by Ian Kuah
The performance wing of Mercedes has been on a roll of late. With AMG sales figures having quadrupled from around 27,000 a decade ago to over 100,000 units last year, the Daimler Board of Management has the confidence to sign off on bespoke AMG models that are far more than just modified Mercedes. The SLS AMG of 2009 was the first of these, and its image as a 21st Century 300SL Gullwing made it a legend in its own time. But even before this, AMG had a plan to develop and build its own bespoke engine range that did not rely on a mainstream Mercedes block and heads.
The first of these was the 6.2-liter M156 four-cam V8 that made its debut in the E63 AMG of 2006. The more powerful M159 derivative featured dry sump lubrication along with a bespoke intake system, valve-train and camshafts powered the SLS AMG. The spiritual replacement for the SLS AMG was the AMG GT, which arrived in early 2015 along with the brand new AMG designed M177 and M178 (dry sump for GT models) 4.0-liter, 90-degree V8 bi-turbo AMG motor. A "hot side inside" V8 engine, with its two turbochargers placed within the vee of the motor and a dry sump configuration, this engine was designed to address ever-tightening emissions laws whilst providing even more power and torque potential than its larger displacement predecessor.
This is the engine that powers the V8 models of the four-wheel-drive-only AMG GT 4-Door Coupe, the third bespoke car in the Mercedes-AMG lineage, and the first to offer four doors and four seats. Constructed from steel, aluminum, and carbon-fiber, the GT 4-Door Coupe is a large hatchback with the family-friendly seat and load space versatility that this implies. However, because AMG is also about choices things are not quite so simple.
The GT 4-Door Coupe range actually kicks off with two models powered by the new 3.0-liter straight-six engine, which features EQ boost from its starter/generator. The GT 43 4Matic+ has 367hp from 5,500-6,100 rpm and 369 lb-ft of torque from 1,800-4,500 rpm. The EQ Boost feature adds 22 hp and 184 ft. lb. under full throttle acceleration. The GT 53 4Matic+ develops 435 hp at 6,100rpm, with 384 lb-ft of torque from 1,800-5,800 rpm. The EQ Boost adds the same extra output as on the 43 engine.
This is the same engine fitted to the current S500 and both these sixes are coupled to the AMG Speedshift TCT 9-speed automatic gearbox with torque converter. The base V8 model is the GT 63 4Matic+, whose M177 motor makes 585 hp from 5,500-6,500 rpm and 590 lb-ft of torque between 2,350 and 5,000 rpm. The S version that we tested has the full-fat 639 hp state of tune, underpinned by 664 lb-ft of torque. The V8 engine sends its power to all four wheels via the AMG Speedshift MCT 9G wet clutch automatic gearbox.
The straight-line go of the GT 63 S 4Matic+ is best described as bombastic. Considering it weighs as much as an S-Class the 3.2-second 0-62 mph sprint and 196 mph top speed are pretty impressive. In fact, despite weighing over 1,000 lbs. more than the GT R, the GT 4-Door's all-wheel-drive system has the traction to help it beat its two-seat brother to this benchmark speed by 0.4 sec. The six-cylinder cars and the base V8 model have a mechanical limited slip differential while the S model has an electronic LSD - this is available as an option on the other models. Active rear axle steering is standard on the V8 models and optional as part of the AMG Dynamic Plus package on the six-cylinder cars.
As you would expect the cabin design combines the latest elements of AMG and Mercedes mainstream for a unique blend of luxury and performance. The big double screen dashboard display behind a single sheet of glass is similar to the latest E and S-Class design, while the center console and steering wheel controls take their cues from the AMG GT and add some new features.
Ferrari may have started the whole F1 style steering wheel control button fashion, but AMG takes the guesswork out of these by using the same pictograms that appear on the center console. It is easier, faster and less distracting to use these steering wheel controls than search for buttons on the center console in a moving car.
The standard sports seats are a good blend of comfort while their side bolsters hold you in position well in the bends. The test cars were fitted with the optional Performance seats that are better on track but require you to climb in over their taller side bolsters, which some might find less practical for a daily driver.
AMG told us that the basic configuration features a non-folding two-seat rear bench with a storage compartment in the middle and a carbon-fiber panel behind the seat back for maximum bodyshell stiffness. Here the trunk space is 16.1 cubic ft. The alternative is the 40-20-40 folding rear seat option that maximizes the versatility of the hatchback design. Without the carbon rear wall, trunk space is 16.2 cubic ft., expanding to 46.76 cubic ft. with the seatbacks folded flat. This approximates the load space of a medium size station wagon.
The third possible configuration is called the High Class Rear and brings two individual rear seats with a Business center console equipped with controls for the infotainment and comfort functions of the vehicle.
And a daily driver the GT 4-Door Coupe most certainly is. The suspension is by four links in front and five links at the rear, with steel springs and adaptive dampers. Three-chamber air suspension is standard on the V8-powered 63 S 4Matic+ model that we drove. In comfort mode, the ride is very compliant despite the optional 9.0J and 11.0J x 21-inch wheels and 275/35ZR21 and 315/30ZR21 tires. To be sure of its credentials as a family performance car I sat in the rear for a while. This confirmed that the AMG engineers have done a fine job with the secondary ride. You can feel the suspension 'breathing' over bumps around town and on country roads, with none of the short, sharp movements and wheel patter you often experience in the back of many high-performance cars.
Back in the drivers' seat Comfort mode helps you to relax even though the 639hp V8 monster under the hood is raring to go. Sport mode sharpens everything up and is the default choice when the tarmac ahead starts to take on interesting angles. On the road, the speed, balance, and grip of the GT 4-Door Coupe is never called into question, nor is its ability to play limousine in Comfort mode one moment and autobahn stormer in Sport mode the next. This is a car with a truly wide spread of talent. And it sounds good too. Despite the EU authorities attempts to make cars quieter on drive by, AMG has succeeded in retaining a lot of their NASCAR grade V8 soundtrack. In Sport mode or with the exhaust valve button depressed this is a good tunnel car.
However, as competent as the five-door AMG is for a 4,508 lbs. machine, you are always aware that it is a 4,508 lbs. machine. And it is precisely because it tips the scales in S-Class territory, on track the laws of physics ultimately temper the GT 4-Door Coupe's impressive turn of speed.
On the fast and fluid Circuit of The Americas near Austin, Texas the GT 4-Door Coupe acquitted itself very well, but with a couple of provisos. When you compare it to a pure sports car like the AMG GT R that was used as the pace car the Coupe's sheer mass, its 55/45 percent front/rear weight distribution, and its smaller front wheels and tires stand out as immediate limitations.
This means that while front-end grip into slow bends can be optimized on turn-in by trail braking, you have to be mindful of your entry speed into the medium speed sequential right and left bends that make up Turn 6 to Turn 9 here.
In an ideal world, this sequence requires the driver to enter the first bend on the right line with the right velocity, and then maintain a fairly constant speed in a perfect right-left-right-left rhythm. However, the turn radius of each bend is not quite the same, and going off line a bit, or picking up speed so that you enter the third bend a tad too fast results in rhythm breaking understeer and a significantly slower exit speed from Turn 10 onto the subsequent straight.
This was the part of the track where the AMG GT R, driven by DTM ace Bernd Schneider effortlessly drove away from its larger brother. Whatever AMG might say about the competence of the GT 4-Door Coupe on track, the lower center of gravity, front-mid-engine transaxle configuration, 48/52 percent weight distribution, and 1,100 lbs. lower curb weight of the GT R threw the empirical differences between their pure-bred, two-seat sports car and their super sports saloon into stark relief.
Elsewhere the GT 4-Door Coupe was downright impressive in its ability to push the performance envelope for a car of its size, weight, and power. I particularly enjoyed the long and fast three corner long right-hand T16, T17, and T18 combination, which you take riding the torque curve in fourth gear with one sweep of the steering wheel, missing the first two apexes and nailing the third. Thanks to the balance of the 4Matic+ all-wheel-drive and the downforce from the rear spoiler there was no problem keeping station with the GT R here.
Even approaching the tight left hander at the end of the main straight the huge carbon ceramic brakes do their job very well indeed considering the car's two-ton curb weight. They were most impressive for their ability to wash off big speeds lap after lap whilst trying to keep up with Schneider.
Coming back to that understeer issue, it was very telling when I questioned an engineer about brake and tire wear during the track part of this launch event and was told that the brakes were holding up well, but that two sets of front tires needed replacing for every set of rears.
What has to be borne in mind though is that the GT 4-Door Coupe was being tracked on Michelin Pilot Sport 4S street tires and the handling and tire wear reflected this. Trackday junkies can also specify a bespoke Michelin Cup 2 tire, which AMG has had developed specifically for the GT 4-Door Coupe since such tires are not normally available for cars of this weight class.
AMG has done an amazing job with their GT 4-Door Coupe. With its shark-like nose profile, classic Panamericana grille, and swoopy profile this four-seater really cuts a dash on the road where its ability to shrink distances in comfort yet be engaging when you find some challenging bends is impressive.
While we are not so sure about AMG's marketing hype describing the GT 4-Door Coupe as a sports car for four, as a versatile super sports sedan with Coupe styling there is no doubt that it commands a class of one.