The first SL with 4 cylinders: Mercedes-AMG SL 43

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Mercedes has premiered the first SL with a 4-cylinder engine. It’s called the Mercedes-AMG SL 43 and uses an electrically driven turbo for the first time.

A 4-cylinder Mercedes-AMG SL seemed like a utopia a few years ago, especially since the new generation was developed by AMG. But we are not talking about a regular 4-cylinder engine, but the first thermal engine with an electrically driven turbo, as part of AMG strategy to electrify the classic propulsion systems.

Mercedes already uses this solution of an electrically driven turbo in Formula 1 and this is an example of technology transfer from Formula 1 to series production. The technology is the same used by the Mercedes-AMG Petronas F1 Team. An electric motor only 4 cm thick is integrated directly on the turbine shaft between the turbine wheel on the exhaust side and the compressor wheel on the intake side. Electronically controlled, this motor drives the turbine shaft directly and accelerates the compressor wheel before the exhaust gases drive it in the conventional way.

This gives an instant boost to the turbine.The turbine operates at 170,000 rpm powered by the on-board 48V network.

The engine used in the SL 43 is a 2-litre M139 engine producing 280 kW (381) HP at 6750 rpm and a maximum torque of 480 Nm, constant between 3250 and 5000 rpm. An integrated belt-driven starter-generator provides an additional 10 kW (14 HP) for short time and support the engine at start and at accelerations.

The engine is mated to an AMG Speedshift MCT 9G automatic transmission in which a wet clutch has replaced the classic torque converter. This  helped to reduce weight and offers very quick gear changes and the ability to downshift several gears very quickly.

The new Mercedes-AMG SL 43 runs on 19-inch wheels and optional 20-inch or 21-inch wheels from V8 models are available.

The SL 43 also features all the active aerodynamics of the V8 models:
– Airpanel active air control system with horizontal louvres behind the upper air intake which are electronically controlled
– retractable rear spoiler which changes its position depending of the driving status (five different angles from 80 km/h)
– Aerodynamics package with larger flics on the front and a large diffuser at the rear.

Like the V8 versions, the Mercedes-AMG SL 43 has multilink front suspension with 5 arms arranged entirely within the wheel and comes standard with AMG Ride Control adaptive suspension. Integral steering where up to 100 km/h the rear wheels steer in the opposite direction to the front wheels is on the option list.

Five driving modes are available – Slippery, Comfort, Sport, Sport+ and Individual plus Race mode if the optional AMG Dynamic Plus package is ordered.

With a kerbweight of 1810 kg, the 2+2 seater model with soft top (the textile roof is 21 kg lighter than the former hardtop and has also helped lower the centre of gravity), the Mercedes-AMG SL 43 is 140 kg lighter than the Mercedes-AMG SL 55 V8 model. Although it only has a 4-cylinder engine, it accelerates from 0 to 100 km/h in just 4.9 seconds and reaches a top speed of 275 km/h.

ModelSL 43
Engine/no. of cylindersL4, electric turbo
Displacement (cmc)1991
Max. power/revs (HP/rpm)381/6750
Max. torque (Nm/rpm)480/3250-5000
Tractionrwd
Transmission9 gears, automatic
L x W x h (mm)4705 x 1915 x 1359
Wheelbase (mm)2700
Boot volume (l)213-240
Kerbweight (kg)1810
Acceleration 0-100 km/h (s)4.9
Top speed (km/h)275
Fuel consumption (WLTP) (l/100 km)9.4-8.9
CO2 emissions (g/km)214-201