Revised OEM PCV and Crankcase Breather Tube

06F129101P Front Detail

In my current quest to return some parts back to OEM spec, I’ve recently purchased the latest revision PCV components.  The latest revision PCV valve is “P” with the part number 06F129101P.  There is also another revision of the rear breather tube, part number 06F103215B.  The valves in the latest revisions seem much stronger compared to my old “G” revision.  The check valves are now spring loaded instead of free moving.  I don’t know when they switched to the spring loaded valves because I completely skipped over the 2 or 3 other revisions.

06F129101P Valve Detail

If you’re wondering why I went back to stock, I wanted to remove the catchcan I’ve been running.  An intake manifold teardown by a forum member  revealed that catch cans do little to aid in preventing the intake valve deposits inherent to direct injection engines.  I have also been thinking about the lack of intake vacuum working on the crankcase.  In the catch can setups, vacuum is sourced from intake air moving over the rear breather tube exit.  I think it is a max of 3″ of mercury according to BSH and this occurs in the higher rpms under boost.  At lower rpms, actual vacuum may be much lower.  Too little flow or stagnant flow through the valve cover may allow the blow-by gasses to start forming deposits.  I’ve noticed a little grime building up around the oil cap area, despite the regular oil changes.  The accumulation of these blow by gasses can contaminate oil and deteriorate it much faster as well.  Another side effect of routing all gasses through the rear breather tube seems to be, ironically, more oil in the charge pipes.  If a recirculation type catch can does not catch all the vapors, the rest end up condensing in charge pipes and intercooler.  The stock system sends them directly to the intake manifold to be burned off.  The way the stock system works, it only reroutes vapors through the charge piping and intercooler under boost.  When I installed my throttle pipe, a good amount of oil came pouring out of the pipes.

06F103215B Check Valve Detail

Now oil vapor in the in the intake charge is detrimental to performance.  This is where a catch can does help.  Oil vapor can effectively reduce the octane level of the intake charge and lead to more knock, which would then decrease performance.  I haven’t noticed a performance difference since I switched back to the stock system but then again, my car isn’t exactly a horsepower monster.  It is a compromise situation but after many miles of thought, I’d rather have the stock system deal with the evacuation of the crankcase gasses.  The stock pcv system flows a lot and I don’t think some of the catch cans flow enough.

06F129101P Rear Detail

The stock pcv valves have not been models of reliability, which is one of the reasons catch catch cans have sold so well. Modified and stock cars alike can blow through them.  These newer parts are now several revisions deep and they seem to be much more robust pieces.  The rear check valve in the breather tube looks much better.  The front pcv check valves have a more positive engagement compared to the “G” revision I compared it to.  I guess only time will tell!


Revision D Diverter Valve – Stock Location

Well it’s official, I’ve gone nuts.  I went back to the stock diverter valve location after all the time I spent thinking about diverter valve relocations.  The mechanical valve was nice but I wanted ECU control.  The ecu controlled relocate was nice but required some rigging to get it to work with the stock intake.  So I’ve gone full circle and landed back at a nearly stock intake system setup.  My stock intake is back in, and the diverter valve is back in its original location.


New piston design

Initial impressions are that the D valve feels better in the stock location than in the relocated position.  Maybe something was leaking?  No logs yet, they will come eventually.  Boost response felt a little “off” with the valve in the relocated position.  It bogged sometimes and the car felt labored in the very low rpms.  The boost ramp up was a little strange, it felt like it would spec too much boost at a low rpm.   I should have run some logs but didn’t think of it at the time.  With the valve in the stock location, boost response feels better and is more linear.

There are a handful of reports stating that the valve does not seal correctly on the FSI, leading to decreased throttle response and delayed boost peak.  The cause was never determined but in most cases the problems were resolved by switching back to a diaphragm version.  It could have resulted from a faulty valve or improper installation.  My valve seals and functions just fine.  The summer heat should really put the valve to the test, we’ll just have to wait and see if it holds up.

I think Volkswagen and Pierburg (manufacturer of the actual valve) have finally come up with a bullet proof solution to an annoying problem (torn diverter valves).  The valve is maintenance free and if it proves reliable, is perfectly fine for a mildly tuned 2.0t.