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I'm piecing together a breather setup for my wet sump turbo motor.
The crank case and head will be connected with a -12 line to act as an additional oil drain from the head and to balance pressure between the two breather lines.
I will have the crank case -12 and head (cam cover) -10 venting into a swirl pot/oil separator and a drain-back to the sump. The separator then vents into a small catch tank.
From the catch tank I have two options - vent into the intake to draw vacuum, or to try exhaust scavenging which I've never tried. I figured the exhaust velocity and therefore vacuum potential would be highest closest to the tailpipes, where it has cooled and expanded (exhaust is the same diameter throughout). Bit more plumbing / fab to do but nothing too taxing. Can anyone offer any experience on this?
I've done this on a n/a engine. Mounted the scavenge pipe just after the header. Make sure to mount it after any Lambda sensors, so you don't oil them down and break them over time.
Never got around to messuring the effect. I had clear tubing connected wich clearly indicated a air flow increase with rpm.
I know some turbo applications with backpressure in the exhaust can cause problems.
Thanks for the reply Marius. I have read some reports that the exhaust scavenging can pull too much vacuum and collapse seals and gaskets, did you find any issues with your trial?
This is quite common with some of the V8 engines we see in drag racing classes however I've never personally tried this out with any of the engines I've been involved with. I'd be quite surprised if the scavenge system could pull enough vacuum to be a real issue but there are vacuum regulators if you're really worried - These are used commonly with dry sump systems. I don't believe I've seen these used with the exhaust scavenge breather systems I've seen at the drag strip.
If you want to know exactly what's going on then I'd recommend fitting a crankcase pressure sensor.
these are usually fitted to open header V8;s as Andre said , they do work on open headers but if you try them on a full exhaust system the back pressure then works in reverse and pressurises the crankcase causing all sorts of issues ...oil leaks etc.
I ran my setup on a full exhaust. Worked just fine, no oil leaks.
You could just install the tube in the exhaust an messure the pressure. And just go from there.
I run this setup on my 3L turbo diesel BT50/Ranger. Factory breather from head, though stainless wool packed can into a downstream facing spike in the mid-pipe. No issues.