[Mk2] [Turbo] Stock BOV one way valve...

[Neil Turbo]

Hi guys. My friend's rev 2 turbo is running the stock recirc dump valve, but is missing the little white one way valve from the pipework. Can anyone tell me what the exact function of this valve is, and what difference it may make running without it?

The reason I ask is that whilst it was boosting nicely as it should, when it's not on boost, the engine seems quite hesitant in picking up the revs - although there is no misfiring or anything. Doesn't appear to be any leaky pipework anywhere, timings are spot on etc, just this valve missing.

Any ideas?

[raptor95GTS]

it's not one way, it's restricted in one direction. I helps to open and close the BOV quickly though how exactly it does this I don't know. The fact it has restricted flow in one direction against free flowing in the other direction would indicate some kind of pressure differential at work.

[Neil Turbo]

Thanks for the reply Allan, that might explain the hesitation then. I remember experimenting with it on my old tubby, reversing it definitely prevented the BOV from opening as it should as you could hear the compressor wheel stalling on the gearchanges.

[gazrev1tubby]

Its know as a VTV or vacuum transmitting valve