What Makes the M177 Engine Special?

The Mercedes-AMG M177 is a 4.0-liter twin-turbocharged V8 that has powered the C63 AMG since 2015. In factory trim, the C63 S delivers 503 horsepower and 516 lb-ft of torque, making it one of the most potent compact performance sedans on the market. However, the M177 is built with forged internals, a robust block design, and a closed-deck construction that can handle substantially more power without internal modification. This inherent strength makes it an ideal candidate for an aftermarket performance kit like APR’s C63 M177 Performance Kit.

While the stock C63 S is already quick, many owners reach the limits of factory tuning relatively quickly. The combination of restrictive intake pathways, conservative ECU timing, and factory boost targets leaves significant headroom. APR’s solution addresses these bottlenecks with a calibrated ECU tune and optional bolt-on hardware upgrades that unlock the engine’s true potential.

APR’s C63 M177 Performance Kit: What’s Included

APR offers multiple stages for the M177, ranging from a simple Stage 1 ECU tune up to a comprehensive Stage 2 or even Stage 3 setup. The “Performance Kit” referenced in the original guide typically refers to a Stage 2 bundle that includes an ECU flash, upgraded intercooler, high-flow intake system, and larger downpipes. Some kits also include a revised exhaust system or a larger throttle body. Here is a breakdown of common components:

  • APR ECU Tune – Patented software recalibration optimized for 93 octane or race fuel. Adjusts boost pressure, fuel mapping, ignition timing, and torque management.
  • APR Intercooler System – A larger, more efficient intercooler with a higher flow core that reduces intake air temperatures (IATs) under sustained loads.
  • APR Cold Air Intake – Replaces the restrictive factory air box with a high-flow filter and smooth intake piping for increased airflow.
  • APR Downpipes – High-flow downpipes with larger diameter (typically 3.0 to 3.5 inches) and optional high-flow catalytic converters to reduce back pressure.
  • APR Exhaust System (optional) – A cat-back system that improves flow and delivers a more aggressive exhaust note.

Depending on the specific kit ordered, power gains from the full Stage 2 setup range from +100 to +150 horsepower at the wheels, with torque figures exceeding 600 lb-ft. These numbers are backed by APR’s extensive dynometer testing and real-world validation.

Tools and Materials Required

Before starting the installation, gather the following tools and safety equipment. A complete list helps avoid mid-project interruptions.

  • Torque wrench (3/8” and 1/2” drives, with ranges from 10 to 150 ft-lb)
  • Socket set (metric, 8mm to 22mm deep sockets)
  • Flat and Phillips screwdrivers
  • OBD-II flash tool (APR recommends a dedicated device provided with the kit, or use a laptop with APR software)
  • Jack and jack stands – for removing the underbody panel and accessing the intercooler and downpipes
  • Panel trim tools – to remove plastic clips and engine covers without breaking them
  • Safety glasses and work gloves
  • Coolant drain pan (if replacing the intercooler)
  • Brake cleaner and shop towels
  • White lithium grease – for reusing silicone hoses

Step-by-Step Installation Guide

Follow these detailed steps for a successful installation. Work on a level surface with the engine cold. Always disconnect the battery negative terminal before any electrical work.

Step 1: Disconnect the Battery and Prepare the Engine Bay

Use a 10mm socket to disconnect the negative battery terminal in the trunk (C63 models place the battery under the trunk floor). Remove the engine cover by unscrewing the five plastic bolts with a T25 Torx driver. Lift the cover straight up and set it aside. Remove any loose trim pieces around the intercooler ductwork.

Step 2: Flash the APR ECU Tune

Locate the OBD-II port under the dashboard on the driver’s side. Connect the APR flashing device or a laptop running APR’s software. Follow the on-screen prompts to read your vehicle’s stock calibration. APR recommends a stable internet connection for the download. Once the file is validated, initiate the flash. Do not interrupt power or the ignition cycle during writing. After completion, verify that the tune is stored by restarting the ignition.

Step 3: Install the APR Cold Air Intake

Disconnect the factory air intake duct from the throttle body. Remove the two airbox halves by unclipping the wire harness along the front of the engine. Install the APR intake pipe and filter according to instructions, ensuring a tight seal at the turbo inlets. It is common to use a small amount of silicone grease on the couplers to ease fitting. Tighten all worm-clamp bands to 5–6 Nm.

Step 4: Replace the Intercooler

Raise the vehicle on jack stands and remove the plastic underbody splash shield. Locate the factory intercooler in the front bumper area. Release the charge air pipes from the intercooler by loosening the T30 Torx clamps. Slide the intercooler out from its bracket. Install the APR intercooler using the supplied brackets and hoses. Reconnect the charge air pipes, ensuring a positive click on the quick-disconnect fittings. Lower the vehicle.

Step 5: Install High-Flow Downpipes (if included)

Working from underneath, remove the heat shields covering the turbo outlets. Disconnect the factory downpipes at the turbo v-band clamp and at the exhaust mid-pipe. Install the APR downpipes with new gaskets. Torque the v-band clamp to 25 Nm and the exhaust flange bolts to 45 Nm. Reattach heat shields. This step can be tricky; patience with clearance around the steering shaft is essential.

Step 6: Reconnect the Battery and Check for Codes

Reattach the battery negative terminal. Start the engine and let it idle for 2 minutes. Listen for any exhaust leaks or unusual noises. Use your OBD-II scanner to clear any stored diagnostic trouble codes (DTCs) related to the downpipe removal or battery disconnection. Allow the engine to reach operating temperature while checking the coolant level (top up if needed).

Step 7: Test Drive and Adapt

Take the vehicle on a gentle test drive. The APR tune often requires a few drive cycles to adapt fully. Note the throttle response, boost behavior, and idle smoothness. If any issues arise, return to the installation steps and verify all connections.

Expected Results and Real-World Performance

After installation, the C63 S with APR’s full Stage 2 Performance Kit typically produces between 630 and 660 wheel horsepower on pump gas, with peak torque around 700 lb-ft. This translates to a 0–60 mph time in the 2.8–3.0 second range (down from stock 3.9 seconds) and a quarter-mile of 10.7 to 10.9 seconds at 127 mph, depending on traction conditions.

Drivability improvement is immediately noticeable: throttle tip-in is sharper, mid-range pull is stronger, and the engine feels less strained at highway speeds. Fuel economy under normal cruising may improve slightly (up to 1–2 MPG) due to the more efficient tune, but aggressive driving will obviously lower it. The larger intercooler helps maintain consistent performance on hot summer days, reducing IAT rise by up to 40°F compared to the factory unit.

It’s important to note that these kits are intended for spirited street and occasional track use. APR recommends upgrading to high-performance tires and considering a transmission tune or TCU calibration for the MCT 9-speed to handle the increased torque.

Reliability and Considerations

The M177 engine is robust, but adding 150+ horsepower increases stress on the cooling system, spark plugs, and fuel delivery. APR’s kit is designed to keep within safe AFR and boost limits, but regular maintenance becomes even more critical. Replace spark plugs every 15,000 miles with one-step colder plugs. Monitor fuel trims and check oil frequently. Some owners opt for a water-methanol injection kit for added safety on high boost.

Warranty is a concern for those still under factory coverage. APR’s tune can be reversed to stock, but any failure traced to the modified software or hardware may void the warranty. Choose a reputable installer and keep all receipts.

Conclusion and Final Thoughts

Installing APR’s C63 M177 Performance Kit is one of the most effective ways to transform your Mercedes-AMG C63 from a formidable stock vehicle into a genuine supercar hunter. The step-by-step process outlined here covers the essential phases: ECU tuning, intake, intercooler, and downpipes. With careful preparation and attention to detail, the installation can be completed in a long weekend. The performance gains are dramatic, and the driving experience becomes more visceral and capably than ever.

For those considering the upgrade, visit the official APR product page for the latest kit options and pricing. Additional real-world experiences can be found on Mercedes-Benz forums and independent tuning platforms like Audizine (which covers VAG/turbo engines). Always validate that the kit is compatible with your specific C63 model year and region.

With the proper tools, patience, and a willingness to get under the hood, the APR C63 M177 Performance Kit can unlock the full potential of one of the best engines ever built by AMG. Drive responsibly and enjoy the newfound power.