The Mercedes-AMG A45 S punches well above its weight class. Packing a handcrafted 2.0-litre turbocharged engine built in Affalterbach, this compact hatchback delivers supercar-slaying performance without sacrificing everyday practicality. It hits 0-62 mph in just 3.9 seconds and charges all the way to an electronically limited top speed of 168 mph (270 km/h), or 174 mph when specified with the optional Driver's Package.
Understanding how this machine achieves such staggering figures requires looking beyond basic marketing sheets. Beneath the sculpted hood lies the M139 engine, currently the most powerful mass-production four-cylinder turbocharged unit in the world. This piece breaks down the exact mechanics behind the speed, real-world handling characteristics, and common compromises you need to accept before buying one.
Core Performance Metrics and Powertrain Engineering
Numbers tell only part of the story, but the baseline specifications for the A45 S set a clear benchmark for the hot hatch segment.
- Horsepower: 416 bhp (421 PS) at 6,750 rpm
- Torque: 500 Nm (369 lb-ft) available between 5,000 and 5,250 rpm
- Transmission: 8-speed AMG Speedshift DCT dual-clutch automatic
- Drivetrain: Fully variable 4MATIC+ all-wheel drive with AMG Torque Control
The heart of the car is its twin-scroll turbocharger, which uses roller bearings to minimize friction and spool up faster. Unlike older turbo setups that suffer from noticeable lag, the M139 responds instantly when you stab the throttle. Peak torque arrives high in the rev range, encouraging you to wring out every gear rather than relying solely on low-end grunt.
Power gets routed through an eight-speed dual-clutch transmission that snaps off shifts faster than a manual driver ever could. Combined with the 4MATIC+ system, traction is absolute. The rear axle features two electronically controlled multi-plate clutches—one for each rear wheel—allowing the car to actively vector torque. This setup doesn't just keep the car glued in a straight line; it enables a dedicated Drift Mode that sends power aggressively to the outside rear wheel to help rotate the car through corners.
Real-World Acceleration and Speed Tests
Official manufacturer claims often lean toward conservative, but independent testing confirms that the A45 S meets its lofty promises.
In ideal dry conditions, launching the car using Race Start (launch control) yields a brutal shove into the seat. The all-wheel-drive system eliminates wheel slip, translating every ounce of that 416 horsepower directly into forward momentum. Reviewers testing the car on damp or cold tarmac regularly log 0-60 mph sprints right around 4.0 seconds, trailing the official 3.9-second 0-62 mph metric by mere fractions.
Mid-range pull is where the car truly feels unhinged. Overtaking slower traffic on a two-lane road takes seconds. You simply point the steering wheel, squeeze the pedal, and the transmission drops down multiple gears instantly, rocketing past slower vehicles with a sharp exhaust crackle on upshifts.
Handling, Chassis Dynamics, and Braking
A high top speed means nothing if a car cannot handle corners. AMG stiffened the body shell significantly compared to a standard Mercedes-Benz A-Class, adding a shear panel under the engine and strut tower braces to reduce chassis flex.
The front suspension utilizes a McPherson strut layout paired with wider front tracks, while the rear features a sophisticated four-link setup. Adaptive dampers come standard, letting you toggle between comfort-oriented cruising and track-ready stiffness via the steering wheel-mounted AMG buttons.
Stopping power matches the acceleration. Massive six-piston calipers clamp down on 360mm ventilated and perforated discs up front, while single-piston sliding calipers handle the 330mm rear discs. Brake pedal feel is firm, offering progressive bite that instills confidence when scrubbing off triple-digit speeds on a twisty backroad.
Common Compromises and Ownership Realities
Owning Affalterbach's smallest performance weapon comes with specific trade-offs that buyers frequently overlook in pursuit of raw numbers.
- Ride Quality: Even in Comfort mode, the suspension setup remains firm. Potholes and rough city asphalt send sharp impacts through the cabin.
- Fuel Consumption: While official metrics claim around 31 mpg, aggressive driving drops that figure quickly. Track days or heavy spirited driving sessions can see fuel economy plummet into single digits.
- Interior Space: Rear seat room is tight for adults on long journeys, and the aggressive front sports seats steal some visibility and knee room for back-seat passengers.
- Maintenance Costs: Consumables like performance brake pads, high-spec tires, and specialized dual-clutch transmission fluid changes carry steep price tags compared to standard economy hatchbacks.
Frequently Asked Questions
Is the Mercedes-AMG A45 S electronically restricted?
Yes. Out of the factory, the top speed is capped at 168 mph (270 km/h). Opting for the AMG Driver's Package raises this limit to 174 mph.
Can the A45 S do burnouts or drift?
While it is an all-wheel-drive car, engaging Drift Mode through the stability control settings decouples the front axle bias and routes power specifically to the rear wheels, allowing for controlled powerslides on a closed circuit.
How does the A45 S compare to the Audi RS3?
The Audi RS3 uses a larger 2.5-litre five-cylinder engine with a distinct exhaust note and slightly more low-end torque, whereas the A45 S relies on a higher-revving, punchy four-cylinder layout with sharper track-focused steering reflexes.
What fuel type does the engine require?
To achieve its rated 416 horsepower and protect the high-compression turbocharged components, the vehicle requires high-octane premium unleaded fuel (98 RON / 93 AKI recommended).
