Arriving in what is AMG's 50th year, the 600bhp-plus four-door saloon concept will provide clear hints to a production version that's due on roads in 2019.
Designed with a coupé-like roofline and four door body, the GT concept sports a large rear diffuser that hints at hardcore performance capabilities for the future production car. It will use a twin-turbocharged 4.0-litre V8 engine, and will replace the CLS Shooting Brake in Mercedes' line-up.
As AMG's third dedicated series production model line, the GT four-door will follow on from the SLS and the existing GT, and arrive after AMG’s recently announced limited-volume, F1-inspired hypercar.
Targeted at the the Porsche Panamera, BMW 6 Series Gran Coupé and Audi A7/RS7, the new saloon, codenamed X290, is the brainchild of AMG boss Tobias Moers.
Original plans for a model in the mould of the GT four-door were first aired in a series of patent applications filed by AMG in 2012. At the time, plans centred around a long-wheelbase version of the SLS featuring two gullwing doors and a pair of small, rear-hinged rear doors.
More recent plans for the performance saloon subsequently became more closely linked to the GT. But while the latest addition to AMG’s line-up will share key styling cues and elements of its mechanical package with the company’s headlining sports car, sources say it will be based on a different platform from the bespoke aluminium structure used by the GT.
The basis for the GT four-door is parent company Mercedes-Benz’s modular rear architecture (MRA), as used on the C 63, E 63 and S 63. It has been specially modified for the four-door GT, with what AMG insiders describe as 'unique' wheelbase and track width measurements.
Other dedicated features include the greater use of lightweight materials within the floorpan and body structure, most notably aluminium and hot-formed high-strength steel, the adoption of which is aimed at lowering the weight of the new model to below that of Mercedes-AMG’s existing MRA-based models in the search of greater performance potential and enhanced handling characteristics.
Power for the 2019 model will come from the latest evolution of AMG’s twin-turbocharged 4.0-litre V8, already confirmed for the new E 63. Among its developments is the adoption of new twin-scroll turbochargers mounted between the cylinder banks. These new units are claimed to provide improved induction qualities over the more conventional ones used in the existing version of the M177-designated engine.
The new engine is tipped to be offered in two states of tune from the start of sales, with both standard 4Matic+ and S 4Matic+ models. In initial range-topping S 4Matic+ guise, the GT4's engine output is expected to top the 603bhp of the new E 63 S 4Matic+.
It is also understood that AMG is considering coupling the engine with a newly developed integrated starter generator (ISG). The move would not only provide it with the ability to deliver short periods of added performance via a 20bhp electric motor mounted within the gearbox, but also to offer instant start-up, with what one engineer with knowledge of the new system described as 'seamless' stop-starting.
The ISG operates via a 48V electrical system, suggesting the GT4 could adopt a moderate-sized lithium ion battery as part of its arsenal of high-tech developments.