Following the two variants with V8 engines, Mercedes-AMG presents the SL 43 a technically innovative entry-level model of the newly developed roadster icon. Under the bonnet of the open-top 2+2-seater with fabric soft top is an in-line four-cylinder petrol engine with two litres displacement that provides the befitting propulsion. This is the first time in the world that an electric exhaust gas turbocharger is being used in a production vehicle. This technology comes from Formula 1™. The system in the SL 43 is a direct derivative of the development successfully used by the Mercedes-AMG Petronas F1 Team for many years in the premier class of motorsport. The new form of turbocharging guarantees particularly spontaneous throttle response across the entire rev range, thereby offering an even more dynamic driving experience while increasing efficiency at the same time. The turbocharger is operated via the 48-volt electrical system, which also feeds the belt-driven starter-generator (RSG). As a result, the Mercedes-AMG SL 43 has an output of 280 kW (381 hp) and a maximum torque of 480 Nm, plus an additional short-term boost of 10 kW (14 hp) from the RSG in certain driving situations. The new entry-level model in the SL family also shines with extensive standard equipment. In addition, numerous options that enhance comfort and safety offer a wide range of possibilities for individualisation.
“In its long history, the SL has repeatedly set technological milestones. For example, while the legendary 300 SL Gullwing in 1954 was the world’s first series-produced passenger car with direct petrol injection, the new Mercedes-AMG SL 43 is now the very first series-produced vehicle with an electric exhaust gas turbocharger. With this technology, the SL also has an outstanding performance range in its entry-level version”, says Philipp Schiemer, Chairman of the Board of Management of Mercedes-AMG GmbH.
“The electric exhaust gas turbocharger is a fascinating example of the extensive transfer between Formula 1 technology and the development of production vehicles. In implementing this in conjunction with our powerful M139 four-cylinder, we were also able to draw on the enormous wealth of experience of our colleagues at Mercedes-AMG High Performance Powertrains. The technology increases agility and thus driving fun, while at the same time improving the efficiency of the drive system”, says Jochen Hermann, Chief Technical Officer of Mercedes-AMG GmbH.
In the 70 years of its development history, the SL experienced the transformation from a thoroughbred racing car to an open-top luxury sports car – and has long enjoyed legend status, not least for this reason. The new Mercedes-AMG SL now marks another milestone in the model’s history. It combines the distinct sportiness of the original SL with the unique luxury and technological excellence of the modern Mercedes-AMG models. As the new entry-level model in the series, the SL 43 is a particularly good example of this. It is the world’s first series-produced vehicle to feature an electric exhaust gas turbocharger. This technology comes directly from Formula 1™ and solves the trade-off between a small, fast responding supercharger that nevertheless achieves comparatively low peak power and a large supercharger with high peak power that only responds delayed. With its innovative engine concept, the new entry-level model of the 2+2-seater roadster is aimed more at particularly tech-savvy buyers. With its combination of a comparatively light four-cylinder engine on the front axle and rear-wheel drive, the SL 43 also displays distinctly discrete handling characteristics.
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. In combination with the internally named M139 two-litre, in-line four-cylinder engine, the innovative technology in the SL 43 produces a rated output of 280 kW (381 hp) at 6750 rpm. The maximum torque of 480 Nm is available between 3250 rpm and 5000 rpm. Depending on the situation, the system also guarantees an additional boost of 10 kW (14 hp) for a short time from the belt-driven starter generator (RSG). The second-generation RSG also functions as a mild hybrid in the 48-volt on-board electrical system, which in addition to the temporary power boost enables functions such as gliding mode and energy recovery for maximum efficiency. At the same time, the 48-volt technology also increases comfort, as the transitions between the start-stop function and the gliding mode function are almost imperceptible.
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 four centimetres thin 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 stream starts to drive it conventionally. This significantly improves immediate response from idle speed and across the entire engine speed 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 revs. This also increases agility and optimises acceleration from a standstill. Even when the driver takes their foot off the accelerator or applies the brakes, the technology of the electric turbocharger is able to maintain the boost pressure at all times. This ensures so that a continuous immediate response.
The four-cylinder engine known as the M139, which has long been used transversely in Mercedes-AMG compact models without an electric exhaust turbocharger, is positioned longitudinally in the SL 43. In the entry-level model in the SL series, which always features rear-wheel drive, it is also combined with the AMG SPEEDSHIFT MCT 9G transmission (MCT = Multi-Clutch Transmission) for the first time. A wet start-off clutch replaces the torque converter. It reduces weight and, thanks to its lower inertia, optimises 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 if required. In addition, the intermediate throttle function in the “Sport” and “Sport+” driving modes delivers a particularly emotionally appealing gearshift experience. There is also the RACE START function, which ensures optimal acceleration from a standstill. The driving performance is up to par: from a standstill, the SL 43 accelerates to 100 km/h in just 4.9 seconds if required, and the top speed is 275 km/h. In addition to the performance it offers, the entry-level model of the series is also distinguished by comparatively low consumption and emission figures.
The new SL of the R232 series is based on a completely new vehicle architecture developed by Mercedes-AMG. The new dimensional concept allows a 2+2 seating configuration for the first time since 1989 (Mercedes SL model series R129). This makes the new SL even more versatile. The rear seats increase daily practicality and offer space for people up to 1.50 metres tall (up to 1.35 metres with a child seat). Constructed from lightweight aluminium composite, the chassis consists of an aluminium space frame with a self-supporting structure. The design guarantees maximum rigidity and is thus the perfect basis for precise driving dynamics, high comfort, optimal packaging and sporty body proportions. The aim of the body shell architecture is to realise the typical AMG Driving Performance with a focus on lateral and longitudinal dynamics, while at the same time meeting the high standards on comfort and safety. In the new SL, the intelligent material mix enables the highest possible rigidity at a low weight. The materials used include aluminium, magnesium, fibre composites and steel, from which the windscreen frame is made, for example. This serves as roll-over protection in conjunction with the roll bar system behind the rear seats, which pops up at lightning speed when needed.
