Mercedes SLS AMG (C197)

	Mercedes SLS AMG
	Debut: 2009 Maker: Mercedes-Benz Predecessor: SLR McLaren

Published on 21 Dec 2009

AMG proves that it can build better cars than McLaren SLR, even at half the price !

From 2003 to 2009, Mercedes-McLaren built about 2,100 units of SLR, making it the highest selling supercar ever made. However, the SLR has never got the admiration Mercedes expected. People criticized its excess weight, stiff ride, numb steering and brake. No one regarded it as great as contemporary supercars like Porsche Carrera GT, Ferrari Enzo or Bugatti Veyron, and most prefer to drive a (much cheaper) Ferrari 599 GTB instead. It's no secret that the Anglo-German partnership has never been a happy memory to both parties. Although they did not blame each other openly, they thought they could do much better had they went on their own. Eventually, they broke up – both in F1 and road car – and started their own ventures.

On September 8th, 2009, McLaren unveiled its own supercar, MP4-12C, to the public. Interestingly, in less than 24 hours, Mercedes responded with its new SLS supercar. The SLS is the first car developed by AMG division from ground up, rather than modified from Mercedes' mainstream models. Costing an estimated £150,000, it will compete with the McLaren supercar as well as established rivals like Ferrari 458 Italia, Lamborghini Gallardo LP560-4, Porsche 911 GT2 and Audi R8 V10. However, I suppose most comparison will be drawn with the new McLaren. Now both companies are given full freedom to design their cars, which one will be better? We won't get the answer until the McLaren goes on sale in 2011, but right now the Mercedes supercar is available for our evaluation.

This is easily one of the most distinctive cars in the world since Weinermobile...

At first glance, the SLS does not look like a proper supercar. This is because it has an ancient appearance deliberately resembling the 1950s 300SL Gullwing, which is still the definitive Mercedes sports car until today. It has a big mouth, followed by a long long bonnet, an upright windscreen and a small cockpit that sits near the rear axle. This profile speaks little about speed and aerodynamic efficiency. Moreover, its low, sloping tail clearly works against the requirement for downforce, so it needs a retractable rear spoiler to provide the necessary stability at speed. Modern aerodynamics usually shape supercars like wedges. In contrast, the SLS looks like a big German sausage, especially in red. This is easily one of the most distinctive cars in the world since Weinermobile.

A beauty it may not be, but the SLS is unquestionably very well engineered. Its wide and long-wheelbase chassis is constructed entirely from aluminum, i.e. extrusions, castings and pressed sheets, as are the outer body panels. Lacking carbon fiber in its construction does not prevent it from undercutting SLR on the scale – at 1620 kg with fuel and coolant, it is between 30 and 70 kilograms lighter than its carbon-fiber predecessor, although you may say Ferrari 458 and Lamborghini Gallardo are lighter still.

The whole engine is mounted well behind the front axle...

The AMG chassis is also very well balanced - or indeed perfectly balanced - with 47:53 weight distribution front to rear. This is easily understandable when you see its engineering drawing. The whole engine is mounted well behind the front axle (that explains why the bonnet is so long) and counter-balanced by a transaxle mounted at the rear axle. Linking between them is a strong aluminum torque tube, inside which a lightweight carbon-fiber drive shaft is spinning at engine speed to drive the gearbox and rear wheels. This arrangement can be seen in every front-engined Ferrari or manual-box Maserati. It goes without saying that it delivers excellent balance and low polar moment of inertia. Worth noting is that, unlike Ferrari or Maserati, AMG puts the gearbox aft of the rear axle in order to achieve the rear-biased weight distribution. This theoretically increases its polar moment of inertia a bit.

Compared to SLR, the biggest advancement of SLS is probably its gearbox. Here comes a modern 7-speed dual-clutch gearbox, versus the outgoing 5-speed automatic. It compensates the reduced torque output of the naturally aspirated engine with its closer ratios and far quicker gearshift. The gearbox is supplied by Getrag based on the one debuted in Ferrari California. About 70 percent of its components are common to the Ferrari's, but the ratios and program are unique to AMG.

6.3-liter V8 gains even more firepower in this car...

At first, I was a little bit disappointed to hear that the SLS engine is again that AMG 6.3-liter V8. You know, these days there are no less than eight AMG models employ this engine, including the entry-level C63 and the mud-on-your-face ML63. It sounds not exotic enough for AMG's flagship supercar, doesn't it ? Think twice, however, there seems to be nothing wrong. We always regard the 6208 cc V8 as one of the world's best engines. It has great horsepower, great torque and great sound to shut up the unbelievers. Moreover, the new version codenamed M159 (instead of M156 in other AMG models) has undergone considerable improvements. Now the V8 is converted to dry-sump lubrication in order to lower its center of gravity. Its intake manifolds, intake ports and exhaust are modified to enhance breathing, while hotter cams and valvetrain, lighter forged pistons and stronger crankshaft also contribute to extra power. The result is 571 horsepower at 6800 rpm, 46 ponies higher than the most powerful version of its siblings. Maximum torque inches up 14 pound-feet to 479 lb-ft, and appears earlier at 4750 rpm instead of 5200 rpm. This makes the SLS slightly more powerful than rivals 458 Italia and Gallardo, and significantly more torquey than them. It is not as powerful as the V12-powered 599 GTB though, but it has more twisting force to haul a lighter body, so theoretically its performance should be comparable to the flagship Ferrari GT.

SLS is the most beautiful with its gullwing doors opened...

Then how fast is it ? AMG claims it can sprint from 0-60 mph in 3.7 seconds if you activate the "Race Start" gearbox mode. That rests on the same level as the outgoing SLR and the absurdly expensive Lexus LF-A. However, if the manufacturer's figure is accurate, it won't be as quick as Ferrari 458 and 599 in straight line acceleration. These Ferraris utilize their ultra-responsive gearbox and sophisticated traction control to achieve 0-60 in the range of 3.2 to 3.4 seconds, and 0-124 mph in less than 11 seconds. The latter is 1 full second quicker than the AMG. They can also easily crack into the 200 mph barrier. Strangely, AMG claims SLS is "electronically regulated" to 197 mph, some 12 mph slower than the outgoing SLR 722, so it won't be the fastest Mercedes-Benz road car in history. I suspect even with regulator disabled, its top speed would be much the same due to its poor aerodynamic drag of 0.36. Adding speed regulation is just a way to save its face.

Other aspects of the car are quite conventional. Its suspensions are all-round aluminum double-wishbones with fixed rate dampers. Standard stoppers are large steel brakes (390mm discs and 6-pot calipers up front, 360mm discs and 4-pot calipers at the rear), while ceramic brakes are optional. The AMG design wheels are 19-inch and 20-inch front and rear respectively. They wear Continental high-performance tires measuring 265/35 and 295/30 respectively. Electronics are simpler than Ferrari's. You get ABS, ESP and four choices of transmission mode (including the aforementioned "Race Start" launch control), but it lacks an integrated chassis control system, or the ability to alter suspension or differential setting, because both are passive devices.

Remember to grab the door handle before dropping into the seat...

On the Road

Visually, the SLS is the most beautiful when it is parked stationary and has its gullwing doors opened. In this form, few cars can cause as much sensation. The original 300SL adopted gullwing doors because of its unusually wide sills, which required the driver to climb from above, hence the need of opening part of the roof. The new car's sills are much narrower. You sit on the sill, thread your legs into the footwell and drop yourself into the deep bucket seat. Now you may wonder how to close the door. Mercedes should have installed power doors, but for weight saving it didn't, so you will need to climb back to the sill, grab the door handle and close the door while dropping into the seat. Fortunately, the aluminum doors are fairly light and easy to close.

Once you are in the cockpit, you will find a very snug environment. The dashboard and the upright windscreen are very close to you. There is no space behind the seats, so fore and aft adjustment is limited. People over 6 feet tall may find headroom and legroom tight. Interior storage is limited to a tiny glovebox. The dashboard design is classical, with some chromed gauges and air vents, aluminum or carbon-fiber decors on the center console. You can order red stitched leather to enhance the classical ambience further. Anyway, it doesn't look very like a supercar cabin as it lacks the exotic factor. Visibility is another problem. Forward view is hampered by a long bonnet. Rearward view is better, but the swoopy tail means you can hardly judge its exact location. Parking takes special precaution.

Classical rather than exotic here...

However, all these faults become insignificant when the motor roars into life. Those accustomed to the SLR's supercharged V8 will immediately notice its new found enthusiasm - the throttle response much sharper, the power delivery more linear and the sound more delicious. The bottom-end punch might be softer, but once into 2000 rpm, where 369 lb-ft is available for disposal, it becomes really really strong, and the car accelerates with the urgency you would expect for a junior supercar. Its smoothness and its enthusiasm for rev are remarkable for such a big-capacity V8. As rev rises, the V8 rumble is gradually substituted by a race car thunder towards its 7200 rpm cut-out. Having said that, the AMG V8 is not the best sounding engine in the class. Ferrari's V8, Lamborghini's V10 and Toyota's V10 produce more addictive sound when they approach 8000 or even 9000 rpm.

The AMG voice and linear power delivery are also slightly hampered by the 7-speed dual-clutch gearbox. While its smoothness is beyond criticism, the gearchange has noticeable delay compare with the dual-clutch gearboxes on Ferrari or Porsche. Although AMG said its calibration is yet to finalize, I suspect the tremendous torque of its engine may present greater difficulties to quicken its gearchange.

AMG cars used to be big on power and weak on chassis. The SLS is totally different...

The big surprise is its chassis. AMG cars used to be big on power and weak on chassis. The SLS is totally different. Storm it on a race track, you will be amazed with its great balance and immense stability. The low center of gravity is obvious, as is the incredible stiffness of its chassis and the formidable brakes. You can go very fast and deep into bends without breaking its grip or distorting its neutral attitude. Its steering is swiss-watch accurate, if not as sharp as the helm of Ferrari or as tactile as Porsche's. Being a front-mid-engined machine, its handling is inherently tidier than its mid or rear-engined rivals. You have to be really aggressive to swing it into oversteer. If you succeed to do so, you may discover the raw side of its handling, because the way its tail break loose is sudden and unpredictable. However, on public roads it will be very difficult to approach its limit, especially with the safeguard of ESP.

The most impressive of all is its combination of fluid handling and a forgiving ride. The lack of adaptive suspension is compensated with well-judged damping, so the SLS is a terrific long-distance cruiser.

In many ways the SLS is a strong rival to Ferrari 599. Ultimately, it is not as sharp or as engaging to drive as the Ferrari. However, it is unquestionably the best sports car Mercedes has ever built, one that easily wash away the unhappy memory of SLR. Well done AMG.

Verdict:

Published on 10 Nov 2012

SLS AMG GT

The "GT" label is often misused. It originally referred to those large and powerful high-speed long-distance coupes. By this definition, Mercedes SLS AMG should be a GT. So what does it mean when Mercedes add a "GT" label to the SLS? The GT of GT? I wonder if Stuttgart can give a satisfying answer.

If I were the product planner of Mercedes, I would have called it SLS AMG+ instead, because this car is actually an SLS plus something – slightly more power, slightly better control and slightly quicker gearshift. It doesn't transform the car, but it is definitely a plus to keen drivers.

You might have trouble to tell the additional 20 horsepower that the 6.2-liter V8 produces through its modified intake manifold and ECU, but you can easily tell the 7-speed dual-clutch gearbox now shifts faster in attack mode, with less delay between ratios, although it still fails to match Ferrari 458 or McLaren MP4-12C. There is no change to the Getrag hardware, just a new software can make a big difference.

The suspension is no lower than the standard car, but it gets 30 percent stiffer springs, thicker anti-roll bars and stiffer shock absorbers as well. The adaptive damping – added to the standard car since last year – in the GT skips Comfort mode, leaving only Sport and Sport+. Never mind, the former is good enough to take on the majority of road surfaces while the latter is best reserved to race tracks. The suspension mods sharpens the turn-in and improves cornering balance a little. Body roll and understeer are both reduced, leading to a more stable rear end. Compare with these improvements, the slightly less comfortable ride and more road noise are worthwhile tradeoffs.

Nevertheless, with price inflated by 7 percent to £180,000, the SLS GT is uncomfortably close to its Ferrari and McLaren rivals, which are obviously the more desirable yet accomplished choices. Add another £60,000, you can even get the latest Ferrari F12, which overwhelms the AMG in every area. After all, the GT of GT is no match for the Supercar of GT.

Verdict:

Published on 30 Mar 2013

SLS AMG Black

If the mildly tuned SLS AMG GT cannot satisfy you, this SLS AMG Black series could be the answer. Headline numbers include 631 horsepower and 1550 kg kerb weight, which is better than the GT by 40 hp and 70 kg respectively. Moreover, the car gets closer to the territory of GT3 race car, as you can see from its extended fenders and aggressive aero kits. Apparently, the Black is strongly oriented to race tracks.

The engine is still that M159 6.2-liter naturally aspirated V8 – expect to be the last incarnation before turbocharging taking over – but it gets hotter tuning such as faster cams, high-flow intake manifolds, low-friction tappets and revised ECU to boost top-end output. Now output peaks at 7400 rpm (up 600 rpm) and the maximum rev is raised from 7200 to 8000 rpm, incredible for a large V8. It comes at the expense of torque though - peak torque is down 11 lbft to 468. In order to withstand the hard use on race tracks, the engine gets strengthened oil and water cooling system, as well as new main bearings and gas-filled strut brace.

The 7-speed DCT gearbox gets faster shift program for Sport+ and Manual mode. It is also mounted 10 mm lower in the chassis to improve CoG. A gas-filled mounting strut controls its movement more tightly. Meanwhile, the mechanical limited slip differential has been replaced with an electronically controlled unit. This should correct the biggest flaw of the SLS, i.e. a wayward tail.

The chassis is also heavily modified. Wider fenders conceal wider tracks (+20mm front and +23mm rear) and wider tires (10 mm wider up front and 30 mm wider at the rear). The tires are super-sticky Michelin Pilot Sport Cup 2, same as those to be used on Porsche 918 Spyder. The already quite stiff suspensions are stiffened further by as much as 50 percent front and 42 percent rear, so don't expect a GT ride. Ceramic brakes become standard fitment. Least change is the steering, which gets only recalibrated assistance curve.

The 70 kg of weight reduction is achieved with a titanium exhaust (-13 kg), carbon-fiber torque tube (connecting between engine and transaxle, cuts 13 kg compared with the cast aluminum one on standard car), Lithium-ion battery (-8 kg), ceramic brakes (-16 kg) and lightweight alloy wheels (-4 kg). Besides, a lot of external panels are made of carbon-fiber, such as the bonnet, front air splitter, winglets, side skirts, rear spoiler, diffusers and diagonal underbody braces.

So how does it drive on the road?

No one knows, actually. The first round of road test was limited to the super smooth Paul Ricard racing track in France – AMG dismissed the chance to test it on the public roads outside. However, even on the pit lane of Paul Ricard you can feel the harshness of its suspension. No doubt it will turn out to be a nightmare on regular public roads. If you don't do track days, you had better to avoid it. The regular SLS GT will be much better to use as a day-to-day supercar (even though itself is not as great as Ferrari 458 or McLaren MP4-12C in our eyes). In contrast, the SLS Black series is essentially a road-legal track car. It is easily the most track-oriented AMG ever made, with the exception of CLK-GTR. Therefore it is a niche of the niche. No wonder only 350 cars will be built, each costs £230,000, some £60,000 more than a standard SLS and even eclipses Ferrari F12 Berlinetta!

Back to the track, the car performs very well. Its engine revs harder, reacts faster to throttle and sings angrier like a racing motor. AMG people must be extremely proud what they have done before sending their big naturally aspirated V8 into history! Not so good is the dual-clutch gearbox. Although its gearshift gets faster, it is still too slow at times compared with the DCTs on Ferrari or McLaren. Perhaps the inertia of the big V8 is too difficult to overcome. That said, it is no doubt that the SLS Black is a very fast machine, perhaps faster than the 0-60 mph time of 3.5 seconds suggested.

The handling is improved even more. Not only the new tires generate more grip and the aero kits generate more downforce to enable higher cornering speed, the tail is also much better tamed with the widened track and electronic LSD. Now it feels more planted, more stable in corners, allowing you to get back on throttle earlier in corner exit with more confidence. There is some understeer in the turn-in phase though, as you can sense the big V8 is lying near the front axle, but it helps stabilizing the car. Other aspects are just excellent. Thanks to the stiff suspension setup, there is precious little body roll. The chassis also feels more rigid due to the carbon-fiber torque tube. The ceramic brakes are truly capable for track use, with good feel from the pedal, too.

That said, the SLS Black is not the last word of its kind. A Porsche 997 GT3 RS feels even sharper and more precise as a track tool, yet it should ride better on roads and cost half the money. On the other hand, Ferrari F12 is a far more accomplished road car, being faster, more sophisticated and far more versatile. The Black series' appeal is too narrow. That is why its production has to be limited.

Verdict:

Published on 30 Mar 2013

SLS Electric Drive

The SLS Electric Drive is not only the fastest electric car in the world but also the most powerful Mercedes-AMG model ever made. Its 751 electrifying horsepower and 738 pound-foot of instantly available torque eclipse even SLS Black series (631 hp / 468 lbft) and the late SL65 AMG Black (670 hp / 738 lbft). Equally staggering is its price tag – €350,000 plus tax in Europe, or more than twice the price of the standard SLS! Is AMG getting crazy?

No, the SLS Electric Drive is not about business. It is a tour de force of technology. I have no doubt that this car will be built at a loss if its development budget is taken into account. It is admirable that Mercedes-AMG does not care about money and concentrates solely on exploring the technology of the future. Tesla Roadster might be the pioneer of electric sports car, but SLS Electric Drive takes the technology to a different level. It utilizes not just one or two but 4 identical AC synchronous motors, each of them drives an individual wheel through a step-down gearbox so that it can assign whatever amount of torque to each wheel as desired. The result is the most variable 4-wheel drive and torque vectoring ever seen. Theoretically, it can be programmed to deliver faster and more accurate maneuvering than conventional cars.

To keep unsprung weight low, AMG mounts the motors inboard near the center line of the car rather than using in-wheel motors. They drive the associated wheels with half shafts. Unfortunately, the latter is not compatible with the standard car's double-wishbone front suspensions owing to the lack of space, thus the latter are replaced with a new multi-link setup with pushrod-operating inboard spring/damper units. In this aspect the Electric Drive looks even more racy than SLS Black.

The aluminum spaceframe chassis is vastly modified, too. Its aluminum backbone is replaced with a highly rigid carbon-fiber monocoque which houses the lithium-ion battery, protecting the latter from crash damage. The 60kWh battery weighs an immense 548 kg as it needs to provide a range of 200 km (124 miles). It lifts the kerb weight to 2.1 tons thus explains why the Electric Drive is slightly slower than the standard SLS, with 0-60 mph claimed at 3.8 seconds. Top speed is limited to 155 mph to avoid abusing the battery and power inverters. On the plus side, the mass of the battery concentrates in the center and close to the floor of the car, lowering center of gravity and reducing polar moment of inertia.

How does it work in reality? As expected, with 738 lbft of torque delivered right from startup, the sense of acceleration is immense, much stronger than the SLS Black. The integrated traction / stability control / torque vectoring system called "AMG Torque Dynamics" manages wheel spin very well, so it feels very much like a Bugatti Veyron in acceleration. There are 3 modes on offer: Comfort limits power to 590 hp and gives a more relaxing handling characteristic; Sport weighs up the electro-hydraulic steering, sharpen the turn-in through torque vectoring and reduces the intervention of ESP; Sport+ releases the full power and sharpen the handling even further. Their characteristics are more differentiated than in conventional cars as the 4-motors system gives much higher freedom of tuning. In Sport+, the car feels keener to steer and more neutral than the standard SLS so that you don't feel the extra weight at all. It can still oversteer if you push hard, but the torque vectoring engages quickly to settle the tail. The only problem is your correction might conflict with the computer's. Its software still needs some fine tuning to deal with all kinds of conditions.

That said, the driving experience is not as exciting as the petrol-drinking car. The civilized, washing machine-like noise of electric motors is absolutely uninspiring. Not even the artificial engine noise generated by the audio system can compensate. Likewise, the instantly available torque makes the power delivery feels more digital than analogue, lacking the organic build-up of combustion engines. The regenerative braking is also not as intuitive to use as conventional brakes, although it is not as non-linear as in some EVs. Besides, with 2.1 tons of weight to carry, not even the ceramic brake discs can claim to be reassuringly powerful. These problems mean the Electric Drive is not as engaging to drive as its petrol-powered siblings.

Verdict: