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Air intake and plenum performance

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Hello everyone,

My name is konstantin, I own a NA air cooled Porsche 964 from 1992 and considering buying an RS4 B8, the one with the NA 4.2 L engine from 2012.

I watch the very interesting video by Andre Simon regarding the Air intake.

I am trying to improve my air intake and the plenum on my Porsche 964, and eventually the one from the RS4 NA,

The goal is increase, improve the torque, maybe towards the lower side of the RPM range.

There is a few options I am thinking and you I would appreciate your opinion and experience,

a) Use the AT Power shaft less throttle bodies, providing the could fit.

b) Extend the inlet pipe before the throttle (lenght to test)

c) extend the plenum before the heads by fitting an accurate size and bore spacer. (length to be tested)

Thanks for your input


The two examples you are trying to improve upon are not the most basic starting points to begin with.

The B8 RS4 with the 4.2l V8 has got intake runner flaps and port dividers, which are used to try maintain higher intake velocity at lower engine speeds. They are also notorious for the plastic linkages failing. In these engines, often cleaning the oil and carbon build up (due to no port injectors) is the biggest performance gain for these engines.

Some people have also made/sell phenolic spacers for themal insulation of the manifold and to increase port volume slightly, but in my experience any misalignment from the spacers negates any potential benefits.

The porsche 964 has a resonance flap, which effectively changes the volume of the intake manifold (among other things) when the flap is switched.

Hello Nathan,

Thanks for your advise !

Yes the Porsche has the resonance flap that open at around 4,2 k and it is working very well.

It is also important to check his function, as all closed you lose top end and all open you lose torque. my 964 has an Emerald ECU, cat less and an inlet pipe with ITG filter, it is producing 294 BHP and 264 Ft/lb (lots of weight removed but still nice on roads)

Regarding the B8, I am aware of the carbon build up, the cleaning needed every 30 K I guess, and all the basic remaps, apparatly the E85 remap is giving good results.

I am still to understand how the runers and separators are functioning and still quite intrigue to the reason carbon is building up, is it because the mapping at lower end is set rich to preserve the engine ....

Many thanks


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