Developed in partnership with the German car maker’s High Performance Engine offshoot based in Brixworth, England, the new engine is the most powerful four-cylinder ever placed in a Mercedes production model.
"Our goal right from the start was to match the output of the larger turbocharged 2.5-litre five-cylinder engine used by the RS3," says Tobias Moers, head of development at AMG.
By way of comparison, the RS3’s EA255 engine delivers 335bhp and 332lb ft torque, while the M135i, which is powered by an uprated version of BMW’s N55 turbocharged 3.0-litre six-cylinder unit, pushes out 316bhp and the same 332lb ft.
As first revealed by Autocar, the A45 AMG channels its drive through a seven-speed dual clutch gearbox and, in a layout that mirrors that of the RS3, a specially tuned Haldex-style multi-plate clutch to all four wheels.
To provide the new car with typical rear-wheel drive AMG handling traits, the engine’s torque is delivered primarily to the rear wheels under load.
No performance claims have been made prior to the A45 AMG’s official unveiling at AMG’s Affalterbach headquarters in Germany this week, but Mercedes-Benz insiders suggest it will match the claimed 0-62mph time of the M135i, which BMW puts at 5.1sec for the six-speed manual equipped version.
The inclusion of fuel saving features such as automatic stop/start and brake energy recuperation also has Mercedes-Benz claiming the A45 AMG will be the most economical car in the hot hatch ranks.
In a bid to provide the price leading AMG model with class leading dynamics – including what one AMG insider described to Autocar as "the highest corner speeds among its rivals", AMG’s engineering team has provided it with a largely unique chassis set-up – the likes of which has undergone extensive testing both on the road and at the Nürburgring.
The basic components of the MacPherson strut (front) and multi-link (rear) suspension are carried over from the A250 Sport but the elastokinematic properties, including the bushes used to attach it to the body structure, have been greatly altered. Other changes include wider tracks, firmer springs and dampers, larger diameter anti roll bars and reduced ride height.
The standard electro-mechanical steering system has also been reworked for added on-centre sensitivity and a meatier feel, while the brakes have been upgrade with larger crossdrilled and vented discs as well as more powerful calipers.
As with other recent AMG models, the A45 AMG also receives a three stage electronic stability program (ESP) that includes a "sport handling" mode which allows you to turn the electronic safety net off completely.
The A45 AMG is differentiated from standard third-generation A-class models by an extensive body kit. Included is a deeper front bumper, altered grille, widened front fenders, carbonfibre look exterior mirror housings, wider sills underneath the doors, a prominent spoiler atop the rear hatch and new rear bumper with an integrated diffuser element as well as characteristic chromed tail pipes.
Inside, the new car receives an upgraded interior with unique front sport seats along with more upmarket trims.