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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
I'd like to know how they managed control pressure in the 934. With CIS it has to be lowered quite a bit during full throttle boost somehow and I don't see a recognizable control pressure regulator in there anywhere.

..did a trunk monkey reach in and push the metering plate down when the driver pressed the go pedal?

It would be interesting to rotate that 30* angled air duct around the other way and see if the power output of the motor changes during boost.
The 30* angled duct is directing air down onto the metering plate at an angle slighty opposite the direction the air will be traveling in after it flows around the plate and leaves the air flow meter housing.

I can't see through the screen on it in the picture Cole posted but I remember sometimes seeing fiberglass vortex generators mounted just on the turbo compressor intake on early turbo Porsches to make the air spin around before hitting the spinning compressor wheel when I was around those cars 27 years ago.

I wonder if there is a vortex generator under the screen on that air duct. They look sort of like a stationary fan blade mounted edge to edge inside duct and they make the air spin around as it passes through. If there is one under the screen in that 5" duct then maybe making the air spin before it has to flow around the sensor plate makes it so more air can flow around it.

edit: In the second picture jcc911 posted you can see through the screen a little better.
It looks like a 4 bladed vortex generator with very little or no pitch to the blades but you would have see it without the screen while looking straight down on it to know.

Another thought is it's not a vortex generator and the 4 blades go straight down with no swirl almost touching the sensor plate in it's closed at rest position. That would make it so incoming air would have to flow more equally over and around the entire circumfrence of the sensor plate which would probably push it down farther instead of most of the air taking the shortest route and flowing over the plate on the side closest to the 3" hole for the intake hose in the side of the air flow meter housing.
I think the 30* angle of that 5" duct would also help force the sensor plate down farther because of the turn the air has to make in the rounded chamber under the sensor plate as it turbulates around and flows out the 3" hose connection hole.

The stock metal air cleaner housing is offset a little to the right before it reaches the air flow sensor and that would make the air flow spin or swirl clockwise to a degree right above the sensor plate and there is a little cone shaped air director in the middle right above the sensor plate that looks like it's there to direct the swirling air flow outward while it's circulating and flow more evenly over all 360 degrees of the sensor plate as it makes that 90 degree turn downwards.. or something closer to it.

With out some kind of air flow director above the round CIS sensor plate most of the airflow over the sensor plate is going to take the shortest route possible over the far side closest to the 3" exit hole in the side of the housing just under the sensor plate.

Last edited by JFairman; 03-10-2012 at 08:28 AM..
Old 03-10-2012, 07:44 AM
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