[urq] Too much Crankcase ventalation?

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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.  
 
I had a 12 second GLH turbo, my wife drove regularly.  Never had a  catch 
can, never needed it, no windage tray either.
 
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.
 
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.
 
My 02
 
SJ
 
 
 
 
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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