Need a catch can for the 320, tired of oil on the back of the intake (out the vent filter on the valve cover).
Was thinking just a single inlet with the breather filter on the top, but a bit of reading, including some GRM posts, says running a can with a line back to the intake is beneficial?
Some confusion for me as to running it before or after the throttle blades.
If I ran something like this from a West Coast bmw vendor, bottom in from the valve cover, top back in to the air cleaner (if I have space)?
Yes, no, maybe?
My car is carbed (38/38) with an aftermarket Canon manifold (so running a line after the throttle blades will be a bit harder, no additional ports for emissions, assuming later 02's vented there...).
I've read that running a line back to the intake allows a small amount of vacuum to be pulled on the crank case, which helps the piston rings seal better. I've always called this a "closed system" and have seen it done two ways: a line straight to the intake or air box before the throttle or a line to the intake manifold after the throttle through a PCV valve to meter flow. I feel like the better sealing claim is dubious but I have seen less condensation in the crank case as a result of running a closed system.
Hmmm, maybe the difference is pcv/intake manifold, airbox/non-pcv.
I'll give the latter a whirl, I think.
A closed system with a PCV works better, there are a few different benefits to running a vacuum in the crankcase (mainly reducing condensation and aerodynamic drag on the crank & pistons), and with a good filtered catch can the intake contamination downside is vanishingly small. A vent-to-atmosphere setup can keep the intake slightly cleaner but it eliminates crankcase vacuum and isn't great for engine bay cleanliness/smells or the environment either.
In reply to GameboyRMH :
If it's pcv, does it need to plumb behind the throttle blades?
ГУЛАГ мальчик УР следующий said:
In reply to GameboyRMH :
If it's pcv, does it need to plumb behind the throttle blades?
That's the usual way to do it and it provides more vacuum more often (assuming mostly street use). If you plumb it to an airbox before the throttle, you'll only get vacuum at higher throttle levels.
Also, don't know if this is obvious or not but with a closed system you need to have a fresh air source into the crank case. You don't want a hard vacuum on the sump but enough to circulate air to collect condensation and oil vapor. OEMs usually have two port to the crank case - one goes to the intake manifold, post throttle, via a PCV valve, and the other goes to the intake or air box behind the mass airflow sensor (if equipped). This allows fresh air to circulate but also allows to vent in either direction depending on engine load. Light throttle = vacuum into intake manifold. Wide open throttle = vacuum into intake. I've seen people run two catch cans, one on each line. Radium Engineering has a good info page: http://www.radiumauto.com/Webpage.aspx?WebpageId=15&PostID=102
