Servo to Plenium pipe

[F908 Tim]

Can anyone tell me the purpose of the pipe between the back of the plenium and the top/front of the brake servo?
I guess its to do with vaccum to the servo but don't really see what it does or how it does it.
What would happen if there wasn't one???

[tvrgit]

The plenum chamber operates under vacuum because the engine is sucking in air.

The hose transfers the vacuum to the servo - where the vacuum provides brake assistance by drawing on a large diaphragm (in the large round bit on the servo) when you press the pedal.

No hose = no servo assistance = very hard pedal = both feet and prayers to stop.

No hose also = air leak to manifold = serious fuel map problems.

[F908 Tim]

Thanks tvr, follow all that.
I will keep that bit then!