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Really big weight loss and big improvement. Really nice. You will for sure notice that in every way. Like acceleration, braking, suspension. Heavy *** car will behave different after that swap.
M278 CLS550 performance build – rear SAM wiring integration and exhaust flap control
Quick update on the project.
Spent some time working through the electrical side and got everything sorted with the rear SAM module. Ordered the correct terminals and fuse blocks so the wiring can be integrated properly into the factory system rather than patched in.
I also got my hands on a friend’s donor CLS box of leftover wires, which should allow me to reuse factory wire colors for everything relevant. The plan is to keep everything consistent with OEM wiring conventions so it stays easy to trace and debug later on.
I’ll be repurposing fuse 89 for the additional fuel pump — it’s an unused slot in my car, but on M157 cars it’s assigned to the fuel system control unit. That makes it a good candidate to integrate the extra pump in a way that stays clean and logical.
Also started working on a mockup for the exhaust flap control in the center console. This is still in a very early stage — the basic layout is there, but I still need to figure out proper mounting to the compartment wall and finalize the design.
The idea is to keep the switch hidden behind the console lid so it stays protected and doesn’t interfere with anything stored in the compartment.
As with the rest of the build, the goal is OEM+ integration rather than something that looks added on.
I see you have the ESM button like the amgs do, did you get it to program to stay in whichever mode after shut off like they do too? Also the exhaust valve button looks dope but if you have any charger/radar detector wires coming through from the 12v port opening that every time might be a pain
I see you have the ESM button like the amgs do, did you get it to program to stay in whichever mode after shut off like they do too? Also the exhaust valve button looks dope but if you have any charger/radar detector wires coming through from the 12v port opening that every time might be a pain
Yes, I coded the ESM to remember the last position before ignition off — fairly straightforward to do.
Good point about the 12V port — I didn’t have an actual glove box available at the moment to check that. I’ll need to look into it and possibly relocate it to a better position. Thanks for pointing it out 👍
Just checked it — the button won’t interfere with the 12V port after all. It will sit closer to the media interface port, but that’s not an issue for me since I’ve disabled it to use AUX for my aftermarket wireless CarPlay module. Thanks again for pointing it out.
Interior reassembly, custom console mockup and lightweight brakes
Quick update on the project
Interior is slowly coming back together — everything that could be reinstalled at this stage is now back in. Still waiting on the upholstery shop to finish the seats, pillars, headliner and the remaining pieces. The black carpet paired with the Alpaca gray interior turned out really well in my opinion. The contrast sure makes the whole cabin a lot nicer.
Also worked on a revised mockup of the center console section. The new design integrates both the exhaust flap control and the Snow Performance meth controller into one unit. Still in the prototype stage, but the layout and positioning are now where I want them.
On the mechanical side, the lightweight front brake rotors are now installed along with larger dust shields. Fitment is spot on and everything went together as expected. Also brought in some help to move things along a bit faster — and yeah… hours disappear very quickly when you’re deep into this kind of work 😄
Managed to finish the exhaust flap control / Snow Performance methanol controller pod this weekend. The design integrates both into a single unit mounted to the center console, keeping everything contained and OEM+ in appearance. Fitment turned out exactly how I wanted — it clears all USB and multimedia ports inside the armrest without any interference. This was iterated a few times to get the positioning, mounting and overall proportions right, but the final result sits naturally within the console lines and doesn’t feel like an add-on. Wiring will be fully enclosed within the structure, so everything stays protected and hidden once installed.
I guess I can finally call this part done and be happy with how it turned out 🙂
Just checked it — the button won’t interfere with the 12V port after all. It will sit closer to the media interface port, but that’s not an issue for me since I’ve disabled it to use AUX for my aftermarket wireless CarPlay module. Thanks again for pointing it out.
I was more so referring to the opening/closing the hatch every time you wanna toggle it. I have my radar detector and phone cables coming out throught the dedicated cable channels at the front of the box by the lever and without fail they get in the way of it shutting properly every single time. Might be inconvenient for frequent on/off presses, but assuming you're probably gonna keep it on or off depending on the drive it might not be that big of a deal. Your solution looks elegant and that interior is HOT!
also I haven't figured out what that media interface port is for or anything compatable I have (iirc the sd card reader is on the dash, so not that?) but now I want to try again.
I was more so referring to the opening/closing the hatch every time you wanna toggle it. I have my radar detector and phone cables coming out throught the dedicated cable channels at the front of the box by the lever and without fail they get in the way of it shutting properly every single time. Might be inconvenient for frequent on/off presses, but assuming you're probably gonna keep it on or off depending on the drive it might not be that big of a deal. Your solution looks elegant and that interior is HOT!
also I haven't figured out what that media interface port is for or anything compatable I have (iirc the sd card reader is on the dash, so not that?) but now I want to try again.
Oh I see now. Opening the hatch isn't going to be an issue -- I'll mostly drive the car semi-silently anyway. Thanks for the compliments!
Regarding the media interface and sd card reader -- I would recommend getting a CarPlay box from someone like https://www.mr12volt.com/collections...em-mic-support instead. I have a Chinese one that doesn't support MOST bus. I wish I wish I would've known about the other one when I made my order
I had no idea that was even a thing, now I have to go down a rabbit hole to figure out what else it can do. Do you know if it supports the USB connectors for "wired" carplay? I've never had carplay before and it'd be a good test of if I like it enough to get the plug in if it works. I'll definitely be looking into it.
Edit: seems like I had the wrong idea about it. I'll look into that if I ever wanna modernize the infotainment, but it still has to have the head unit removed so not what I thought. Thanks for linking it!
Last edited by Blazingtrain; Apr 7, 2026 at 01:54 PM.
@ervg this is one of the coolest projects. I am visiting from the c207 forum, i typed in M278 under tech forum since sometimes I like looking up what people are doing, and I came across your excellent and inspiring project. I always wanted to do this for my e550, to upgrade the stock engine with all the necessary other parts like what you are doing here. I am not a mechanic so wouldn't be able to do it myself, so I really admire someone like you that's hands on and able to do great work to not only upgrade the mechanics of the vehicle, but so many other things you are in process with. Can't wait to see the final result. I hope the rest of the project goes really smooth and easy.
Thank you for your kind words, really appreciate it — messages like this are a great motivation boost.
I’m not doing everything on my own though, I do get help from mechanics where needed — the whole project is a bit overwhelming and too time-consuming to handle completely alone. The engineering, design and planning side is what I handle myself.
Luckily I have friends like @PekkaH who contribute greatly with ideas and share their know-how.
Hopefully the final result will justify all the effort 🙂
Engine is now pretty much back together and ready to go back onto the front subframe. Spent some time cleaning up the engine bay as well so everything is ready for the install this weekend.
The charge pipe and BOV setup turned out to be very tight in this configuration. Took quite a bit of trial and error to get everything to fit properly without interference, but it all came together in the end.
Pretty happy with how the whole assembly looks now — next step is getting it back where it belongs.
M278 CLS550 build – engine in, downpipe fitment reality check
Another step forward — engine is back in the car for fitment.
As expected, the downpipes turned out to be the limiting factor. They had to be cut apart, reworked and basically forced into place to make everything fit. Cosmetically, they’re pretty much destroyed at this point — but they were always meant to be prototypes, and it definitely shows now.
The fitment in this area is extremely tight. The pipes had to be deformed to clear everything, and even now there’s only about ~10 mm clearance to the engine bay heat shields.
I’ll redesign that section properly next season and build a revised version with correct geometry. For now, the goal is to get everything working and validated as-is. Let the pictures speak for themselves.
Small side note — I also picked up an AMG instrument cluster. @PekkaH is to blame for that one, that definitely wasn’t part of the plan until yesterday 😄
As @PekkaH mentioned in his thread: “Soon here will be another M278 build thread. A friend has built his coupe with great passion. A lot of mods and good quality. Will be excellent stuff!”
Here it is.
This is a long-term performance build on a 2013 CLS 550 4MATIC (M278), approached as a complete system rather than a collection of individual parts. The focus is usable, repeatable acceleration and proper load-based calibration, not chasing dyno numbers.
Current Direction & Targets
Load-based MED17 calibration
Shaped torque delivery
Safe torque target: ~950 Nm
Fuel: 98 RON pump gasoline
Water–methanol used strictly as a protective cooling measure
Key Hardware Highlights
Engine & Induction
TurboSystems M157 upgrade turbochargers
Custom ceramic-coated charge pipes
Bridge pipe between banks
Single central 60 mm BOV
WMI (Snow Performance Stage 2)
100% methanol
Pre-turbo
Cooling only (not part of fueling or ignition strategy)
Intercooling & Thermal Control
Upgraded primary intercooler heat exchanger
Additional front-mounted heat exchanger
Split intercooler cooling system (separate from engine cooling)
Pierburg CWA100.2 intercooler pump
Fuel System
Stock M278 LPFP (primary)
Additional boost-activated Walbro 450
Stock HPFP and injectors
Exhaust
True 3.0” system from turbo outlets to rear
Custom ceramic-coated downpipes
JRSpec 200 CPSI sport catalytic converters
AMG rear mufflers
Electric exhaust cut-outs before the mufflers
Drivetrain
Final drive changed from 2.47:1 → 2.65:1
25% limited-slip differential
Calibration Philosophy
The M278 is load-based, not boost-based. Boost is a result, not a target.
Torque and load models scaled to actual airflow
Early torque is shaped, not spiked
Load is extended where fuel system allows
Calibration remains safe without WMI
Transmission calibrated for acceleration:
I’ll update this thread with dyno data, logs, and real-world acceleration results as the build progresses. Hopefully this will be useful for others working on the M278 platform.
More to come.
charge pipes done and ceramic coated downpipe flange prototype printed in PLA 316L stainless prints from China ready to be ceramic coated final product stock turbine wheel stock compressor wheel a little upgrade on both fuel pump bracket (I really should make it yellow, so it would retain it's duckling look ) test print in PAHT-CF I think it might be ready to be printed in aluminum
M278 Build Update – Engine Installed, Quaife LSD & Custom 3D Printed Parts
Engine is now back in for good as part of the M278 build. Fitment is extremely tight across multiple areas, but everything clears as it should.
Quaife rear LSD has arrived as well — not installed yet, but that’s next on the list.
The rest of the exhaust will be fabricated this week, so things are finally moving towards getting the car fully together.
While finishing up the engine bay, I installed the foam injector noise suppression covers and noticed that 2 out of 4 original clips were already broken. Of the remaining two, one snapped with very little pressure, leaving only a single usable clip.
Couldn’t find a proper OEM replacement, so I modeled and printed my own set. They turned out well — stronger material, tighter fit, and a more secure solution than the originals.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
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