Unlocking the True Potential of Your W204 C63 AMG

The Mercedes-Benz W204 C63 AMG, with its naturally aspirated 6.2-liter M156 V8, is a legend among performance sedans. Its raw, thunderous exhaust note and relentless power delivery have made it a favorite among enthusiasts. Yet even this masterpiece can be pushed further. The APR Stage 2 Turbocharger Kit transforms the W204 C63 from a formidable naturally aspirated machine into a forced-induction monster, drastically increasing horsepower and torque while maintaining drivability. This comprehensive guide walks you through the installation process, what to expect in terms of power gains, and how to optimize your car's handling to cope with the new levels of performance.

Why the APR Stage 2 Turbo Kit?

APR has long been a trusted name in Volkswagen and Audi forced induction systems, but their Stage 2 kit for the M156 engine is a bolt-on turbo system that doesn't require engine disassembly for installation. The kit uses a single large ball-bearing turbocharger, a custom cast exhaust manifold, intercooler, and all necessary plumbing. It delivers proven gains of over 200 horsepower at the wheels, pushing output well past 600 hp with proper fuel and tuning. Unlike centrifugal supercharger kits, APR's turbo setup offers a more linear, aggressive mid-range punch that is both exhilarating and surprisingly streetable.

Before diving into the install, it's critical to understand that this upgrade requires supporting modifications: upgraded fuel injectors, a high-flow fuel pump, and a custom ECU tune (included with the kit). You'll also want to address weak points like the driveshaft, differential, and cooling system after the installation.

Tools and Materials Required

To ensure a smooth installation, gather all necessary tools and parts beforehand. Working in a clean, well-lit garage with a vehicle lift or sturdy jack stands is highly recommended.

  • APR Stage 2 Turbocharger Kit (includes turbo, manifold, intercooler, piping, gaskets, hardware, and ECU calibration tool)
  • Metric socket set (including 8mm, 10mm, 13mm, 15mm, 18mm deep sockets)
  • Torque wrench (0–150 ft-lb range)
  • Combination wrenches (10mm–19mm)
  • Screwdrivers (flathead, Phillips, Torx T25/T30)
  • Pliers, hose clamp pliers, and a pry bar
  • Engine oil (5W-40 or manufacturer spec) – ~8 quarts
  • Coolant (OEM spec or equivalent) – ~3 gallons
  • New gaskets for manifold, turbo oil feed/return line seals, and exhaust gaskets
  • Thread-locker (blue 242 recommended for critical bolts)
  • Shop towels, brake cleaner, and safety equipment
  • Optional: OEM oil line gasket set

Preparation: Pre-Installation Checks

Proper preparation prevents headaches later. Follow these steps before lifting a wrench:

  • Park the C63 on a level surface, engage parking brake, and chock the wheels.
  • Disconnect the battery negative terminal and wait 5 minutes for the ECU capacitors to discharge.
  • Let the engine cool completely—the M156 runs hot, and the exhaust components will be dangerous if still warm.
  • Remove the engine cover (10mm bolts or push pins).
  • Drain the engine oil and coolant to avoid spills when disconnecting turbo oil lines and water lines.
  • Inspect your current intake and exhaust system; if you still have stock headers or restrictive catalytic converters, now is the time to upgrade.

Stock Turbo Removal

While the W204 C63 doesn't come with a factory turbocharger, the APR kit replaces the factory exhaust manifold and uses the space where the exhaust housing would be. The process essentially removes the factory exhaust manifolds and adapts the turbo system. Here's the detailed approach:

Step 1: Remove Intake and Exhaust Manifolds

  • Disconnect the mass airflow sensor and remove the air intake assembly.
  • Unbolt the factory exhaust manifolds (19mm nuts, 25–30 ft-lb). Access can be tight; use swivel sockets and extensions.
  • Remove the factory exhaust system from the manifolds back to the mid-pipe. You'll need to unbolt the downpipes from the stock cats.

Step 2: Disconnect Oil and Water Lines

  • Locate the oil feed line for the turbo (on the block near the oil filter housing). Use caution: it's under pressure even after draining.
  • Unbolt the two oil return line fittings on the block.
  • Disconnect the water lines (two rubber hoses) at the thermostat housing and water pump using hose clamp pliers.

Step 3: Extract the Remaining Components

  • Unbolt the secondary air injection pump (if equipped) and move it aside (do not disconnect hoses).
  • Remove the heat shields covering the upper part of the bellhousing and the passenger side wheel well liner.
  • Unbolt the factory exhaust manifold studs (some may snap; be prepared to extract them).
  • Carefully wiggle the manifolds out from the top or bottom, depending on clearance.

At this stage the engine bay should reveal the cylinder head exhaust ports, the block oil return ports, and open cooling passages.

APR Stage 2 Turbocharger Installation

Now the real work begins. Work methodically and use torque specs provided in the APR manual.

1. Install APR Exhaust Manifold

  • Clean the cylinder head exhaust port surfaces with brake cleaner and a razor blade to remove any old gasket material.
  • Place new OEM exhaust gaskets onto the head studs.
  • Position the APR cast manifold onto the studs and hand-tighten the new locknuts.
  • Torque in sequence from the center outward to 20 ft-lb, then final torque to 30 ft-lb.

2. Mount the Turbocharger

  • Install the turbo center housing onto the manifold, using the supplied gasket. Torque the bolts to 18 ft-lb.
  • Attach the turbine housing components per APR instructions (V-band clamps, actuator bracket).
  • Connect the oil feed line from the block to the turbo. Use new copper crush washers. Torque banjo bolts to 15 ft-lb.
  • Connect the oil return line from the turbo to the block (usually a braided line). Ensure it slopes downward to allow gravity drainage.
  • Attach the water feed and return hoses. APR provides silicone hoses with spring clamps; ensure they are fully seated.

3. Install Intercooler and Piping

  • Remove the front bumper and crash bar for access (check APR instructions—some kits allow installation with minimal disassembly).
  • Mount the APR intercooler in the lower front bumper opening, using brackets provided.
  • Route the charge air pipes from the turbo outlet to the intercooler, and then to the throttle body. Use couplers and T-bolt clamps. Tighten to 5–6 ft-lb (do not overtighten).
  • Install the blow-off valve (if included) on the cold side pipe.
  • Reinstall the crash bar and front bumper.

4. Finalize Connections

  • Reconnect the intake duct from the air filter to the turbo inlet. Use a quality silicone hose and ensure no leaks.
  • Reconnect the battery, but do not start the engine yet.
  • Fill engine oil to proper level (APR recommends a high-quality full synthetic 5W-40).
  • Fill coolant system with the bleeding procedure: fill slowly, run engine with heat on full, top off as needed.

ECU Calibration and First Start

APR provides a handheld programming tool (similar to Cobb AccessPort) that installs their Stage 2 calibration. Follow these steps:

  • Connect the APR programming tool to the OBD-II port.
  • Select "Stage 2 Turbo Kit" calibration for your fuel grade (91, 93, or E85 if available).
  • Let the tool automatically detect your ECU and flash the tune. This takes about 10–15 minutes. Do not interrupt the process.
  • After flashing, turn ignition off for 30 seconds, then start the engine.
  • Let it idle for 10 minutes to allow the turbo to oil and for any air to purge from the coolant system. Check for smoke, coolant leaks, or oil drips.
  • If the car idles smoothly and no warning lights appear, do a gentle test drive (no full throttle for the first 50 miles to allow rings to seat with new boost).

For those seeking even more performance, APR’s official page offers additional tuning options and data logs.

Handling Upgrades to Match the Power

With over 600 hp, the W204 C63's chassis needs attention. The factory suspension is biased toward comfort and moderate handling, but under heavy throttle the rear end can become unstable. Consider these complementary upgrades:

  • Coilover suspension – KW V3 or Bilstein B16 adjustable coilovers reduce body roll and improve traction.
  • Rear subframe bushings – Polyurethane or aluminum bushings eliminate axle hop during hard acceleration.
  • Brake upgrade – A big brake kit (e.g., Brembo GT or StopTech) with six-piston calipers front and four-piston rear is essential to stop safely from 150+ mph.
  • Wider wheels and tires – 19x9.5 front and 19x10.5 rear with 265/30 and 295/30 Michelin Pilot Sport 4S tires provide grip.
  • Differential upgrade – Wavetrac or Quaife limited-slip differential helps put power down on corner exit.

These changes transform the C63 from a heavy grand tourer into a genuine track-day weapon. BimmerWorld offers excellent wheel and brake packages for the W204 platform.

Common Pitfalls and Troubleshooting

Every serious upgrade has potential issues. Here are the most common ones with the APR Stage 2 install:

  • Boost leaks – Crank down all T-bolt clamps; a loose coupler will cause a loss of power and lean conditions.
  • Oil line leaks – Ensure crush washers are new and banjo bolts are torqued evenly. Use antiseize on threads.
  • CEL after install – Most commonly due to a post-cat O2 sensor reading. APR tune should disable secondary monitors, but if you have an aftermarket exhaust, you may need spacer adapters.
  • Overheating in summer – The M156 produces immense heat. Upgrade to a larger radiator or CSF aluminum unit if you track the car.
  • Clutch slip – If your C63 is manual (rare), the stock clutch won't hold 600+ hp. Upgrade to a twin-disc setup. For 7G-Tronic automatics, a torque converter upgrade and transmission cooler are needed.

For detailed troubleshooting, MBWorld forums contain thousands of posts from owners who have performed this exact conversion.

Post-Installation Maintenance

After the first 500 miles, change the engine oil and filter to remove any debris from break-in. Inspect all turbocharger bolts and couplers for loosening. Perform regular checks every 5,000 miles:

  • Oil level – The turbo consumes a small amount; check weekly.
  • Coolant level – Ensure no air pockets develop.
  • Intercooler core – Clean bugs and debris out for maximum efficiency.
  • Wastegate actuator – Ensure linkage moves freely; adjust for boost creep if needed.

Consider an oil catch can to prevent hydrocarbon buildup in the intake tract, as boosted engines produce more blowby.

Performance Results: What to Expect

On a dynojet, a properly tuned W204 C63 with APR Stage 2 kit installed on 93 octane produces approximately 620–650 wheel horsepower and 580–600 lb-ft of torque. That’s a 0–60 mph time in the low 3-second range and a quarter-mile in the mid-10s at 135+ mph. The car feels relentless from 3,500 rpm to redline, with a shove that pins you back in the seat.

Street manners are surprisingly civil: the turbo spools quickly, with minimal lag, and the calibration provides smooth part-throttle response. Only at wide-open throttle do you realize you're driving a vehicle that rivals modern supercars at a fraction of the cost.

Conclusion

Installing the APR Stage 2 Turbocharger Kit on your W204 C63 AMG is a transformative project that turns an already iconic car into a true high-performance legend. It demands time, mechanical skill, and attention to detail, but the reward is an unparalleled driving experience. By following this guide, using proper tools, and addressing supporting modifications, you can safely and effectively unlock your C63’s full potential. Always consult APR's official instructions during installation, and don't hesitate to reach out to a certified performance shop if you encounter difficulties. Your bravery and patience will be rewarded with a car that dominates both the street and the track.

For more information on APR products for the M156 engine, visit APR's official website or speak with an authorized dealer.