SO, for the last year there has been this booming exhaust sound from the motorof my 745.
It is a low frequency, and is most like a large diameter performance exhaust (like I had on my Datsun 510...what a cool car!).
I have measured with sound level meter in the car, and compared it with my 744.There is 3-4DB more low end noise in the 745
It is definately engine speed related, could be exhaust noise as it is louder when accelerating and cruising and lessens on closed throtte.
I've checked around the intake too.
I replaced the entire exhaust cat back..no difference.
Replaced the cat pipe to exhaust downpipe gasket, no difference
I wonder if it could be the cam belt, a mechanic told me they are noisy if they have too much tension, but I wouldn't expect this kind of noise, maybe a whine.

Interstingly, when I replaced the head gasket on my 744, and had to re-bolt on the exhaust manifold, THAT car seems to have the noise now (but it's back n the garage ..see 16v mistake post). But I had to put on a new belt too, could it be the tension?

Sorry this is so vague and rambling, but I know if some one had this problem they'd know it (even us old guys can hear low frequencies).

Any ideas for looking for exhaust leaks or other theories welcome...


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744-16v,745-16v,242Turbo.245DLT