Hi,

I just purchased a 2016 Mercedes Benz C63s AMG (4-door). I think I may have made a mistake through a local muffler shop and I'm told I'm over-analyzing things and my concerns are no other than a placebo effect. With the stock exhaust, whether in Comfort, Sport, Sport+ or Race mode, when I would hammer the gas and paddle (up or down shift), you would get an insane crackle and pop. I LOVE IT! I was reviewing this car on youtube and I saw lots of modifications which enhanced this effect.

I went to a local muffler shop and their feedback was to remove the 2 only cats (secondary cats) this vehicle has and this will increase the sound somewhat but to really enhance, I should replace the mufflers. Knowing nothing about these cars, I went on recommendation and they did the following:

- Cut out secondary cats, mandrel bend straight tubing and weld
- Remove stock AMG mufflers and weld on borla mufflers and hangers

I notice the vehicle has four tips at the rear of the vehicle (dual exhaust on each side). With the stock AMG mufflers, these were huge and had 2 pipes on each which corresponded to each rear tip (4 total). With the borla mufflers, these looked cheesy and had 1 pipe each therefore, if looking at the rear tips, you only see a pipe in each outer tip but the two inner tips are thereby empty and simply cosmetic.

The AMG mufflers looked round and are heavy and the borla looked like something you would put on a 1989 honda civic lol. When the job was completed, upon cold start and idle, the car has a deeper sound. When driving, the car has limited torque, shifts at higher RPM intervals and if pushing to the limit and doing up/down shifts, you do not hear any popping or crackling. I addressed this matter and the shop said it's no different than before but I'm not crazy and know there's a difference.

Not being a car enthusiast, I'm curious if you experts can comment. Did the removal of the cats screw things up or are the AMG mufflers simply better performing. If I ask the shop to reverse the process but want the deep sound with the pop/crackling, should I leave the cats out and just replace with the existing AMG mufflers I originally had? I'm at a total loss as some have told me with the 2016 model AMG's, the cats are what gives the torque and removal will screw up my shifting while removal of the AMG mufflers will cause the pop/crackling to disappear as this is proprietary to their muffler systems.

I just don't know how to move forth and don't want a big labor bill with the shop taking me for a ride. I'm thinking if I just request the AMG mufflers to be put back on and leave out the cats, I'll get the sound I want but I'm completely confused. Also, with deleting the cats and removing the original AMG mufflers, if I reverse the process, will everything be OK or is there a possibility I did any harm? Any help is appreciated and thanks for tolerating a newbie!

 

I can't believe you replaced the AMG Sport Muffler's with some cheap *** Borla mufflers...SMH.

I removed the secondary cats only and it sounds and drives amazing.

 

Yeah, like I said, I'm a newbie and I'm surprised a muffler shop who specializes in high performance vehicles would recommend doing this. So... based on your opinion, I should leave the cats out and request my original mufflers be welded back on? Anything else I can do to increase the sound while not affecting my torque or RPM shifting levels? Also, with what I've done removing the old AMG mufflers and then welding them back on, this has not decreased any functionality of my vehicle has it? Lessened any effects? Thank you for your help!

 

Doing mods are not for everyone I guess. The AMG mufflers are on of the best pieces of exhaust engineering in the world. My exhaust shop actually told me how well Mercedes constructed the entire exhaust system. I have no idea what made you think a cheap borla muffler would even remotely improve the sound. Take it back to a legit shop have it re-welded and pray you did not mess something else up. These cars can go into limp mode with any abnormal exhaust back pressure. And for the future, do not mod the car anymore. The secondary cat delete should have been good enough for you. Just put the mufflers back on. Also get it checked for another legit exhaust shop if the secondary cat delete was done right. Hope you kept the original ones too.

May be upload a picture here and the guys here can probably tell you what is going on as well.

 

Like Munis said, the car can go into limp mode if it senses too much back-pressure in the system (to prevent damaging the turbos/engine).

At low RPM, the flaps don't open up as much (to keep the exhaust quiet while cruising).

At high RPM, they open up for more sound (and perhaps power).

You replaced an exhaust with adjustable valves, with some cheap *** Borla meant for a Mustang or Honda Civic, so just put the stock exhaust back on and keep the secondary cat delete (which many people on this board have done with no issues).

 

Ideally for a turbo engine, you want the most free flowing exhaust after the turbo outlet, so the less muffling and restriction in there, the better. Welding and hacking up stock exhausts you have a higher chances of leaks in the future bc most of these muffler shops can't do these welds good enough. Have the shop put the stock mufflers back on, or weld in straight pipes instead of the Borla.

 

 

Yes, I had the performance exhaust. I am new to the whole mod scene and wanted more rumble and popping over what I currently had. I looked at full exhaust systems but they were quite expensive albeit you get what you pay for. As a result, I spoke to a local shop who specializes in high performance cars from what I'm told and it was recommended I remove the two cats and go with the Borla mufflers to give a more deep sound.

I phoned today based on your feedback and was told the exhaust valves ARE disconnected. The shop said they simply cut out the old mufflers and welded in the borla. They said the car is definitely in limp mode but I could buy a simulator that the valves would plug into and this would communicate with the ECU to give the sound I desire even better than if I would to have the AMG mufflers on.

I don't believe this so I requested they remove the Borla mufflers and replace with my original AMG mufflers. When they do this and hook the exhaust valves back up, will the ECU recognize everything or will I need to have the ECU programmed? I spoke with Mercedes who said if the car remains in limp mode and does not shift properly or pop/crackle, I may want to disconnect the battery for 30 minutes then reconnect and this should reset everything. If not, they said I would need to reprogram.

Question... Even if the car was in limp mode, when the old AMG mufflers are welded back into place, I assume (once programming is done on the ECU if needed), it will be back to it's bad-as* sound or do you think it's possible I may have done damage? Mercedes told me no damage could have occurred as long as the welds are good since it was simply cutting and welding of pipes but I want to make sure as I'm new to all this and just hope I didn't shoot myself in the foot. Thank you!

 

Ok, so that confirms limp mode via exhaust valves. You need to have those exhaust valves plugged back into the motors of the stock AMG mufflers (if you intend on returning back to stock), or you need to purchase exhaust valve simulators for each motor that was disconnected. You can buy them in sets of 2 here (towards the bottom, SKU: 1310-11018): https://www.awe-tuning.com/mercedes-c63-exhaust

I once threw my car in limp mode when testing exhaust valves and was able to get out of limp mode by disconnecting power/putting car into sleep mode, correcting the issue (exhaust valve plug), reconnecting power, and driving it hard. The ECU is usually smart enough to realize the valves are now functioning normally and will get out of limp mode in most cases. However, in some cases, you need a dealer Xentry tool to reset and get out of limp mode. Obviously, try correcting the issue and resetting first to see if that gets you out of limp mode. Otherwise, you'll need a trip to the dealer or shop that has Xentry.

Also, don't worry about any damage. The car will be fine, you just need to get the motors plugged back in. I'm surprised this exhaust shop didn't know about this since they work on high end vehicles, most cars will go into limp mode if you unplug exhaust valves (not just AMG).

 

Thank you everyone for the support thus far. I was able to speak with the shop and they in turn replaced the crappy mufflers with my original AMG PE. I left the secondary cat delete and this machine is a BEAST!! Just with the secondary cat delete, it pops and crackles about 30% more than it previously did and when it pops, it's INSANE! It sounds like it went from a kernel popping in a popcorn maker to a cherry bomb being lit off on the 4th of July! What a difference but a classy difference! It doesn't sound like trash and I can control it based on the mode I'm in and/or how heavy I want my foot to be.

I received an apology from the shop, didn't have to pay to have the job reversed and was refunded for the purchase of incorrect mufflers. I'm happy with how things resolved themselves, the sound is perfect based on a slight mod and all is good!