The Mercedes-AMG A45 S, powered by the hand-built M133 engine, is already a benchmark in the hot hatch segment, delivering 421 horsepower and 369 lb-ft of torque straight from the factory. But for those who crave more, cracking the 600-horsepower barrier transforms this compact rocket into a genuine supercar slayer. Achieving this level of output requires a carefully orchestrated combination of hardware upgrades, precise calibration, and a respect for the engine’s limits. This guide breaks down the necessary modifications, the realistic costs involved, and proven installation strategies to help you hit 600 hp without turning your A45 S into a grenade.

Understanding the Mercedes-AMG M133 Engine Platform

The M133 is a 2.0-liter turbocharged inline-four that pushed the envelope when it debuted. Unlike its predecessor, the M270, the M133 uses a closed-deck block, forged steel crankshaft, forged connecting rods, and a cylinder head with dual overhead camshafts and variable valve timing. The turbocharger is a twin-scroll BorgWarner unit with electronic wastegate control, allowing peak boost of up to 2.1 bar (30 psi) from the factory. The A45 S variant adds a larger turbocharger, revised pistons with lower compression (9.0:1 vs. 9.3:1), and a reinforced crankshaft drive. These upgrades make the M133 DE20 AL a surprisingly stout foundation for big power, but the stock internals still have limits. At the 600 hp goal, you are at the edge of what the factory bottom end can reliably handle, especially if you plan to track the car or run sustained high loads.

M133 vs. M133 DE20 AL: Key Differences

  • Factory A45 (non-S): ~381 hp, smaller turbo, lower compression pistons, single intercooler.
  • Factory A45 S (CLA45 S, GLA45 S): ~421 hp, larger turbo (GT25 type), lower CR 9.0:1, reinforced bottom end, twin intercoolers.

The S-model already benefits from stronger connecting rods and better thermal management, making it the preferred starting point for a 600 hp build. If you own a standard A45, expect to invest in forged pistons and rods before pushing past 550 hp.

Essential Modifications to Reach 600 Horsepower

Reaching 600 hp on the M133 is not about a single “magic part.” It requires a holistic upgrade path where each component supports the next. Below is the recommended sequence of modifications, with detailed explanations of why each is critical.

1. ECU Tuning and Software Calibration

The factory ECU uses a Bosch MG1 architecture, which is extremely locked down. You will need a bench unlock or a clone of the ECU to gain write access. Reputable tuners such as Celtic Tuning or RENNtech offer custom maps for the M133. For 600 hp, you’ll need a full custom tune via a platform like ECUTek or HP Tuners. Expect to pay $1,200–$2,500 for a complete tune including multiple revisions and pre–and post–dyno runs. Never rely on a generic “stage 3” file from an unknown source—the M133 is sensitive to fuel quality and boost curve.

2. Upgraded Turbocharger

The stock A45 S turbo runs out of steam around 470–500 whp. To hit 600 crank horsepower (approximately 510–530 whp), you need a larger unit. Options include hybrid rebuilds (e.g., PTP Turbo) or a complete replacement like the Pure Turbos M133 Stage 3 or the Forced Performance HTA76. These turbos can push 38–40 psi and flow 50+ lb/min. Installation requires removal of the intake manifold and heat exchanger. Cost: $2,500–$4,500. Consider adding a turbo blanket and a heat shield to protect the plastic intake parts.

3. High-Performance Intercooling

The A45 S already has dual intercoolers, but under sustained boost they heat-soak quickly. A front-mount intercooler (FMIC) upgrade from brands like CSF or Mishimoto provides a larger core with superior flow. For 600 hp, you must also upgrade the auxiliary radiator and consider a water-methanol injection kit (e.g., AEM or Aquamist) to suppress inlet temperatures. Intercooler cost: $600–$1,500. Methanol kit: $400–$800.

4. Fuel System Upgrades

At 600 hp, the factory high-pressure fuel pump (HPFP) can’t keep up. You’ll need a modified HPFP (N63 TU or M177 pump conversion) or a port-injection add-on system. The simplest approach is a drop-in upgraded HPFP from TorqAMP or Autotec, paired with larger injectors. Expect to spend $1,200–$2,000 on fuel system upgrades. Do not skip this—lean conditions cause rapid piston failure.

5. Full Exhaust System

The M133 benefits from a 3.0–3.5-inch downpipe and cat-back exhaust. Removing the catalytic converters (or using high-flow cats) reduces backpressure and spool time. A properly designed exhaust adds 15–25 hp and helps the turbo breathe. Downpipe: $500–$1,000. Full system: $1,200–$2,500. Ceramic-coating the downpipe is recommended.

6. Induction and Intake

An open-element intake or a sealed cold-air box (e.g., Eventuri, aFe) reduces intake restriction and lowers IATs. For 600 hp, a 4-inch or larger intake pipe is necessary. Cost: $400–$900. Pair with a turbo inlet pipe upgrade for smoother flow.

7. Supporting Engine Hardware

While the A45 S rods and pistons can survive 600 hp on a conservative tune, it’s highly recommended to install forged rods (Carillo or Pauter) and coated pistons (JE or CP-Carrillo) if you plan to track the car or run race fuel. This is expensive ($2,500–$4,000) but provides peace of mind. Similarly, upgrade the valve springs and retainers to handle higher RPM. Do not exceed 7,200 RPM on stock valvetrain.

Cost Breakdown: A Realistic Budget for 600 HP

The total investment for a reliable 600 hp build on a Mercedes-AMG A45 S ranges from $10,000 to $16,000 in parts alone, plus labor. Below is a detailed cost table based on mid-range, quality components and professional installation (labor estimated at $125–$175/hour).

ModificationParts CostLabor CostTotal Estimated
ECU Tuning (custom dyno tune)$1,500$500$2,000
Upgraded Turbocharger (hybrid)$3,000$800$3,800
Front-Mount Intercooler$1,000$400$1,400
Water-Methanol Injection$600$300$900
Fuel System (HPFP + injectors)$1,800$400$2,200
Exhaust (downpipe + cat-back)$2,000$600$2,600
Intake System$600$100$700
Forged Rods & Pistons (optional, recommended)$3,500$2,500$6,000
Miscellaneous (gaskets, fluids, dyno time)$500$200$700

If you skip the forged internals, the build totals approximately $10,000. With engine reinforcement, expect $16,000–$18,000. Keep in mind that these figures do not include potential drivetrain upgrades (clutch packs, transmission software) which may be needed if you plan to launch hard.

Installation Tips and Best Practices

DIY installation of these modifications is possible with a well-equipped garage and a lift, but many steps require specialized tools. Here are critical installation considerations for each component group.

Turbocharger Installation

  • Remove the front bumper, crash bar, and radiator support to access the turbo. The stock turbo sits behind the engine, making it a tight fit—plan for 6–8 hours of labor.
  • Replace all oil and coolant lines. The small oil feed line is a common failure point when using a larger turbo. Use a -4AN braided line.
  • Upgrade the turbo-to-intercooler charge pipe to a silicone or aluminum unit. The stock plastic pipe can burst under 40 psi.
  • Use a new gasket kit (turbo manifold, downpipe) and torqued to factory spec.

Intercooler and Cooling System

  • If adding a larger front-mount, you may need to trim the lower bumper grille for airflow. The stock dual intercoolers can be retained as secondary coolers—plumb them in series or parallel.
  • When installing water-methanol, mount the nozzle downstream of the intercooler, at least 12 inches before the throttle body. Use a failsafe controller to prevent injection without fluid.
  • Consider an auxiliary oil cooler. The M133 runs oil temperatures in the 220–240°F range stock; a 19-row Setrab cooler helps keep oil under 210°F even on track.

Fuel System Upgrade

  • The HPFP is located on the rear of the engine, under the intake manifold. Remove the wiper cowl and intake for access.
  • When installing larger injectors, use Bosch EV14 or equivalent. Ensure they are flow-matched. The injector cups often crack—replace them with upgraded brass units.
  • Fuel line upgrade: Use Teflon-lined hose for ethanol compatibility if you plan to run E85. Run 5/16″ or 8mm line from the pump to the rail.

Engine Internals (if building)

  • Remove the engine from the car for rod/piston changes. This is an engine-out job—budget 20+ hours of shop time.
  • Check the main bearing clearance with the new rods. The M133 uses a torque-to-yield head bolt; replace with ARP head studs.
  • After assembly, run the engine on a break-in oil change (15 minutes then drain) before loading the tune.

Real-World Dyno Results and Performance Gains

A properly tuned 600 hp A45 S will produce approximately 510–530 whp on a Mustang dyno (higher on a Dynojet). With the mods listed, expect 0–60 mph in the 3.1–3.3 second range (with upgraded tires) and a quarter-mile time in the low 11-second range at 125+ mph. On the Autobahn, traction becomes the limiting factor—consider using Michelin Pilot Sport 4S or Cup 2 tires in 235/35R19 fronts and 255/30R19 rears. The car will feel explosive from 3,500 rpm to redline. Keep in mind that at these power levels, the 7-speed DCT transmission may slip on upshifts—a transmission tune (TCU flash) is strongly recommended.

Common Pitfalls and Reliability Considerations

  • Heat is the enemy. The M133 is a high-strung engine; without adequate cooling (oil, water, intake air), a 600 hp tune will cause detonation quickly. Monitor IATs and EGTs on every pull.
  • Boost spikes. When tuning, request a progressive boost curve rather than a spike. The stock MAP sensor can read up to about 45 psi—use a secondary sensor for safety.
  • Clutch pack wear. The DCT has wet clutches that can’t handle constant hard launches. If drag racing, budget $3,500 for an upgraded clutch pack from RENNtech or Performance Package.
  • Legal & warranty concerns. These modifications void your factory warranty. Emissions equipment removal may be illegal in your region—check local laws before installing catless downpipes.

Conclusion

Achieving 600 horsepower in the Mercedes-AMG A45 S M133 is an ambitious but fully achievable goal with the correct parts and tuning approach. The most cost-effective path starts with an S-model, focuses on turbo, fueling, and cooling upgrades, and uses a conservative custom tune. While the investment—typically $10,000 to $18,000—is substantial, the result is a sub-3.5-second 0–60 car that can embarrass far more expensive machinery. Always prioritize reliability over peak numbers, and work with a specialist who understands the M133 platform intimately. With careful planning and quality installation, your A45 S will become one of the most potent hot hatches on the road.