that pressure gets injected into the intake elbow via the crankcase ventilation system. There is so much of the oil vapor that the car won't start (since it's unmetered air).
But it repeatedly tests out at the above mentioned 165psi in compression tests (I don't have a leakdown tester and have heard conflicting information on their value).
Thoughts?
Bryan
