[urq] Too much Crankcase ventalation?

Wed Sep 5 13:21:40 EDT 2007

Scott,

All kidding aside... you must be forgetting what I do for a living.? No misunderstandings on my part about how a PCV system works, or its purpose... or why valve cover area presents a good space to work with.? FWIW, the AAN doesn't use the valve cover at all... it only looks like it does (I'm sure you know this).

Again, I have no disagreement on either the purpose or benefit of a PCV system.? I think Ben hit the nail on the head last night... his system is oversimplified.? Based on his description, I think he's left out a few key components of a stock PCV implementation.? Put those in, and he'll be fine.? He's running a K24... so we're not talking about an?engine that's?doing anything more than a typical "chipped" car.? He likely doesn't need to change anything in the design... he just needs to put all the parts in place.

Anyway... beaten to death...

Dave

-----Original Message-----
From: QSHIPQ at aol.com
To: Djdawson2 at aol.com; urq at audifans.com
Sent: Wed, 5 Sep 2007 10:40 am
Subject: Re: [urq] Too much Crankcase ventalation?

Dave

The reason the valve cover is tied to the PCV system at all, is to present a dead air space for drainback, that's part and partial to this type of design, that dead air space is to allow the oil vapors to separate from the any raw oil.? I don't believe that modifying the PCV valve to have protection against ingesting roiling valve cover oil from the valvetrain is really that hard.? Audi did a great job of it on the double walled 5k's.? I've seen a lot of turbo/SC applications that don't ingest oil.? 

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I had a 12 second GLH turbo, my wife drove regularly.? Never had a catch can, never needed it, no windage tray either.

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PCV is only a problem, because audi didn't do a good design with the 20vt, and to date?on these forums, catch cans are the easy answer.? I look at closed loop PCV as the given answer, and figuring out the problem of getting it designed right as the problem.? In Ben's case IMO, it's a simple matter of getting back to the original vacuum balance.? I just don't see that as a catch can problem.? I'm also a firm believer that venting to atmosphere PCV reduces the service life of oil.? You need vacuum to pull off the vapors as apposed to re-saturating them in aerated oil.

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Is some sort of design change necessary?? Yes.? Does it dictate that performance gains will come from a catch can?? No.? Does it dictate that a proper PCV circuit shouldn't and won't ingest oil?? Yes.? Can it be done properly?? Sure.? Audi actually has a few SAE articles specifically?on the I5 oiling that are worthy of read wrt this discussion.? Given Ben's abilities, I'd bet he can?get this right without using a catch can.

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My 02

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SJ

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In a message dated 9/5/2007 11:21:21 A.M. Central Daylight Time, Djdawson2 writes:

Before we start slapping me around for having a fast pig (they call them "Razorbacks" down here in NW Ar-kansas)... let's remember that the weight of said pig has nothing to do with anything at all.? That powerful I-5 20v could be bolted to my piggy, or bolted to a go-kart frame... it is irrelevant.

What is relevant is the fact that when significant acceleration occurs, oil will go where it is not wanted.? As stated before... to me, this has little to do with the breather/PCV setup, and much more to do with poor oil control within the engine... both valve cover and pan.

SO... the stock breather/PCV system WILL AND DOES?work fine... if you are OK with the concept that your turbo will be inhaling oil now and then.? If you are not OK with that, some modification will have to be made to allow the oil to separate from the ventilation flow, and drain back to the crankcase... prior to any chance of that oil being drawn into the intake charge.

Now what king of guy would let his sig-o anywhere near a 12 second street car... let alone ask her to empty his catch can?? ;)

Dave

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