964 induction system question

[LARRY SHARP]

does a 964 engine have only a two stage throtlle body ? or does it have a valve that opens at a set rpm from a vaccumn signal?

[Shamus911]

The latter - the resonance valve inside the intake piping opens at 5500 rpm

[LARRY SHARP]

thanks shamus

[Bill Verburg]

Originally Posted by LARRY SHARP

does a 964 engine have only a two stage throtlle body ? or does it have a valve that opens at a set rpm from a vaccumn signal?

there were 2 different throttle bodies
early used w/ aluminum manifolds


late used w/ plastic manifolds


a different question is the intake manifold, which has dual geometry's controlled by 2 resonance flaps. The resonance flaps are are activated by the DME via a vacuum operated electronically triggered solenoid after reaching 5500rpm, then close when the rpm drops below 5400. Additionally the flaps are activated briefly each time the ignition is turned on.

[rothaus]

I have some question: I have the plastic manifold, and the solenoid is not operating when the ignition is switched on. The green/black wire has 12V when the ignition is on. When I connect the gray/white wire to the ground it operates. Could the issue be in the DME ?

Also from what year was the plastic manifold used, my engine is supposed from a 1990 car.

Thanks for any info on that.