Quote:
Originally Posted by boyt911sc
Joe,
A good o-ring will prevent the unmetered air from going inside the motor. A smoke machine needs only a very low pressure (1~2 psi.) to detect an air leak. If air or smoke gets through the opening, cracks, space, etc. it will show during the test.
You will never have a good running CIS if you allow these leaks to persist. There should be no smoke coming out of the air box, intake runners including rubber boots, injector o-rings, pop-off valve, vacuum lines, etc. during a smoke test. The POV works better under vacuum. This is how you test the integrity of your vacuum system.
What the smoke test does is locate the hard to find leak source/s. If the smoke could escape from the system under test, imagine what will happen to the ambient air if sucked by the vacuum producing motor.
Summary:
A smoke generator is very effective in locating those hard to find air leak sources in a CIS motor particularly underneath the airbox. This is more efficient than the pressure air and soapy water method. Fix all sources of air leaks and your CIS will be running reliably for a long time. It is the lack of understanding about CIS that makes people hate this system in some way.
Tony
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Tony,
Sorry for the misunderstanding. I couldn't agree with you more how vacuum leaks are very detrimental. What I was trying to convey was that positive pressure no matter how slight would cause the appearance of a leak from the outside but be totally sealed when under negative pressure.
How is that possible? Well, the plastic sleeve (bushing) also has an exterior "O" ring that seals it against the manifold. But the bore it fits in is slightly funnel shaped so the slightest amount of positive pressure is enough to displace it and cause it to leak similar to a one way valve.
A very clever design but very deceptive.
Cheers,
Joe
87 Carrera