Originally Posted by
1967brutus
Nope... In a good functioning engine with a good liner and ring condition, my tests have shown that blowby is near zero at full load, and remains near zero all the way down to a certain RPM (in my test engine, the 91 ASP fourstroke that RPM was between 3500 and 4000) where it suddenly strongly increases and then also remains more or less constant.
I believe this to be the combustion pressure forcing the ring to seal up against the liner above certain loads/RPMs, and I have no idea if every engine responds the same, but I DO know by logical deduction that ingestion of dirt WILL disturb the parameters of this behaviour..
With a single ringed piston, as rpm rises, combustion pressure does in fact seal the ring against the cylinder wall, and against the ring groove in the piston, that was my statement blowby decreases with rpm, so tank pressure would drop when the throttle was opened, and with sustained rpm... 2 stroke crankcase pressure would respond to rpm changes, rise and fall with rpm.
Shaker pump, or engine driven vane pump??