DDK - Die Deutschen Klassiker

I’ve been told today by an old Porsche specialist that Vacuum Limiter on my 77 991S is on its last legs.

Could someone explain what the part actually does please, I know the vacuum pipe slots on the top,, but that’s about as much as I know?

Anyone shed some light on it why it’s there what it does, what are the pipes that connect to it?

Cheers

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I don't know a great deal about post-'73 models but as far as I'm aware the vacuum limiter (which is also sometimes referred to as the deceleration valve) is part of the CIS emissions equipment.

I think it works by regulating rapid pressure changes in the inlet manifold when the throttle is suddenly closed - which can otherwise create increased emissions.

I'm fairly sure the original 2.4 CIS models didn't have a vacuum limiter so can't see any reason why yours couldn't be disabled/removed/by-passed if it proves to be unreliable.

Someone who knows more about CIS models will be able to confirm - or disagree ...

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