I have noticed that when the engine speed of my car reaches 2500rpm in any gear, the engine makes a smooth humming sound that does not appear to happen at any other rpm.

Is this just the natural frequency of the motor at that speed making the noise, or is it related to the fact that the peak torque happens around that point?

I like the sound anyway, especially when you drive past buildings and soild walls with the windows down!

 

I have that also!! I have no idea what it is. But it happens right around 2500. It's this humming sound. Kind of hard to explain it. I also have something rattling around that rpm too i think it's a lose exhaust pipe mabye the exhaust pipe is making that sound somehow?

I just noticed something else also we both have 95 M6's hmmmmm.

 

Our engines make max torque around 2500 rpm.

Blaze, i have no exhaust and i still have the rattle. It's not the exhasut, i havent figured out what it is yet. I removed all of the exhaust to the cat and hangers and i sitll get the rattle from the passenger rear of the car. Where is your rattle?