super_monkey

Not 'the engine knock' but a knocking sound that comes some place on the car under heavy acceleration. Sounds like something is smacking something. I only noticed it yesterday when going in a tunnel. I know this is vague but does anyone have any ideas before I take it in? It's an 04 SL55

IngenereAMG

How about a little more detail?

Maybe a loose heat shield?

kamilclk430

Loose exhaust hanger, muffler bouncing. Happened to me before.

super_monkey

I don't know where the sound is coming from but it only happens when the engine revs high under load. It sounds like a flapping flag for the lack of a better expression. The sound is very consistent, with a set frequency.

I can't even imagine how this could be diagnosed without taking the car to a drag strip or a dyno.

sound 8

I had something really similar in a CL65, and the noise seemed to come from around the gear selector getting worse with revs, fear not it was some pipes that the tie wrap had slipped and needed re dressing. No charge either