Resolved MBC how exactly does it work?

[4g63tc]

does it work on a meter in, or metered out principle? does the pressure flow both ways? i'm just wondering cause i was gonna order a needle valve, from a pneumatics supply compny that my work buys from.

Most of the Mbc's ive seen look like standard metering valves, and can be purchased with fittings for about 20 bucks, also how critical does the metering have to be?

 

[steve]

Most people nowdays run what's called a ball valve MBC. It blocks the boost signal from reaching the wastegate actuator until the boost pressure exceeds the spring pressure holding a ball against the input nipple. Since there isn't any pressure applied to the WGA it stays closed until the moment the ball valve opens. There is also a vent hole, usually in the outlet nipple to allow any trapped pressure to leak off after the ball valve closes to make sure the WGA closes again. Ball Valve MBC are directional. the boost signal must be applied against the spring pressure.

The BSC and older bleeder style MBCs bleed off some of the boost signal to delay the full opening of the WGA. There is a restrictor in the line from the pressure source to limit the flow to the WGA and the bleeder can lower the pressure after the restrictor by allowing more air to escape than the restrictor allow in. Bleeder's typically would be non-directional.

Then there are all sorts of electronic boost controls.

Steve

 

[4g63tc]

so basically it's a pressure relief valve right?

 

[steve]

Only a bleeder style MBC is.

Steve

 

[4g63tc]

so could i do it with say a metered out pneumatic valve to restrict the amount of flow to the wg?

 

[steve]

When people were running bleeder MBC's they used the pneumatic valves to control the pressure released from the line. There is lots of old discussion in the Talon Digest.

Turboxs offers a MBC that uses both ball valve and bleeder for fine adjustment.

Steve