The Mercedes-AMG A45 has long been the benchmark for compact performance, packing a ferocious four-cylinder engine that rewrites expectations for what a hot hatch can deliver. Yet, for a select group of enthusiasts, even 416 horsepower from the factory floor leaves room for ambition. Enter Pure Turbos, a name synonymous with forced induction excellence, offering a comprehensive turbo upgrade that catapults the A45 to 480 horsepower. This is not merely a parts swap; it is a systematic re-engineering of the car's breathing apparatus, unlocking latent potential while preserving the daily-driver civility that makes the A45 so compelling.

In this deep dive, we examine the engineering behind the Pure Turbos upgrade, the measurable performance gains, the installation realities, and what 480 horsepower means behind the wheel. Whether you are a seasoned tuner or a curious owner weighing your next mod, this article provides the authoritative technical context you need.

The Mercedes-AMG A45: A Foundation of Performance

Before understanding the upgrade, it is essential to appreciate what the stock A45 brings to the table. The current-generation A45, particularly the S variant, arrives with a hand-built M139 engine that, in its most potent factory form, produces 416 horsepower and 369 lb-ft of torque. This engine is a masterpiece of downsizing: a 2.0-liter turbocharged inline-four that uses a twin-scroll turbocharger with an electrically actuated wastegate, direct injection with multiple injection strategies, and a charge-air cooler integrated into the intake manifold.

Engineering Excellence from Affalterbach

Mercedes-AMG's approach to the A45 was never half-hearted. The M139 engine is mounted transversely, but unlike most front-wheel-drive-based platforms, it features an advanced all-wheel-drive system with a rear-axle torque vectoring unit. This setup gives the A45 remarkable agility, but it also places unique thermal and packaging constraints on the turbocharging system. The factory turbocharger is already a high-flow unit with a billet compressor wheel, but it is tuned to meet global emissions standards and warranty longevity targets. Those constraints are precisely where Pure Turbos identifies opportunity.

The M139 Engine: A Four-Cylinder Marvel

The M139 engine block is an aluminum die-casting with closed-deck construction, designed to withstand immense cylinder pressures. The cylinder walls are coated with a patented NANOSLIDE friction-reducing layer, and the forged steel crankshaft, forged pistons, and forged connecting rods are all chosen to handle sustained high-speed operation. The cylinder head features four valves per cylinder with variable valve timing and lift on both intake and exhaust sides. This robust foundation means that the engine is not the weak link; the turbocharger itself becomes the primary airflow bottleneck once you ask for more than factory output. Pure Turbos engineers its upgrade specifically around this engine's capacity, ensuring that the increased airflow is matched by the hardware's ability to handle it.

The Pure Turbos A45 Turbo Upgrade: Engineering Breakdown

Pure Turbos does not offer a generic "big turbo" kit that forces the owner to accept lag, poor drivability, or compromised reliability. Instead, the upgrade is a precision-engineered package that reworks the entire forced induction system with a focus on flow efficiency, thermal management, and control precision.

Turbocharger Core Design and Materials

At the heart of the upgrade is a billet compressor wheel machined from a single piece of 2618 aluminum alloy. This material is chosen for its high strength-to-weight ratio and its ability to maintain dimensional stability at elevated temperatures and rotational speeds. The wheel geometry is proprietary, featuring an extended tip design that increases the inducer diameter without sacrificing surge margin. This allows the turbo to move a significantly higher mass of air per revolution compared to the factory wheel.

On the hot side, the turbine wheel is manufactured from Inconel 713C, a nickel-based superalloy that retains its mechanical properties at exhaust gas temperatures exceeding 1,800°F. The turbine housing is ported and smoothed to reduce backpressure, which helps the engine expel exhaust gases more freely. The combination of a larger compressor and a higher-flow turbine section means that the turbo can support higher boost pressures at lower engine speeds, reducing the traditional trade-off between peak power and transient response.

Wastegate and Boost Control Optimization

The factory electronic wastegate actuator is retained and recalibrated, but Pure Turbos fits a larger wastegate port and a revised flapper valve. This modification provides finer control over boost pressure, particularly during transitions between partial and full throttle. The result is boost that builds progressively and predictably, without the spiky behavior that can unsettle the chassis or stress the drivetrain. Boost pressure is typically increased from the factory maximum of around 30 psi to approximately 36-38 psi, depending on the fuel quality and tuning strategy.

Intercooler and Thermal Management

Air density is the enemy of combustion efficiency. The Pure Turbos upgrade includes a high-capacity intercooler core that is approximately 30% larger in frontal area than the stock unit. The end tanks are cast aluminum with smooth internal transitions to reduce pressure drop across the core. Coupled with upgraded charge-air piping that eliminates the restrictive factory coupling joints, this system reduces intake air temperatures by as much as 40°F under sustained boost. Lower intake temperatures directly translate to a higher knock threshold, allowing the engine to run more aggressive ignition timing and produce more power safely.

Custom Engine Calibration

No turbo upgrade can deliver its potential without a corresponding recalibration of the engine management system. Pure Turbos works with leading calibration houses to provide a custom ECU tune that is delivered via a handheld flashing tool. The calibration adjusts fuel injection timing, ignition advance curves, camshaft phasing, boost control PID parameters, and throttle mapping to suit the new airflow characteristics. Importantly, the tune retains all factory safety systems, including knock detection, exhaust gas temperature monitoring, and torque limit strategies. The result is a calibration that is both aggressive for performance and conservative for long-term durability.

Performance Gains and Driving Dynamics

The numbers speak for themselves. With the Pure Turbos upgrade installed and running on 93-octane pump fuel, the A45 delivers 480 horsepower at the crankshaft and approximately 440 lb-ft of torque. On race fuel or ethanol blends, output can climb higher, but 480 hp is the reliable, repeatable figure that Pure Turbos guarantees.

Horsepower and Torque Curves

Peak horsepower arrives at around 6,500 rpm, but the torque curve is the real story. The upgraded turbo achieves peak torque as low as 3,800 rpm and holds a plateau above 400 lb-ft all the way to 5,500 rpm. This broad, flat torque curve transforms the driving experience. Where the stock car requires a downshift for highway overtaking, the upgraded car simply pulls from any engine speed with linear, forceful acceleration. The area under the torque curve is substantially larger than stock, which means that even in daily-driving scenarios where you never touch redline, the car feels significantly faster.

0-60 mph and Quarter-Mile Acceleration

Independent testing has verified a 0-60 mph time of 3.6 seconds with the Pure Turbos upgrade on a prepped surface, compared to the factory claim of 3.9 seconds for the A45 S. The quarter-mile drops from the mid-12-second range to approximately 11.8 seconds at 118 mph. This places the upgraded A45 in territory once reserved for far more exotic machinery. The all-wheel-drive system's ability to put down the extra torque without excessive wheel spin is a critical enabler; the upgraded car hooks hard off the line and continues to pull strongly through the traps.

Top Speed and High-Speed Stability

The factory A45 is electronically limited to 155 mph. With the Pure Turbos upgrade, the limiter can be raised to 180 mph, and the car has the power to reach that speed under favorable conditions. At these velocities, the aerodynamic stability remains composed, thanks to the factory's attention to underbody airflow and the optional aero package. The upgraded turbo does not introduce any unexpected turbulence or heat soak issues at sustained high-speed running, a testament to the thermal management improvements built into the package.

Installation Process and Technical Considerations

Installing a turbo upgrade on a modern M139 engine is not a driveway job. The transverse layout, tight packaging, and the integration of multiple cooling circuits demand mechanical competence and specialized tools. Pure Turbos provides a detailed installation manual, but most owners elect to have the work performed by a qualified AMG specialist.

Pre-Installation Preparation

Before beginning, the vehicle should be inspected for any existing issues: oil leaks, coolant system health, and the condition of the accessory belts. The engine oil and filter should be replaced with a high-quality full synthetic of the correct viscosity. It is also advisable to replace the spark plugs with a colder heat range that suits the increased thermal load. The battery should be fully charged, and the ECU should be updated to the latest factory software revision to ensure compatibility with the calibration file.

Step-by-Step Installation Overview

The installation involves removing the entire intake and exhaust system upstream of the catalytic converter. The factory turbocharger is unbolted from the exhaust manifold and the charge-air cooler assembly. The new turbo is mounted using the same bolt pattern, but with upgraded studs and fasteners where specified. The intercooler, charge pipes, and intake ducting are replaced with the supplied components. The wastegate actuator rod is adjusted to the prescribed length.

The entire system is then pressure-tested to verify there are no boost leaks before the calibration is flashed.

Pure Turbos recommends that the vehicle be run through a break-in procedure: 500 miles of varied driving without sustained full-throttle operation, followed by an oil change. This allows the turbo bearings and piston rings to seat properly under the new thermal and mechanical conditions.

Tuning and Calibration

The calibration file is loaded via the OBD-II port using a handheld device that retains the factory diagnostics capability. The process takes approximately 15 minutes. After flashing, the car performs a series of adaptive learning routines for throttle position, wastegate position, and fuel trims. The first few drives may feel slightly different as the ECU dials in its learned values. A datalogging session is recommended after break-in to verify that boost targets, air-fuel ratios, and ignition timing are within spec.

Reliability and Durability

A 480-horsepower four-cylinder engine naturally raises questions about longevity. The M139's forged internal components are up to the task, but the upgrade does place greater demands on the cooling and lubrication systems. Pure Turbos has engineered around these demands.

Component Quality and Stress Testing

Every turbocharger is individually balanced and tested on a flow bench before shipment. The bearing housing uses a single water-cooled center cartridge with a thrust bearing rated for the increased axial loads generated by higher boost. Pure Turbos subjects its prototypes to extended dyno sessions at full load, followed by thermal shock testing where the turbo is heated to operating temperature and then doused with cold water. This level of validation is uncommon in the aftermarket and explains why the product carries a robust warranty.

Maintenance Considerations

Owners should expect more frequent oil changes on a heavily modified car: every 5,000 miles is prudent. Using a high-zinc oil that meets Mercedes-Benz specification 229.52 is recommended for flat-tappet camshaft protection. The air filter should be inspected every 10,000 miles, as the increased airflow will pull more particulate through the intake. The intercooler core should be checked for debris and washed gently with a low-pressure hose if needed. With proper maintenance, the Pure Turbos upgrade has proven reliable for tens of thousands of miles in real-world service.

Real-World Feedback and Community Reception

The enthusiast community has embraced the Pure Turbos A45 upgrade with enthusiasm. Owners report that the car retains its factory drivability in traffic and comfort mode, only revealing its true nature when the throttle is opened fully. The sound character changes subtly; the exhaust note gains a deeper, more industrial tone as the larger turbo moves more air, but it does not become obtrusive or droning.

Track and Street Driving Impressions

On track, the upgraded A45 is a revelation. The power delivery is smooth enough that it does not overwhelm the chassis or the tires, provided the driver uses a quality set of summer performance tires like the Michelin Pilot Sport 4S or Cup 2 R. The car rotates on throttle with confidence, and the all-wheel-drive system's torque vectoring can be felt pulling the nose into corners. Enthusiasts note that the upgrade makes the A45 competitive with cars like the Porsche 718 Cayman GTS and the BMW M2 Competition in straight-line acceleration, while maintaining the A45's practical hatchback utility.

Common Praise and Points of Note

The most common praise centers on the lack of compromise. Many big turbo kits introduce noticeable lag, making the car feel lazy in everyday traffic. The Pure Turbos upgrade, by contrast, maintains sharp throttle response while delivering a substantial power increase. Some owners note that the clutch in the eight-speed dual-clutch transmission is now the limiting factor; repeated hard launches can trigger thermal protection, and a transmission tune is a recommended complementary upgrade. A few owners have also observed that the rear differential can overheat during extended track sessions, and an auxiliary cooler is a wise investment for serious track use.

Conclusion: Is the Pure Turbos Upgrade Right for You?

The Pure Turbos A45 turbo upgrade is not a budget modification. It requires a significant financial investment, specialized installation, and a commitment to more attentive maintenance. For the owner who values a complete, engineered solution that delivers measurable performance gains without sacrificing daily usability, it is one of the most compelling upgrades available for the platform.

480 horsepower in a car that weighs less than 3,500 pounds creates a power-to-weight ratio that rivals dedicated sports cars. The upgrade transforms the A45 from a hot hatch that punches above its weight into a genuine high-performance machine that can hold its own on any road or track in the world. If you are ready to unleash the M139 engine's full potential, Pure Turbos provides a proven, well-researched path to get there.

For further reading, visit the Pure Turbos official product page for detailed specifications and ordering information. To understand the engineering behind the M139 engine, consult the Mercedes-Benz media site for technical white papers. For community discussions and owner experiences, the BenzWorld forums offer a wealth of real-world data.