POWERTRAIN
At the heart of a McLaren road car lies its powertrain.
An integrated engineering approach to the development of the engine, transmission and exhaust systems defines the character, performance and usability of the vehicle. This requires a powertrain with a high specific output, good mid range torque delivery and a low centre of gravity in a lightweight and small package.
ENGINE & GEARBOX TECHNOLOGY
Using technology direct from the Team McLaren Mercedes Formula 1 cars, the AMG engine of the Mercedes-Benz SLR McLaren a road car delivers power and torque to the vehicle in an optimum range and amplitude, but also in a controlled manner.
This requires the centre of gravity to be as low a possible, demanding small distances from the crankshaft centre line to the lowest point on the powertrain.
For this reason a McLaren always uses dry sump engine lubrication systems. Similarly transmission technology offers a spread of gear ratios defined for optimum performance in a range of conditions and an exhaust system optimised for weight, engine performance, tailpipe emissions, thermal management and acoustics.
The engine, vehicle and transmission control systems are also integrated together to give the highest, balanced performance to the driver. This is realised through communication of ECU, TCU, ESP and differential controls with acceleration, position and speed sensors around the vehicle architecture via CAN signals.
DESIGN & DEVELOPMENT
The powertrain design process uses predictive analysis tools and engine simulation software, tuning the engine to achieve desired performance targets, before any hardware is produced or engines run on dynamometers. This CAE analysis works closely with CAD design as an iterative process to ensure systems can be packaged and manufactured to appropriate cost, weight and quality constraints.
Powertrain systems are predominately made of cast aluminium and forged steel, with titanium used for components requiring combined high performance and low mass. Various grades of stainless steel are predominantly used for the exhaust system with inconel considered for high temperature shielding of components.
Early prototype vehicles are crucial for powertrain development, validating elements of performance, function, durability, emissions, certification and diagnostics.
Early development of a robust communication between the control unit on the engine, transmission and other vehicle systems and a robust engine calibration allows the many other vehicles in the development programme to have an acceptable level of driveability and to be operated safely at a range of engine and vehicle speeds and loads.
