Found what I was looking for, another reason to use the search
Quote:
Originally Posted by modme
Actually, crankcase pressure/airflow are completely different from NA versus FI. In NA, you will never reach positive pressure inside the intake manifold. During WOT, pressure in the manifold will drop down to zero, the PCP valve will close and crankcase air will vent minimally through the crankcase vent.
However, in FI, your manifold pressure will reach up to 12 psi or whatever boost level you are running during WOT. So now the PCV valves close, but you have significantly more pressure venting from the crankcase vent to the air intake piping. How much oil vapor is blown through during this process, I am not sure.
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Quote:
Originally Posted by wstar
Yes, that's basically true. Given positive manifold pressures from FI, I wouldn't be surprised if some of your crankcase venting ends up exiting the fresh air inlet tubes under hard acceleration as well (as you'll be building crankcase pressure from blowby, but the positive manifold pressure will keep the PCV valve forced closed). I doubt the factory puts one-way valves in them (which aren't a great idea), so you might want to experiment with canning those as well.
Another thing could affect all of this on NA cars is your driving patterns I guess. Engine braking produces more vacuum than idle or steady-state driving (faster rate of PCV system flow), whereas hard accel (WOT) produces almost no vacuum (slower rate of PCV system flow). If you use engine braking a lot, you could be scavenging from the crankcase at a higher average long term rate.
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This was from
Who's running a catch can?
Id delete my post but I figured it might help someone out down the road.
It also makes me wonder about TT kits that keep this crankcase vent hose in their intakes, when you do this your essentially loading your crankcase up with the same amount of boost that your intake tubes are seeing, and this cannot be good for the seals. Not to mention your not working the piston both ways as they try and move the air about the crankcase.
So if you wanted to do the Catch can setup and vent the outlet to ATM then there is no reason you would need to run this second breather.