Vacuum system in a s/c setup

[michaelw]

A quick question. The vacuum system in a car (for brakes and such) comes from the inlet manifold. If the car is supercharged the inlet manifold pressure is above 1 atm. Thus how does the vacuum system still function?

The only thing I can think of is that the vacuum runs off an venturii system so the vacuum is caused by the flow of air and not the low inlet manifold pressure.

Mike.

 

[BillK]

The same amount of vacuum is present when the throttle is closed compared with a normally aspirated engine.
Obviously this occurs when the brakes are used so there is no real problem.

However, small valves are used in the vacuum lines to stop the positive pressure affecting vacuum driven units such as the brake boost unit.

Additionally, the PVC system has to be addressed and components from turbo manufacturers are usually supplied with kits.