Installing a BMC air filter on your W205 C63 can lead to slight but noticeable power improvements, sharper throttle response, and a more aggressive intake sound. Unlike oiled cotton gauze filters from other brands, BMC filters use a unique cotton-gauze design combined with a lightweight aluminum mesh that increases airflow while maintaining high filtration efficiency. This guide provides a detailed, step-by-step approach to safely replacing your stock air filter with a BMC performance filter. We’ll cover everything from tool selection and safety precautions to post-installation testing and long-term maintenance. By following this guide, you can expect a measurable improvement in intake performance without compromising engine protection.

Tools and Materials Needed

Before starting, gather all necessary tools and materials. Having everything at hand prevents interruptions and ensures a smooth workflow. The following list covers the essentials for a W205 C63 (including the C63 S and C63 Sedan/Coupe with the M177 engine).

  • BMC air filter (part number FB512/03 for W205 C63) – confirm fitment for your specific model year
  • Socket set (metric, 8mm, 10mm, 13mm)
  • Torx bits (T20 and T25, commonly used on Mercedes-Benz intake housings)
  • Screwdriver set (flathead and Phillips)
  • Torque wrench (for tightening fasteners to spec, if available)
  • Gloves (mechanics gloves to keep hands clean and protect the filter from oils)
  • Safety glasses
  • Shop vacuum or compressed air (optional, for cleaning the air filter housing)
  • Trim removal tool (optional, for prying plastic clips without scratching)

If your BMC filter is purchased from an authorized dealer, it will come pre-oiled and ready to install. However, if you are using a previously cleaned filter that has been dry for a while, consider purchasing a BMC re-oiling kit to ensure proper oil coverage before installation. Note: Check the official BMC website for the latest fitment guide and part numbers.

Preparation Steps

Proper preparation minimizes the risk of damage to your engine, electrical system, or the new filter. Follow these steps before touching any components:

  • Park on a flat, level surface and engage the parking brake. Ensure the engine is completely cool – a hot engine can cause burns, and hot intake components can distort filter housing seals.
  • Open the hood and locate the air filter box on the passenger side (right-hand side for left-hand drive vehicles). The W205 C63 uses a dual-intake system with two separate air filter boxes, one for each turbocharger. You will need to replace both filters, or at least both if you are using a set of two BMC filters (typically sold in pairs).
  • Disconnect the negative battery terminal using a 10mm socket. This prevents accidental triggering of the electric throttle motor, fuel pump, or any electrical shorts while you are moving sensors or loosening clamps. Wait at least 5 minutes after disconnecting to allow any residual voltage in the ECU capacitors to dissipate.
  • Remove any engine cover trim that blocks access to the air filter boxes. On the W205 C63, there is a plastic engine cover secured by several Torx screws (T25) and push-clips. Carefully lift it off and set aside.
  • Disconnect the mass airflow (MAF) sensor connectors if they are attached to the air filter box top covers. On this engine, each air filter box lid houses a MAF sensor. Gently press the release tab and unplug the connector without pulling on the wires. Inspect the pins for corrosion.

If you see debris, leaves, or dirt in the area around the air filter boxes, use a shop vacuum or compressed air to clean the area. This prevents contaminants from falling into the intake tract when you remove the filters. Also, note the orientation of any hoses or electrical connectors you disconnect – take a photo with your phone for reference.

Removing the Stock Air Filters

The W205 C63 uses two identical air filter boxes, both requiring removal of the stock paper filters. The process is identical for both sides. Proceed with patience – the space is tight, and forcing plastic clips can break them.

  1. Remove the air filter box lid. Each lid is held by three to four Torx screws (T20 or T25). Use a Torx bit and a ratchet or screwdriver to loosen all screws. Do not remove the screws completely – they often have captive washers that prevent them from falling into the engine bay. Once all screws are loose, lift the lid gently.
  2. Carefully separate the lid from the lower housing. The lid may be stuck due to rubber seals. Tilt it upward and forward to clear the MAF sensor and any attached wiring. If the MAF sensor is mounted to the lid, leave it attached to the lid; do not force the sensor out of its housing unless necessary.
  3. Remove the stock paper filter. The filter will slide out easily. Note the direction of the airflow arrow – the arrow should point toward the engine. Set the old filters aside for disposal. Do not reuse paper filters.
  4. Inspect the air filter housing interiors. Look for any dirt, oil residue, or foreign objects. Use a clean microfiber cloth slightly dampened with isopropyl alcohol to wipe the interior. Avoid leaving lint behind. Also check the condition of the rubber gaskets on the lid and bottom housing; if they are torn or flattened, replace them to maintain an airtight seal.
  5. Clean the MAF sensor (optional but recommended). If you have MAF sensor cleaner, spray the sensor element carefully while avoiding touching it. This can improve air measurement accuracy. Let it dry completely before reassembly.

While the stock filters work adequately for stock power levels, they are restrictive compared to a high-flow BMC filter. The paper media and limited surface area create a bottleneck at higher RPMs. By replacing both filters, you allow each turbocharger to draw air more freely, reducing intake restriction and potentially lowering intake air temperatures slightly due to better flow.

Installing the BMC Air Filters

Now that the old filters are removed and the housings are clean, it’s time to install the BMC filters. Follow these steps carefully to ensure a proper seal and avoid air leaks.

  1. Prepare the BMC filter(s). If the filters are brand new from a sealed package, they are pre-oiled. Gently massage the filter material between your hands to distribute the oil evenly. Avoid over-oiling – if oil drips from the filter, blot it with a paper towel. Over-oiling can contaminate the MAF sensor.
  2. Align the BMC filter with the air filter housing. The filter must sit flat against the bottom housing. Ensure that the rubber gasket around the outer perimeter of the filter aligns with the housing edge. The filter element should not be bent or compressed; it should fit snugly without forcing.
  3. Press the filter into place. Starting from one corner, gently press the filter down until it rests evenly. Do not use excessive force – the filter will seat itself once the lid is tightened.
  4. Install the air filter box lid. Place the lid back onto the housing, making sure the MAF sensor (if attached to lid) aligns correctly and that no wires are pinched. Ensure the lid’s rubber gasket sits flush along the entire perimeter.
  5. Install and tighten the Torx screws. Hand-tighten all screws first, then tighten them in a cross pattern to ensure even pressure. Torque specification for these screws is typically 2–3 Nm (very low). Do not overtighten – the plastic housing can crack. Use a torque wrench if you have one set to 2.5 Nm. If not, just snug them until you feel resistance, then stop.
  6. Repeat for the second air filter box. The process is identical on the driver’s side (left-hand side on LHD models).
  7. Reconnect the MAF sensor connectors. Plug each connector in until you hear a click. Ensure they are fully seated and locked.
  8. Reinstall any engine cover trim. Place the plastic cover back and secure with the Torx screws and push-clips. Do not overtighten – the plastic cover can crack.

After installation, double-check that all screws are present and tightened, and that no tools remain in the engine bay. A common mistake is leaving a screwdriver or socket under the hood, which can cause damage on start-up.

Reconnecting the Battery and Initial Checks

With the filters installed and housing sealed, it’s time to reconnect the battery and verify the installation.

  • Reconnect the negative battery terminal. Tighten the 10mm nut securely – a loose connection can cause electrical issues. Do not overtighten; spec is about 8 Nm.
  • Before starting the engine, turn the ignition key to position 2 (or press the start button without pressing the brake). Wait for the dashboard lights to stabilize. Listen for any unusual clicks or buzzing from the intake area – if you hear air hissing, check that the air filter box lids are fully sealed.
  • Start the engine. Let it idle for about 30 seconds. No check engine light should appear. If the check engine light illuminates, it may indicate a MAF sensor connection issue or an air leak. Turn off the engine and re-check connections.
  • Allow the engine to reach normal operating temperature. During the first few minutes, you may notice a slightly different intake sound – a deeper, throatier growl under acceleration. This is normal and expected with a high-flow filter.

If you have access to an OBD2 scanner, check for any stored faults. In most cases, the ECU will adapt to the increased airflow after a short drive. Some owners report a temporary lean code (P0171 or P0174) if the air leak is present; if this occurs, inspect the filter seating and lid screws.

Test Drive and Performance Observations

After the initial checks, take the car for a test drive. The W205 C63’s ECU will adapt to the new airflow characteristics over several drive cycles, but you should feel an immediate difference in throttle response.

  • Acceleration feel: At partial throttle, the car should feel more responsive, especially from low RPMs. Many owners report a sharper tip-in.
  • Sound: Expect a more audible intake roar under hard acceleration, particularly between 3,000–5,500 RPM. The supercharger-like whistle of the turbos may become slightly more pronounced.
  • Power gains: BMC claims gains of 5–8 hp on the W205 C63, with similar torque improvements. These gains are modest but can be felt in mid-range acceleration. Combined with a software tune, the filter can support higher airflow targets.
  • Fuel trims: On a stock ECU, you may see a minor adjustment to short-term fuel trims (STFT) as the MAF readings change. This is normal and should stabilize within 50–100 miles.

If you notice any hesitation, surging, or check engine light, return home and re-inspect the installation. A small air leak can cause drivability issues; ensure the filter gasket is fully seated and the lid is tight.

Maintenance and Cleaning Schedule

One advantage of BMC filters is that they are reusable. With proper cleaning and re-oiling, they can last the lifetime of the vehicle. Regular maintenance ensures consistent performance and prevents dirt buildup that could restrict airflow.

  • Inspect the filter every 12,000–15,000 miles (or at every oil change). Remove the filter and hold it up to a light – if you can see light clearly through the gauze, it is still clean. If it appears clogged with dirt or discolored, it’s time for cleaning.
  • Clean using the BMC cleaning kit. Spray the cleaner onto the filter and let it soak for 10 minutes. Gently rinse with low-pressure water (from the inside out) to flush dirt away. Do not use high-pressure water or compressed air, as this can damage the cotton gauze.
  • Allow the filter to air dry completely. Leave it out of direct sunlight for several hours or overnight. The filter must be fully dry before re-oiling.
  • Re-oil using BMC oil. Spray oil along the pleats, holding the nozzle 6–8 inches away. Let the oil soak in for 20 minutes, then blot any excess. Too much oil can coat the MAF sensor and cause inaccurate readings.
  • Reinstall as described above. Remember to replace the rubber gasket if it becomes worn.

For best performance, use genuine BMC cleaning products. Other brands’ chemicals may degrade the BMC filter material or incompatible with the adhesive used on the filter’s seams. BMC offers detailed instructions on their website for filter care.

Potential Pitfalls and Troubleshooting

Even a simple filter swap can present challenges, especially on a high-performance vehicle like the W205 C63. Here are common issues and their solutions:

  • Check engine light with lean codes (P0171/P0174): Most likely caused by an air leak. Verify that the air filter box lids are fully seated and that all Torx screws are tight. Also check that the MAF sensor o-ring is present and not pinched.
  • Whistling noise at idle: A high-pitched whistle can indicate a vacuum leak from a loose hose or a poorly sealed filter lid. Inspect all connections around the intake tube.
  • Oil smell from vents: Over-oiling the filter can cause oil to be drawn into the intake system and burn off. If you smell oil, remove and blot excess oil from the filter, then reinstall.
  • Loss of low-end torque: Some high-flow filters may slightly reduce low-end torque on turbo engines if the intake velocity is affected. On the W205 C63, most owners report no loss – if you experience it, check for a kinked intake hose or a blocked snorkel.

If you encounter persistent issues, consult a forum dedicated to the W205 C63, such as MBWorld, where experienced owners can help diagnose. Many users have documented their BMC filter installations and can provide specific tips for your model year.

Conclusion

Installing a BMC air filter on your W205 C63 is a straightforward, rewarding modification that can yield slight but tangible power improvements. The process, as outlined, is safe when proper precautions are taken: working on a cool engine, disconnecting the battery, and ensuring a clean, sealed installation. The performance gains – better throttle response, a more aggressive intake sound, and modest power increases – make this one of the best simple upgrades for the M177 engine.

Remember that while the BMC filter improves airflow, it is only one part of an overall performance strategy. For greater gains, combine it with a high-quality tune, exhaust modifications, and a cold air intake system that retains the factory ducting. The filter’s reusability means you are making a one-time investment that saves money over replacing disposable paper filters.

Always source your BMC filter from an authorized dealer to avoid counterfeit products. A genuine BMC filter includes the company’s batch number and comes with a warranty. Reputable retailers like FCP Euro stock certified filters and offer lifetime replacement on some parts. With proper maintenance, your BMC filter will deliver consistent performance for many miles.

By following this guide, you can safely complete the installation in under an hour and enjoy the enhanced driving experience that a free-flowing air filter provides. Always double-check your work and drive responsibly. Your W205 C63 will thank you.