Thread: oil catch can pcv 20v valve cover question

Ah the home depot catch can. Save yourself the money and just buy an eBay one. The homedepot one is plastic and falls apart from the heat. At least the eBay one is metal. You will need to seal all the cracks that it has, otherwise lots of unmetered air.

well i just got it installed. I put a T fitting in between the line hose from the pcv valve to the intake mani and ran that hose off the T to the 1st catch can port. Then i tried putting the hose from the top right of the vc to the 2nd port on the catch can and the car barely ran and was a little rough. Kinda confused. So i just put those top right hose from the vc back to the nipple on my intake tubing and capped off the other port on the catch can and problem solved for now. I didnt understand why the car acted like that. IDK. But imma Put a T in the line hose that connects from the bottom right of the vc to the block and run a hose off the T there back to the second port on the catch can.

hopefully all goes well. Thanks vadim and everyone for all the advice soo far

well that didnt work. I hooked up the 2nd T from bottom right vc to the catch can and the car did the oppsosite and idled really high. HMM???? So i just put it back the way i had it, any thoughts

Keep it how it is.

are you running the factory restrictor and wire brush in the hose that goes from the top right VC to the intake pipe/hose?

That little hogs tail brush is awesome!!!

Put the tools down and step away from the car.

lol im not stupid but let me know what went on with the car. Ive had my car turboed for several yrs now but never messed around with a catch can. I take constructive critisism very well. So why did it do that. Im here to learn man

Because you are changing pressures and the vacuum in the engine to something it was either not originally intended for or you are causing a leak by poor seals around whatever you are disconnecting and re-connecting.

Vadim has a huge thread on this and the conclusion, leave it.

All right I'll take the time to explain your mistakes.

Okay right away we have a problem. Crank case fumes are going to go from the valve cover straight through the "T" and into the intake manifold. The catch can is basically useless in this configuration because nothing is going to go through it.
And if you don't cap the other end of the catch can, you're going to have a huge unmetered air source (air can get into the engine without the MAF reading it). Idle will rise quite high as you're also by-passing the throttle body and allowing tons of extra air in. You will have a high idle and it will run lean.

I don't think you stopped there though, so let's continue.

Okay so now instead of sucking in clean-ish unmetered air through the catch can you're now sucking in crank case fumes again (through two sources of the valve cover, one through the catch can and other bypassing the catch can) into the intake manifold. Really, nothing too crazy going on there and not the cause for your trouble. The car barely ran and was rough because when you unhooked the top-right hose from the intake and hooked it up to the catch can you opened up a huge hole in the intake system after the MAF so you're taking in tons of unmetered air (before the throttle body) and running very lean.

Good.

See what I wrote way at the beginning. You now have a catch can attached that is doing absolutely nothing.

You really need to study up on crank case ventilation. It's a complicated system you're fucking with.

!!!!!!!!!!!!

No.

Don't do it.

Do. Not. Do. That.

It won't. It will be pointless.

Really?

You effectively by-passed the throttle body. Air could get into the engine as much as it wanted without going through the throttle body or the idle control vale. That's why your idle spiked. Here's the path the air took:

Air filter -> intake tube -> large intake nipple for crank case ventilation -> "T" you added -> bottom-right of valve cover -> valve cover -> top-left of valve cover -> PCV check valve -> PCV hose -> "T" you added -> PCV hose -> intake manifold -> intake valves

Edit: After thinking about this some more, I don't know why this caused a high idle, as the factory system is similar...

I gave you the three options you had way earlier in this thread. If you want to ignore those suggestions and make up your own system then by all means, go ahead. Just don't expect it to work.