What is GT4?



IT’S NEVER nice to be caught off guard. Feeling that way as you’re strapped into a $380,000 racing car and stare with wide-eyed fascination as its slimline, button-infested steering wheel is snapped into place in front of you, however, is appreciably worse.

Bang! The mechanic who was tightening my five-point harness slams my door, only to reappear seconds later through the windscreen. He gives me a thumbs up; the signal to ignite the big V8.

This is all considerably more serious than was expecting. When Mercedes asked if I’d like to drive its newest racing car – this rather ferocious-looking AMG GT4 – at Sandown, I’d mentally defined ‘GT4’ as meaning a slightly faster, track-focused version of the road-going GT R with slicks and a roll cage. Sounded fun.

Now though, cocooned as am within a carbonfibre safety cell, my gloved mitts only inches away from multi-stage dials for the ABS and traction control, I feel as though I’m ready to line up on the front row of the Bathurst 12 Hour. Time for a mental recalibration.

It’s true that the burgeoning GT4 category is designed to sit beneath GT3, both in terms of performance and cost. Created in 2007, it’s now recognised worldwide and sees drivers compete alongside GT3 cars in some of motorsport’s highest-profile events. There’s plenty of machinery to choose from, too, with manufacturers as wide-ranging as Ford, McLaren, Alpine, Chevrolet, Porsche and BMW all building factory-spec GT4 cars.

The appeal is obvious. At around half the outlay of a fully fledged GT3, and with lower running and maintenance costs to boot (see sidebar, p42), GT4 seems an ideal playground for well-heeled gentleman racers, and for eager youngsters looking to develop their confidence and ability on the way up to burlier tin-top racers. And as I’m learning, ‘GT3 lite’ doesn’t mean scrimping on the theatre of GT racing. Or, as it turns out, a degree of intimidation.

First, some numbers. Power comes from the same 4.0-litre twin-turbo ‘hot vee’ V8 as the regular GT R, though its outputs are different, and not in the direction you might expect. To comply with GT4’s stringent balance of performance regulations, the AMG’s V8 produces between 295-375kW, depending on boost. Today the donk is set to its maximum setting, though even so, 375kW is well below the road car’s 430kW. Offsetting this reduction in grunt is an even heftier drop in weight. Removing all of the road car’s creature comforts and liberally coating the cabin in carbonfibre has saved 300kg, meaning AMG’s GT4 hits the scales at a hot-hatch-rivalling 1390kg. Nice.


Lower running costs and a longer maintenance schedule are obvious GT4 attractions. Many of the GT4’ components are identical to the road car’ so should something go wrong, it’ likely a replacement part can be sourced from your local Mercedes dealer rather than Germany. Most components are ‘lifed’ at 18,000km, except for the gearbox, which needs to be checked after 12,000km. And the engine? AMG recommends an overhaul after 40,000km, which is well up on the GT3 car’ donk. That’ require a rebuild after 22,500km.

Now, the clutch. Racing clutches are notoriously malicious, yet pulling away is surprisingly simple. The pedal is light and the bite point easy to find; exactly the combination you want in a car pitched at less experienced racers. The following 100 metres or so, however, are decidedly less civilised. Clearly unhappy with my chosen speed and throttle position, the car jerks and strains, the cockpit a clumsy cacophony of diff chatter and transmission whine.

Much of this recalcitrance can be attributed to the gearbox. Unlike most GT4s, which use the same ’box as their production car donors, AMG removes the regular GT R’s seven-speed dual-clutch and replaces it with exactly the same six-speed sequential unit as its GT3 car. It’s a full racing ‘box with beefier internals and faster shift times, and combined with the noisy diff, it makes the AMG feel raw. Mechanical. As though it won’t suffer fools.

The opposite turns out to be true. Feeding in some revs sees the drivetrain mesh and power through the first four gears towards Sandown’s first turn, each shift hammered home with a pleasing decisiveness. It’s wonderfully intuitive, this thing. The steering is sharp and naturally weighted, the massive slicks offer a surplus of grip, and the braking performance is intoxicating. Delve deep into the middle pedal’s travel and it’s a glutton for punishment that can be smashed without mercy or fear of locking a wheel.

Cocooned within a carbonfibre safety cell, I feel as though I’ m ready to line up at the Bathurst 12 Hour

The electronics help here, of course. Like the gearbox, the GT4’s wiring loom is lifted straight from the GT3 car and there are 11 stages for the ABS and traction control. leave both in their middle setting, with the only sign that the ABS is working delivered by flashing purple lights on either end of the steering wheel.

Set-up wise, there are the usual chassis parameters to tweak: rebound and compression for the dampers, ride height (and hence rake), and alignment alterations for camber, toe and castor. Today the car is configured to a ‘middle’ baseline, which also includes the angle of the adjustable rear wing. Retaining the sanctity of their competitive advantage means AMG’s mechanics won’t reveal how much downforce the GT4 generates, though it’s clearly well down on the figure produced by the GT3 car’s more aggro aero package. One advantage to that is less drag, meaning that on the straights, the GT4 is actually quicker.

Does the big V8 feel as vastly accelerative as it does in the regular GT R? Not quite, especially in the first few gears, though where the GT4 absolutely monsters the road car is through the corners. Pitch that long nose into a turn and it’ll ride kerbs with stunning control and surprising pliancy, but it’s the corner exit that’s most addictive. So high are the grip levels that the GT4 taunts you to feed in the throttle earlier and earlier, the rear diff reacting with confidence to drive the car out the other side.


A key difference between the AMG GT4 and the GT3 car is found in the engine bay. While the GT4 uses AMG’ current 4.0-litre twin-turbo V8, the GT3 sticks with Affalterbach’ old naturally aspirated M159 6.2-litre unit. Proven reliability is cited as the main reason for retaining the old lump, which produces around 390kW depending on the balance of performance regs. One similarity between the cars is the settings for the cockpit’ carbon safety cell and pedal box, which can be transferred straight across for the step up to GT3.

Model Mercedes-Benz AMG GT4

Engine 3982cc V8 (90°), dohc, 32v, TT

Max power 375kW @ 6000rpm (est)

Max torque 600Nm @ 1900rpm (est)

Transmission 6-speed sequential

Weight 1390kg

0-100km/h 3.8sec (est)

Price €198,850 (approx A$380,000

It all feels nicely predictable and balanced, which, of course, is precisely how it should be. What amateur racer is going to feel comfortable improving their ability in a snappy, mean-spirited machine? No, this needs to be a car capable of tolerating some degree of ineptitude. Which duly give it.

With my commitment growing, decide to accelerate between Sandown’s final right-left complex and try to make the second corner on a trailing throttle, where I’d previously been bleeding off the brake. Mistake. With no weight on the nose the GT4 delivers such a woeful armful of butt-puckering understeer that fear I’m headed for the fence. My fault, not the GT4’s, though it’s a lesson in how sensitive cars like this are to weight transfer and, when the speeds increase, aero balance.

Be mindful of that and AMG’s GT4 is remarkably rewarding. There’s something thrilling about nailing a corner exit, revelling in the grip of a hot slick tyre and then watching as the shift lights glow green, then yellow and red as you wait to feed in another ratio to a hard-headed racing gearbox. It’s proper GT race car stuff and – interestingly – substantially more exciting than other GT4s on offer. I’ve since driven a McLaren 570S GT4 and it did feel like a road car with slick tyres. The AMG is more like a de-specced GT3 car.

Which brings us to the question of value, and the deeper conundrum of whether such a word can exist in the realm of motorsport. At €198,850, it’s feasible that at today’s exchange rate and allowing for tax and delivery charges, you could park an AMG GT4 in your garage for $380,000. That’s a big number, but consider that it’s only $30K more than a regular AMG GT R and suddenly it seems a justifiable and decidedly more captivating place to spend your money.