The purpose of this modification is to remove the resonator from the exhaust system. The resonator is a device that reduces the noise level of the exhaust by running the exhaust flow through perforated tubes running through fiberglass baffles housed inside what looks like a second muffler. The resonator is found before the rear muffler. By removing the resonator you slightly reduce the backpressure in the exhaust system, remove about 25lbs of weight from the car and make the exhaust sound quite a bit better.

First the sound...What you will notice will be an increase in the overall sound level of the exhaust by maybe 20% over stock at idle and while cruising so pretty minimal if even noticeable unless you know what it should sound like. The biggest difference will be at full throttle, the exhaust will really open up with a wonderful and smooth growl that is appropriately loud for the car. It sounds very good and will not cause any unwanted or annoying resonance in the exhaust note or in the car. Do not expect it to sound like a V8 muscle car or a Japanese car with the muffler removed because it won't. It will sound like what you already have "kicked up a notch" during normal operation and "kicked up" about five notches at under load.

Secondly the performance gain...the slight reduction in back pressure seems to improve the bottom end coming off the line just a bit but this has not been confirmed with a dyno run yet. Although, I expect it to make a much larger difference verses stock when the car is modified with a Renntech ECU, cams and pulley kit which is where I am going next. There is also a slight gain from the weight reduction.

This being said, it is a simple and inexpensive mod($250-400 depending on the shop). The factory resonator is removed along with a couple of feet of factory exhaust piping. The front cut is made about 6-8" behind the crossover equalization pipe found in the rear exhaust section about 4" behind the bolting flanges. The rear cut is made about 5" in front of the rear subframe right before the exhaust bends to clear it. The resonator takes the dual pipes going in and the reduces them to a single larger pipe heading back to the rear muffler so a "Y" or "collector" must be fabricated. As can be seen from the photos, the factory exhaust feeds dual 2.5" pipes that dump the exhaust into a smooth and gradual collector(this is key as you don't want any turbulence in the exhaust system) which then exits into a single 3" pipe in almost a straight line to the factory pipe that goes to the muffler. The 3" size is about .2" bigger than stock so it allows for slight restrictions caused by any slight bending or working of the pipe. Other things to not are that the factory ground strap from the resonator to the car is replace and a hanger is installed to go from the new exhaust section to the old rubber mount for the resonators. The fabricated parts are all stainless steel like the factory uses(tough to weld so not as pretty as it could otherwise be) and have been sprayed in a silver hightemp paint but there is no real reason for this.

Make sure you use a good shop for this or you will have a disaster, mine was done at a race shop. They must understand performance and be will to remove the rear exhaust section to properly weld and fabricate the new system. Also, all connections to the stock exhaust system must be made over the outside of the pipes to prevent any restriction of the factory system.

Also, for those wondering, the factory AMG muffler is excellent and high flow. There are some slight restrictions in the factory headers but this would be really expensive to correct and likely not worth the trouble.