New Mercedes SL 43, convertible with a 2-liter F1 turbo

Mercedes-AMG SL43

After the two SLs with a V8 engine, Mercedes-AMG is expanding its offer and launching the roadster with the 2-liter turbo petrol engine. A known unit, were it not for the absolute novelty of the electric turbo. The operation is inspired by the MGU-H of Formula 1

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2 liter engine for the SL 43

The four-cylinder engine delivers 381 horsepower and 480 Nm of torque and is supported by a 48 volt mild hybrid, with belt starter-generator. The latter is able to provide an additional 14 horsepower in the boost phases, as well as it is able to recover energy in the deceleration phases and to extend the soaring with the engine off.

Well, so far nothing new. Where, on the other hand, it is worth concentrating the technical narrative is on the turbocharger. We are not exactly at the Formula 1 MGU-H technology but we’re getting pretty close.

How the electric turbo works

The electric turbo proposed by Mercedes on the SL 43 AMG is able not only to reset the turbo lag but to combine the advantages of a large turbo (greater development of boost pressure, therefore more power) to a compact turbocharger, quick to reach pressure supercharging: therefore, very low thrust delay, albeit with a compromise on lower power output.

Here, the Mercedes-AMG electric turbo is characterized by the installation of an electric motor – a 48-volt actuator – of 4 centimeters and positioned on the shaft that joins the turbine (exhaust side, activated by flue gases) to the compressor (accelerates the air, compresses it in the intake ducts).

The electric motor is able to operate the compressor at the correct rotation speed, with a maximum value that can reach 170,000 rpm.

This causes that the driver always has the turbo at the ideal operating speed to develop the greatest torque (constant 480 Nm between 3,250 and 6,750 rpm) and power possible. The electronics coordinate the work of the electric motor and the speed of rotation of the turbocharger.

Turbo always under pressure, even after braking

The advantage is greatest in the driving phases in which the accelerator is released or after braking. These are the transients in which the rotation of the turbocharger is reduced due to the decrease in the pressure of the exhaust gases. The contribution of the electric motor ensures that the rotation speed of the turbocharger remains high and at the gas pressure it produces the maximum possible thrust.

The differences between electric turbo, MGU-H and electric compressor

It must be said how Mercedes-AMG takes the palm of the first brand to offer this electric turbo configuration on the market. In recent years they have emerged Ferrari patents on a similar and even more advanced solution, with turbine and compressor physically separated by the presence of the electric motor. What the Mercedes SL 43 offers is inspired by the F1 turbo hybrid even if there is not the same level of technical complexity, given the energy recovery capacity of the MGU-H of the Grand Prix single-seaters.

The series production, so far, has proposed some signed solutions Audi, with additional electric compressor to build up the boost pressure when releasing the gas. On closer inspection, something substantially different from the integration of an electric actuator directly on the turbocharger, as proposed by Mercedes-AMG SL 43.

Supersport performance for the Mercedes-AMG SL43

The the performance of the roadster remains very sportywith a zero-hundred per hour in 4 “9 and 275 km / h of maximum speed. Adopting the light 4-cylinder 2-liter engine allowed to reduce the weight to 1,810 kg, against 1,950 kg of the two SL with V8 engine. Consumption thanks: 8,9 lt / 100 km the figure declared by Mercedes on the SL 43.

To complete the technical data sheet, a 9-speed double-clutch gearbox, different from the automatic 9G-Tronic for replacing the torque converter with a clutch to coordinate the connection-disconnection between the engine and transmission.

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