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Puny Bird
Join Date: Nov 2002
Location: Port Hope (near Toronto) On, Canada
Posts: 4,566
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Quote:
Originally Posted by targa72e
Hi Mark,
intake style is somewhat dictated by the camshaft choice. Individual throttles help with reversion for cams that have a lot of overlap. Common plenum with single throttle limits cam choice to those that typically have less overlap. Plenum over ITB is a way to run more aggressive cams and use resonance tuning to help broaden and enhance the power curve. GT3 intake is often referenced for larger engines and 964 plastic runners for smaller. When used on top of ITB the front crossover where the throttle would normally be becomes a air filter inlet. The rear cross over tube has the resonance flap that is opened or closed depending on RPM. I do not know enough about intake design to know if there is a reason Porsche did not use a single center chamber or if it was a packaging decision.
john
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Quote:
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The rear cross over tube has the resonance flap that is opened or closed depending on RPM.
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I'm well versed in the 996 and 997.1 plenums, I have one of each here on the wall.
This EFI system was spec as a turbo system (930) IIRC this system has extra relays that can be programmed to turn on/off certain items like fans, etc. and likely this flap. I know this resonance flap runs off of vacuum and has a "can" under the plenum but it also has a electric valve controlling something to do with this as well.
I think I'll dry fit the 2.7 for a jig and work from there.
__________________
'74 Porsche 914, 3.0/6
'72 Porsche 914, 1.7, wife's summer DD
'67 Bug, 2600cc T4,'67 Bus, 2.0 T1
Not putting miles on your car is like not having sex with your girlfriend, so she'll be more desirable to her next boyfriend.
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