You know to think of it, thats the way i have mine, and i'm only pulling 8lbs of vaccum at idle. So i should run a vaccum line to pre turbo, but POST maf so it's bringing in metered air. I thought about that before and it never relaly clicked.

So upon reflection: Leaving the PCV as is, taking the filler neck vaccum port thingy running a line from it to the air intake would solve my low vaccum then. Putting a catch can between would solve the oil in the intercooler right? It sounds right atleast.

Btw, my car is draw-thru MAF.

 

If your running a draw thru turbo. You should run the pcv 1 way check valve before the turbo and before the maf but after the air filter. Basically inbetween the air filter and maf.

 

That doesnt make sense your metering already metered air. Thinking of how the stock system works, the TB to filler neck is post maf, putting that tube infront of the maf you are metering already metered air, which doesnt make sense. This should be no different than the stock system, you just have more stuff(turbo, intercooler, piping) inbetween the maf and the TB.

Are you sure? I'm not following you...

This is a system in which the MAF is PRE-turbo.

 

okay guys i got a good idea that might help. i know i'm a noob but i was thinking about this. what if you take that valve cover idea where one valve cover pulls vacuum from the PCV system and uses a one-way check valve so it closes off during boost, but on the other valve cover when you use the breather put a tube in between the valve cover and the breather so you can fit a one way check valve in the tube so when vacuum is applied it closes the opening to the breather an lets the crank case retain vacuum but when boost is applied it opens the breather to vent the boost pressure but the other valve cover check valve closes so boost doesn't creep from the intake to crank case.

so does this idea sound like it would work and is it plausible?

 

Visual 1:1

#ad

 

Okay that turbo is like a vacume pump. Its sucking crank case air from your filler neck vacume line which is attached to the left valve cover descripted on pic.

However since the crankcase is not totally sealed off b/c the right side valve cover has a breather on it. That means the turbo is sucking the crankcase air but also sucking the rightside valve cover air which has the breather on it.

Thats the reason why you have unmetered air b/c the turbo is also sucking thru the right side valve cover breather filter b/c the crankcase is not sealed off.

So your car is acting like a naturally aspirated car with a hole between the stock maf location and stock throttle body location which the engine is sucking unmetered air bypassing the maf which isn't exactly good.

2 fix your setup correctly is easy to do. All you do is move the line before maf so its in the middle between maf and filter. That way the maf will take readings from two air filters the turbo air filter and the valve cover breather filter.

 

I have no breathers right now, just the filler neck , that line is what i was proposing..

 

Oh okay i got you now.

However that line will not work. Why?

B/c when your boosting boosted air will enter the pcv and boosted air will enter the crank case. That pressure from crank case will now go towards your filler neck vacume line and leak back into the turbo.

Basically its now simulating a bosh bpv that always leaks under boost and vents back into turbo.

However you did mention a 1 way check valve at the pcv and yes that can work. That way when your boosting the1 way check valve closes so no boost enters the crank case. Then that filler neck vacume line you proposed will do the job of sucking out all the crank case under boost.

So yes your are right that diagram will work with a one way check valve on the pcv pipe

 

also, I didn't see anyone post this,,,

If you use a pcv from a 88 turbo coupe it helps considerably.. an old supercharger trick I learned........

 

check valve installation 101


1. install valve in pcv line so you can not pressurize the system


2. run the filler neck line to inlet before the turbo and in the that line have a filter/oil collector

now we have hords of vaccuum maybe even too much vaccuum

 

I got the idea from this article.

http://boostedfoxbody.com/jump.php?url=anti-leech/download.php?file=DIY_Evac_System.pdf

I WAS sucking the fumes from the unused drain bung from my vortech days. It was drawing up too much oil though so I switched it to the nipple on the oil filler. I don't know how much the pump is doing I'd think you'll be fine without it if you have breathers on both valve covers.


EDIT: BTW, I don't worry about "unmetered" air since I'm using speed density.

the motorcraft turbo coupe PCV valve did not seal the intake enough to prevent boost from pressurizing the crankcase. you need a one way valve there if you go that route.

 

I have my setup exactly the way you've drawn it. The turbo will always create a vacuum in the crankcase (unless the crankcase pressure is high and the hose between the valve cover and turbo inlet is too small to overcome). You're also correct, the line must be connected post-MAF, otherwise you'll get unmetered air.

The only downside I'm aware of is what someone has already mentioned, oil can be drawn into the turbo inlet and intercooler.

 

wouldnt a catch can solve that problem?

 

I assume so, but I'm not familiar enough with how a catch can works. Is it esentially a filter?

 

I ran the 1 way check valve in mine but it never worked all that great.. I run a breather on the valve cover and put a freeze plug in the PVC hole to block it off..


Jeremy

 

thats all u did and it runs fine with one valve cover breather? I have a vaccuum pump here that i can use. could i do the same thing as you did but have the vacuum pump sucking out the valve cover?

edit: damnit this is gt40_5.0 again signed under my pops name. lol

 

and also could i just leave the PCV valve vented to atmosphere and plug up the vac line on the manifold ?

 

Gut the PCV valve and run a line to a catch can wth a breather on it.

 

Is it nessecary to have a constant vaccum on the crankcase? If i did that with the PCV and routed the filler neck to that catch can too. would i be fine?