AMG has played its hand with the 2-litre 309kW A45 S with a sub-4sec 0-100 time

So the war goes on. The hyper hatchback battleground has been reaffirmed upon the reveal of the new Mercedes-AMG A45 S, the new flagship hot hatchback that not only has more power than the current RS3 at 309kW, but also the highest specific kW-per-litre at 155/litre of any production engine on sale, short of a few incumbent seven-figure hypercars.

AMG has done this by engineering a bespoke four-cylinder engine built on a new assembly line at the AMG engine works in Affalterbach. Dubbed M139, the new engine features a host of technology including a new twin-scroll turbocharger, heavy-duty internals, extensive cooling, and cylinder linings derived from technology developed in F1.

The figures, as mentioned above, sit at 309kW at 6750rpm, with 500Nm available at an also high 6000rpm. This considerable grunt will help the new A45 S rocket to 100kmh in just 3.9sec, aided by a new eight-speed dual-clutch transmission and all-wheel drive system. Also new for the A45 S is a Ford Focus RS-style torque vectoring rear differential, which is able to send power to either of the two rear wheels mechanically to adjust the cornering attitude depending on the selected driver mode. There’s even a drift mode, provided you have enough space.

To contain all this grunt, AMG has also worked hard on upgrading the A45’s underlying chassis, with extensive underbody strengthening running the whole way down the chassis, while new strut braces and an under-engine shear panel aid overall rigidity. Bespoke to the A45 is a wider front track borrowed from the slightly wider CLA, which combined with wider tyres and a new domed bonnet give the A45 S some extra visual attitude compared to lesser versions.

As standard, the A45 packs six-piston front brake calipers, gripping 360mm discs, behind 19-inch wheels. Adaptive dampers are also fitted, controlled both independently or via AMG’s numerous driver modes. Unfortunately, all of this hardware has a cost, namely the A45’s relatively porky 1635kg weight figure.

The general styling treatment is typical AMG, with the usual ‘Panamerica’ grille, wing, dive planes and skirts all featuring. Inside is also rather familiar, although AMG’s complex but lovely steering wheel, bucket seats and trim elements give it a useful hike in perceived quality.

A 284kW non-’S’ A45 will be available.