• The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary

The SL43 ditches the traditional V-8 found in other SL models for a four-cylinder and an electric exhaust turbo – the first of its kind on a production car.

It’s been about six months since Mercedes revealed the all-new SL Roadster – a car that is designed to make up for the mundane car that came before it with a number of unique features and enhancements. A new AMG GT coupe is expected to arrive as a sidekick to the SL, and an entry-level version of the SL has been rumored for months. Now, that car has arrived, and the rumors were right – it’s powered by a four-cylinder engine. This isn’t your typical four-cylinder engine, though, and it still boasts some impressive power thanks to clever engineering.

The Four-Cylinder Mercedes-AMG SL43

The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary
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Under that long, sleek hood of the SL43 sits AMG’s turbocharged M139 2.0-liter inline-four. This engine is very familiar and is used widely within Merc’s lineup, but this specific engine is different, thanks to the impressive use of F1 technology. While other versions of the M139 inline-four feature your typical exhaust-driven turbocharger, the SL43 has an electric exhaust gas turbocharger. This is the F1 tech I’ve been telling you about, and it’s powered by a 48-volt electric system. The basis behind this electric gas turbocharger is simple. The turbo’s turbine is spooled up by an electric motor until the engine is up to speed enough for the exhaust to take over. This essentially eliminates turbo lag altogether and, as Mercedes puts it, allows the engine to offer “particularly spontaneous throttle response across the entire rev range.” It also helps to increase efficiency, so there’s that too.

The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary
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All told, this engine is able to put out 381 horsepower at 6,750 rpm and 354 pound-feet of torque as low as 3,250 rpm before it starts to fizzle out at 5,000 rpm.

The starter-generator system throws in an extra 14 horsepower in short bursts, so technically the SL43 is a mild hybrid, even if it’s not being advertised as such. Power is sent exclusively to the rear wheels via a nine-speed MCT. The end result when you put the hammer down is a 0-62 mph sprint in 4.9 seconds and a top speed of 171 mph.

The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary
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Those are pretty impressive numbers for something with a four-banger under the hood, and it speaks to the impressive engineering of the SL and the M139 engine. We’re talking about half the turbos, half the cylinders, and half the displacement, but the end performance is far from halved. Outside of this, Mercedes claims that the smaller engine’s reduced weight compared to the V-8 gives the SL43 unique and dynamic handling that is totally different from the V-8 models. Lighter torsion bar stabilizers are also part of the equation, which makes it seem like AMG was trying to make this the lighter, more agile, driver’s car.

The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary
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As for the SL43’s appearance, you won’t see much that set it apart from its stablemates. The vents in the lower front fascia are a bit different, while the rear bumper is new smooth without any rear vents whatsoever. Oval exhaust tips are unique to the SL43 as are the obligatory SL43 badging. 19-inch wheels come standard but you can opt for 20- or 21-inch units if you want. That said, the 43 doesn’t ditch much in terms of features compared to the SL55 and SL63. It can still be optioned with rear steering, numerous drive modes, the Dynamic Plus Package, and let’s not forget about the standard tech-laden cabin with lots of screen real estate and the latest MBUX system.

The Mercedes-AMG SL43 Is As Strange As It Is Revolutionary
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As of now, there’s no word on pricing or availability, but Mercedes plans to release this information closer to the start of production.

Robert Moore
Robert Moore
Editor-in-Chief and Automotive Expert - Robert.moore@topspeed.com
Robert has been an auto enthusiast his entire life. He started working cars at a young age, learning the basics from his father in the home garage on the weekends. As time went on, Robert became more and more interested in cars and convinced his father to teach him how to drive when he was just 13 years old. Robert continued working on cars in his free time and learned as much as he could about engines, transmissions, and car electrical systems, something that only fed his curiosity more and eventually led him to earn a bachelors degree in automotive technology with a primary focus on engine performance and transmission rebuilding.  Read full bio
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