[200q20v] Audi 20V Turbo Crankcase Breather System Tuning

[Phil Rose]

At 7:10 PM -0500 11/1/00, Brett Dikeman wrote:

>At 10:43 AM +0200 11/1/00, tommy.arnberg at nokia.com wrote:
>>Hello  !
>>
>>THE BIGGEST PROBLEM IS THAT WITH HIGH
>>BOOST THE CRANKCASE OIL/AIR MIXTURE FLOW GETS INTO THE
>>INLET VALVES AND STICKS TO THE VALVE SURFACE
>>AND AFTER LONGER HARD USE THE INLET VALVES ARE PROBABLY NOT
>>94% TO 97% TIGHT ANY MORE !
>
>
>
>>STE 5122  $ 95.79
>

[snip]
>is...it looks like a sizeable widget.  Where would it get placed?  I
>can only think of room in back of the engine, maybe mounted where the
>washer bottle used to be in the 5k's...but there is a fair amount of
>heat from the exhaust in that area that might be torture for the
>hoses(then again, the windshield bottle did just fine; a little
>aluminium shielding...)


Yep, as was said in yesterday's posts? :-)

Anyway,  Tommy A. seems to believe the device should be  a _vented_
oil-separator, whereas I had assumed that any oil collection device would
need to maintain the closed crankcase breather system. Tommy says (of the
bottle w/vented cap):

>This "vented thing" is very handy and important because
>the oil/air -pressure has to come out of the system
>when the original connection to Turbo charger
>input is disconnected !  And the bigger the
>hole is the easier is the pressured air to come out !
>
>Disconnection from Turbo input (see Audi chart Audi S2 ABY
>and there the part numbers 13, 12, 15)
>is needed for stopping the air contamination
>before inlet valves !

My own naive view is that you need to maintain a closed loop and just take
out as much oil as possible from the crankcase air flow before it reaches
the MAF, turbo, IC, MM-hose or IM. Seems to me that the "vented" approach
will have inherent problems (unmetered air, carbon canister fumes, etc.)

An important preliminary step was indicated by Chris, which is to establish
whether or not the oem crankcase pressure regulator is at fault if
excessive quantities of oil are observed to coat (contaminate) the intake
tract. Possibilities are (1) that the crankcase pressure regulator is
simply defective, or (2) that if not defective it is inadequate; that is,
that minimum breather pathway (0.180" dia aperture) through the
regulator--when seeing turbo-intake vacuum--is simply too large for boost
levels that exceed the stock 1.8 bar design.

One further question that comes to mind is: to what extent is a
crankcase-breather problem caused by an air filter that's too restrictive
(e.g., too dirty)? I raise this point since the turbo intake-tract vacuum
(which is what pulls in the crankcase gases) ought to be be significantly
impacted by the airbox/cleaner restriction, right? Hence, I wonder if the
people who use K&N air filters (and have boost mods) experience less severe
"contamination" from the crankcase breather, since wouldn't they be
operating with a lower vacuum at the turbo intake?

Phil


Phil Rose				Rochester, NY
'91 200q				mailto:pjrose at frontiernet.net