Mercedes-AMG SL (R232)

	Mercedes-AMG SL (R232)
	Debut: 2022 Maker: Mercedes-Benz Predecessor: SL (R231)

Published on 19 Nov 2022

SL turns 2+2 in attempt to steal sales from Porsche 911.

From R231 to R232 seems to be a small change, but it actually represents a step change in many ways. First of all, the SL is now responsible by the AMG division, so the familiar label SL500 finally rests into history. In recent years, the once popular luxury roadster faces dropping sales in a market trend that shifts from coupes and roadsters to SUVs and crossovers. Not even a brand as strong as Mercedes could resist the trend. On the one hand, it puts the S-class Coupe and Cabriolet into retirement. On the other hand, it hands over the SL-class to its AMG division so that the latter can build it on the platform of the next generation AMG GT to save money. This means, the R232 has a narrower but more upmarket range, consisting of SL43, SL55, SL63 and, later on, SL63 E Performance plug-in hybrid.

The second and third changes are reverting to soft top and 2+2 layout, both last seen on R129. Why? I guess the intent is to broaden its customer appeal. The AMG GT is already a 2-seater, so there is no reason to build another. By adding a pair of rear seats – even though they are suitable to only small children or most likely to be used as extra luggage space – the SL may steal sales from Porsche 911 Cabriolet. This would not have been possible with a bulky retractable metal roof. Modern soft top is not only lighter and more space-saving but also provides similar level of heat and noise insulation. That's why no one builds retractable metal roof anymore.

As it needs to accommodate rear seats, the new SL has its wheelbase stretched by 115 mm to 2700 mm. Even though the overhangs have been shortened, its 4705 mm length still exceeds the old car's by 74mm. It is also wider by 38 mm and taller by 44 mm. In short, this is the largest SL ever. This reflects on scale as well, even though it doesn’t look that way in photos. The SL55 has a DIN kerb weight of 1875 kg, 155 kg more than its predecessor SL500. The SL63 weighs 1895 kg, 125 kg heftier than the old car. Part of the cause is getting 4-wheel drive.

4-wheel drive and 4-wheel steering are standard on V8 models.

On the plus side, torsional rigidity of the chassis is lifted by 18 percent, while transverse and longitudinal rigidity are up by 50 and 40 percent, respectively. As before, the chassis is primarily an aluminum spaceframe structure, but now some parts are made of hot-formed high-strength steel (e.g. windscreen frames and pop-up roll over bars), magnesium (dashboard support) and a mixture of glass-fiber and carbon-fiber composites (transmission tunnel). Needless to say, all suspensions use forged aluminum links.

The exterior styling is a mixed bag in my opinion. Compared with its predecessor, it is far rounder and more refined in detailed design, while “Panamericana” grille gives it a more distinctive AMG look. On the downside, the waistline has been raised considerably and the tail slopes like 911 – it does look like a 911 from behind. It loses the low-slung, light and airy feel of traditional SL. AMG said it just returns to the roots of the original 1954 300SL, but hey, that one was originally a race car, even with gullwing doors!

If you think the rounder body returns better aerodynamics, you will be disappointed. The R232 has a drag coefficient of 0.325 for the base model, while its angular-looking predecessor managed 0.27. Sure, the fabric roof has some influence in it, but the fact that BMW 8-Series Cabriolet achieves 0.29 should give Mercedes some thought. Mercedes is right at the top of aerodynamics game, so we should expect better results.

A sloping back should generate a lot of aerodynamic lift, requiring active aerodynamic aids to counter. A retractable rear wing pops up from 50 mph and adjusts its angle according to speed. This is balanced by an active aero foil located at the underbody of front overhang, which extends downward by 40mm at speed.

Poor packaging means a smaller boot and nearly useless rear seats.

Both SL55 and SL63 are powered by the familiar 4.0-liter twin-turbo V8. Their chief differences are turbos and intake system. The SL55 produces 476 hp and 516 lbft, good for 183 mph and 0-60 in 3.8 seconds. The SL63 lifts those figures to 585 hp, 590 lbft, 196 mph and 3.5 seconds. They are so quick in standing start because they employ 4matic+ system and 9-speed MCT gearbox as standard. Yes, this is the first all-wheel-drive SL.

It is also the first 4-wheel-steer SL. To counter the longer wheelbase and extra mass, AMG equips all SL models with active rear-wheel steering as standard. The rear wheels steer in opposite direction at speeds up to 62 mph, sharpening turn-in and shortening turning radius.

Apart from more power, the SL63 gains active engine mounts, electronic-controlled LSD, larger wheels and wider tires, although it shares the same brakes with SL55. These brakes consist of 390mm discs and 6-piston calipers up front, 360mm discs and single-pot calipers at the rear. Ceramic brakes are optional.

To me, the most interesting part is suspension. The rear axle remains a multi-link setup as before, but the front suspension has been changed from 4-link to 5-link, which is housed entirely within the wheel rim. Being an exclusive AMG model, the SL employs conventional steel springs instead of the air suspension preferred by Mercedes' production cars. The SL55 is served with adaptive dampers, while SL63 introduces a new kind of suspension technology called "Active Ride Control". What is it? It sounds very similar in principle to the Tenneco Kinetic suspension used by McLaren. At each axle, the compression chamber of the right wheel damper is linked hydraulically to the expansion chamber of the left wheel damper. Vice versa, the expansion chamber of the right wheel damper is linked hydraulically to the compression chamber of the left wheel damper. There is a fluid accumulator in each hydraulic circuit, whose pressure can be changed by a pump. Meanwhile, flow rate at each chamber can be altered by control valves. By increasing or decreasing the fluid pressure in each accumulator, fluid can be pushed to the compressed wheel to resist body roll. By adjusting the flow rate via control valves, damping rate can be changed. In short, ARC is a hydraulic suspension that achieves the function of both adaptive damping and active anti-roll. As the car can skip a conventional anti-roll bar, ride comfort in straight is improved. Judging from the superb ride comfort and control displayed by McLaren, ARC is very promising. It is fitted to SL63 as standard but also available to SL55 as option.

Prominent transmission tunnel eats into passenger space. V8 is still a highlight.

Inside, the cabin gets more like a cocoon as you are now surrounded by a higher cowl and wider shoulders. The sense of airiness downgrades, although you are also less likely to be exposed to buffeting. In terms of packaging, it is a nightmare. The prominent transmission tunnel takes a lot of passenger space. The rear seat is nearly useless, but because of its existence, very tall drivers will complain for lack of legroom up front.

The interior design theme is far sportier than before, thanks in part to turbine-style air vents and a flat-bottom steering wheel. Instrumentation is implemented by a 12.3-in TFT screen housed in a small instrument pod. The 11.9-inch portrait touchscreen on transmission tunnel can be adjusted for an incline angle between 12 and 32 degrees to avoid reflection, something useful on an open car. Build quality looks classy, but some materials feel flimsy in touch. The seats are supportive yet comfortable, and completed with “Airscarf” neck warmer. Mercedes’ MBUX system is both powerful and fancy, though conventional physical switches would have been easier to use.

The fabric soft top can be opened or closed in 15 seconds and at speeds up to 37 mph (60 km/h). As before, a pair of protection bars pop up from the rear bulkhead during roll over. The soft top saves 21 kg compared with retractable metal roof, thus helps lowering center of gravity. Unfortunately, boot volume has taken a setback, and considerably. Theoretically, a soft top should save luggage space, but perhaps due to that 911 tail or the rear seats, the boot suffers. While the old car swallowed 345-485 liters depending on the position of metal roof, the new car leaves only 213-240 liters at the boot, even though Mercedes insists it is sufficient to place a pair of golf bags. The new SL is a packaging disaster.

Another disappointment is the wind blocker behind the seats, as you need to fit it manually in place. For a car costing so much money – £148K for SL55 and £172K for SL63, about 10 percent more than comparable 911 Cabriolet models – it sounds too cheap.

Even in Comfort mode, the suspension feels firm, more sports car than grand tourer.

On the Road

It is hard to define the new SL in a few words. It is a very sophisticated car, equipped with 4WD, 4WS, a complicated hydraulic suspension and 5 driving modes (Slippery, Comfort, Sport, Sport+ and Race), plus an Individual mode to let you customize everything. The stability control alone has 4 modes. Immersed in the snug cockpit, surrounded by flashy screen graphics and data and looking forward through a shallow windscreen over the long bonnet, the driving environment feels definitely more serious, or even stressful, than in any old SLs bar the first generation race machine.

First thing to notice is the impressive rigidity of the chassis, but as soon as you ride over bumps, you also notice a stiffness not seen in any of its predecessors. Now you realize this is a thoroughbred AMG rather than a Mercedes SL badged AMG. On smooth highway, the SL feels composed and highly stable. On poorer surfaces, however, it borderlines on the acceptability of most drivers. Even in Comfort mode, the suspension feels firm, more sports car than grand tourer. Road roar from the fat rubbers also hurts its cruising refinement.

On the flipside, the handling is much improved, particularly SL63. It grips hard, resists roll remarkably and turns in responsively. The steering is very direct at only 1.75 turns lock to lock, if not totally transparent. The car is also well balanced, although the front axle takes 54 percent of all weight. However, it is also less talkative and less interactive with the driver than a 911, Ferrari Roma, Portofino or Aston Martin DB11 Volante. Despite the tremendous power offered by the twin-turbo V8, there is so much grip to overcome. It is harder to oversteer and flow in the twisty. The only undisputable strength is the V8 engine, but you can get a more powerful version with less money in the form of E63 S.

The new SL is neither a true sports car nor a competent GT. It tries to deliver the best of both worlds, but ends up satisfying neither sides. It seems to me that Mercedes has lost its own vision in an attempt to replicate the success of Porsche 911. The SL used to be a luxury-oriented, laid-back roadster. There is no point to try to be a Mercedes 911 or a 2+2 version of AMG GT. If Mercedes wants to broaden its appeal, it should shift towards the GT side, taking inspiration from Maserati GranCabrio or Bentley Continental GTC, especially as the S-class Coupe has retired.

Verdict:

Published on 19 Nov 2022

SL43

Some might accept a 4-cylinder SL, but at £108,000, it is another matter.

Ridiculously, Formula One is ditching the complex MGU-H electric turbo from the next generation power units coming out in 2026, but Mercedes-AMG is introducing the same thing to its road cars. The new SL43 is the first road car to employ electrified exhaust gas turbocharger, and Mercedes is probably the only manufacturer to do so before the ultimate demise of internal combustion engines.

The said engine is based on the existing M139 2.0-liter four-cylinder that powers A45. In that application, it employs a large turbo to produce up to 421 hp and 369 lbft of torque. On the SL43, however, the focus is not on big power but refinement and drivability. By replacing the conventional turbo with a smaller but electrified turbo, it can be spooled up immediately on throttle, eliminating turbo lag. The result is 381hp at 6750 rpm and 354 lbft of torque from 3250 to 5000 rpm. The latter compares fabourably with A45 S, whose full torque does not arrive until 5000 rpm.

Electric compressor is not new, of course. Mercedes, Audi, Land Rover and Hyundai have such devices on their road-going engines. However, these are actually electric superchargers instead of electric turbochargers, because they don't have anything to do with exhaust gas. Exhaust gas turbo is still the most efficient way to recapture the energy that would be otherwise wasted in exhaust. The only downside is turbo lag.

In Formula One engines, the MGU-H (Motor Generator Unit - Heat) is actually a turbocharger added with a thin electric motor between the compressor wheel and exhaust turbine. At lower revs when the exhaust gas is not sufficient to drive the turbine, the electric motor takes the responsibility to spool up the turbine and produce boost. When the engine revs up and produces more exhaust gas than the turbocharger needs, the MGU-H acts as a generator, recapturing the heat energy from exhaust stream that would be otherwise released from the wastegate. It sounds easy, but the most difficult is to minimize the size of this electric motor to fit into the limited space of turbocharger while is also heat-resisting enough to sustain the high temperatures found in a turbocharger.

SL43 is the first production car to get F1-style electrified turbo. Probably the last one as well.

After succeeding in F1 racing for so many years, Mercedes-AMG finally transfers its know-how to production engines, even though that could be short-lived. Its electric exhaust gas turbo is developed in partnership with Garrett and produced by the latter. Its chief function is to cut turbo lag and maintain a linear power delivery. However, it is not known whether it includes the energy recovery function of MGU-H, as the press release did not mention. Its power comes from a 48V electrical system, which can be supplied by the belt-driven starter motor generator of mild-hybrid system.

On the SL43, the M139 is mounted longitudinally and drives the rear wheels only, unlike the V8-powered SL55 and SL63 which have standard 4WD. It takes 4.7 seconds to go from 0-60 mph, and top speed is 171 mph. No match for the V8 siblings, of course, but pretty good for an entry-level SL model.

However, downsizing from 8 to 4 cylinders is a step too far, and I suppose not many buyers will be pleased, especially as this one costs £108,000. A 911 Carrera Cabriolet undercuts it by nearly £10K yet offers 6-cylinder boxer power and higher performance. No matter how technologically advanced it is, a four-cylinder is still a four-cylinder. Its smoothness and sound are no match for a proper 6-cylinder engine, such as Mercedes’ own 3.0-liter straight-six with turbo and electric supercharger. That one produces more power and torque as well – 435 hp and 383 lbft. It would be a nice fit under the long bonnet of the SL. Could have revived the legendary 300SL badge, too. Yes, the SL43 is not the first four-cylinder SL, but the last time Mercedes built such an SL was almost 60 years ago, and the tiny 190SL was never regarded as a true SL. The new one will be the same.

Verdict:

Published on 4 Aug 2024

SL63 S E Performance

Excess power, excess luxury.

Since 1992, the flagship model of Mercedes SL-class had been powered by V12 engine, badged as either 600SL, SL600 or SL65. Extra weight means they were not necessarily quicker than SL500 or SL63, while inferior balance might turn off keener drivers. However, the V12 models were the symbol of excess luxury. You buy them just because you can afford.

Following the retirement of Mercedes V12 engine, the excess luxury model becomes SL63 S E Performance. Considering the regular SL63 already possesses 585 horsepower and good for 0-60 in 3.5 seconds, I don’t think you really need more power and performance on an open-top car. However, there are always some wealthiest customers willing to pay the extra to make them look different. Mercedes-AMG also needs this halo model to keep it at the very top of performance luxury motoring.

The powertrain of this car is directly transplanted from its hard-top sibling GT63 S E Performance. It has the usual twin-turbo V8 up front, but dialed up to 612hp. The rear axle is added with a 6.1kWh battery pack, a 204hp electric motor and a 2-speed gearbox. Combined output is 816 horsepower, accompanied with an astonishing 1047 lbft of torque. This conversion adds 225 kg to the kerb weight, but the car is still able to crack 60 mph in 2.85 seconds. Not long ago that was the territory of hypercars.

Predictably, the SL63 S E Performance is so quick that you might feel sick in full-bore acceleration. However, it is not a scary experience, since the two power sources mate seamlessly, and the 4-wheel-drive system offers enough traction to cope with. The hydraulically interconnected suspension keeps body roll in check in sportier modes. Moreover, the extra weight is placed at the back to help balancing the car, so it is not like the SL65, whose extra weight was all at the nose.

Nevertheless, the plug-in hybrid is still a compromised package. You cannot deny that 2120 kg has some adverse effect on ride and handling. In Comfort mode it jumps up and down over bumpy surfaces. Sport mode calms it down but ride comfort suffers more noticeably than the lesser SL models, while Sport+ is a pointless function suitable to only racing tracks.

Compared with its hard-top GT sibling, the compromise is more obvious still. The SL is no heavier, surprisingly, but it loses almost 40 percent chassis rigidity while both the front track and front tires are narrower. Its adaptive damping is tuned to be a bit more relaxing, allowing more body roll and less incisive cornering. The steering feels even more remote. The hypercar performance is not matched with adequate engagement.

While this is a so-called “plug-in hybrid”, the small battery offers an electric range of only 8 miles, rather pointless. AMG said the battery has remarkable power density, but I don’t know why it still eats half of the boot, leaving only 110 liters of luggage space. Fortunately, the useless rear seats can be used for storing luggage.

The name SL used to mean Sport Light. Now weighing in excess of 2.1 tons and costing almost £200K, I think it should refer to Super Luxury instead.

Verdict: