Crankcase Evac

Nigel

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Jun 16, 2001
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.




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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.
 
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.
 
This is an approach you'd see on your everyday big block chevy (carbureted) setup. I'm curious how well its working and if anyone else has plumbed evac this way.
 
An elegant solution, to be sure!
Is there a reason that u didn't just buy a pan evac kit like Hooker, Mr. Gasket, and others sell? You drill a hole, and weld it into the down pipe. But the lower the exhaust restriction behind it, the better any of those systems will work.
I don't use a dump because I'm too lazy or forget to activate it, and since I have been known to partake in an impromptu display of accelerative ability, I don't want to alert either the victim or cops as to what is going to happen.
I have a dual 3" exhaust with a beautiful transition right off of the downpipe.
And yes, there is horsepower to be had with an evac system!
AHA! You could run a "Y" between the PCV and pan evac so that the PCV functioned normally, and when the exhaust velocity is up, the pan evac would draw a better vacuum on the crankcase, allowing more H.P. Thanks for the idea! I think I'm gonna do that!
If you can't make 30 H.P. in one place, make 3 H.P. in 10 places...
TIMINATOR
 
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This is an approach you'd see on your everyday big block chevy (carbureted) setup. I'm curious how well its working and if anyone else has plumbed evac this way.
The video shows how far it will pull crankcase pressure, that pressure gauge was hooked to the dip stick tube. Under full throttle that is an inch of vacuum in the pan area. I am happy with the result.
 
An elegant solution, to be sure!
Is there a reason that u didn't just buy a pan evac kit like Hooker, Mr. Gasket, and others sell? You drill a hole, and weld it into the down pipe. But the lower the exhaust restriction behind it, the better any of those systems will work.
I don't use a dump because I'm too lazy or forget to activate it, and since I have been known to partake in an impromptu display of accelerative ability, I don't want to alert either the victim or cops as to what is going to happen.
I have a dual 3" exhaust with a beautiful transition right off of the downpipe.
And yes, there is horsepower to be had with an evac system!
AHA! You could run a "Y" between the PCV and pan evac so that the PCV functioned normally, and when the exhaust velocity is up, the pan evac would draw a better vacuum on the crankcase, allowing more H.P. Thanks for the idea! I think I'm gonna do that!
If you can't make 30 H.P. in one place, make 3 H.P. in 10 places...
TIMINATOR
I tried a hooker setup at the dump tube outlet and the at the bottom of the down pipe, saw positive pressure (the check valves were junk) and it did not pull any vacuum just being placed in the exhaust stream. That was measured at the connection, pressure in the crankcase was higher. I forget the exact number, but the ejector setup I have will pull a few inches vacuum down at the connection to the exhaust, with the pressure drop that equates to an inch of vacuum in the crankcase. I believe the pan evac is meant for a header collector, which acts just like the air ejector I made, but only better.
 
I guess yours works better, I'll scrub my idea! Thanks!
My only experience with that so far was on my Super E dragster, when we had the engine on the dyno, it pulled 3 or 4" vacuum, but that was in the collector and nothing behind it.
TIMINATOR
 
I guess yours works better, I'll scrub my idea! Thanks!
My only experience with that so far was on my Super E dragster, when we had the engine on the dyno, it pulled 3 or 4" vacuum, but that was in the collector and nothing behind it.
TIMINATOR
That makes sense, a header with a 30" plus extension off the collector would maximize the vacuum.
 
Must have!
From end of primaries to end of collector was about 22".
Side port was closer to the 4 tubes.
TIMINATOR
 
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