2018 Mercedes-AMG GLC 63 S 4Matic Coupe Full Review

It's worth remembering, as the leaves change color and the air begins to chill, that sooner or later most of us are hammered by a winter virus. We just got it done sooner than most, in the forests of Germany's Schwabian Alps, from an unlikely assailant.

AMG's 4.0-liter, twin-turbocharged V8 is the kind of European winter virus we like, though. It's relatively tiny, given the damage it can mete out. Wherever it spreads, it takes machines born from corporate business plans and turns them into snarling, bellowing brutes. Take the GLC 63 and the GLC 63 Coupe. Friendly, cheerful and solid as the donor Mercedes-Benz GLC might be, the bite of the 4.0-liter virus turns it all belligerent and shockingly fast.

Mercedes-Benz plans to bring "63" gristle to the GLC from somewhere around $68,000 for the GLC 63 4Matic and about $5,000 to $7,000 more for the same power level in the GLC 63 4Matic Coupe, with the S version of the Coupe body style demanding early-$80K money. The S version will only be available in the Coupe bodystyle.

There are other ways to look at it. It has extra luggage space and a higher driving position over the C 63 sedan stablemate for more or less the same money, while stepping up from the $60,400 GLC 43 Coupe is a lot less painful than it is in the GLE model range. But getting all the good stuff you probably want will cost more. AMG won't say how much more, but it's a safe bet that expanding the mode-shifting Dynamic Select system to include Sport + and Race will end up being somewhere around $1,250, because that's what it costs in the C63 that shares this very same virus.

The justification for asking so much more for an S version is that it lifts the power of the modular motor from 469 horsepower to 503 and boosts the torque peak up from 479 pound-feet to 516. It's not as if either of them lack potency, though. To 60 mph, the GLC 63 S — the fastest and most expensive of the breed headed stateside in the middle of next year – will steal the lunch of even Porsche's just-launched Cayenne Turbo, hitting 60 mph in 3.7 seconds (even though it's aimed at the Macan Turbo). The base car is only about two-tenths of a second slower — even if it doesn't feel right to call that "slower."

It's not like it struggles to do it, either. We tested the S version of the Coupe (though only on 21-inch Pirelli winter tires that add squishiness, in order to comply with German law at this time of year), and it didn't just feel like it would bang out 3.7-second blasts to 60 mph, but felt like it would do it all day.

It helped that it used the optional Race mode to wind up the nine-speed automatic transmission's AMG-spec clutch pack (which replaces the stock torque converter), but in wet conditions it wasn't even necessary.

 We just cranked up the revs it would swallow and then stepped off the brake pedal. And hung on. And on. And then hung on some more. And the GLC 63 S Coupe was the only one that didn't notice it was raining, hard.

Its first gear ratio is an astonishingly low 5.35:1, and it's only ever used fleetingly, especially on full throttle in Sport, Sport + or Race modes. It snaps you back in the seat, and the clean launch — with virtually no wheel chirp much less spin — takes every one of those engine revs and turns them into straight-line speed.

There's an electronically locking diff on the rear axle that takes 69 percent of the torque under normal conditions, but the center differential can swing around to shoot half of it up front (where an open diff does its best).

And it does it loudly, and you'll never confuse the engine note with a sugary-sweet V8 or V10 from the pre-turbo days. It's deep and angry when it fires up in the default Comfort mode, but it gets even more upset when you stab the gas pedal, and downright furious if you combine that with a piece of blacktop to take all that vocal frustration out on. Basically, it's all the muscle and fury of that bear in "The Revenant" (before it gets killed, obviously), plus pops and crackles on the overrun and downshifts that would put a hot rod with a four-barrel Holley to shame.

The shifts snap cleanly and quickly, though the jolt goes from zero in Comfort mode to oh-there-it-is in Sport and keeps going until the exaggerated thumps of Race mode (another good reason not to actually use R on the road). It's also so ridiculously clever in Sport and Sport+ that you're better off forgetting about the paddle shifters and just letting it do it all for you.

A full third of its nine speeds are overdriven, and it reaches its 174-mph top speed (up 19 mph on the electronically limited stock GLC 63) with those three gears to spare. They're used for cruising and saving gas (though there is no official mileage figure yet), especially the 0.60:1 ninth gear. It takes this a step further by "sailing" — disengaging the powertrain in Comfort mode between 37 mph and 99 mph — to gurgle even less.

Besides borrowing the engine from the armada of AMG models, the GLC 63 S Coupe also borrows heavily from their suspension features, too. It scores a three-chamber air spring system, active damping, more negative camber and a four-link front end with unique steering knuckles. The rear end steals heavily from the E 63 S's five-link rear-end architecture, and wheel bearings now sit further out than on the standard Mercedes version.

For all its SUV stance and the mean look of the Panamericana-style grille, assume it's not ready for the Rubicon. Because it isn't. Not with standard 265/45 R20 tires up front, 295/40 R20s at the back (an inch bigger and a lot wider than the standard GLC 63 Coupe). If you want another hint, there's not a single off-road setting built into the mode switch.

A cold, wet road test on squishy winter tires isn't conclusive, but it does leave us with some questions to answer once the ball of fire is finally over here.

Firstly, we're not absolutely sure how it handles. There's plenty of grip there even when you start throwing it around, but at 4,511 pounds (up 36 on the entry version), it doesn't wash the same calm sense of assurance over the driver that a Macan Turbo does. It was also difficult to feel truly at one in the bends, and its skid-control systems chimed in so hard, so early, that it must have felt the same lack of power-down confidence we did. Or the conditions were just that bad. It improved in Sport and Sport + modes, where the skid-control let the car slide just a little on the way out of corners.

At least half the problem in the winding, saturated roads we had was that there is just such a broad range of ferocious thump from the V8 even at half throttle that it's giving everything, almost all the time. The torque peaks at 1,750 rpm and stays there until 4,500, while the power peak hits at 5,500 rpm and doesn't fall away until 6,250. There's no linearity in the power delivery, and the first three gears are all so short that throttle modulation demands enormous attention.

That's going to be a lot less critical on dry roads and less critical again on faster, open bends where the SUV felt tremendously stable, with its nicely weighted steering making it easy to point and the effortless power always at the ready. It's also quiet when it's cruising, and the ride is relaxed enough in its Comfort setting to be an everyday car. And there is the usual luxurious array of AMG leatherwork draping the cabin.

So, maybe it doesn't go around corners like a Macan Turbo. And maybe it does, when we get it on the right tires and it's not raining and it's a few degrees above freezing. But we do know this: It sure flings you out of corners in a hurry. And just keeps flinging you on.

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