Sports-Star of AMG - an extensive weight saving programme, plus refined double-wishbone suspension and a new V8 twin-turbo give the #Mercedes-AMG-GT
everything it needs to succeed in the highly competitive premium sports car segment.
AMG did a great job with its SLS, the company's first ever, in house built supercar. But having to reinterpret the styling cues of the iconic Gullwing was a double-edged sword. The adoption of the upright front screen and relatively flat front of the #Gullwing
was reflected in the SLS's drag coefficient of 0.36, and the gullwing doors required a reinforced roof that put extra weight in an undesirable area for a thorough bred sports car, where a low centre of gravity is de rigueur.
AMG GT comes with no such compromises. With a sharper nose profile, contemporary windscreen rake and other design features aimed at efficiency as well as beauty, the GT’s design pays homage to the forward looking AMG ethos. With an aluminium space frame, steel hatchback and magnesium front slam panel, the body shell weighs 231kg, making it the lightest in this segment and 10kg lighter than the SLS’s.
Extensive wind tunnel work has resulted in a Cd of 0.29, equal to Porsche's 991-series #911
Carrera, and superior to the 0.31 of the wider Carrera S at which the GT is squarely aimed in terms of pricing and customers.
Practicality is also a #Mercedes-AMG
GT strong suit, the hatchback opening easing access to an impressive 330 litres of luggage space.
Apart from the brittle ride on the early cars before the adoption of adaptive dampers, the SLS AMG’s chassis felt right from day one, and the mighty #Black-Series
version is one of the best sports cars I have ever driven, irrespective of the price. The SLS’s double-wishbone front suspension design was pretty much spot on, and has been carried over to the Mercedes-AMG GT with some geometric refinements. However, the new sports car’s rear axle is a clean sheet design aimed at even more Linear, and thus consistent dynamic behaviour. All the suspension arms are made from forged aluminium.
The heart of the new double-wishbone rear suspension is a unique upper wishbone design that brings the input (wheel movement) to output ratio (dampers) closer to the ideal 1:1. In a pure race car, this is normally achieved by using long travel horizontal pushrod style springs and dampers inclined towards the centre line of the car. This 1:1 ratio is harder to achieve on a road car with vertically acting suspension, but the clever AMG engineers have come up with a wishbone design that allows a 10:9 ratio of wheel to damper movement, which, for the GT’s purpose as a road car, is as close to 1:1 as makes no difference.
In combination with the more rigid design of the new suspension uprights that increases resistance to horizontal forces, the new rear axle has improved geometrical consistency under lateral loading. This in turn helps characteristic velocity, the linearity with which the chassis responds once the limits of mechanical grip are broached.
The GT uses 360mm cross-drilled, vented discs all round, while the more powerful GT S has 390mm discs up front, distinguished by red brake calipers. Ceramic composite brakes with 402mm front and 360mm rear discs are an option on both models.
GETTING THE BASICS RIGHT
Some manufacturers of rear-wheel drive cars tout their 50/50, front/rear weight distribution as being ideal, but this is not always true. With its rear mounted transaxle gearbox, joined to the motor by a rigid torque tube, the Mercedes-AMG GT follows the basic chassis design formula of the #SLS
, with the same 47/53 per cent, front/rear weight distribution for better traction in all conditions. With this as a basis, the extra help from the #Getrag
mechanical limited-slip differential in the case of the base GT model, and the electronic limited-slip differential on the more powerful GT S model, is the icing on the cake.
A key piece of technology that helps the handling of the GT S is the optional dynamic engine and gearbox mounts. Soft mounts improve comfort and lower NVH, while stiff mounts prevent the heavy drivetrain moving about during fast cornering and thus help to stabilise the car. By continuously reacting to road conditions, the active mounts provide the best of both worlds. With bundles of torque from its twin-turbo V8 and near perfect chassis balance, the new AMG sports car is a natural drift machine, the three-stage ESP system helping its cause here.
French tyre manufacturer Michelin provides the bespoke rubber for these cars, and the GT comes with 9J x 19 front and 11j x 19 rear alloy wheels shod with 255/35ZR19 and 295/35ZR19 rubber respectively, while the GT S uses 9J x 19 front and 11j x 20 rear wheels with 265/35ZR19 and 295/30ZR20 tyres. Forged alloys are an option on both models, as are #Michelin
Pilot Sport Cup 2s on the GT S in combination with the #AMG
Dynamic Plus package.
Climb into the GT’s cabin, close the door, and the solid thunk is reassuring. You immediately feel cosy, ensconced in a high quality environment that successfully blends sporting luxury with cutting edge technology. From the stitched leather on the dashboard top roll, to the carbon fibre surrounds of the central battery of air vents and centre console, and the tangible quality of the aluminium switchgear on the centre console, everything looks and feels expensive.
In a traditional sports car, the manual gearshift lever was the most prominent item on the centre console. The fact that the E-Select lever for the Getrag made AMG Speedshift DCT seven-speed dual-clutch gearbox has been relegated to the rear of the GT’s centre console, with the Comand Online controller now taking centre stage, shows how much things have changed in the intervening years.
The partner for the Comand controller is the free-standing 7.0-inch (8.4-inch with Comand Online) widescreen display that is now part and parcel of all current #Mercedes
models below the S-Class #W222
saloon and coupe ranges. ‘Connectivity’ is the new watchword, and even a raw sports car like the GT is not exempt from this internet based world. Music fans will be glad to know that the GT features a bespoke Burmester surround sound system with 10 speakers and 640W of amplification. The optional Burmester high end system has 11 speakers and 1,000W.
The all new, 3,982cc, 90-degree AMG V8 biturbo (M178) debuts with its own set of firsts. While ‘hot inside V’ engines, which have turbochargers placed within the vee of the motor, are used by both BMW and Audi, this is the first time that such a V8 engine has been used in conjunction with a dry sump configuration. In a dry sump motor, the main oil reserve is kept in a separate tank, which allows the whole engine package to be reduced in height, both as a unit, and in terms of where it sits in the car. The resulting lower centre of gravity directly benefits the car’s handling and allows it to pull more sustained lateral g-forces on a race track.
An undersquare motor with a bore x stroke of 83.0x92.0mm, the M178 runs a 10.5:1 compression ratio and 1.2bar of boost for 456bhp at 6,000rpm, and 442lb ft of torque between 1,600 and 5,000rpm. The more powerful GT S version has 503bhp at 6,250rpm, with 479lb ft of torque from 1,750 to 4,750rpm. With the GT S’s AMG Dynamic Plus package, peak power is maintained from 6,000 to 6,500rpm, and maximum twisting force from 1,750 to 5,000rpm.
The GT S model’s headline performance numbers of 0-62mph in 3.8 seconds and 193mph electronically limited top speed are supported by a very reasonable 30.1mpg on the combined cycle, with 219g/km CO2 emissions. These compare with the GT’s four-second run to 62mph, 189mph top speed, 30.4mpg and 216g/km CO2 emissions.
Tipping the scales at 1,540kg in GT and 1,570kg in GT S specifications, the new car is significantly lighter than the 1,620kg SLS #AMG-Coupe
, which boasts 563bhp. The 503bhp GT S has a lesser power-to-weight ratio, but as it is torque rather than power that gives you acceleration, the younger AMG coupe, with its more slippery shape, will still come out on top for two reasons.
THE CAR IS SHARP LIKE A RAZOR BLADE
The boot takes 330 litres, so who says that a sports car cannot be practical?
Firstly, drag increases with the square of speed, so the SLS’s power advantage will be negated with velocity. Secondly, while the GT S may have the same peak torque as the SLS, the latter’s naturally aspirated motor does not reach its peak m torque until 4,750rpm. Carrying 50kg less, but with the same 479lb ft torque available much earlier in the rev range, gives the GT S a decisive edge over its older brother in intermediate gear acceleration. Only in top speed, where the SLS reaches 198mph, is the GT S found wanting. But in the real world, where a car’s vmax is largely academic, the GT S driver will be in command of the faster and more accomplished, point-to-point machine.
AMG chief, Tobias Moers, who was the firm’s head of development until his promotion last October, was very candid about AMG’s objectives for the GT programme. “We were determined to develop a real sports car, and it took us a full two years to achieve this,” he said. “It was very important for us to get the basics right. By that I mean the mechanical parts, because if these are right and the car has a fine inherent balance, you do not need many electronics to act as a safety net,” he continued. “If the mechanical bits are not right to start with, then it is hard to hide the fact with electronics.
“The car is sharp but user friendly, like a razor blade that does not cut you,” says Mario Spitzner, AMG’s Director of Marketing. That sums up what AMG set out to do with its new GT and GT S, and I can’t wait to get behind the wheel at Laguna Seca in November - read our first driving impressions very soon.
While AMG suggests that the entry level GT will start at #Porsche
Carrera S money (around £85,000), which is just over half the price of the SLS, the J reality is that the more expensive GT S will be quicker than the SLS against the stopwatch, as well as more capable in the corners.
That makes it stunning value for money and potentially the best round sports car in its class. Expect to see the UK from spring 2015.