Mercedes SLS AMG Black Series vs SRT Viper GTS (2014) review

Published:24 February 2014

Mercedes SLS AMG Black Series vs SRT Viper GTS (2014) review
  • At a glance
  • 5 out of 5
  • 5 out of 5
  • 3 out of 5
  • 5 out of 5
  • 5 out of 5

Photography by Greg Pajo

This is a battle between two of the most aggressive street racers in the USA. A financial gulf separates £75,000 SRT Viper from £230,000 Mercedes SLS AMG Black Series; an ocean divides their character: blue-collar grafter meets white-collar big shot.

But besides a common interest in hoovering up the horizon they share something else: family connections. There’s an old score to settle, Daimler having jettisoned Chrysler when the going got tough.

We’ve come to Los Angeles to collect our gladiators, but we won’t be staying, just hanging around long enough to take in a few of those admiring glances, which, like it or not, are as much a reason to buy a car like this as a headline-grabbing Nürburgring lap time.

No, we’ll be swapping the concrete jungle for the endless square miles of desert waiting for us in our favourite Californian playground, the Anza Borrego Desert State Park.

But first we’ve got to get there, and that means a two-hour freeway cruise and a chance to test these cars’ GT talents. Road test ed Ben Pulman takes the lead in the SLS, while photographer Greg Pajo and I bounce along behind in the Viper, windscreen full of the AMG’s carbon diffuser and optional – but visually essential – rear wing. Having already driven the SLS on track earlier this year I know it’s going to put up a strong fight.

But the Viper is something of an unknown quantity, at least to me. After Jonny Smith, now of TV’s Fifth Gear, took one on a CAR lunchtime sandwich run that turned out so costly we could have dined out at the Ivy all year and still had change, Chrysler’s insurance company hasn’t been keen to lend us another. So, based on my seat time, the last decade of Vipers didn’t happen.

Mind you, this one nearly didn’t happen either. Gripped by the financial crisis, Chrysler and new owners Fiat had more pressing priorities than sinking millions into a low-volume sports car. Fortunately, the good guys won, and a new Viper, this time sold under the SRT performance banner, hit US showrooms in 2013. Though it shares the old car’s steel chassis and 2510mm wheelbase, the latest Viper has a wider front track, revised suspension geometry and employs lightweight carbonfibre for the bonnet, roof and rear hatch, plus aluminium for the doors and sills, and magnesium for the bulkhead. Capping off a 50% increase in torsional stiffness, there’s a humungous cross-brace atop the familiar V10. 

Rigidity is certainly in the forefront of my mind as we head south west along Highway 91, before switching south to I-15. The Viper’s ride is terrible. Imagine driving over a cattle grid that stretched from London to Birmingham and you’ll have some idea of how the Viper copes with short frequency bumps, even on the more compliant of its two damper settings. It’s noisy too, and not in a ‘who needs a radio?’ kind of supercar way, the tuneless blare of the V10 sounding more tugboat than track terrorist, and emitting some uncomfortable frequencies at part throttle that make cruising a pain. You just know it was built to do so much more. Or, at least you hope.

On the plus side, the Viper’s cabin is leagues better than the old one’s. We’re not talking German quality, but it’s no longer an embarrassment. Our car is a plusher GTS version, which adds full leather trim, a 12-speaker Harmon Kardon sound system, and multi-stage dampers, plus we’ve got the tasty SRT Laguna Premium Leather option. You sit upright with the near vertical A-pillar unfashionably close, semi-digital instruments and modern touchscreen infotainment system just ahead. The fat steering wheel tilts but doesn’t telescope, instead there’s a button on the steering column that slides the pedal box in and out.

When we swap cars just outside of Temecula, the Mercedes feels vast in every direction. Pajo seems so far away in the passenger seat, it’s like I’m looking at him through the wrong end of a pair of binoculars, and the huge flat expanse of bonnet stretching ahead suggests 1970s land yacht, not the lightning reflexes of a supercar. But those suggestions are wrong, because even changing lanes at 80mph on the freeway, you can feel how agile the SLS is. The steering is spectacularly good, so feelsome and perfectly judged for weight and speed. It never feels nervous, but the response to a twist of the steering wheel is instant, and I can only presume that some of the credit must go to the new Michelin Pilot Sport Cup 2 rubber tucked under each arch.

Compared with the standard SLS (and for £65k extra!) this Black Series gets some modest engine tweaks, uprated suspension and a noticeably shorter seventh gear that has me repeatedly reaching for a non-existent eighth ratio. It’s also a substantial 70kg lighter than its plainer SLS GT sibling, thanks to a titanium exhaust, lithium-ion battery and extensive use of carbon for body panels, the torque tube and prop, and brake discs.

By the time we leave the freeway, the light has long gone, so we overnight in Julian, just west of Anza Borrago. Famous for apple pies and an 1870 gold rush, it’s nothing but a tourist town these days, and unfortunately for us, the season is finished and the streets are as empty as our bellies. I reckon it’s worth battling the late evening fog in search of some action 25 miles away in Ramona, but Pulman has other ideas, namely putting in an hour of pilates before bed (was the Viper’s ride that bad?), and we finish the evening eating takeaway burritos in my doily-festooned hotel room like the square kids in our first week at college. Rock’n’roll! Never mind throwing TVs out of windows, lets re-read that bitchin’ Christian theology textbook together guys!

The hell-raising quotient gets a boost the next morning because we’re up at 6am to make the most of the short daylight hours. And so is everybody else when we ignite all 18 cylinders. I’m back in the Viper and keen to see what it can do on some serious roads. And I mean serious. If you’re still labouring under the misapprehension that America doesn’t do corners, you’d be quivering like a mid ’70s Caddy after an emergency stop within a minute of leaving Julian for Borrego Springs.

This is Route 78, and it’s got everything from tightening, tyre-torturing second-gear switchbacks to fast sweepers and every variant in between. There are elevation changes too, and some long, long straights for us to run the things ragged from a standing start until we’re spuds deep into fourth gear and can see which car really does have the muscle.

Here’s one now. With over a mile of clear road ahead, we pull side-by-side, the splattery chugging of the Viper’s side-exit pipes drowning out the Merc’s more cultured, and more classically American, burble. In terms of sheer power, these two naturally aspirated mills are incredibly close, the Viper’s 640bhp giving the SRT a meagre 18bhp advantage.

They’re almost neck-and-neck for weight too, the 1550kg Mercedes giving away just 6kg to its rival. But look at the torque numbers: 468lb ft for the SLS, but a stupendous 600lb ft for the Viper. That’s what 8390cc of swept volume will do for you, even if the rest of the package – two valves per cylinder and a solitary cam buried deep within the vee – looks comically low-tech besides the quad-cam, multi-valve Benz eight. When the SLS dies this year, so will the much-loved 6.2, which is fortified in Black trim by a 500rpm loftier redline, which now stands at 8000rpm. This helps it deliver 59bhp more than a regular SLS, to a rear end equipped with an electronically controlled limited-slip diff.

All we need now is a girl in pedal pushers and a white shirt tied just below a perky bosom to wave us off. Sadly the only females we can find out here have eight legs, more hair than Captain Caveman and a nasty bite, so we settle for a scruffy Kiwi bloke with a Canon wrapped round his neck, gun our engines and let ’em rip. Unusually for a car with a manual ’box, the Viper has a launch-control function, but in typically pig-headed male fashion, I reckon I can do better. I’m wrong, and while I’m busy fighting the P-Zero bonfire in the rear wheelarches, Pulman has inched ahead, hitting 62mph in 3.6sec, which is roughly what the Viper should rattle off when approached with a sensitive touch.

Finally I’m hooked up, and shovel in the power. First gear seems to last forever, but once into its stride the Viper has the SLS locked solid. For a couple of hundred metres they stay like that, engines screaming, cacti blurring in the side windows, me hurling the SRT’s shifter around like a baseball, Pulman tapping paddle shifters like he’s gently brushing crumbs from a tablecloth, neither car gaining an inch. They might be priced £150k apart but you’d struggle to slip a George Washington between them in a drag race.

Maybe some curves will help one find an edge. As we head along 78 towards Salton Sea, two things become apparent. First, that the Viper demands serious elbow grease to give its best. The meaty steering needs the arm muscle of a prize arm-wrestler, and changes in the six-speed manual ’box like to stop for a breather on their way across the gate like a gossipy pensioner on her way to shops.

The second thing? That it’s actually pretty handy. Yes I know that the Viper’s back catalogue is littered with endurance racing wins and that the ACR version made its name by breaking the Nürburgring lap record a few years back, but from the Yurpean side of the Pond it’s hard not to suspect that the Viper is all a bit grunt over grin.

Let’s redress that unfair assumption. If you have the talent and the trouser tackle, this is a proper weapon across country. The amount of mechanical grip on offer is colossal, and that’s no surprise given the vast quantities of rubber on each corner. Guide that long nose into a corner and roll is almost non-existent, the upside of the choppy short-wave ride being excellent body control on the longer stuff. As you lean on the outside front tyre, waiting for understeer that never comes, then start leaning on that right foot, you can’t help but be impressed by how much traction the thing has got. Far from wanting to spit you into the scenery at the first opportunity, the Viper feels stable, balanced and controlled, its 335-section rear boots parrying almost every attempt by the big V10 to send them off course. Even in the wet there’s nothing to fear, because US legal requirements means the Viper finally has a stability system, two-stage in the standard car, and four in the case of our GTS.

When I switch to the SLS, the impressions come thick and fast: how much better the SRT’s steel brakes bite in response to initial pressure than the Merc’s ceramics; how much more refined the SLS’s drivetrain is, how much less tiring it is to drive. But most of all, I’m blown away by that front end. We touched on it earlier, but this SLS Black is night and day better than the standard car, connecting you to the front wheels in a way that’s almost unheard of in a front-engined 1500kg car – although to be fair, both cars have almost 50:50 weight distribution.
To my mind though, the SLS is crying out for a better drivetrain. The V8 might have been massaged but it can’t hold a candle to a Ferrari F12’s V12. Not for power, for noise or response. Likewise, the gearbox. The week before I came to LA for this story I was in Italy driving the 458 Speciale. Both SLS and 458 use the same transmission hardware, but you’d never guess from the Benz’s tardy downchanges.

The F12 and 458 comparisons are particularly pertinent when you consider that all three cars cost £200k and change. And much as I love that steering and the theatre of those doors, I’d take either Italian over the Black. The Viper needn’t fret; it’s never going to lose a sale to a car costing three times as much. But in its home market it’s come up against the surprisingly excellent new C7 Corvette, which costs half as much. Viper sales are way off target as a result, and production has been scaled back.

There are no plans to sell the SRT through official channels in the UK this time round, but of course there’s nothing to stop you bringing one in as a grey import. But in GTS trim and fitted with the tasty Laguna seats our Viper stickered at $140k. Add your shipping, import duty and the dreaded VAT to that, and you’re looking at the best part of £120,000. A Nissan GT-R is £77,000; a 911 GT3 £23k more.

Ambition has pushed both of these cars deep into new territory populated by a glut of talented rivals, which makes finding owners hard work. Both are endearingly capable machines, but they’re searching for owners prepared to look beyond the obvious and pay handsomely for the privilege. Their disparate characters make them hard to separate but, objectively and by a short head, the SLS is the better car.

Specs

Price when new: £230,000
On sale in the UK: Both on sale now
Engine: (Mercedes) 6208cc 32v V8, 622bhp @ 7400rpm, 468lb ft @ 5500rpm (SRT) 8390cc 20v V10, 640bhp @ 6200rpm, 600lb ft @ 5000rpm
Transmission: (Mercedes) Seven-speed dual-clutch, rear-wheel drive (SRT) Six-speed manual, rear-wheel drive
Performance: (Mercedes) 3.6sec 0-62mph, 196mph, 20.6mpg, 321g/km CO2 (SRT) 3.5sec 0-62mph (est) 206mph, 20mpg (est) n/a CO2
Weight / material: (Mercedes) 1550kg/aluminium and carbonfibre (SRT) 1556kg steel, carbonfibre
Dimensions (length/width/height in mm): (Mercedes) 4646/1977/1264 (SRT) 4463/1941/1246mm

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