Mercedes-AMG C218 CLS63s & W212 E63s M157 Modder's Guide
CLS63 S C218 & W212 E63 S Overview
Produced during the peak of AMG's 5.5L twin-turbo era, the Mercedes-AMG CLS63 S C218 and E63 S W212 are powered by the hand-built M157 5.5L BiTurbo V8. Both platforms combine strong factory performance with significant aftermarket tuning potential, though not as tunable as the reworked M177 variants.
Later S models pair the M157 with AMG's 7-speed MCT transmission and 4MATIC all-wheel drive. With basic bolt-on modifications and quality ECU and TCU tuning, both cars can gain substantial power while remaining comfortable daily drivers.
The CLS63 and E63 share much of their drivetrain and aftermarket support, making the modification path for both platforms very similar.
CLS63 & W212 E63 Pre-Facelift vs. Facelift Differences
Pre-Facelift
Earlier W212 E63 and C218 CLS63 models use the M156 6.2L naturally aspirated V8 or, depending on model year, the M157 5.5L BiTurbo V8. Because of these major drivetrain differences, always confirm your engine and model year before purchasing performance parts. Pre-facelift models also primarily used a RWD configuration.
Facelift
The facelift W212 E63 and C218 CLS63 received updated styling, interior technology, and major drivetrain changes. In the U.S. and Canada, the later E63s and CLS63s paired the M157 with 4MATIC AWD, providing dramatically better traction for tuned cars.
For owners focused primarily on straight-line performance and tuning potential, the facelift M157-powered cars are generally the strongest starting point; they feature 30-40 more hp from stock, and the turbocharged configuration yields significantly higher power figures when tuned. However, one potential drawback is a weight gain of roughly 120-150 lbs, though the extra power largely negates this in terms of straight-line speed.
For the purposes of this article, we will primarily be discussing facelift W212 and C218 models with the M157, since these are the most commonly modified due to their stronger aftermarket tuning potential.
CLS63 S & W212 E63 S Aftermarket Platform Stages
Note: Stage terminology varies between tuners. Power figures depend heavily on fuel quality, dyno type, vehicle condition, supporting modifications, and calibration.
CLS63 & W212 E63 Stage 1
Stage 1 typically consists of a quality M157 ECU tune on premium pump fuel, often paired with upgraded air filters or intakes and TCU tuning.
The M157 responds extremely well to software alone. Owners can expect 125+ crank hp and 135+ lb ft torque gains from a strong custom ECU + TCU tune.
Before tuning, we recommend fresh spark plugs, healthy ignition coils, fresh fluids, and a complete inspection for boost, oil, coolant, or other leaks, as well as any existing fault codes.
CLS63 & W212 E63 Stage 2
Stage 2 adds catless or high-flow downpipes along with ECU and TCU tuning. Reducing exhaust restriction allows the factory M157 turbochargers to produce considerably more power while also creating a deeper and more aggressive exhaust note.
For most CLS63 S and E63 S owners, Stage 2 offers the best balance between performance, cost, and everyday drivability, with gains of up to 150+ crank hp and 170+ lb ft torque from a custom ECU & TCU tune from one of our select tuning partners.
Supporting modifications can include: Catless or high-flow downpipes, ECU and TCU tuning, Upgraded air filters or intakes, Fresh spark plugs and ignition components
CLS63 & W212 E63 Stage 2+
Stage 2+ builds typically introduce more aggressive fueling, ethanol blends, upgraded cooling, or additional supporting modifications.
On a stock fueling system, it is safe to run up to an E35 blend on the M157 platform. Owners who wish to run higher ethanol concentrations should consider upgraded high-pressure and low-pressure fueling upgrades.
At this level, owners typically see gains of 200+ crank hp and 220+ lb ft of torque with a strong custom ECU and TCU tune from our select tuning partners.
At this level, monitoring fuel pressure, ignition timing, intake temperatures, and overall engine health becomes increasingly important.
CLS63 & W212 E63 Stage 3
Stage 3 builds combine upgraded or hybrid turbochargers with downpipes, custom ECU and TCU tuning, and supporting fueling (HPFP & LPFP) and cooling modifications.
Properly built M157 setups can produce extremely high power while retaining much of the drivability that makes the E63 and CLS63 attractive street cars. We recommend stage 3 only if the vehicle features the 4Matic AWD system to ensure optimal traction.
It is difficult to estimate hp and tq figures for a stage 3 M157 build, as stage 3 encompasses a much broader range of upgrades (hybrid vs full frame turbos, fueling upgrades, ethanol concentrates, built transmission, etc.) and depends heavily on individual tuning skill.
For custom tuning, we recommend working with experienced Mercedes-AMG specialists such as A1 Automotive, MPE California, and Eurocharged.
Please contact Gapped Industries via email at contact@gappedindustries.com or Instagram @gappedindustries if you are interested in tuning your Mercedes-AMG.
CLS63 & W212 E63 Exterior Modifications
Carbon fiber exterior modifications are popular on both platforms and work particularly well with their aggressive factory styling.
Common upgrades include carbon fiber front lips, rear diffusers, trunk spoilers, side skirts, and mirror caps. If interested in carbon fiber parts for your W212 E63s or Cls63, please contact us via the email given above for more information.
A subtle OEM+ approach generally complements the CLS63 and E63 best. Larger aero components should primarily be considered cosmetic unless their aerodynamic performance has actually been tested.
Quality forged wheels can also reduce unsprung weight while dramatically changing the appearance of either platform.
CLS63 & W212 E63 Suspension and Handling
The CLS63 and W212 E63 are heavy, high-powered performance cars, making tires, alignment, and suspension condition particularly important.
Lowering springs, adjustable suspension components, or compatible lowering solutions can reduce wheel gap and improve the stance of the vehicle. Moderate lowering generally provides the best balance between appearance, handling, and everyday usability. The easiest way to lower the facelift Cls63 and W212 E63S models is through our lowering module, which uses the stock Airmatic system to adjust ride height remotely with software.
After lowering, we strongly recommend checking alignment and tire clearance. Excessive negative camber or incorrect toe can dramatically accelerate inner tire wear.
High-quality performance tires are particularly important on modified M157 cars because additional power can quickly overwhelm available traction.
Our Recommendations for the CLS63 & W212 E63
For an OEM+ street build, we recommend preventative maintenance, quality tires, forged wheels, subtle carbon fiber exterior components, and a mild lowering setup.
For a balanced performance build, we recommend Stage 2 ECU and TCU tuning, downpipes, fresh spark plugs, quality tires, and appropriate supporting maintenance. This provides a significant performance increase without requiring upgraded turbochargers.
For owners chasing maximum M157 performance, upgraded turbos, fueling, cooling, custom tuning, and drivetrain preparation can unlock considerably more power.
The C218 CLS63 and W212 E63 remain two of AMG's strongest modern modification platforms. Their combination of the M157 BiTurbo V8, luxury, aggressive styling, and extensive aftermarket support makes them excellent platforms for anything from a comfortable OEM+ daily driver to a high-horsepower street build.
Frequently Asked Questions About the CLS63 & W212 E63
What maintenance should I do before tuning my CLS63 or W212 E63?
Before tuning an M157-powered CLS63 or E63, make sure the vehicle is fully up to date on maintenance. We recommend fresh engine oil, properly gapped spark plugs, healthy ignition coils, clean air filters, and inspection of all major fluids.
The vehicle should also be checked for oil leaks, coolant leaks, boost leaks, and stored fault codes before increasing boost.
How reliable is the M157 engine?
The M157 can be a reliable performance engine when properly maintained, but age and maintenance history are increasingly important as these vehicles get older.
A pre-purchase inspection is strongly recommended when buying a used CLS63 or W212 E63. Tuned cars should receive more frequent maintenance and regular inspection of ignition, cooling, fueling, and drivetrain components.
How much power can a CLS63 S or W212 E63 S make?
Power depends heavily on fuel, modifications, turbochargers, and calibration. The M157 responds strongly to ECU tuning and downpipes, while upgraded turbo and fueling setups can support substantially higher output.
Rather than targeting a specific dyno number, we recommend building around your intended use and working with an experienced M157 tuner.
Are CLS63 and W212 E63 downpipes the same?
The C218 CLS63 and W212 E63 share significant M157 drivetrain architecture, but fitment can vary by model year, drivetrain, engine configuration, and downpipe design. Always verify the exact year, chassis, engine, and AWD or RWD configuration before ordering downpipes.
What are the best first mods for a W212 E63 or CLS63?
For most owners, the best starting modifications are ECU tuning, TCU tuning, downpipes, fresh spark plugs, quality tires, and preventative maintenance. Cosmetic upgrades such as wheels, lowering, and carbon fiber aero can then be added depending on the owner's goals.