Crankcase Evac


Well-Known Member
Since my car is a street car I decided to do something with the crankcase evac system. Got tired of the fumes and oily breathers (like many others).
I hooked the factory PCV back up with the RJC check valve inline and put a catch can in, like a number of others have done. I bought a cheap Chinese can just prove out the system. I may upgrade that part later, we will see.
For evacuation under boost, since we do not run collectors going to atmosphere the typical exhaust evac systems won’t work, I built a real simple air ejector and installed it on the outlet of my boost activated exhaust dump valve. I basically have a stock cat back exhaust system, which is quite restrictive and helps push flow out of the dump. The boost activated dump works really well, plus I get a quiet exhaust for street cruising. I figured the small restriction that the air ejector adds would be worth the evacuation system. See ugly sketch and pictures.
The linked video shows initially the PCV pulling about 1” Hg, then I roll into it at about 30 mph and shut down at about 100 mph. You can see as the manifold goes from vacuum to positive, crankcase vacuum goes to zero, then pulls back down to a tad over 1” Hg. The pressure is measured at the dip stick tube, so it is actual crankcase pressure. No real power gains at the small vacuum, but it ensures that there is no pressure on the seals/gaskets and the blow by exits the back of the car. Figured I would post for those interested. (I have a nice long ramp that I hit, and get on the brakes before entering, no chance of traffic.)
I wonder how much vacuum a high horsepower car with an external gate and a screamer pipe could generate with the screamer pipe feeding a purpose designed system. I just cobbled some stuff together, but with some design and testing it could be worth some horsepower as long as it did not interfere with boost regulation. That exhaust coming out of the screamer pipe is wasted high energy gas. I bet 10” Hg would not be out of the question, and that would definitely show up on the dyno.





Caustic Cacophony
Nice work, sure make things go well. This is the first time ever my own engine hasn't had an oil leak after revising my pcv system.


Well-Known Member
Old school approach there, nice, using the exhaust is an efficient use of existing energy to help.

I went with...
Pcv to catch can to inlet pipe
This uses the turbos vacuum under boost.
The above is sort of like how the factory valve cover breather went into the turbos housing but the factory didn't have a catch can.