Thread: Crank Case Ventilation fully explained. (Turbocharged edition.)

I've added more to the technical description (about intercoolers acting as oil separators when fed blow-by), and I've put up two new diagrams. I'm hoping to get to the rest pretty soon. I know this thread is seriously lacking in example diagrams.

Ben there is some discrepancies about your diagram. It needs to be explained if they are during boost or off boost. As the diagrams appear they are off boost diagrams. With your PCV valve still in place, never is your crankcase pressure going to be higher than your boost level so the pcv valve being a one way valve (at least one in good working order) is going to shut during time in boost where the intake manifold is under boost pressure. So all blowby will be exiting the motor via the valve cover T on the right side.

For most setups i recommend to leave the PCV valve in but on larger setups its recommended to remove the pcv and change it to vent crankcase pressure. On larger setups the more boost, the more power, the more air, the more crankcase pressure you will need to vent and its very important to keep the crankcase from pressurizing and keep at a 0 pressure during time in boost. This is why many people remove the pcv for one to prevent intake manifold pressure trying to pressurize the crankcase even more and with those cheap plastic valves any type of age to them will allow pressure back through into the crankcase.

This is why big builds usually always add ventilation to the block and valve cover to aid in ventilation. A lot of the honda b-series guys use 6 total vents, 4 on the valve cover and 2 on the back of the block by removing the casting plugs and installing fittings all hoses running to a large catch can.

Downfall of not having any PCV, especially during cold mornings during warmup, the condensation that builds up in the motor during heating and cooling especially in humid areas or times of year will evaporate some and work their way to the catch can as well as blow by gases past the rings which usually during warm up you running a richer a/f mixture which will cause higher amounts of blowby gases. They will work their way into the catch can and will smell like you have fuel in there. When you drain it, it will look like a mixture of oil and fuel from what ive seen on my setup.

On my motor since I went to the 60 trim t3 setup i have always had the PCV eliminated and turned into a breather line going to the catch can along with another line from the T on the valve cover. I leave my lower crankcase hose going up to the other portion of the T. So far I havent had any issues with crankcase over pressurizing and the way you can tell is usually your dipstick will pop out if your are pressurizing it enough.

The only time my dipstick would pop out is when I had a kink in my Valve cover breather line that goes to the turbo intake. My PCV valve and system is untouched too. This is on 12 psi boost on a T3 turbo.

Now if your PCV valve gets worn, I can see it having big issues .

Eh i dont like the fact of condensation and heavy blowby gases and oil going into the intake and back through the motor. F the EPA. My car on the 60 trim setup got 40mpg on the highway and 30+ around town getting on it on occasion. They can deal with some blowby gases going into the atmosphere for all I care, lol.

I don't like it either, but without it connected my dip stick would be out and oil would be squirting out of the valve cover. Guess my piston rings are worn afterall

I was more refering to the PCV valve than recirculating the valve cover vent back to the intake system. Again thats why you need a catch can. I had excessive blowby on my motor from those initial starts with no oil pressure which took the chrome off the top rings and seized one side of the ring into the groove. While I had slightly lower compression I also would get more blowby than normal under boost. But eliminating the PCV and turning it into an additional vent along with venting the T to the catch can as well, I never had issues with my dipstick blowing out. It definitely put oil into the can along with the blowby gases and condensation but as much as i would drive it I would only have to drain the can once a month or so and it was only about 1/4 full.

The PCV is where most of your blowby gases are gonna make its way back to the manifold at while out of boost, in boost yes the vent from the valve cover.

I just dont feel like coating my entire piping and intercooler in oil as well as the intake manifold. No thanks. Again the EPA can deal with the slight blowby gases im putting into the atmosphere while I got 40mpg on the highway. lol.

Are there any consequences to plugging the PCV line?

Not really, you will just have more blowby gasses and fuel vapors and moisture vapors going into the catch can or back into the intake tract during cold start. Under fully warm conditions, theres really no downfall to it. If you can id use it as an extra vent to the catch can if your running one.

The pink hose is what im currently doing right now, as soon as i get a longer hose.

I removed the 1-way valve and put a straight thru fitting. Im hoping this will pull the extra oil that ive been seeing to the oem catch can but still allow gas vapors to continue being "eaten" by the engine.

Ill pull the intake pipe off every couple days to see if any oil is getting thru. But my main concern is keeping oil off my spark plugs.

I would not block the breather coming off the right side off the valve cover. You want to have more ventilation than just one breather. I know you have one coming off there to the catch can but id definitely have at least two.

One might be alright but I wouldnt.