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The new Mercedes-AMG SL: engine, transmission and all-wheel drive
At the time of its market launch, the new roadster will be launched with two output levels of the AMG 4,0-liter V8 biturbo engine. And for the first time in its history, the SL also transfers power to the road with all-wheel drive.
In the top model SL 63 4MATIC + (combined fuel consumption WLTP 12,7-11,8 l / 100 km, CO2-Emissions combined WLTP 288-268 g / km) the proven engine has an output of 430 kW (585 PS) and provides a maximum torque of 800 Nm over a wide speed range from 2.500 to 4.500 rpm. The top engine of the roadster conveys absolute sovereignty in every speed range. The acceleration from 0 to 100 km / h in 3,6 seconds illustrates this, as does the top speed of 315 km / h. In the Mercedes-AMG SL 55 4MATIC + (combined fuel consumption WLTP 12,7-11,8 l / 100 km, CO2Emissions combined WLTP 288-268 g / km) the V8 engine provides 350 kW (476 hp) of power and 700 Nm of maximum torque. The sprint from standstill to 100 km / h takes 3,9 seconds, the top speed is reached at 295 km / h.
The further developed AMG 4,0-liter V8 engine still works with biturbo charging, in which the two turbochargers are not arranged on the outside of the cylinder banks, but in between in the V of the cylinder. The advantages of the “hot inside V”: compact engine design, spontaneous response of the turbocharger and low exhaust emissions thanks to the best possible flow to the catalytic converters close to the engine.
Turbochargers with twin-scroll technology are used to further improve responsiveness. The charger housing is divided into two parallel flow channels. Together with two also separate exhaust ducts in the exhaust manifold, this enables the exhaust gases to be controlled separately on the turbine runner. One duct is fed by the exhaust gases of the first and second cylinders of a cylinder bank, the other by the exhaust gases of the third and fourth cylinders. The aim is to prevent the individual cylinders from influencing each other negatively during gas exchange. This reduces the exhaust gas back pressure and improves the gas exchange. The result is more power thanks to better cylinder filling with fresh gas, higher torque even at low speeds and a very spontaneous response.
The engine features also include weight-optimized pistons, adapted air intake and charge air cooling, as well as extensive software developments. The spray-guided direct petrol injection with piezo injectors, the all-aluminum crankcase, the 4-valve technology with camshaft adjustment, the air-water charge air cooling, the generator management, the ECO start / stop function and the sailing function have been retained.
Special modifications for use in the SL
For use in the SL, the engine, known internally as the M 177, received a new oil pan, repositioned charge air cooler and active crankcase ventilation. The inlet and outlet channels have been optimized for an even more effective gas exchange and the exhaust gas routing for the catalytic converter box and Otto particle filter has been enlarged. The developers achieved the extra power of the SL 63 4MATIC + primarily through higher boost pressure and greater air throughput as well as modified engine software. All in all, the eight-cylinder impresses with its extraordinary power development with powerful thrust in all engine speed ranges, combined with the highest possible efficiency for low fuel consumption and emissions.
In the SL 63 4MATIC +, the eight-cylinder has active engine mounts. The SL 55 4MATIC + can optionally be equipped with it as part of the AMG DYNAMIC PLUS package. The bearings solve the conflict of objectives between the softest possible connection of the drive train for high comfort and the stiffest possible connection for optimal driving dynamics by continuously and quickly adapting their stiffness to the respective driving conditions. These are liquid-filled rubber bearings. The vehicle sensors recognize the current driving situation and the resulting vibration behavior of the engine and pass this information on to a control unit. This regulates the force with which the engine is coupled to the body and thus optimizes driving behavior. For this purpose, a magnetic damper fluid is pressed through an annular gap of a coil in the bearing. Different currents generate a magnetic force that regulates the flow and thus the motor mounting according to the information from the control unit.
Three cooling circuits for optimal temperature management
So that the new Mercedes-AMG SL does not get too hot even when it is forced to work on racetracks, three cooling circuits ensure that the temperature is balanced. The high-temperature circuit cools the AMG 4,0-liter V8 biturbo engine and the two exhaust gas turbochargers. It also supplies the heating heat exchanger for convenient and needs-based temperature control of the interior. The mechanical water pump is placed on the engine block to save space and is driven reliably and directly via the timing drive, with a pinion on the camshaft engaging the gearwheel of the water pump. The pump circulates a total of 12,3 liters of coolant at up to four bar pressure and 400 liters per minute.
The three-row main cooling module (high-temperature cooler, low-temperature cooler, condenser), the flange-mounted suction fan and the additional bow cooler (for the high-temperature circuit), which are installed "horizontally" for a low center of gravity, are positioned behind the large-format radiator cladding in the middle in front of the engine. In this way, they can be flown optimally and with a large volume of air. The thermal management is not only influenced by the three-stage thermostat and the shut-off valve (when the engine is cold, the cooling circuit is stopped so that the engine reaches operating temperature more quickly), but also active aerodynamic elements such as the two AIRPANELS in front of the main cooling module or the active aerodynamic element in the front underbody.
With a volume of 7,2 liters, the low-temperature circuit is somewhat smaller. It operates the intercooler, the AMG SPEEDSHIFT MCT 9G transmission and the engine control unit. The performance of the main cooler is supported by an additional cooler in the left wheel arch. Thanks to the indirect air-water charge air cooling, the developers were able to ensure efficient charge air cooling for high performance even in difficult external conditions. The plastic air inlet box is designed in such a way that maximum uniform distribution of the air over the pipes - with minimal pressure loss - is made possible. The dimensioning of the charge air cooling components makes it possible to keep the charge air temperature in precisely defined values above the ambient temperature.
The third cooling circuit is responsible for the engine oil. The oil-water heat exchanger ("oil cooler") in the right wheel arch enables the oil to be heated up quickly. This has a positive effect on the service life of the engine and reduces consumption after a cold start. This circuit also prevents the engine from overheating and being damaged as a result. The external oil cooler is controlled via its own oil thermostat. The oil and water pipes are made of aluminum instead of steel, which helps to reduce weight.
Manufacture manufacturing digital and smart: "One Man, One Engine"
The motor is assembled entirely by hand. In the AMG engine manufacture at the Affalterbach location, the “One Man, One Engine” principle is linked to Industry 4.0 manufacturing methods. This is designed according to modern knowledge of ergonomics, the flow of goods, quality assurance, sustainability and efficiency. Smart production is characterized by maximum flexibility, is transparent and highly efficient. It secures and increases the quality of the engines and the production processes with digital technologies.
Short shift times, high efficiency: the AMG SPEEDSHIFT MCT 9G transmission
The AMG SPEEDSHIFT MCT 9G transmission (MCT = Multi-Clutch Transmission) is specially tailored to the requirements of the new SL. A wet starting clutch replaces the torque converter. It reduces weight and, thanks to its lower mass inertia, optimizes the response to accelerator pedal commands, especially when accelerating and when changing loads. The elaborately coordinated software ensures extremely short shift times and, if necessary, multiple downshifts, and thanks to the double-declutching function in the “Sport” and “Sport +” drive programs, it delivers a particularly emotional shifting experience. Defined ignition interventions enable even faster gear changes here than in the other modes. In all driving programs, you start off in first gear to ensure a dynamic driving experience at all times. In addition, the RACE START function is applied, which guarantees optimal acceleration from a standstill.
The highlights of the gearbox are:
- Adaptation of the shift characteristic to the selected AMG DYNAMIC SELECT driving program
- In manual "M" mode, the transmission reacts directly and precisely to manual shift commands from the driver and implements the commands at lightning speed.
- The short-term M program enables a spontaneous change to manual "M" mode - simply by using the shift paddles.
- Automatic double-declutching function when downshifting: this effect is automatically active in the “Sport”, “Sport +” and “RACE” drive programs (standard on the SL 63 4MATIC +).
- The ECO start / stop function is automatically active in the "Comfort" drive program.
- The “sailing” function can be activated in the “Individual” driving program.
Fully variable all-wheel drive AMG Performance 4MATIC +
For the first time in its almost 70-year history, the SL is available with one drive on all four wheels. The two V8 models are equipped with fully variable AMG Performance 4MATIC + all-wheel drive as standard. The intelligent system combines the advantages of various drive concepts: The fully variable torque distribution between the front and rear axles not only guarantees optimal traction at the physical limit. The driver can also rely on a high level of driving stability and driving safety under all conditions: on dry roads as well as in wet conditions or on snow. The cross-fading from rear-wheel to all-wheel drive and vice versa takes place continuously on the basis of a sophisticated matrix that integrates the intelligent control into the overall vehicle system architecture.
An electromechanically controlled clutch connects the continuously driven rear axle variably with the front axle. The best possible torque distribution is calculated continuously - depending on the driving situation and the driver's wishes. The new roadster can be driven continuously variably from traction-oriented all-wheel drive to pure rear-wheel drive. In addition to traction and lateral dynamics, the all-wheel drive also improves the longitudinal dynamics for even more powerful acceleration.
Performance hybrids with an exclusive AMG concept
At a later date, Mercedes-AMG will also be offering the SL with a powerful performance hybrid drive. The AMG E PERFORMANCE drive strategy aims to offer an electrified drive train that increases driving dynamics but is also highly efficient at the same time. With the increase in performance through the additional electric motor, the development team was also able to improve the efficiency of the entire vehicle at the same time - and achieve lower emissions and lower consumption.
