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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
I’ve added a few comparison images below showing stock M278 turbos, stock M157 turbos and different hybrid options.
The TTE turbo shown is from another build I was somewhat involved in. That car was completed about a year ago and is now getting tuned, so it will be interesting to see how it performs in practice. Both cars will have a similar tune.
It should be a useful real-world comparison of how different hybrid approaches behave on the M278 platform. Personally, I’m curious to see how the TurboSystems (TTS) units compare against the TTE turbos, especially in terms of response and load holding.
More data to come once tuning progresses.
stock m278 stock m157 hybrids by the Turbo Engineers hybrids from Turbosystems
One thing that really stood out visually is how BlackBoost turbos appear extremely similar to the Turbosystems (TTS) units in overall layout and wheel geometry. I have no direct experience with BlackBoost turbos and haven’t run them myself, but the resemblance is hard to ignore when looking at the side-by-side images.
I managed to source a set of OEM AMG brake calipers at a very reasonable price and installed them on the CLS.
Because the W218 front knuckles differ from the W212, the standard AMG front rotors do not bolt on directly. Instead I repurposed the original CLS 550 front rotors. They are heavier than the AMG discs, but the dimensions work correctly with the knuckle and caliper geometry.
Fitment notes:
Front clearance to the wheel barrel is extremely tight, but fully functional with no contact.
The caliper mounting holes in the W218 front knuckles had to be drilled to a slightly larger diameter to accept the AMG caliper bolts.
No adapters were used; the calipers are mounted directly to the knuckle after drilling.
Rear setup uses stock AMG rotors.
It is not the lightest configuration, but braking performance and pedal feel are a significant step up from stock.
rears installed front calipers came pre-scratched, so one less thing for me to worry about. front knuckles being modified fronts installed, clearance is really tight
I installed a new intercooler heat exchanger together with a Pierburg CWA400 pump for the charge cooling circuit. The idea for this setup came from @PekkaH.
The heat exchanger itself is an FMIC upgrade unit originally designed for the A45 AMG, but it fits well in this application. Compared to the original CLS unit, it is significantly larger. Unfortunately, I don’t have side-by-side photos of the stock exchanger and the upgrade, but visually the new core looks almost almost twice the size of the original.
To make it fit, the heat exchanger enclosure had to be cut and modified. The images below give a good idea of the scale difference — the new heat exchanger protrudes noticeably compared to the factory unit.
I installed a new intercooler heat exchanger together with a Pierburg CWA400 pump for the charge cooling circuit. The idea for this setup came from @PekkaH.
Looks serious! My only thought is that since methanol is a fuel, you're going to have to adapt it into your fueling strategy whether you like it or not. Only water can be used for cooling only.
Looks serious! My only thought is that since methanol is a fuel, you're going to have to adapt it into your fueling strategy whether you like it or not. Only water can be used for cooling only.
That’s a fair point in general, but it really depends on how and where the methanol is used.
In my case the methanol is injected pre-turbo, far upstream, and in relatively small amounts. The goal is evaporative cooling of the intake air before compression, not fueling the engine. From a calibration standpoint, the engine is set up to meet all load, lambda, and knock requirements on gasoline alone.
Yes, methanol is chemically a fuel, but at this injection point and flow rate any contribution to combustion energy is incidental rather than something that can be controlled or relied upon. Even if it were to slightly enrich the mixture beyond what the ECU trims for, that condition is thermally safer than running lean under boost.
The tune is intentionally not dependent on methanol being present, so if the system is disabled or fails, nothing fundamental changes.
I'm sure @Cifdig could step in and correct me if I'm wrong
I’ve also been playing around with a custom air intake design. Rather than going with one of the off-the-shelf solutions, I decided to build my own. Partly for packaging, partly out of curiosity, and partly because designing things is half the fun anyway. The image below is an early CAD mock-up, still very much work in progress, but it shows the general idea: compact layout, smooth inlet path to the turbos, and keeping things tidy in the engine bay. Details like final geometry and filter selection are still being worked out. Nothing final yet, but I’ll share more once this moves from CAD to something physical.
I printed a very quick and dirty first version of the airbox just to get some real-world references. The final version will be roughly 70 mm wider and longer — the current size is mainly limited by what fits on my home printer. The turbo inlet pipes will also be quite different in the final version.
I originally planned to use a 3” outlet air filter, but ended up going with a 4” filter instead. For now I’m using a coupler just to test fitment on a CLS tomorrow. The plan for the turbo inlet pipes is likely 3” for most of the length, then gradually tapering down to match the turbo’s 65 mm inlet. The thinking is that the larger diameter helps airflow especially through tighter-radius bends.
The black pipe is only there to demonstrate the smoothness and general routing — it’s not part of the final design. The front section of the box is white simply because I printed the box in two parts and used some leftover filament I had lying around.
Still very much work in progress, but it’s nice to move from CAD into something physical and see how things actually fit.
Great stuff with the DIY airboxes. The only ones I could find were like $1800 and only good for scaring my BMW owning friends with the price. I do wonder if the different filters will make the engine throw a lean code or if it'll adapt (or not have any impact at all). If you can track the air % in the mixture on some tune/dyno runs with it on/default it would be interesting to see the impact.
Great stuff with the DIY airboxes. The only ones I could find were like $1800 and only good for scaring my BMW owning friends with the price. I do wonder if the different filters will make the engine throw a lean code or if it'll adapt (or not have any impact at all). If you can track the air % in the mixture on some tune/dyno runs with it on/default it would be interesting to see the impact.
They won’t trigger a lean code. I’ve been driving around for quite a while with the filters installed, and even without the enclosures during testing, and there have been no issues or fault codes.
I had to revise the design and go back to 3” inlet filters due to limited vertical space. I’m planning to use a lid on the airboxes instead of relying on the hood, most likely made from plexiglass. That gives a fixed, predictable top geometry, allows visual inspection of the filter condition, and makes it practical to use the same airboxes on W221, W222 and R231 chassis, where I actually plan to run them.
The next iteration is printing as we speak and I should be able to test-fit it sometime next week.
Once the design is finalized, I’ll do dyno runs comparing the stock intake setup to my own airboxes.
And yes — the ~$1800 price tag on the off-the-shelf options is ridiculous.
Test-fitted the box and now I have a very clear idea of what needs to be changed for a perfect fit. I’ll need to adjust some of the side-profile angles so the boxes sit and look more OEM once under the hood. A segment of the updated design is printing as we speak. The fasteners worked exactly as intended.
I saw a fella using the squished cone filters from dodge 6.2's (pic below). His design wasn't as thought out as yours but that could help with the clearance issue, supposedly same airflow
It's cool that the car can compute the airflow and not throw a lean code. I saw someone on the other guys process say it would throw which is why I was curious. I would LOVE to hear how these affect the exhaust note.
I’ve used similar filters before, but unfortunately they don’t fit our engine bay very cleanly. The space is really tight. I’m nearly finished with the design now and should hopefully get to the final prints soon. I may even end up dropping the lid idea depending on how things work out.
I’ll be test-fitting some new filters later today.
Note: in the photos, the air filter tube is just lying there and isn’t attached to anything.
The turbo inlet pipes are now fully modeled. I printed a quick all-3” round pipe in black purely for test-fitting on the car and checking clearances. That one is not the final design.
The final version uses smooth, long-radius bends with a gradual transition down to the turbo inlet and OEM-style turbo connectors. That version is currently printing (about 14 hours per pipe).
The goal is simple: maximize usable cross-section, keep the internal surface as smooth as possible, and use the available space under the hood efficiently. Test fitting with the prototype confirmed the routing works, so this print is mainly about dialing in the details.
More updates once the final pipes are test-fitted.
Quick update on the intake side, and thanks to everyone for the encouraging comments — much appreciated.
I’ve just finished printing the prototype pipe for the other side, now with the correct turbo inlet interface and a smooth taper toward the compressor.
The pipe is printed in red, which obviously makes it a performance part. Based on solid engineering logic, I therefore expect at least double the horsepower from this pipe alone. This seems realistic, considering the factory pipe currently makes exactly 0 hp while sitting on a shelf all alone.
The prototype is shown on the wrong side turbo for photo purposes only.
I redesigned and printed new true 3” pre-turbo intake couplers/boots (the connector between the airbox pipe and the turbo inlet pipe, including the PCV return). The couplers are printed in TPU, and the barbed PCV hose fitting is printed in nylon and integrated into the boot. This removes the stock neck-down and keeps the whole pre-turbo tract a true 3”. The photos include a stock boot for comparison. I will also add PCV catch tanks to the system during reassembly. Next step is test-fitting everything in the car and checking clearances and sealing before final prints.
Test-fit done on the intake pipes. Both sides mount to the turbos; passenger side is basically spot-on and just needs ~1–2 mm tweak for perfect aesthetics. Driver’s side needs a small geometry change as it touches the charge pipe and doesn’t quite clear yet. Clearance in the bay is generous on both sides, so space won’t be an issue once the centerlines are adjusted.
Airbox update: the airbox is pretty much finalized. It needs ~15 mm more height on the firewall side and ~10 mm less on the front side, but it already seals perfectly against the hood liner. Driver’s side box will get one last PLA print for final fitment, then it’s time for the final prints.
Quick update on the intake pipes: driver’s side is now fixed and reprinted. I shortened the pipe slightly so it fits the printer in one piece; the “lost” length is moved to the air filter tube instead of the turbo-side tube, so overall geometry stays the same. Fit is now spot-on and clears everything properly. Passenger side will be reprinted in one piece next, then both sides are ready for final material prints.
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