Plenum butterfly?
12-27-2011, 05:40 AM
#1
Instructor
Thread Starter
Plenum butterfly?
I searched around and couldn't find much information on this. In the intake manifold there's a crossover tube which shares the left and right plenums and a butterfly separating them.
Does the butterfly open at idle to smooth intake pulsing, and then close at high rpm? I briefly read a post where someone mentioned wanting to remove their butterfly, but not sure what purpose this would serve.
Brett,
Does the butterfly open at idle to smooth intake pulsing, and then close at high rpm? I briefly read a post where someone mentioned wanting to remove their butterfly, but not sure what purpose this would serve.
Brett,
12-28-2011, 07:29 AM
#2
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Hi, not running the 964 n/a intake on my turbo (am using the earlier ally Carrera unit) but have also read something about this valve, and iirc, it gets removed when folk use this intake for a turbo EFI conversion from CIS. Not sure but it may be removed due to the plenum being pressurized, and not being robust enough to handle it...have to be honest, I didn't pay too much attention as it didn't apply to my application, I stumbled upon it whilst looking for the Carrera >intercooler throttle housing rotation mod
12-28-2011, 02:58 PM
#3
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12-28-2011, 11:18 PM
#4
Instructor
Thread Starter
Just found an interesting article on autozine's website concerning the crossover plenum. Interestingly enough, it specifically mentions the 964.
http://www.autozine.org/technical_sc...h_engine_2.htm
Resonance intake system.
Boxer engines and V-type engines (but not inline engines) may employ resonance intake manifold to boost mid to high rev efficiency. Each bank of cylinders are fed by a common plenum chamber through separate pipes. The two plenum chambers are interconnected by two pipes of different diameters. One of the pipes can be closed by a valve controlled by engine management system. The firing order is arranged such that the cylinders breath alternately from each chamber, creating pressure wave between them. If the frequency of pressure wave matches the rev, it can help filling the cylinders, thus improved breathing efficiency. As the frequency depends on the cross-sectional area of the interconnecting pipes, by closing one of them at low rev, the area as well as frequency reduce, thus enhance mid-rev output. At high rpm, the valve is opened thus improves high-speed cylinder filling.
Resonance intake system has been used in various Porsche starting from 964 Carrera. Since 993, Porsche combined it with an additional variable length manifold to form a 3-stage intake system names Varioram. However, it is very space-engaging so that the 996 employs only the resonance intake system. Honda NSX is another rare applicant for resonance intake system.
http://www.autozine.org/technical_sc...h_engine_2.htm
Resonance intake system.
Boxer engines and V-type engines (but not inline engines) may employ resonance intake manifold to boost mid to high rev efficiency. Each bank of cylinders are fed by a common plenum chamber through separate pipes. The two plenum chambers are interconnected by two pipes of different diameters. One of the pipes can be closed by a valve controlled by engine management system. The firing order is arranged such that the cylinders breath alternately from each chamber, creating pressure wave between them. If the frequency of pressure wave matches the rev, it can help filling the cylinders, thus improved breathing efficiency. As the frequency depends on the cross-sectional area of the interconnecting pipes, by closing one of them at low rev, the area as well as frequency reduce, thus enhance mid-rev output. At high rpm, the valve is opened thus improves high-speed cylinder filling.
Resonance intake system has been used in various Porsche starting from 964 Carrera. Since 993, Porsche combined it with an additional variable length manifold to form a 3-stage intake system names Varioram. However, it is very space-engaging so that the 996 employs only the resonance intake system. Honda NSX is another rare applicant for resonance intake system.
