CIS Engineering Question

[1982911SCTarga]

What engineering problem was Bosch and Porsche solving in using the springs and screws to attach the CIS airflow/mixture control unit to the top of the airbox? Vibration?

What's a good rule of thumb on reattaching with these screws? To compress the spring halfway? More? Less?

Thanks!

Brian

[Scott R]

Factory manual says "tighten lightly, then loosen by 1 turn."

[bkreigsr]

spring mounting might have been to enable it to 'give' a little for the inevitable start-up backfire?
Bill K

[1982911SCTarga]

spring mounting might have been to enable it to 'give' a little for the inevitable start-up backfire?

I've thought about this, but it doesn't seem possible -- that's a lot of weight on top of the airbox. I'm thinking the mounting and the foamy gasket underneath provide protection against vibration/harmonics that would affect the unit and all of the attached lines. However, I'm completely guessing.

"Tighten lightly, then loosen one full turn" sounds to me like basically compress the spring slightly so the screw can't back out.

Brian

[oneblueyedog]

The foam gasket is a cushion as I found out after I tried RTV to seal the CU housing to the airbox. It indeed ran horribly. As soon as I removed it and used the foam gasket from Porsche, it solved it. I could not believe it made such a huge difference. It does.