Best PCV/Breather setup for a turbo car

[Aaron]

I need to have my turbo 3.4 DOHC's PCV and breather systems redone before my track day, but I'm not sure what my best option is.

The car has a breather port on the front valve cover, and a PCV port on the lifter valley cover. I can add a breather to the rear valve cover if I need to, but I'd rather not.

I also have a catch can, and check valves if needed. I have access to intake manifold vacuum (But will have boost at times), or can get some vacuum before the turbo. Engine pulls like 12 in-Hg at idle.

Ideas?

[Series8217]

Mann+Hummel ProVent 200 is the new hotness

http://www.republicsales.com/prodcat/MA ... oC6rDw_wcB

Hook the inlet up to as many crankcase / valve cover breathers as you have and/or can fit. Hook the outlet up between the turbo and the air filter. The bottom drain goes back down to the pan to allow separated oil to get back into the motor.

[Shaun41178(2)]

you dont need something as expensive as Will suggests unless you want to be cool, but whatever you get, hook it up the way he describes

however, you don't really need a breather that way. Keep the pcv valve the way it is, and the breather on the one valve cover run a line from that to the intake pipe feeding the turbo but after the filter. Natural vacuum effect when turbo is boostin to create vacuum in the crankcase. just make sure the breather on the other valve cover isn't tied into the intake after the tb.

Edit: are you just wanting a breather system, or to create a vacuum in the crankcase when under boost?

[Series8217]

y
however, you don't really need a breather that way. Keep the pcv valve the way it is, and the breather on the one valve cover run a line from that to the intake pipe feeding the turbo but after the filter. Natural vacuum effect when turbo is boostin to create vacuum in the crankcase. just make sure the breather on the other valve cover isn't tied into the intake after the tb.

The idea of the breather system is to drop the velocity of the gasses enough that the oil drops out of suspension and doesn't get sucked into the intake. What you are suggesting is the PCV system is normally set up. Under conditions of high windage and blow-by, the stock system has too small and too short of tubing to effectively prevent blowing all the oily air into the intake. The separator / catch can is intended to solve that problem.

[Aaron]

So how does this sound. T the breather and the PCV line into a single line, run that to my catch can. On the other port of my catch can run a line to the intake in between the turbo and air filter. So this pulls a constant vacuum, but any oil will get caught in the catch can.

[Shaun41178(2)]

sounds right. catch can won't catch all oil vapor. so it will still draw some oil into the turbo inlet but it will be small.

I have a mishimoto catch can here, if I can find it, you can have it. Summit has them for $120 It came off Kohburns old turbo car. Its painted red. lmk if interested

[The Dark Side of Will]

So how does this sound. T the breather and the PCV line into a single line, run that to my catch can. On the other port of my catch can run a line to the intake in between the turbo and air filter. So this pulls a constant vacuum, but any oil will get caught in the catch can.

Without a connection to MANIFOLD vacuum, there won't be any flow through the system.

Not sure where this whole idea of "between the turbo and air filter" came from, but there are things that need to be understood about running it that way.

There's basically NO vacuum between the filter and turbo. This is the SOURCE of air for a correctly designed PCV system.
The flow through the intake tube can be used to pull on a PCV system, just like the flow through a header collector can be used to pull a vacuum on the crank case. HOWEVER, because the VELOCITY upstream of the turbo is pretty low (this is because there's very little pressure difference, which is evidenced by not having any vacuum there), there won't be much pull on the PCV system. Doing it this way will be much LESS effective than using an exhaust connection to pull on the crankcase.

The way a PCV is *supposed* to work is that at part throttle manifold vacuum causes flow through the PCV system. When the throttle is opened far enough that there's very little manifold vacuum, the PCV valve closes and prevents back-flow from the manifold to the PCV (and crankcase).The ideal PCV system is connected from the air filter to one cam cover and from the other cam cover to manifold vacuum. The oil separator is plumbed in immediately upstream of the manifold connection.

For the PCV system to work, there MUST be a connection to manifold vacuum.

Crankcase evacuation at WOT is something different. This can be accomplished with an exhaust fitting as mentioned, but is NOT the same thing as PCV. For this to work, you actually want to STOP the flow of air into the PCV system so that the Bernoulli effect can use exhaust gas velocity to pull a vacuum on the crank case, which increases engine power.

[Shaun41178(2)]

under boost, there will be a lot of vacuum between the filter and the compressor, thus creating your vacuum to pull on the crankcase. the rest of the time it works like a breather.

The way aaron described doing it will work. It will also work if aaron leaves pcv valve where it is, and then the breather line on the valve cover goes to the can, then from the can to air intake tube pre turbo. That way is exactly the way it is setup on a stock fiero 2.8 sans catch can. Pull the intake tube off a 2.8 and its got oil all inside it.

I asked aaron if he plans to just use it as a breather or to pull vacuum. That determines how to run the lines. if he wants vacuum, I would run it to the exhaust to pull vacuum. Terrible for emissions but keeps the intake oil free

[The Dark Side of Will]

under boost, there will be a lot of vacuum between the filter and the compressor, thus creating your vacuum to pull on the crankcase. the rest of the time it works like a breather.

No, there won't. If there is, then the system is suffering reduced performance because it's pulling through a clogged air filter or a soda straw.

There may be some amount of usable Bernoulli effect in the air stream, but there will always be MORE on the exhaust side (i.e. right off the turbine outlet).

Also... a breather allows for the change in volume of air in the crankcase due to changing temperature, BUT it allows crap (blow by gases, water vapor) to accumulate in the crank case, eventually turning the oil acidic... properly functioning PCV is *GOOD* for an engine that's driven on the street and accumulates miles.

[Shaun41178(2)]

hmmm you are right. there shouldn't be vacuum. I know there is a suction, I guess I was thinking that equaled vacuum.

just make it a breather system aaron and call it a day

[The Dark Side of Will]

just make it a breather system aaron and call it a day

After building the rest of the system the way he's done, that would be sloppy.

[Aaron]

Here's what I've used for a while now, and seems to be working well (No smoke).

Valve cover breather runs to catch can, other port on catch can is open. So basically just open air vented, but it won't pull in trash or dump oil anywhere.

PCV line from lifter valley to the stock PCV valve, then to a check valve, then to the intake manifold. So it pulls a vacuum under light throttle and idle, on boost it closes that check valve so as to not pressurize the crank case.

Am I doing it wrong? I know a lot of guys prefer to run the PCV line to the catch can so the oil doesn't go into the motor to get burned. I could T the breather and PCV together, then go to the catch can, with the other side of the catch can going to the intake manifold with a check valve for a vacuum source.

[The Dark Side of Will]

Here's the way it's supposed to work:



Forget you even heard the word "breather". PCV is POSITIVE CRANKCASE VENTILATION. If you're using a "breather" then you're stuck in ignorant 1950's backwoods redneck hot rodding. Raise your front suspension to help weight transfer while you're at it.

Positive ventilation means that there is essentially a forced flow of air through the crank case. This pulls blow-by gases and other crap out of the crank case and slows the deterioration of the oil. The benefits of PCV have been known since before PCV was mandated by the Department of Defense to reduce maintenance costs, increase maintenance intervals and reduce catastrophic failures on airplanes in World War II.

Manifold vacuum draws air through the PCV valve. Immediately upstream of the PCV valve is the best place for the catch can or oil separator.

What you CAN do is run the PCV from two vacuum sources... the intake manifold can draw on it when there's manifold vacuum, and the exhaust can draw on it when at WOT... this can be accomplished with a Y or T fitting and a couple of check valves. An interesting trick would be to shut off the filtered air supply at WOT so that the exhaust extractor could pull a vacuum on the crankcase and help your power figure a bit.

[Series8217]

so that the exhaust extractor could pull a vacuum on the crankcase and help your power figure a bit.

... AND promote oil pump cavitation! Yay!

[The Dark Side of Will]

To some extent. Any idea how much vacuum an exhaust extractor can actually pull?
Drag cars can run them and not blow up, so it's not fatal.

[ericjon262]

so that the exhaust extractor could pull a vacuum on the crankcase and help your power figure a bit.

... AND promote oil pump cavitation! Yay!

I'd love to see just how much vacuum it would take to make it cavitate. I would imagine, as low as the pickups are, and as heavy as oil is, your pan would probably have to be damn near dry for it to be a problem.

[ericjon262]

Forget you even heard the word "breather". PCV is POSITIVE CRANKCASE VENTILATION. If you're using a "breather" then you're stuck in ignorant 1950's backwoods redneck hot rodding.

no kidding, it's crazy how often I see cars running around without them, because rednecks think they're "Smog garbage" or some such nonsense...

[fieroguru]

Forget you even heard the word "breather". PCV is POSITIVE CRANKCASE VENTILATION. If you're using a "breather" then you're stuck in ignorant 1950's backwoods redneck hot rodding.

You can use a breather/filter and have it plumbed properly. The PCV system needs clean filtered air. It can come from the air inlet tract post filter, or you can use a dedicated air filter on a valve cover - either way works as long as it is plumbed properly on the dirty side. The MAF only cars might see some idle/cruise instability with the valve cover filter as it isn't "metered" air from the MAF, but the SD cars won't care.

[The Dark Side of Will]

as long as it is plumbed properly on the dirty side.

Exactly my point.

[Aaron]

My car is MAF only and as of right now is getting unmetered air, so hopefully driving improves when I change that. So far my new plan is to go from the valve cover to the intake tube after the air filter before the turbo. Then my PCV will go from the valley to the PCV valve, to the catch can, to a check valve, and then to the intake manifold for a vacuum source.

From my very limited understanding of this system, shouldn't we need PCV the most at hight throttle/RPM? Semmes to me like that's when we'd get the most blowby right?

Thanks guys!