Crankcase ventilation

[s1ngletracker]

If you want suction in your crankcase, do a slash cut in your exhaust, with a check valve to keep exhaust surges from pushing back into your crankcase. Slash cuts will actually increase in vacuum as boost/load increases, as opposed to intake manifold which will close the PCV valve and give you none. The intake tube port has a similar effect (though not as much) but also will spray discharge into your intake.

You don't need crankcase vapors to lubricate your wastegate actuator and BOV - a lot of the time your crankcase discharges are steamy (water vapor) nasty fluid anyway. Plus your turbo willl almost always spray a finite amount of oil there anyway.

[Dizmm]

Originally Posted by s1ngletracker

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You don't need crankcase vapors to lubricate your wastegate actuator and BOV - a lot of the time your crankcase discharges are steamy (water vapor) nasty fluid anyway. Plus your turbo willl almost always spray a finite amount of oil there anyway.

this is mostly why i chose to vent my catch can rather than route it back into the intake pipe. not much vacuum is created anyways. Big thread on DSMtuners and EvoM about this.

What was in my catch can (mostly water):


(this was my testing valve cover) I did 2 large NTP ports on the end, used a tap, some $2 NTP fittings, and routed them to my catch can. I used to get some blow by smoke and now i get none.

[Tachyon]

Originally Posted by s1ngletracker

If you want suction in your crankcase, do a slash cut in your exhaust, with a check valve to keep exhaust surges from pushing back into your crankcase. Slash cuts will actually increase in vacuum as boost/load increases

A couple years ago I was interested in this idea. It appeared to gain popularity the Civic and Supra crowd a while back and did net some gains on the dyno. I think I might finally give this a try since my DSM is my experimental tech donkey.

I am thinking 2x -8 fittings and lines within an inline baffle box system, then 2 beefy check valves into opposing slash cut tubes. IIRC, the main issue people were having at the time were the valves getting clogged with coked oil. I am thinking the baffle box could prevent this if done correctly.

Paul, do you have any experience with this in a quasi-race environment?

[s1ngletracker]

Originally Posted by Dizmm

the other problem you have with doing large crankcase ports routed to a catch can, then routed to the intake, is you will significantly alter the metered are by the MAF. If you are running the stock size port from the valve cover, you can get away with it.

Can you explain this more? Hasn't that air been metered?

Originally Posted by Tachyon

A couple years ago I was interested in this idea. It appeared to gain popularity the Civic and Supra crowd a while back and did net some gains on the dyno. I think I might finally give this a try since my DSM is my experimental tech donkey.

I am thinking 2x -8 fittings and lines within an inline baffle box system, then 2 beefy check valves into opposing slash cut tubes. IIRC, the main issue people were having at the time were the valves getting clogged with coked oil. I am thinking the baffle box could prevent this if done correctly.

Paul, do you have any experience with this in a quasi-race environment?

Yeah, I have a slash cut on the chumpcar. This weekend will be the first time it will be run in a race. We had an awful problem with a rapid filling catch can last year, I even posted on here about it, and I got little or no help. I'm much more confident in our new setup, it also has a drainback to go back into the block so we don't have to waste time at pit stops draining it. On a street car draining it is acceptable, on a race car where you need to have ~4 minute pit stops, you want as little to do as possible.

I'll let you know how it goes! In theory it should be ok, but I have some concerns about it, namely the hose I have connected to the slash cut getting too hot.