The Mercedes-Benz C63 AMG, powered by the legendary M156 naturally aspirated V8, remains a benchmark for raw, unfiltered driving excitement. For many owners, the desire to extract more from this already potent engine leads to aftermarket tuning. Among the most respected names in this space is Kleemann, a Danish company with decades of experience in high-performance Mercedes modifications. The Kleemann Power Kit for the C63 M156 is not just a simple tune; it is a carefully engineered package designed to liberate hidden horsepower without sacrificing reliability. This article provides a comprehensive breakdown of the costs, performance results, and everything you need to know before taking the plunge.

What is the Kleemann Power Kit?

Kleemann’s Power Kit for the W204 C63 AMG (M156 engine) is a multi-component upgrade that addresses the main bottlenecks in the factory air intake, engine management, and exhaust systems. Unlike a basic ECU flash, this kit is a holistic approach that ensures each modification works harmoniously.

Core Components of the Kit

The standard Kleemann Power Kit typically includes four primary elements, each engineered to yield specific gains:

  • Kleemann ECU Tune: The heart of the kit. Kleemann replaces the factory ECU with a reflashed unit (or reflashes your existing ECU) that optimizes air-fuel ratios, ignition timing, and throttle response. Critically, the M156 responds extremely well to increased timing and leaner mixtures within safe limits.
  • High-Flow Air Intake System: The factory airbox is restrictive. Kleemann’s intake uses a large, conical dry filter housed in an insulated box, paired with a larger-diameter intake tube. This reduces inlet restriction and provides a denser, cooler air charge to the intake manifold.
  • Performance Headers (Optional but common): While not always included in the base kit, many installers recommend Kleemann’s long-tube headers to maximize exhaust flow. These replace the restrictive factory catalytic converters with high-flow cats (or off-road pipes) and larger diameter primary tubes.
  • Upgraded Throttle Body or Intake Manifold Spacer: Some versions of the kit include a ported throttle body or an intake manifold spacer to reduce intake charge temperature and increase air volume. This is particularly effective on the M156, which suffers from heat soak.

Kleemann offers multiple tiers of the Power Kit: Level 1 (usually just tune + intake), Level 2 (adds headers and sometimes the throttle body), and Level 3 (which may include a ported intake manifold or upgraded intercoolers for supercharged variants, though the N/A M156 kit stops at Level 2). For the naturally aspirated C63, the Level 2 kit is the most popular. For reference, you can learn more about Kleemann’s product range on their official website: Kleemann A/S.

Cost of Installing the Kleemann Power Kit on the C63 M156

The total expenditure varies depending on the kit level, the shop performing the work, and your geographic location (labor rates differ significantly between, say, a specialty shop in California versus a general performance garage in the Midwest). Here is a realistic breakdown:

Kit Pricing

  • Kleemann Level 1 Kit (ECU Tune + Intake): Approximately $3,500 – $4,500. This is the entry point and yields around 40–60 horsepower.
  • Kleemann Level 2 Kit (Tune + Intake + Headers + Throttle Body): Typically $5,500 – $7,500. This is the full N/A package and achieves the claimed 90–100 horsepower gains.
  • Optional Extras: Ported intake manifold (~$800), upgraded spark plugs (~$200), and a Kleemann carbon fiber engine cover (~$400) can be added.

Labor Costs

Installation of a full Level 2 kit is not a simple bolt-on job. It involves significant time, especially for the headers which are notoriously tight on the M156 chassis. Expect labor costs to be:

  • Basic installation (intake + tune): 3–5 hours labor, roughly $500 – $800 at a good independent Mercedes shop.
  • Full Level 2 installation (intake, tune, headers, throttle body): 12–18 hours of labor. Many shops charge between $1,200 – $2,500 depending on the rate ($100–$175 per hour).

Total Estimated Investment

  • Level 1 (DIY installation possible for experienced mechanics): $4,000 – $5,500
  • Level 2 (professional installation recommended): $7,000 – $10,000

It’s wise to budget an extra $500 for unforeseen items like gaskets, bolts, or an updated MAF sensor. Additionally, if your state requires smog testing, factor in the cost of a custom tune to pass emissions (Kleemann headers with high-flow cats can sometimes trigger OBD readiness issues).

Performance Results: Real-World Dyno and Track Data

The claims of up to 100 horsepower and 80 lb-ft of torque are not mere marketing hype—they have been verified by many independent C63 owners. However, actual results depend on the condition of the engine, fuel quality, and ambient temperature. Here's what you can realistically expect:

Dyno Testing

On a standard hub dyno (e.g., Dynojet or Mustang), a bone-stock C63 M156 usually puts down around 400–410 whp (wheel horsepower) and 380–400 lb-ft at the wheels. After a Kleemann Level 2 installation, many owners report:

  • Wheel Horsepower: 490–510 whp on 93-octane pump gas.
  • Wheel Torque: 460–480 lb-ft.
  • Peak gains: Approximately 90–110 whp over stock. The torque curve is also significantly flatter, with more power available from 3,000 rpm onward.

One widely cited result from the MBWorld forums shows a C63 with a Kleemann Level 2 kit hitting 504 whp and 471 lb-ft on a Dynojet. The same car ran a quarter-mile time of 12.0 seconds at 118 mph, improving from a stock 12.5 at 114 mph. 0–60 mph drops from 4.1 seconds to roughly 3.6–3.7 seconds with good traction. For further reading on user experiences, check out this MBWorld discussion thread: Kleemann Power Kit Results - MBWorld.

Drivability Improvements

Beyond raw numbers, the Kleemann tune dramatically improves throttle response. The factory throttle mapping, which can feel slightly laggy from a stop, becomes sharp and immediate. The intake and exhaust note also deepen, with a more aggressive growl under load. The headers reduce back pressure, allowing the M156 to rev more freely to the 7,200 rpm redline.

Installation Process: What to Expect

Installing the full Level 2 kit is a substantial job. While an experienced DIY mechanic can handle the intake and tune (the ECU is shipped pre-flashed or a core exchange is performed), the headers are the major challenge.

Step-by-Step Overview

  1. ECU Tune: The original ECU is removed, sent to Kleemann (or a certified dealer) for reflashing, and reinstalled. Some shops offer a rental ECU to minimize downtime.
  2. Intake Installation: The stock airbox is removed, and the Kleemann intake box, filter, and aluminum tube are fitted. The MAF sensor is relocated if required.
  3. Throttle Body Upgrade: The stock throttle body is unbolted, cleaned, and replaced with a Kleemann-ported unit that has a larger butterfly plate.
  4. Header Installation: This is the most labor-intensive part. The factory manifolds are tightly wedged against the frame rails and require removing the engine mounts and jacking the engine slightly to access the bolts. The bolts are prone to seizing, so penetrating oil and patience are essential. Kleemann’s headers are made from 304 stainless steel and feature 1.75-inch primary tubes leading to 3-inch collectors.
  5. Exhaust Reconnection: The headers are bolted to the stock or upgraded mid-section. Kleemann often recommends their X-pipe or a high-flow cat setup to maintain street legality.
  6. Final Tuning and Testing: After everything is installed, a professional dyno session is crucial to verify air-fuel ratios and check for knock. Kleemann provides a base calibration, but each car’s specific adaptation values should be fine-tuned.

Expect the total installation time to be 8–12 hours for a well-equipped shop performing the header job. The intake and tune alone take about 2–3 hours.

Potential Risks and Considerations

No performance upgrade comes without trade-offs. The Kleemann Power Kit is known for its robustness, but prospective buyers should consider the following:

Warranty and Insurance

  • Factory Warranty: If your C63 is still under warranty, the Kleemann kit will almost certainly void powertrain coverage. Aftermarket parts are not covered, and the ECU flash is detectable even if reversed (the "flash counter" in the ECU increments).
  • Insurance Premiums: Performance modifications increase risk in the eyes of insurers. Expect a premium increase of 10–30%. Notify your provider and consider adding agreed-value coverage to protect your investment.

Engine Reliability

The M156 is a robust engine, but it has known weak points: the camshaft adjusters (cam lobes and lifters) can wear prematurely, and the head bolts on early 2008–2010 models are prone to stretching. Adding 100 hp pushes the engine closer to its limits. Key reliability considerations include:

  • Heat Management: The M156 runs hot in stock form. with the Kleemann kit, exhaust gas temperatures rise further. An upgraded radiator and oil cooler (e.g., from CSF or Setrab) are strongly recommended for track use.
  • Fuel Quality: Using low-octane fuel can cause knock and detonation. Always run 93 octane (or 91 if that's the best available). Some owners also add a methanol/water injection kit for added safety margin.

Emissions Compliance

Kleemann headers with high-flow catalytic converters are legal in most states that follow federal standards. However, California (CARB) does not approve aftermarket headers that remove primary cats. Be prepared for smog check failures if you live in a strict emissions region, and consider keeping the stock headers for swaps.

Alternatives to the Kleemann Power Kit

Kleemann is not the only player in this space. Here are two notable alternatives for the C63 M156:

Renntech

Renntech offers a similar Level 2 package that also includes intake, headers, and a tune. Their numbers are comparable (around 510 whp), but Renntech often emphasizes drivability and a smoother power delivery. Pricing is similar, typically in the $7,500–$9,500 range installed. Learn more at Renntech Mercedes.

Weistec Engineering

Weistec is famous for supercharger kits, but they also offer a naturally aspirated "N/A Package" with ported heads, cams, and a tune. This is an extreme option that can push power well above 550 whp. However, it costs significantly more (over $15,000) and requires more invasive engine work. For those who want to stay naturally aspirated, Weistec’s package is the next step up.

DIY Tune and Headers

Budget-conscious owners can achieve 80% of the Kleemann results by purchasing a custom ECU reflash from a tuner like Eurocharged or Jersey Performance Tuning, combined with a set of aftermarket headers (e.g., Solo Performance or ARP). Total cost can be around $4,000–$5,000, but you lose the integrated engineering and support that Kleemann provides.

Maintenance After Upgrading

To keep your Kleemann-equipped C63 running strong, pay extra attention to these maintenance items:

  • Oil Changes: Shorten intervals to every 4,000–5,000 miles. Use a high-quality 0W-40 or 5W-40 oil that meets MB 229.51 specifications.
  • Spark Plugs: Upgrade to one heat range colder spark plugs (e.g., NGK Iridium IX). Replace every 15,000 miles instead of the stock 35,000-mile interval.
  • Air Filter: Clean the Kleemann dry filter every 10,000 miles. Over-oiling can foul the MAF sensor.
  • Cooling System: Flush coolant annually. Consider an upgraded coolant reservoir that handles pressure better.

Conclusion

The Kleemann Power Kit transforms the Mercedes-Benz C63 M156 from a muscular GT car into a genuine track-capable performer. With verified gains of 90–100 wheel horsepower, a more responsive throttle, and a glorious V8 soundtrack, it is one of the most effective naturally aspirated upgrades available. However, it comes with a significant financial outlay (typically $7,000–$10,000 installed), potential warranty and emissions complications, and increased maintenance demands. For the enthusiast who values a purpose-built, proven package and is willing to invest in the supporting modifications (cooling, fuel, maintenance), the Kleemann Power Kit is an excellent choice. Before committing, have a detailed conversation with a trusted Kleemann installer about your driving goals and ensure your particular C63 is in top mechanical condition—the kit will only magnify strengths and weaknesses alike.