How many of you run PCV valves on your boosted aircooled engines?

bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 · 9 Sep 2013, 8:17 pm

#969389

Just reading up on oil catch can applications and it seems stock turbo cars come with one-way pcv (Positive crankcase ventilation) valves. This is new to me, coming from a n/a background and finally buying my first turbo car this yr.

What concerns me, is that I can't recall vee dub turbo conversions mentioning such a thing for the crankcase ventilation. I thought people just run the breather on the boosted side of the intake to pressurise the crankcase and run sand seals on rear pulley.

Has anyone ran with or without these?

I'm wondering whether to put it on the future shopping list.

Thanks,
Chris.

(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

Camo Custom Title Time!

1,936 posts · joined Oct 2007 · 9 Sep 2013, 10:19 pm

#969402

bajachris88 wrote:I thought people just run the breather on the boosted side of the intake to pressurise the crankcase and run sand seals on rear pulley.

Shit, you don't want to be putting boost pressure into your crank case. You will be blowing out the seals and the oil in no time. Have a read of this, it may help you understand what the PCV does.

The blowby vapors that end up in an engine's crankcase contain moisture as well as combustion byproducts and unburned fuel vapors. The crankcase is sealed to prevent the escape of these gases into the atmosphere, but the vapors must be removed to prevent oil contamination that leads to sludge formation. The positive crankcase ventilation (PCV) system siphons these vapors from the crankcase and routes them into the intake manifold so they can be reburned in the engine.

I think the one way valve you are thinking of on the catch can is so that the oil vapors are sucked out, but when the engine is under boost the one way valve stops the catch can from being pressurised.

Hope that helps for starters, Kev

I thought rebuilding a VW would be cheap - Shit I was wrong, just don't let the wife know !!!!

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bajachris88 The international telephone dialing code for Antarctica is 6

6,661 posts · joined Apr 2005 · 9 Sep 2013, 10:26 pm

#969404

Thanks Kev 👍

So the pcv valve is emissions gear mainly hey. Hmm... so do i run the breather lines to a filter in atmosphere without the catch can then?

Plumbing it back on the suction side has me worried. I don't think i'd want vapours passing through the suction side of the turbo into the intercooler.

(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 👍
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta!

Camo Custom Title Time!

1,936 posts · joined Oct 2007 · 9 Sep 2013, 10:33 pm

#969406

Chris,

I am definitely no expert on this and my engine which is still n/a has no vacuum line going to catch can.

Don't think if the suction line being prior to turbo, it will be on the inlet manifold. The manifold will see vacuum and boost whilst driving, that why if it goes to your catch can you need a one way valve. They also have these one way valves on turbo cars with a brake booster. The brake booster still get vacuum when off throttle and the one way valve stops the booster then being placed under pressure when engine making boost.

I hope that sort of makes sense for you.

Kev

EDIT: Yes the PCV is an emissions item. In simple terms it just takes the contaminated air within the sump etc and re-burns it so that it isn't all going directly into the atmosphere.

I thought rebuilding a VW would be cheap - Shit I was wrong, just don't let the wife know !!!!

Click here for my (slowy) modded 1961 Beetle build.

vlad01 Compulsive Aussie Vee Dubber

4,270 posts · joined Jun 2010 · 10 Sep 2013, 9:28 am

#969427

PCV valves are one way, so connected on the boost side work ok when there is vac. Though I am not sure how safe or reliable this will be.

71 notchback,
Past owner of, 70 NB, 73 SB and 72 FB TLE

ian.mezz I never said, I could write or spell

3,913 posts · joined Sep 2004 · 10 Sep 2013, 3:12 pm

#969462

This is the Crank case E-Vac
It is a one way valve that will
alow the exhaust passing by the
pipe inside the exhaust pipe
to suck the extra blow-by from
the case. You will hook it up to your breather box.
Its a must to keep your
motor looking clean!.

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SuperOwen Fahrvergnugen

868 posts · joined Jan 2009 · 10 Sep 2013, 8:12 pm

#969496

Run your breather lines to a decent catch can with baffles to separate the oil from the air and either vent to atmosphere, the intake side of the turbo or use an exhaust evac like above. You need a good can though which seperates the air and oil otherwise your going to be pulling a lot of oil vapour through the motor. I like the CSP breather boxes, thin enough to fit on the firewall nicely.

Just vent to atmosphere if in doubt, nice big box with decent sized filters.