Mercedes-AMG presented the SL 43, a technically innovative new entry model for the AMG SL roadster, arriving in US dealerships in summer 2023, starting from $109,900. Under the hood of the open-top 2+2-seater is an AMG-enhanced 2.0-liter turbocharged M139 engine featuring an electric exhaust gas turbocharger. This technology is a direct derivative of the development successfully used by the Mercedes-AMG Petronas F1 Team.

Mercedes-AMG SL 43 (European model shown)

The new form of turbocharging guarantees spontaneous throttle response across the entire rpm range to deliver an even more dynamic driving experience. The turbocharger is operated via the 48-volt electrical system, which also feeds the belt-driven starter-generator (RSG). As a result, the SL 43 has an output of 375 hp and a maximum torque of 354 lb-ft (481 N·m).

The electric exhaust gas turbocharger solves the conventional trade-off between a small, responsive turbocharger yielding a lower total output and a large turbocharger capable of high peak power with less responsiveness.

The operating principle of the electric exhaust gas turbocharger is based on the same technology used by the Mercedes-AMG Petronas F1 Team. An electric motor around 1.6 inches (4 cm) is integrated directly on the turbocharger shaft between the turbine wheel on the exhaust side and the compressor wheel on the intake side. Electronically controlled, this drives the shaft of the turbocharger directly and thus accelerates the compressor wheel before the exhaust gas flow takes over the drive in a conventional manner.

This significantly improves immediate response from idle and across the entire rpm range. The combustion engine responds even more spontaneously to accelerator pedal input, while the overall driving experience is more dynamic.

In addition, the electrification of the turbocharger enables higher torque at low rpms. This also increases agility and optimizes acceleration from a standstill. Even when the driver takes their foot off the accelerator or applies the brakes, the innovative technology is able to maintain the boost pressure at all times to ensure a continuously direct response.

The turbocharger, which is operated via the 48-volt on-board electrical system, works at speeds of up to 170,000 rpm, which enables a very high airflow rate. The turbocharger, electric motor and power electronics are connected to the combustion engine’s cooling circuit to create an optimal temperature environment at all times.

The engine uses a combination of direct gasoline injection and intake manifold injection for mixture formation.

In combination with the AMG-enhanced M139 engine, the innovative technology in the AMG SL 43 produces its output of 375 hp at 6,750 rpm. The 354 lb-ft of torque is available between 3,250 rpm and 5,000 rpm.

The second-generation RSG also functions as a mild hybrid in the 48-volt on-board electrical system enabling functions such as gliding and recuperation to maximize efficiency. The 48-volt technology also increases comfort, as the transitions between the start-stop function and gliding mode function are almost imperceptible.

The M139 engine is positioned longitudinally in the AMG SL 43. In this exclusively rear-wheel drive model, it is combined with the AMG SPEEDSHIFT MCT 9G transmission (MCT = Multi-Clutch Transmission), in which a wet start-off clutch replaces the torque converter. This reduces weight and, due to its lower inertia, optimizes the response to accelerator pedal input, especially during spurts and load changes. The elaborately calibrated software ensures extremely short shift times as well as fast multiple downshifts as required. In addition, the intermediate throttle function in the “Sport” and “Sport+” driving modes delivers an emotionally appealing gearshift experience.

The AMG SL 43 accelerates from 0 to 60 mph in 4.8 seconds on its way to an electronically limited 170 mph top speed.

The new SL model range is based on a completely new vehicle architecture developed by Mercedes‑AMG. Constructed from lightweight aluminum composite, the chassis consists of an aluminum space frame with a self-supporting structure. The design offers maximum rigidity and the basis for precise driving dynamics, high comfort, optimal packaging and sporty body proportions. The aim of the body shell architecture is to realize the driving performance typical of the Mercedes-AMG brand with a focus on lateral and longitudinal dynamics, while also meeting high standards for comfort and safety.

The intelligent material mix enables the highest possible rigidity at a low weight. The materials used include aluminum, magnesium, fiber composites and steel, from which the windshield frame is made. This serves as roll-over protection in conjunction with the roll-bar system behind the rear seats, which pops up when needed.

Compared to the previous model series, the torsional rigidity of the body shell structure is increased by 18%. The transverse rigidity is 50% higher than the already outstanding value of the AMG GT Roadster, while the longitudinal rigidity is 40% higher. The weight of the body shell without doors, hood and trunk lid is approximately 595 lbs (270 kg). Together with the low center of gravity, the systematic lightweight construction ensures optimal driving dynamics.