PCV system/ explanation and mod

[jimi87-t]

All right, I haven't seen a good write up/explanation on the PCV system for the turbo guys, so I thought I would get one going. (the N/As is a no brainier)
So first a brief description on how the stock system works.
I've made two diagrams to help show this.

On the stock system, both the turbo intake hose and the TB hose are needed in order to function properly.

Under VAC, air flows from the turbo inlet hose, through the valve cover PCV pipe, into the TB port.
This is due to VAC pulling air though the system.

Under boost, air flows from the TB port, through the valve cover PCV pipe, and into the turbo inlet hose. (opposite flow direction from VAC)
This is due to boost pressure pushing air though the system.

As air passes though the PCV pipe (in either direction), it flows over the two valve cover pipes creating a suction effect, and drawing out blow-by gasses from the crankcase.

 

[jimi87-t]

Ok so with that info, you can see that the TB port is what is powering the PCV system.
And as most of us have done to install a catch can, we plumb just from the valve covers - to the catch - to the turbo intake. This will not cut it, there is nothing "powering" the system.

To do it right when installing a catch can, you would actually need 2 cans.
One between the valve covers and turbo, and one between the valve covers and the TB.

Well, I am not running a stock TB, turbo intake, or intake manifold. I could install an orifice off of my intake mani, and make a set up similar to stock.
But I did some research, and came across what the turbo Buick guys are doing for PCV.

They are using an air pump to draw VAC on the crank case. Some use a belt driven pump, some use an electric pump. Both seem to work well. But for a daily driven car, I would not go the electric route.
The buick guys favor an LS1 environmental air pump (electric). These pumps come on many cars from the factory, and their purpose is to pump air into the exhaust and dilute it, (basically cheating the emissions test IMO, as the same amount of exhaust gasses exit the tail pipe but in diluted form).
Link: Turbo-Buick PCV

Anyway, I don't like the LS1 pump, you have to take it apart and mod it.
I'm using an electric air pump from BMW, no mods needed, and it pulls huge amounts of air. It is an impeller style fan, similar to a turbo impeller.

So my plan is it plumb, valve cover - catch - air pump - turbo intake.

Here is a pic of my pump. Dimensions are aprox 5.5" round and 6" deep.

 

[Mk3runner]

Good thread!

 

[dumbo]

Good thread!

Good oil

I like the idea.

 

[Mk3runner]

Emissions cheat.. I like it

 

[dumbo]

Emissions cheat.. I like it

Not if you run it to pre turbo, like the OP said.

 

[Mk3runner]

LOL, yea I was letting my mind wonder.. Either way, this thread was needed since lately there's been a few people running without half this stuff hooked up and threads in why don't my car run right pops up

 

[dumbo]

It's a GREAT idea, IMHO. Being it ran to pre turbo(MY RECOMMENDATIONS) or to atmosphere. Props OP!!


But the stock setup works well for those who have the provisions.

 

[kotu100]

great write up!

i only have 1 question, if the pcv system reverses when under boost with the stock setup, whats to stop it from blowing pressurized air back into this impeller pump? Could this potentially damage the pump?

other than that i like the idea, i've been trying to figure out a way to clean up my PCV hoses and install a CC but was always confused about how they worked in these cars. Thanks!
Rick

 

[jimi87-t]

With the pump there is no TB port involved, no reversal of direction. It will always be under VAC. It totally eliminates the stock system

 

[Mk3runner]

Pics of progress

 

[jimi87-t]

Progress in the past hour? I'm fast, but not that fast

 

[Mk3runner]

Nah bro. As you go. I want to watch this and try it at some point

 

[kotu100]

thanks for clearing that up, so which of those numbers on that beemer pump is the part#? or where can i find one on a bmw and what years? thanks

 

[isnms]

Doesn't this introduce un-metered air?
Is this only for folks gone MAP?
Maybe I am missing something.

 

[dumbo]

It simply puts a vacum on your crankcase, that is all. Simple...yet ingeniuos.

 

[crisp]

subscribed



...let's see... is there any reason why you WOULDN'T WANT to have constant vacuum out the valve covers???


Just wondering.

GOOD thread topic.



-crisp

 

[isnms]

So the pump is between the valve cover ports and the intake?
That must be the part I'm missing.
How long can the pump handle drawing oil vapor though it?

 

[RiyadYar]

so can you hook up two catch cans and "T" them to the valve covers like this :

 

[kotu100]

So the pump is between the valve cover ports and the intake?
That must be the part I'm missing.
How long can the pump handle drawing oil vapor though it?

thats why the pump is after the CC, that'll catch the oil.