Quote:
Originally Posted by mr.nismo.
Felt like this thread is reasonable to post this. Ive been tossing around the idea of using an electric pump for crank case evacuation (sr20). I still want to keep the OEM pcv side intact. My idea was using a secondary air injection pump (they max out at 3-4" hg) that's triggered on a 1 psi pressure switch. So basically is idle/cruise the regular PCV will handle evacuation, and then in boost the PCV will close and the pump will take over. The point of the switch is so the pump isn't in constant operation.
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This would work, yes.
Quote:
Originally Posted by S14rebuild
Why? Wont the inlet suction of the turbo create enough vacuum todo just that?
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If you are using a high-flow air filter, there is very little, if any, vacuum in the intake pipe. Even if you were to run a very restrictive air filter, you don't want the intake pulling lots of vacuum out of the crankcase without some way to filter oil out. It also kind of defeats the purpose because now you have a restrictive air filter and you're not going to make more power from pulling a bit more pressure out of the crankcase. It's a compromise.
Also, technically speaking, the pipe that attaches to the air intake isn't to draw pressure out of the crankcase, it's to allow fresh air into the crankcase when the PCV valve is doing it's job at cruise. This allows it to pull the combustion gases (which are acidic) and water vapor out of the crankcase and dump them in the intake manifold more easily.
So it really comes down to whether or not you want to risk getting oil vapor in your intake pipe. You should be able to mitigate the risk with a properly setup catch can with good baffling, or you could just run an open catch can with an air filter and not worry about it.
Engine longevity does rely heavily on good air filtration though, so that's something to consider in itself.
It's all about
balance.