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Exhaust F/Up! Mystery?

I recently encountered a guy who was not happy with the performance of his A6/18T. So he removed the exhaust catalitic converter and installed a straight section at that point. Now the engine has a rattle. No loose retainer bolts or anything. It sounds like a bit of mettal oddly rolling around in a chamber of sorts. The car went to the Audi dealer (to the head mechanic) and no one had a clue as to what's causing the rattle. Remember...just the converter was removed. He initially tried to sell me this car, but the rattle could not be explained. The chief mechanic says "other than that...the car works fine". I'm sorry. But this is an AUDI A6 18T and that is just not acceptable. Just think of the emotional stress of having to make excuses for that annoyance. There could be long term damage.

Reply to
Shimbo
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I think that engine relies on being set up with the correct exhaust, removing the cat does work with some cars to increase power but not with all, it could be valve rattle, he could try replacing the cat & see if the problem disappears, or to compensate the removal of the cat, an ecu re programming may be required to set the ignition curve which may now be different with reduced exhaust back pressure,

Steve.

Reply to
Steve68s

Reply to
Tony

The car is very sound proof when driving at mid range engine speed. I only detected the rattle standing outside the engine area. Steve68 says "it could be valve rattle". What valve exactly Steve?

Reply to
Shimbo

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