The McLaren P1 features a 3.8-litre twin-turbo V8 petrol engine. The twin turbos boost the petrol engine at 1.4 bar to deliver 727 bhp (737 PS; 542 kW) and 531 lb·ft (720 N·m) of torque at 7,500 rpm, combined with an in-house developed electric motor producing 177 bhp (179 PS; 132 kW) and 192 lb·ft (260 N·m). With both engine and the electric motor, the P1 has a total power and torque output of 904 bhp (917 PS; 674 kW) and 723 lb·ft (980 N·m) of torque respectively. The electric motor can be deployed manually by the driver or left in automatic mode, whereby the car's ECUs 'torque fill' the gaps in the petrol engine's output, which is considered turbo lag. This gives the powertrain an effective powerband of almost 7,000 rpm. The car is rear-wheel-drive with a seven-speed dual-clutch transmission developed by Graziano.