Mercedes-AMG SL 43 (R232) — the roadster built entirely by AMG

Two things about the SL 43 have never happened before in the model’s history. For the first time in seventy years there is a four-cylinder engine under the bonnet of an SL. And for the first time the SL was developed from start to finish not by Mercedes-Benz engineers but by Affalterbach. The easiest way to tell whether that’s good or bad is from behind the wheel — but first it’s worth understanding what exactly came out of it.

In short. The Mercedes-AMG SL 43 R232 is a soft-top roadster, 2+2. M139, turbocharged 2.0-litre inline four. Rear-wheel drive. 0–100 km/h in 4.7 s (current engine version), top speed 275 km/h.

What this car is

The R232 is the eighth generation of the SL, counting from the W198 of 1954. Formally it’s the successor to the R231; in reality it’s a different car. Previous generations were designed at Mercedes-Benz, and AMG received a finished car and developed it into the 55, 63 and 65 versions. With the R232 the scheme was turned on its head: the project was run in Affalterbach from a clean sheet, rethinking the suspension, packaging and body architecture from scratch. AMG’s technical director compared the approach to how the SLS AMG was once created.

The result shows in the stiffness figures. The R232 body is 18% stiffer in torsion than the R231’s; transverse stiffness is 50% higher and longitudinal stiffness 40% higher than the AMG GT Roadster’s. The price was paid in mass: the bare body gained around 270 kg over its predecessor.

Another change, less visible in the specifications: the SL has returned to a soft top. The folding metal roof was introduced on the R230 in the early 2000s, and the argument about a ‘convertible with a tin roof’ dragged on until the very end of the R231’s life. The R232 has closed that argument.

And the SL is a 2+2 again. The rear row has returned to the model for the first time since 1989 — though there’s exactly enough room to throw a bag there or put a child in for a short hop. An adult can’t ride in the back, and you shouldn’t count on four when booking. On the other hand, the boot is no longer the only place for belongings, and on a trip of several days that makes itself felt.

Technical details

The SL 43 is the only R232 version with rear-wheel drive. The senior SL 55 and SL 63 come only with 4MATIC+ all-wheel drive, and this distinction matters more than it seems: the junior SL is simpler not out of frugality but by design.

The key technical component here is the turbocharger. Built into its housing is an electric motor about forty millimetres thick, mounted directly on the turbine shaft. It spins the shaft up from within, without waiting for the exhaust flow to gather strength. Power comes from the 48-volt on-board system.

The difference from a conventional turbo engine is simple: there, the turbine responds only to exhaust gas, hence the hole at low revs and the lag in response. Here there is no hole, and boost is maintained even when you lift off the throttle. The difference from the electric supercharger AMG fits to some other engines is subtler: that one works as a separate unit, whereas here the electric motor is built into the turbocharger itself and turns its standard shaft.

The press calls the solution Formula 1-inspired, and the kinship is real — F1 hybrid power units carry an electric motor-generator on the turbine shaft. But the kinship is conceptual. AMG made a literal transfer of the technology, with energy recovery, only in the AMG ONE hypercar. In the SL 43 the electric motor eliminates turbo lag and stops there.

On power it’s worth being precise. At the start of sales in 2022 AMG quoted 376 hp; after the engine update the official figure is 421 hp and 500 Nm. Which version a particular car has depends on its year of manufacture — confirm when booking.

How it drives

This is where it gets interesting, because the press verdicts split exactly the opposite way from what you’d expect from the price list.

The senior V8 versions, the SL 55 and SL 63, are described by Top Gear and evo reviewers as over-engineered. The steering is called two-dimensional and uninformative, the body wanders on uneven tarmac, and the set of systems — adaptive anti-roll bars, all-wheel drive, rear-axle steering — hinders trusting the car more than it helps. The complaint isn’t about speed: there’s enough of it. The complaint is that behind all the layers of electronics, the dialogue with the driver gets lost.

Against this backdrop the SL 43 turned out to be the most coherent model in the range. It’s lighter, it has fewer systems between the steering wheel and the road, and that is exactly why it’s called the most ‘fluid’ and engaging SL of the generation. Top Gear says outright that the four-cylinder engine hasn’t spoiled the car: thanks to lower mass and simpler electronics, the SL 43 drives in a more composed way than the senior versions.

There’s a caveat too, and it’s worth accepting up front. This engine has none of the charisma of a six- or eight-cylinder rival like the Porsche 911. The sound is the sound of a good turbo four, nothing more. evo draws a harsher conclusion from this and denies the SL 43 the status of a proper driver’s car altogether, judging the loss of engine character to be decisive. Both views are fair; the question is what you value more — precision or voice.

A separate word on the genre itself. The SL has historically wavered between sports car and grand tourer, and that question is older than the AMG era. Even before development was handed to Affalterbach, the SL was described as a car that rivals the 911 in image but not in substance. The R232 hasn’t settled that argument. The SL 43 is a fast and pleasant open GT, not a track-day tool, and that is exactly how it should be treated.

Interior and practicality

A soft top instead of a metal roof gives two things at once: less mass over the rear axle and more space beneath it. Boot space with the roof up and down doesn’t differ as dramatically as on roadsters with a folding hard top.

The press does have complaints about the finish — in evo’s SL 55 review the design is called too generic and the trim is described as drifting into glitter. This is put down to a shift in priorities towards the AMG performance brand at the expense of the SL’s traditional luxury character. How critical that is depends on taste: the quality of the materials raises no questions; the question is about the manner.

For a trip of several days the picture is this: two travel comfortably, belongings for two fit, and the rear row works as an extra shelf. A third and fourth passenger are not what this car is about.

In Czech conditions

An open roadster in the Czech Republic is a seasonal but perfectly workable proposition. A few things are worth keeping in mind.

Speed limits. In built-up areas — 50 km/h, outside built-up areas — 90 km/h, on a road for motor vehicles — 110 km/h, on the motorway — 130 km/h. The 275 km/h top speed remains a line in the specifications in the Czech Republic: there are no unrestricted motorways here; the nearest are in Germany.

Alcohol. Czech law sets no permissible threshold at all. Not 0.3 or 0.5 per mille but absolute zero: getting behind the wheel with any alcohol in your system is prohibited, and so is drinking it during the journey. This is one of the most common misconceptions among drivers arriving from Germany.

Lights. Dipped headlights or daytime running lights are on all year round, regardless of the time of day or the weather.

Motorway vignette. Since 2021 the Czech motorway vignette has been electronic, with no physical sticker — it’s an entry in a register tied to the registration number of a specific car. It can’t be transferred to another car.

Winter. From 1 November to 31 March winter tyres are mandatory if there is snow, ice or frost on the road, or if the weather gives reason to expect it. The minimum tread depth for a winter tyre in the Czech Republic is 4 mm, which is higher than the neighbours’: in Slovakia the threshold is 3 mm. For a rear-wheel-drive roadster, a winter trip into the mountains is a bad idea regardless of what the law says.

Where to go. A good direction for the SL 43 is Karlovy Vary via the D6, about 115 kilometres and a little over an hour each way. The route is mixed: part of it is already full motorway, including the new section near Hořesedly with a 130 km/h limit, and part is still a four-lane first-class road with a lower limit. For an open roadster that’s a happy combination — the pace changes, there’s something to do with your hands, and the route doesn’t turn into two hours of straight highway.

Who it suits and who it doesn’t

It suits you if you’re travelling as a pair, value precision of control over engine volume, and want an open car that doesn’t wear you out on a long run. The SL 43 is a rare case where the junior version in the range is more interesting than the senior ones, and that’s not marketing language but the converging view of several independent publications.

It doesn’t suit you if you need sound. A turbo four doesn’t sing, and no electric turbocharger changes that. It doesn’t suit a party of four adults — the rear row is token. And it’s not the best choice for a winter trip into the mountains: rear-wheel drive plus an open body gives a predictable result.

If you want an open top with six-cylinder character, the more logical choice is the BMW M4 Competition Cabrio. If you want an open top without the sporting element, there’s the Audi A5 Cabrio. Current terms for the SL 43 itself are on the model page.

FAQ

Is it true the SL 43 has only four cylinders? Yes, and it’s the first time in the SL’s history since 1954. The M139 engine is a turbocharged 2.0-litre inline four. This is compensated not only by forced induction but also by lower mass: the SL 43 is lighter than the senior eight-cylinder versions and, according to the press, drives in a more composed way than they do.

How many people fit in the SL 43? Formally four: the R232 brought back the rear row, which the SL hadn’t had since 1989. In practice the rear seats are good for bags or a short trip for a child — an adult is uncomfortable there. You shouldn’t plan a trip for four in this car.

What is an electric turbocharger and what is it for? An electric motor is built into the turbocharger housing and spins its shaft from the 48-volt system without waiting for the exhaust gas flow. The practical point is that there’s no hole in the torque at low revs and no lag in throttle response. Boost is maintained even during a brief lift off the throttle.

How does the SL 43 differ from the SL 55 and SL 63? Engine and drive. The SL 43 is four-cylinder and the only rear-wheel-drive model in the range; the SL 55 and SL 63 are eight-cylinder and come only with 4MATIC+ all-wheel drive. The difference isn’t just power: the SL 43 has fewer electronic systems between the steering wheel and the road, and some reviewers consider it more engaging for that reason.

Can you drive the SL 43 in winter? Technically yes, provided you follow the Czech winter tyre rule from 1 November to 31 March. In practice a rear-wheel-drive open roadster is not a car for snowy mountain roads. For a winter trip to the Krkonoše or Šumava it’s more sensible to take an all-wheel-drive car.

The 275 km/h top speed — can it be used anywhere? Not in the Czech Republic. The motorway limit is 130 km/h, and it applies across the entire network without exception. Unrestricted Autobahn sections exist only in Germany, and the nearest of them are about an hour and a half from Prague via the D8.