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Ok someone tell me there car sounds like this too. At 4,500 RPM my car sounds like every bolt on the engine is loose. Ok maybe not that bad but it is really loud and at 5,000 RPM all the way up to 9,000 RPM it sounds great. Recently i Reset my ECU and I dont have the radio code so i am driving with no music maybe that is why i dont remember it sounding like that.
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Jesse P ~ San Diego ~ 2001 Vortech Supercharged S2000

 

Do you hear this noise all the time? While accelerating? When you take you foot off the gas? How long has it been supercharged?

 

my car has been supercharged for 10,000 miles and the car has a total of 44,000 miles on it. And I hear the noise at any time from 4,500 rpm til about 4,800 rpm. so accelerating decelerating anytime in that rpm range.


Again after that it sounds awesome and there doesnt seem to be any rattiling

 

I assume the noise is coming from the engine bay, try checking the heatshields etc.. That rpm range may be causing the right harmonic frequency to cause a loose heatshield to buzz badly.

If the noise just started happening then this would be my first guess, especially if you can think of any large pot-holes, bumps that could have rattled things.