RS246.com Forum :: The World's #1 Audi R, S and RS Enthusiast Community

Parts #24, front of the engine

Hi,

Could someone explain how are those supposed to work?

Thanks!

Just a one-way non-return valve, isn't it?
Presumably, a diaphragm of some description inside that permits air to travel in one direction, but not the other(?)

Hi Technik,

I've got 2 sets - 4 in total- of those, and except if they are all broken (could be!) they let air go through both ways at standard pressure. So no, it's not a non-return valve, although there's one in the ventilation system (part #16).

It's a pressure limiting valve. It'll allow flow in both directions at low pressure, but close when the pressure (or vacuum rather) increases beyond a certain point, presumably to prevent the turbos trying to suck the contents of the crankcase into the intake. I bet they're dead cheap. Just replace them all and forget about them for a decade.

Thank you Shopp. So what you're saying is that if I close one end and apply vaccum on the other end, it should block the flow when releasing the blocked end. Will try tonight

I think it probably depends on air flow, which isn't the same as pressure, but related. I could be wrong. I'll be interested to know what your experiments give.

Maybe if you use a vacuum cleaner, that might give you the airflow necessary. Assuming you've got a good one like a Miele.

It might not even cut the flow entirely. Given the name, it could be that it just limits the flow which would make testing it more challenging.

Kind of matches my 'findings' : with the vacuum cleaner put on the side of the valve, I can see the piston moving up (actually down when the valve is mounted..), but the flow is definitely not cut. It feels like more restricted but honestly hard to tell without real measurements.

Honestly it's still a bit of mystery to me as to what's the main purpose of the thing and how it operates at different engine conditions (idle, boost, deceleration).