[urq] Too much Crankcase ventilation? - More

[djdawson2 at aol.com]

Dear PCV Boy,

The valve cover's use?on the AAN engine is simply as a tube for the PCV system.? It is essentially a solid pipe running through the valve cover... no venting to the area covered by it.



I encourage you to remove an AAN valve cover.? If you plug one nipple, and blow air into the other nipple, it has nowhere to go.



Dave


-----Original Message-----
From: QSHIPQ at aol.com
To: benswann at comcast.net; Djdawson2 at aol.com; vegener at post7.tele.dk; quattro at audifans.com; urq at audifans.com
Sent: Wed, 5 Sep 2007 2:55 pm
Subject: Re: Too much Crankcase ventilation? - More





Ben

I'll address this to you since you started it, but Claus and Dave's responses are in here as well.

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First, a look at how the 20vt works.? Indeed there is PCV at the valve cover Dave, at least on a 95.5 S6, I just looked.? It's the little hose below the turbo intake breather?hose connection?at the back of the valve cover.? It goes down to the vacuum valve at the crankcase, where crankcase, valve cover and intake feed all converge at the crankcase '8 ball'.? According to TST 218, during high vacuum (idle) the PCV is drawn into the intake via the ck valve at the intake manifold.? During low vacuum or boost, the PCV is drawn into the inlet side of the turbo via the pressure control valve.

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This means that a larger turbo with the same size inlet pipe will have more vacuum pulling on the pressure control valve.? It also means that oil sloshing in the head and oil sloshing in the crankcase, has a really good chance of getting sucked up at idle, just off idle, launches?and at a higher than stock boost level.? Not sure why audi mounted all this so low on the block, it's really conducive to sloshing issues of both the block and the head (guessing the head causes more oil issues than the block, since that 8ball crankcase design on the block has been around a long time without issue).

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WRT what to use for a modded/improved PCV, I would highly suggest the supra twin turbo app (don't forget the gasket) 1993-1998.? It operates per the website I provided, and it has a really good turbo shutoff action on it.? And, discounted, it's less than 10 bucks.? I noticed that the Mustang supercharger boys use this valve as the 'standard' as well.? 

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For hookup on your 10vt Ben, I would consider putting this valve in place of the stock urq pcv valve, and mount it above the valve cover somehow.? I would think you could machine up a simple block that would tie all this together with the stock system.? Since the supra twin turbo uses a really high compression ratio, I'd bet the match to the orifice of that PCV valve would be really good.

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What may screw all this up, is the amount of vacuum present at the turbo inlet.? That's pretty key to making sure the breather is acutally breathing air vs fighting an alternative vacuum source.? Claus, wrt octane vs oil vapor... In a properly designed PCV system, there shouldn't be enough blowby to make this significant.? And if you read the site I posted, if 70% of that vapor is unburnt HC, you aren't affecting octane much at all.? IME, running back to back PCV connected vs not, there appears to be no significant difference in dyno output (read: just another run can result in the same change).

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Martin, PCV is one of my interests along with the black mysteries?of Torsen operation.? Call me PCV boy if you want, but I really believe there are very few that really understand how it works,?more specifically,?how to work it.? I don't see closed loop PCV as a bad thing, and both Eaton and Magnuson advocate running PCV closed loop to carbon treat the blades of the SC and put a coating of deposits in the plenum to screw clearance.? I don't see why this theory also wouldn't hold true for a turbo as well.

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Scott Justusson

PCV Boy formerly known as Torsen Boy

'94 Landcruiser Supercharged with modified PCV 

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In a message dated 9/5/2007 3:19:48 P.M. Central Daylight Time, benswann at comcast.net writes:

Thanks Scott,



This is helpful in furthering my understanding.? I thought I knew what a PVC
valve did and how the system functions - or is supposed to.? I think by the
end of this I'll really understand.? Until the next time that is.



So any recommendation on which valve to use - if you go to FLAPs there are at
least 50 different versions of valves and even more variation when you get
into model, port size and orientation.? Some are simple check valves and some
are apparently much more.



We have to presume that I no longer have the proper remnents of the UrQ setup,
and that the restriction would be significantly different.? I checked out the
early TQ implementation and it works because there is just a slight venture
vac. Used inside the metering box.? With speed density, no such port.



Ben




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