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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Early 911 turbo's had a second saucer shaped throttle body bypass valve that looks alot like a deceleration valve without the 3rd small accuating intake manifold vacuum line going to it.

It was mounted back behind the auxiliary air slide cold start valve and you can't really see it with the factory aircleaner in place.

I've never seen one other than occasional pictures and I don't know what opens it so i can only guess air pressure in the intercooler when you let off the throttle quickly opens it letting air bypass the throttle body during upshifts and initial deceleration.
Probably an emissions and anti turbo compressor surge device.

They got rid of it by 1986 when the turbo came back to US dealers with more emission controls.
Old 12-11-2009, 02:32 PM
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