toddk911

Has anyone put a compressor on the wg line before your MBC that has a vent/bleed hole???

It vents a lot more air than I had thought. Put your finger on it and it is a very noticeable release of air.

I know it is to help eliminate boost spikes, but how much in terms of spool up would it be affecting?

Oddjob

Youre talking about a LBE/Accuboost pressure relief type boost controller? I have tested them w/ an air compressor and felt the air flow blowing out the vent hole.

The vent hole releases pressure in the WG line and WG diaphram after the press relief valve closes. If it didnt vent off that pressure, the WG would hold open, after the valve closed.

Its such a small hole relative to the flow through the intake - its not really adversly affecting boost or spool up.

toddk911

Ok, so it is "reverse venting" ?? Post spool up and bleeding what was in the line.

Thanks!

Jfrahm

I do not think there should be bleed air from there during spoolup if you boost controller is working correctly.

Porschefile

Bleed valve MBC's are a pretty archaic method of boost control, though they do work. I'd highly recommend at least a typical ball valve as the bleeder valves literally are a boost leak. I guess I don't like them purely on principal as, no matter how small the leak, it's still a boost leak when you think about it.

Oddjob

Were not talking about needle type bleeder valves, were talking about ball/spring pressure relief valves. They have to have a small relief vent hole down stream of the ball, otherwise the waste gate line will retain pressure (keeping the WG valve open) after the manifold pressure drops and the ball/spring valve closes.

Todd, it will bleed anytime the valve is open, so at peak boost you will get some air flow through that vent hole. But the volume of airflow of that hole (its literally pin hole size) is insignificant relative to the amount of air the turbo is blowing through the intake. So you wont be losing any manifold pressure due to this pin hole in the WG control line.