Hey everyone,

I think it’s finally time to admit I have a problem. I can’t stop redesigning my exhaust system.

The impetus for the latest evolution of this saga is probably threefold:

1. Pyromania: After my Eurocharged Stage 2 tune, my poor exhaust has been seeing more afterfire than an AMG in a music video—actual flames shooting out of the tips daily. Not sustainable.

2. Identity crisis: The car currently sounds less like a German luxury coupe and more like a lifted V8 truck that’s late to a tailgate.

3. Fresh start: I just picked up the Weistec Stage 2 ECU and TCU tunes, so it seemed like a good time to start from scratch (again).

Current setup:

Renntech short-tube headers → cat & resonator delete → SpinTech H-pipe → Paradox Hot Tamale mufflers → quad AMG tips.

Over the years, I’ve gone from “respectably loud” to “call the HOA” loud, and I think I’ve landed on something that’s just too raw. My mission remains the same: to get as close as humanly possible to the CLK63 Black Series tone and volume—that rich, exotic thunder, without the brutality.

This is probably my last redesign… at least until next spring.

Attached you’ll find a dyno of my current setup and a schematic (forgive the PowerPoint art) of the next version. Here’s where I’d love your collective wisdom:

Resonator placement: before or after the X-pipe?

I’ve always installed them after the X-pipe, but recent research suggests putting the resonators before it—so each bank’s pulses are smoothed before they merge. Supposedly this keeps crossover harmonics clean, reduces rasp, and yields that tighter, more exotic tone we all chase.

Has anyone here actually tried resonators before the X-pipe? I’m bracing for an argument with my exhaust shop, and I’d rather not sound like a lunatic when I walk in quoting wave-harmonic theory.

Tip sizing & diffuser fitment

For those running the VIS DTM carbon fiber diffuser: I was planning on 3.5” titanium tips, but after measuring the AMG ovals (5” wide × 3.5” tall each), it looks like each side can easily swallow quad 4” tips.

Is 4” overkill for the CLK550, or is it the right move to visually fill the diffuser? I’d love some honest feedback here—especially from those who’ve mocked up similar setups.

Bonus question: chasing the Black sound

Aside from relocating resonators and swapping tips, I’m open to other ideas that might get me closer to that CLK63-style wail. Just not willing to give up my trunk to fit Eisenmann cans—I draw the line there.

Appreciate any advice, theories, or war stories you can share. And apologies for starting a new thread—my old ones have more carbon buildup than my deleted cats.

Thanks in advance,

James

 

The closer the X-pipe is to the engine the better it will scavenge and the better it will synchronize the pulses.
I have used vibrant resonator ahead of the x-pipe and I have used secondary cats (magnaflow hi-flow 200 CEL) ahead of the x-pipe. The exhaust note seems smoother IMO.

I am about to see how much better it sounds as I am about to install the x-pipe ahead of the secondary cats. I will do this next week.

I just changed my tips. The old ones filled the CF diffuser too much so. They were too close to the diffuser at the top and created vibration. I may change them one more time after I have run these smaller ones for awhile. They are resonated and the frequency at which it resonates may not be to my liking. If I change them I will go with ones that are not resonated and maybe a little larger but not as large as the ones just changed. I don't think you want them large enough to fill the diffuser openings.

 

After reading and thinking about the original post, I've decided to reinstall the secondary cats where they were before (ahead of the x-pipe). While I was waiting for the new cats I've been running with straight pipes where the secondary cats were. There is a good amount of exhaust clapping when accelerating and the exhaust tone is less "refined". Some of change may be due to the resonated tips, but I think I'll stick with the cats before the x-pipe. I'll minimize the pipe between the cats and x-pipe to et the x-pipe as close to the engine as possible.

The secondary cats (200 CEL) act as a kind of resonator as the pulse wave breaks as it goes through the honeycomb metallic cats.

Your increased exhaust volume could be due the changes in tuning and/or the headers. Headers are louder than OE exhaust manifolds as there is much less collision of cylinder pulses of each bank. OE manifolds are designed to have some collision to quieten the vehicle. The headers have better performance with the sacrifice of a louder engine.

Another potential cause of increased volume is the borla muffer. I think magnaflow and vibrant are more neutral in the tone produced. The changes in exhaust characteristics may causes the resonance of the muffler to shift making the exhaust tone change.

Also, you're using an H-pipe, which will allow you to produce more torque but it will contribute more to a "muscle" tone than an x-pipe. I think the H "sucks" exhaust from the other pipe while the X "drags" the exhaust of the other pipe.

Good luck.

 

Fatz — I’m genuinely glad you replied. Your car was actually the original catalyst for my entire exhaust journey. I watched your videos more times than I’ll admit publicly, and your schematic was the blueprint for my first setup. So really, all of this is partially your fault. (Kidding… mostly.)



Over the years I’ve tried to chase that CLK63 Black-style note, but I suspect I’ve accidentally wandered further away with each iteration. It’s been fun, though — like an acoustic science project where the hypothesis keeps changing.



So to your point: I think you’re saying the Vibrant resonators should go before the X-pipe, and as close to the headers as reasonably possible. I actually did run an X-pipe at one point, but then I decided to experiment with an H-pipe — and that’s when things started sounding suspiciously like a very patriotic American muscle truck. My current mufflers are the Paradox Hot Tamales, which are loud enough that I can unintentionally dominate traffic conversations. I’ve literally driven past lifted Rams with straight pipes and thought, “Oh… I’m the problem here.”



So yes — time to reel it back in and refine the tone rather than crank the volume. That’s why I’m bringing the Vibrants back, considering a Borla for smoothing, and even paying attention to tips for the first time. I’ve run through multiple AMG quad tips from eBay, and they’ve always looked the part, but my tastes have changed and I’m curious how much of the final color of the sound can be shaped by the tip material and geometry. So I’m going all-in on titanium tips this time — probably spending more on tips than I ever imagined I would. Life comes at you fast.



Since you also have the VIS diffuser — what’s your view on sizing? Do you think dual 4” is overkill? Would dual 3.5” strike a better balance? These aren’t exactly “buy two and experiment” prices, so I’d rather make the right call up front.



And finally: I want to redo the entire system with full mandrel bends. I don’t even want to look under my car right now. Every shop was reputable, but I’ve made so many changes over the years that I’m sure it looks like the exhaust equivalent of a quilt. My last dyno session came in disappointingly low, and while I’ve since cleaned up a few maintenance issues, I have a strong suspicion the crush bends are choking things out. Your system, as I recall, is fully mandrel — which is exactly where I want to land: cleaner tone, better flow, and a bit more of that German sophistication back in the character of the car.



Anyway — I appreciate you taking the time. You were the blueprint for this hobby for me, and I still look to your setup as the reference point for what “right” sounds like. Any guidance you can share here is truly valued.

 

If you're using 2.5" tubing, reasonable crush bending is ok for the hp capable of these cars in NA configuration. I think using butt welds are generally more beneficial. There may be a couple of points at the front and exit of the exhaust line where lap/swedge welds are ok if you ensure the fabricator puts the upstream pipe inside the downstream pipe/tip.

I think the 10+" width tips are too much, both in terms of appearance and mechanically they are too close to the diffuser, since 10" width is generally 5" in height. The diffuser is not rigid and tends to vibrate. I am having trouble finding what I consider ideal (8-9" width and 3.5-4" height. As I said before, I don't really like the resonated ones currently installed. I'll give them a few hundred miles to settle before changing them. The tips can have a noticeable effect on the sound. The larger the tips the lower the natural resonance frequency making the exit tone more muscle/trucklike. The resonated tips have their own design resonance and as in my case may not be what you want. Most sellers just say resonated w/o any indication at what frequency range it is resonated.

I do think the resonators/secondary cats ahead of the x-pipe is a better configuration and will keep that arrangement.

When, if ever, I finish my design of a vibration resonator, I plan to reinstall a magnaflow muffler just after the x-pipe of vibrant bottle resonators just ahead of the tips. I removed the muffler so I could better evaluate my career project.

It is my belief that it is best to use as much the same mfr products in a subsystem as possible. Every component in the system bring their own character and they work with those of other components or they are at odds. Using mostly the same mfg lessens the instances of being at odds. Mixing them is a crap shoot, so I've become biased toward magnaflow and vibrant.

 

A point of clarification: For gentle bends, crush bends are ok when using 2.5" pipe on clk. For the 90 degree bends you can purchase mandrel bent sections of the same pipe material and size that the fabricator can butt weld into the exhaust system. I think there are only 6 90 degree points. When I last did mine I used aluminized 2.5" steel, the same as the fabricators stock. The other bends for routing after the x-pipe are gentle bends. I painted and/or wrapped the rearward pipes, so stainless steel was not necessary. Most fab shops do not use stainless steel. It is too hard, costly, and time consuming for them.