Mercedes-AMG A45 S unleashed as 415bhp mega-hatch

Mercedes-AMG is claiming class-leading power, performance and features for its second-generation A45 S 4Matic+ – a car it says will challenge the established mega-hatch order with up to 415bhp, a supercar-baiting 0-62mph time of 3.9sec and a new switchable Drift mode function.

Revealed at the Goodwood Festival of Speed ahead of a UK on-sale date later this year, the A45 heads a quartet of rapid new compact Mercedes-AMG models equipped with the M139-designated four-cylinder petrol engine. These include the four-door CLA45 S 4Matic+ saloon, which is confirmed to reach showrooms at the same time as its five-door sibling.

All the news and reveals from the 2019 Goodwood Festival of Speed

The turbocharged 2.0-litre unit uses many of the technical solutions already developed for Mercedes-AMG’s twin-turbocharged 4.0-litre V8 petrol engine and it will be offered in two distinct power outputs. In the new standard A45 4Matic+ and CLA45 4Matic+, the M139 develops 387bhp at 6500rpm and 354lb ft of torque between 4750rpm and 5000rpm. That’s 85bhp and 59lb ft more than the A35 and CLA35.

In its highest state of tune, with 2.1 bar of turbocharger boost pressure and water injection for its twin-scroll turbocharger, the M139 provides the A45 S 4Matic+ and CLA45 S 4Matic+ with a class-leading 415bhp at 6750rpm and 369lb ft between 5000rpm and 5250rpm.

This marks the new AMG motor out as the world’s most powerful four-cylinder series-production engine. It also represents an increase of 39bhp and 18lb ft on the outgoing M133 engine of the previous A45.

Despite giving away 28bhp and 15lb ft to the A45 S 4Matic+, the standard A45 4Matic is claimed to be just 0.1sec slower to 62mph, at 4.0sec, and its top speed is limited to 155mph.

Both new A45 4Matic+ models have the same combined cycle fuel consumption and CO2 emissions, at 34.0mpg and 189g/km. The new AMG engine comes mated to a standard eight-speed dual-clutch gearbox and a newly developed multi-plate clutch 4Matic+ four-wheel drive system. This features an AMG torque control function that separates electronically controlled clutches within the rear axle to vary the amount of drive sent to each individual rear wheel.

As a result, they can be configured to send the majority of drive to the rear wheels via a new Drift mode function, which is included in an optional AMG Dynamic Plus package, when the car’s stability control is deactivated and the gearbox is set to manual mode. Overall, the new driveline offers up to six driving modes: Comfort, Sport, Sport+, Slippery, Individual and Race – the last of which is standard in range-topping S models and optional as part of the AMG Dynamic Plus package in standard models.

Further changes made to the standard A45 include a new performance brake package. This features 350mm front and 330mm rear discs in combination with four-pot and one-pot calipers respectively in the standard A45 4Matic+. The A45 S 4Matic+ gets larger, 360mm front and 330mm rear discs, with red painted six-pot front and one-pot rear calipers.

AMG has also introduced a re-engineered steering rack with a variable ratio and two different software maps depending on the driving mode. The steering rack itself is mounted on a new carrier, which is claimed to increase precision.

The suspension retains the same MacPherson strut front and four-link rear design as less powerful versions of the fourth-generation A-Class and second-generation CLA. However, the components, including a wider front track and bespoke front axle carrier, are described as being all new with unique geometry and reduced unsprung masses.

AMG Ride Control with adaptive damping is available as an option. The base A45 features 18in wheels, with the S version receiving 19s.

The suspension is supported by a stiffened bodyshell that features a new aluminium plate bolted underneath the engine, a strut brace between the front suspension towers and reinforcements within the lower part of the A-pillars – all of which, AMG claims, leads to “considerably reduced body torsion along the longitudinal and transverse axis”.

Stylistically, the new car builds on the A35 4Matic with an AMG Panamericana grille, wider front wings, flared wheel arches, a uniquely styled front bumper with integrated splitter element and wider sills.

At the rear, there is a prominent tailgate-mounted spoiler and a unique bumper that houses two round tailpipes (82mm in diameter on the A45 4Matic+ and 90mm on the A45 S 4Matic+) as well as a twin-channel diffuser element.