Mercedes-AMG GT R ride

An angrier rendition of the Mercedes-AMG GT S is on the way. We hitch a ride in it around the Nürburgring
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September 28, 2016
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The good-looking cabin is not as spartan as rival Porsche 911 GT3 RS’s.
The good-looking cabin is not as spartan as rival Porsche 911 GT3 RS’s.(10/15)
AMG’s one man, one engine philosophy continues... Rebelo did a good job on this one.
AMG’s one man, one engine philosophy continues... Rebelo did a good job on this one.(11/15)
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Mercedes claims a very specific 7.5 per cent increase in torsional stiffness over the GT S.
Mercedes claims a very specific 7.5 per cent increase in torsional stiffness over the GT S.(13/15)
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There’s not been a great deal of talking since we got in the car and frankly, Thomas Jäger doesn’t need the distraction. We’re on the Nürburgring, nicknamed the ‘Green Hell’ by my countryman Jackie Stewart. It’s a name that’s stuck, for good reason, as the Nürburgring is arguably the most famous and testing stretch of tarmac in the world. Jäger knows it well; he’s as comfortable lapping his AMG racer at 100 per cent here in the dark small hours as the rest of us are when we’re tucked up in our beds sleeping. So he’s driving today, and on this occasion I’m happy to be sat alongside.

We’re in the 2017 Mercedes AMG GT R, a more hardcore take on AMG’s already intense GT S coupé. The GT R is a car that’s more suited to sportscar owners who don’t just want to give the impression of track driving, but actually do it. And do it properly. AMG is giving its customers what they want, and it has approached that in a matter that you’d expect: lighten here, advance technology there, improve the aerodynamics to increase downforce, add grip and traction, and boost output. The specification ticks every box on a race engineer’s checklist, if, of course, you ignore the sumptuous interior, lack of roll cage and the regular, rather than five-point, seat belts.

Weight is down, too, but it’s just 15kg less than the GT S. That quoted reduction does the GT R a huge disservice. AMG’s engineers might not have quite gone down the plastic rear window route their rivals at Porsche’s GT department did with the 911 GT3 RS, but everywhere else they’ve concentrated on shaving mass. To good effect. That’s despite the fact it’s physically bigger for starters. The larger 20in wheels are forged alloy, while the 46mm-wider front wings that cover them are made from carbon fibre. The rears are 57mm wider and aluminium. Those proportions have swelled to clothe a wider track and the bigger wheels, the front rims 10.0J x 19 ET56, the rears 12.0J x 20 ET52 in forged aluminium and shod in Michelin Pilot Sport Cup 2s.

Those details are obvious, the changes elsewhere less so, but just as significant. Behind that 1952 Carrera Panamericana 300SL-aping front grille with its 15 chrome-finished upright slats is a magnesium structure, shifting weight fore of the front axle to the benefit of turn-in. That front, which features on the new GT Roadster, and will, inevitably, be adopted by the standard GT and GT S in time, improves airflow to the engine, with repositioned oil and charge air coolers to improve their effectiveness, meaning the obvious knock-on benefits to the engine’s output. The engine, AMG’s 4.0-litre twin-turbo unit, has received a power bump, to 577bhp, while torque jumps to 700Nm. That’s thanks to revised ‘hot V’-mounted turbochargers with quicker acting and faster spinning compressors, greater boost pressure — up from 1.2 to 1.35 bar — and a completely revised map and combustion process adopted to improve not just output, but the speed of response. The loss of 0.7kg from the  flywheel aids that immediacy, while the whole engine and transmission is held on active engine mounts, the tuning of which have been modified to suit the greater g loadings created by the GT R.

Linking the 4.0-litre V8 to the seven-speed twin-clutch AMG Speedshift transmission at the back is a carbon fibre propshaft, which, at 13.9kg, is some 40 per cent lighter than the aluminium item in its GT S relation. The wider track is hung off forged aluminium suspension wishbones, hub carriers and steering knuckles at the front, the rear axle losing bushings in its joints for uni-ball spherical bearings, while the hollow rear anti-roll bar is thicker for greater control. The coil-over springs allow manual adjustability and the electronically controlled dampers offer the choice of Comfort, Sport and Sport+ modes, selected via the AMG Drive Unit or Dynamic Select Drive systems.

Dr Frank Emhardt, senior manager vehicle development AMG GT Model Range, highlights where weight has been put in, for good reason. There are three carbon fibre braces to add stiffness, two in the engine bay, another across the rear adding 7.5 per cent gain in torsional rigidity. There’s an active aerodynamic element that adds about 2kg of weight under the grille, but the 40mm movement it makes at above 80kph when Race mode is selected adds 40kg of downforce. Its operation creates a Venturi effect under the car, not just benefiting aerodynamic grip, but cooling, as some of the air it accelerates does so around the gearbox and titanium exhaust. That vents out via the new outlets between the rear lights. The rest of the air is managed by the twin diffuser underneath, while airflow around the front wheels is managed via slats in the inner wheelarches to lower pressure and improve brake cooling. Overall downforce at its 318kph v-max is 155kg, which has been achieved despite a reduction in the drag coefficient over the standard car.

Along with that extensive aero upgrade, Emhardt points to the adoption of active rear-wheel steering to the GT R as one of the most significant changes. It’s the first AMG to feature such a system. Two electro-mechanical actuators are linked by wire to the steering, allowing a toe angle change of 1.5 degrees in the opposite direction to the front wheels when running under 100kph to virtually shorten the wheelbase and add agility. Above that they turn in the same direction, improving high speed stability. Jäger says he would love the rear-wheel steer in his racing car, and the benefits it brings to turn-in response is apparent even from the passenger seat, allowing increased entry speed and greater mid-corner stability with a corresponding improvement in exit speed. The rear axle’s electronically controlled limited slip differential and AMG’s fitment of a nine-stage traction control system helps, too.

The track is ours and it’s uncharacteristically dry and warm so Jäger’s ready to add a few more laps to his huge tally around here. He selects the sixth setting on that traction control, saying anything else around the ’Ring brings a bit too much slip angle at the rear, to the detriment of time. He chooses Race mode, to access the most focused and immediate settings for the engine and paddle-shifted transmission, though selects Comfort for the suspension for his out lap. The Nürburgring is bumpy, though Sport is possible around here. Jäger reckons Sport+ is a bit too stiff and brings compromises around the Nürburgring Nordschleife’s famously difficult topography.

The tarmac is particularly testing in the first couple of kilometres, around Hohenrain and Hatzenbach. The GT R rides in Comfort mode with taut control rather than intrusive stiffness. Jäger is quick immediately, discounting the additional ballast in the passenger seat and getting on with the business of monstering the AMG around this automotive playground. There’s a lot to be said for watching someone enjoy their work, and Jäger fits that description perfectly. Before we’re buckled in he says he’d like Sport suspension at some areas of the track, particularly Flugplatz for a bit more control, but as he approaches it in Comfort he doesn’t seem too perturbed by the immense forces acting upon the car.

Having had a few days myself in an AMG GT S a week earlier as a refresher since attending the original Laguna Seca launch, the standard car is fresh in my memory. It reminded me of the GT S’s surprising traction, and the 4.0-litre twin-turbo’s prodigious thrust and rousing soundtrack. The GT R takes all of that to a different level again. The cabin is enveloped by a rich melodious V8 wail, the 4.0-litre unit, despite turbocharging, among the most gloriously sonorous powerplants currently available. With its titanium exhaust adding an exotic metallic layer to the rich sound, improved further by the binning of some weighty sound deadening throughout, the GT R sounds magnificent — even through a helmet.

Throw in the sheer physicality of the engine’s huge acceleration, with the carbon ceramic brake’s massive deceleration and the GT R’s ability to change direction almost regardless of the speed it’s carrying and I’m being flung around the deeply bolstered passenger seat like a rag doll. The effect is worsened by the lack of anything more than a standard seat belt. Jäger is clearly unconcerned about the additional 85kg he’s hauling today; in the moments where I’m not managing my own mass in the seat there’s a chance to look ahead and enjoy the experience.

Two things always leap out here. First, the proximity of the barriers; run-off just was not something that was considered when this track was carved out of the side of a hill. That, and the gradients. It’s so steep, the track climbing and descending like no other, creating a uniquely testing environment. The GT R shrugs off the climbs, the 4.0-litre V8 seemingly defying physics and flinging the GT R up the steepest gradients with relentless ferocity.

That would be true of the standard car in truth; though it’s the chassis revisions, that aero and specifically the adoption of the rear-wheel steering into the dynamic make-up that dominate the changes. They’re clearly effective, too, as Jäger is able to carry more speed everywhere, gaining huge traction even when he’s got those faster turbos spinning at 86,000rpm under full load exiting the tricky transition kick out of the Karussell. The net result is a lap time that the people at AMG are quietly quoting at 7 minutes 20 seconds. That is a sizeable 15 seconds quicker than the GT S, and, coincidentally around the time AMG’s Porsche rival manages in the 911 GT3 RS. Race on then; the twin tests around here are going to be very interesting indeed.

Specs

Model:GT R

Engine:4.0-litre V8 turbo

Transmission:Seven-speed auto, RWD

Max power:577bhp @ 6,250rpm

Max torque:700Nm @ 1,900rpm

Top speed:318kph

0-100kph:3.6sec

Length:4,546mm

Width:NA

Height:NA

Wheelbase:2,630mm

Weight:1,630kg

On sale:NA