This might be a silly question, but something just struck me...

The brake booster operates off vacuum in the intake manifold. But how does the booster function when there's a turbo pushing boost into the manifold? Does it operate off residual vacuum using its 1-way valve?

TIA

 

Most of the time your brake when you're not in boost meaning you have a negative manifold pressure (vacuum)... I've never tried BRAKING while in boost so I really don't know... I'm sure you could slow down but it would be like braking when the car manifold has zero vacuum (at rest)...

 

That's what I thought, thanks

I figured it would be a problem for, say, autoXers who do a lot of brake + throttle to help the car rotate

 

Notice the check valve.

(#5)

Boost pressure never sees the boosters’ diaphragm.

With the engine off, you still have "power assist" for about 4-6 brake applications.

 

yeah, besides, you're not always in boost for more than a certain time, but yes, the check valve saves the day.

 

OK that makes sense

Next question then is, how strong is the check valve? The PCV has a check valve that gives out on mild boost, right? What psi will the brake booster check valve give out on, roughly? Or are they even comparable?