Mercedes-AMG M133 Turbo Upgrade Guide — Stage 4 | A45, CLA45, GLA45
The Mercedes-AMG M133 2.0-litre turbocharged four-cylinder is the engine behind AMG’s compact performance lineup — the A45 (W176), CLA45 (C117), and GLA45 (X156). From the factory, the M133 produces up to 381 HP in its final specification, making it one of the most powerful production 2.0T engines ever built. But with the right turbo upgrade, the M133 is capable of significantly more — well beyond 500 WHP on pump fuel.
This guide covers the turbo upgrade path for all M133-equipped models, including the Stage 4 turbo kit and the supporting modifications needed to extract its full potential.
Factory M133 Turbo Limitations
The factory BorgWarner turbocharger on the M133 is impressively capable for its size, delivering strong boost response and solid mid-range torque. However, it reaches its airflow limit around 420–440 WHP on even the most aggressive tunes. Beyond that point, the compressor is operating outside its efficiency map, exhaust gas temperatures become difficult to manage, and further power gains plateau regardless of fuelling or ignition changes.
For M133 owners who have already maximised their factory turbo with a stage 1 or stage 2 ECU tune and supporting bolt-ons, the turbocharger itself becomes the bottleneck. An aftermarket turbo upgrade unlocks the next tier of performance — moving from the 400 WHP range into genuine 500+ WHP territory.
Stage 4 Turbo Upgrade — 500+ WHP
The YPG M133 Stage 4 Turbo Upgrade replaces the factory turbocharger with a larger-frame unit designed to deliver significantly more airflow while maintaining usable spool characteristics for a 2.0-litre engine. On 98 RON pump fuel with supporting modifications, the Stage 4 kit targets 500+ WHP — a transformative increase over the factory turbo’s ceiling.
The Stage 4 kit includes the turbocharger assembly, gaskets, oil lines, and all necessary hardware for a bolt-on installation. It is designed to work with the M133’s existing exhaust manifold and intake plumbing, minimising the complexity of installation compared to larger turbo setups that require custom manifold work.
Key characteristics of the Stage 4 M133 turbo:
- Targets 500+ WHP on 98 RON pump fuel
- Maintains reasonable spool for a 2.0-litre platform — lag is present but manageable
- Compatible with all M133 chassis: A45 (W176), CLA45 (C117), GLA45 (X156)
- Requires supporting modifications and a dedicated ECU tune
Supporting Modifications for M133 Turbo Builds
The M133’s 2.0-litre displacement means every supporting modification matters more than on a larger engine. The smaller swept volume amplifies the impact of restrictions in the intake, exhaust, and fuel system.
Downpipes
Removing the factory catalytic converter via an aftermarket downpipe is critical for reducing exhaust backpressure and allowing the upgraded turbocharger to spool efficiently. YPG Motorsport offers downpipes for all three M133 chassis:
Forged Internals
At 500+ WHP, the M133’s factory internals are operating near their limits. Forged pistons and connecting rods provide the necessary safety margin for sustained high-boost operation and protect against the increased cylinder pressures that come with a larger turbocharger.
M133 Forged Internals — a complete forged piston and rod kit purpose-built for the M133 2.0T.
Fuel System
The factory fuel system on the M133 is adequate for stock and mildly tuned applications, but a Stage 4 turbo build pushing 500+ WHP requires upgraded fuel delivery — larger injectors and an upgraded fuel pump ensure the engine receives enough fuel at peak boost to maintain safe air-fuel ratios.
Intercooler
The M133’s factory intercooler is a known weak point on high-power builds. Intake air temperatures climb quickly under sustained boost, leading to heat soak and power loss. An upgraded front-mount intercooler is strongly recommended for any M133 turbo build to maintain consistent charge air temperatures.
ECU Tuning
A dedicated ECU tune is essential — the factory ECU calibration cannot manage the airflow, boost pressure, and fuelling requirements of a Stage 4 turbocharger. The tune must be specifically calibrated for the turbo kit, the supporting modifications installed, and the fuel being used.
Fuel Considerations — 98 RON in the GCC
The M133 Stage 4 turbo build targets 500+ WHP on 98 RON pump fuel, which is the highest-octane grade widely available across the GCC. This is achievable with appropriate tuning and supporting modifications. Owners pursuing maximum output beyond 550 WHP may benefit from methanol injection, which provides additional knock resistance and allows more aggressive boost and timing targets.
A45 vs CLA45 vs GLA45 — Any Differences?
The M133 engine is mechanically identical across all three chassis. The turbo upgrade kit, forged internals, and ECU tune are the same regardless of whether the car is an A45, CLA45, or GLA45. The primary differences are chassis-specific — the downpipe routing varies slightly between models (hence the separate downpipe listings), and the GLA45’s higher ride height and slightly different intercooler positioning may benefit from a vehicle-specific intercooler setup.
Watch: M133 Turbo Builds
Subscribe to YPG Motorsport on YouTube for build walkthroughs and dyno results.
Related Guides
- A45 M133 Tuning Guide
- M177 Turbo Upgrade Guide — C63, E63, GLC63, GT63
- M178 Turbo Upgrade Guide — AMG GT, GTS, GTR
Frequently Asked Questions
What power can the M133 Stage 4 turbo achieve on pump fuel?
On 98 RON pump fuel with supporting modifications and a calibrated tune, the M133 Stage 4 turbo targets 500+ WHP. With methanol injection, outputs beyond 550 WHP are achievable.
Do I need forged internals for the M133 Stage 4 turbo?
Forged internals are strongly recommended at 500+ WHP on the M133. The factory internals can survive at this power level on a conservative tune, but the safety margin is thin. For any sustained high-boost use — track days, roll racing, or aggressive street driving — forged pistons and rods provide essential protection.
Is the Stage 4 turbo kit the same for the A45, CLA45, and GLA45?
Yes. The M133 Stage 4 Turbo Upgrade is compatible with all three chassis — A45 (W176), CLA45 (C117), and GLA45 (X156). The downpipes are chassis-specific due to exhaust routing differences, but the turbo kit itself is universal across M133 applications.
What other modifications should I do before upgrading the turbo?
At a minimum: an aftermarket downpipe, upgraded intercooler, and a custom ECU tune. Forged internals and fuel system upgrades are strongly recommended for builds targeting 500+ WHP. Completing these supporting modifications before or alongside the turbo upgrade ensures the engine can safely deliver and sustain the increased power.
How does spool compare to the factory turbo?
The Stage 4 turbo is a larger unit than the factory BorgWarner, so there is some increase in turbo lag — boost comes on slightly later in the rev range. However, the kit is designed to maintain usable spool characteristics for a 2.0-litre engine. The trade-off is a significant increase in top-end power and a much higher power ceiling.