[V8] V8 CV

[Scott Justusson]

 I looked at this system as a possible solution, but it appeared much more complicated than it needs to be. Combined with my experience with early Audi 'vortex' valves, this is a potential nightmare. It is interesting to note that the low output FSI engine uses a single PCV breather (Q7) to bank 2 and the high output version used 2 breathers (as pictured) one breather on bank 1 and one breather on bank 2.  Confirming that changes in engine efficiency, dictates a change in PCV design.

What this does illustrate is the possibility that the valley pan design for fine oil separation is located just too low for proper drain-back properties in a flat sump design the v8 engines use.  That said, I think a vortex type drainback will be prone to clogging problems, btst.   IME, the AAH/AHA v6 engines have the same type of issues using the early 'vortex' style mechanical PCV.  On my 95 C4 Avant (AAH) with this installed, I bypassed this vortex PCV valve and installed a standard FLAPS PCV, and the car hasn't had valve cover problems or expensive vortex clogging problems that come with this design.

Bottom line, if one uses this system, expect to have problems with it.  The heating of the hoses required on this setup alone, makes this a nightmare to retrofit.  Add in that using a non-synthetic oil and/or an older motor can clog these ports (and they are very small) quite easily.

What this does illustrate is that Audi has done a lot of der-technik in attempts to 'improve' PCV on the v8 engine.  That said, other than the location of the breathers not on the end of the valve cover, IMO this system will get a lot of attention and scrutiny as these motors age.

My .02

Scott J
92 v8 ABT Chipped



 

 

-----Original Message-----
From: bw <bw at UDel.Edu>
To: Professor GT gmail <CavalloGT at gmail.com>; v8 <v8 at audifans.com>
Sent: Thu, Oct 4, 2012 8:41 am
Subject: Re: [V8] V8 CV


Audi's solution to our CV problems are graphically illustrated here: 
www.s4-mtm.com/images/RS4V8-StudyGuide.pdf  for the V8 FSI engine

The crankcase is ventilated through both cylinder heads. The valve covers 
incorporate a large settling space. This space acts as a gravity-type oil 
separator. A fine oil separator is connected to the valve covers by means of 
plastic hoses. 

After the blow-by gas has passed through the fine oil separator, the gas flows 
into the intake manifold downstream of the throttle valve. 

Blow-by gas volume is dependent on engine load and RPM. The fine oil (“oil 
spray”) is separated by means of a cyclone separator. 

 Piston ring flutter at very high engine RPMs and low engine load can result in 
a 
very high gas-flow rate.   etc., check it out.

Their PCV unit is an add on that you may improvise from.


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