Wastegate Actuator Question; certainly noob-worthy

[Iheartboost]

So I was thinking about the way a manual boost controller works, and thought "Since this is essentially a ball check valve, wouldn't the wastegate actuator stick open when the valve closes? or does the wastegate actuator self vent?" So if they don't self vent, how do they close with a MBC?

 

[ramsack]

On a ball and spring MBC there is a tiny tiny bleed hole (essentially a boost leak) on the wastegate side of things. On a pressure regulator type it doesn't need one.

 

[Iheartboost]

Must be a very small hole, thanks for the info!

 

[T-mun]

Yup, the hole is very small that the leak is very minimal.. not like the vent type MBC that leaks big time.

 

[JusMX141]

Bleeder-type MBC's must have their own dedicated boost source....do not isntall a bleeder-type MBC into the BOV line or your BOV performance will suffer.

 

[ramsack]

I don't know why anyone would run an MBC to anything but a line right off the turbo. Running it off an intake manifold source just seems silly.

 

[GRAVEDIGGER]

I don't know why anyone would run an MBC to anything but a line right off the turbo. Running it off an intake manifold source just seems silly.

Best performance is achieved with the boost source taken right off the compressor housing or compressor outlet elbow for sure.

 

[JusMX141]

I don't know why anyone would run an MBC to anything but a line right off the turbo. Running it off an intake manifold source just seems silly.

The way I understood is if your MBC is not a "bleeder" style, you need the vacuum source to draw the wastegate shut again so the pressure is not trapped in the line between the MBC and the wastegate. However, there are many guys out there installing bleeder MBC's on their BOV line, and then suffering poor BOV performance as a result of the obvious vacuum leak.

 

[ramsack]

By bleeder style do you mean ball-and-spring? If so then any GOOD ball-and-spring MBC will have a bleed hole to allow the wastegate to shut no matter if you install it on a boost-only line or a vacuum line. I completely agree that an MBC shouldn't be installed on the BOV line. There would be no vacuum leak because a ball-and-spring is a check valve, not allowing vacuum to be pulled, but only boost to be blown through. That's why the bleeder hole is needed on the wastegate side.