I have not done this yet, but I'm seriously considering it and I wanted to get some opinions on it. For those that don't know basically past the secondary CATs the exhaust dumps into a Y pipe then feeds into the resonator then back into a Y pipe that feeds into the two mufflers. For anyone that has removed there resonator they will notice that the cavity that it was in has alot more room now and you'll be able to add a second pipe. The pipes will just need to be slightly smaller.

What I would look to have done is get rid of the Y pipe past the 2nd cats and have two pipes that start from the 2nd cats and go all they way to the mufflers.

A local exhaust shop told me they could probably use 2 1/4 piping and the job would run about $300.

Anyway, post your thoughts on this, good idea, bad idea, do you think I'll loose power, gain power or see no difference?

You will need a y pipe for the muffler cuz your diff is blocking the way.


Also, by using 2 smaller pipes, I really dont think theres going to be any hp gain.. it may sound different i guess.

let us know how everything works out

good luck

To really find out if the current exhaust is enough of a restriction to benefit much from these mods, you would have to take pressure measurements at several locations along the pipes & see where the most backpressure is. I believe the single large in/out pipe by the resonator is approx 3" diameter, correct? That should be enough for stock levels of HP and gives you the same surface area as 2x 2-1/4" pipes.

If it were done correctly, you probably could pick up a few HP with a good true dual exhaust arrangement that makes proper use of an X-pipe, but you'd probably need headers to get that much more out of these engines as I would guess the factory manifolds flow like crap from what I've seen. AMG couldn't have done much tuning work here to scavenge the exhaust from the cylinders. It's really sad that AMG decided to mount the same crappy log style exhaust manifold on all their cars as the standard Merc V8's. Ever seen what a decent header should look like? You'd think for the money they charge us AMG could afford to include them. BMW M does... Heck, even the new Toyota truck V8's have a better header than our cars!

My advice? If you just want to experiment & have a project, give it a whirl (if you know a good muffler shop). Just don't let them use pipe that's not mandrel bent anywhere, and don't expect a huge increase unless you go to 2.5" pipes and then you may have to change more parts than you want.

Sounds like somebody should fab up a complete custom exhaust for these cars, headers to tailpipes... I bet a good hot rod exhaust shop that builds custom headers could do it for less than a set of Renntech headers.

Alright you guys have convinced me its not worth it to try. I guess I'll just wait and hope that when the C63 comes out it has a true dual exhaust.

Sorry, didn't mean to kill your enthusiasm for it. There probably is something to be gained, I just don't think the swap will be as easy as installing 2 new lengths of pipe & calling it a day.