ZR (2009)

Gordon Murray insisted that the engine for this car be naturally aspirated to increase reliability and driver control. Turbochargers and superchargers increase power but they increase complexity and can decrease reliability as well as introducing an additional aspect of latency and loss of feedback, the ability of the driver to maintain maximum control of the engine is thus decreased. Murray initially approached Honda for an NA powerplant with 550 bhp (410 kW; 560 PS), 600 mm (23.6 in) block length and a total weight of 250 kg (551 lb), it should be derived from the Formula One powerplant in the then-dominating McLaren/Honda cars.

When Honda refused, Isuzu, then planning an entry into Formula One, had a 3.5 V12 engine being tested in a Lotus chassis. The company was very interested in having the engine fitted into the McLaren F1. However, the designers wanted an engine with a proven design and a racing pedigree.

In the end BMW took an interest, and the motorsport division BMW M headed by engine expert Paul Rosche designed and built Murray a custom-designed 6.1 L (6064 cc) 60-degree V12 engine, which was 14% more powerful than specified and 16 kg (35 lb) heavier - despite being based on the original specifications of 550 bhp (410 kW; 560 PS), 600 mm (23.6 in) block length and total weight of 250 kilograms (550 lb).

The final result is a custom-built 6.1 L (6064 cc) 60-degree V12 with an aluminium alloy block and head, 86 mm (3.4 in) x 87 mm (3.4 in) bore/stroke, quad overhead camshafts for maximum flexibility of control over the four valves per cylinder and a chain drive for the camshafts for maximum reliability, the engine is dry sump. At 266 kg (586 lb), the resulting engine was slightly heavier than Murray's original maximum specification weight of 250 kg (551 lb) but was also considerably more powerful than he had specified. The bespoke engineered engine for the McLaren F1 is called the BMW S70/2.

The carbon fibre body panels and monocoque required significant heat insulation in the engine compartment, so Murray's solution was to line thThe normal McLaren F1 features no wings to produce downforce (compare the LM and GTR editions), however the overall design of the underbody of the McLaren F1 in addition to a rear diffuser exploits ground effect to improve downforce which is increased through the use of two electric fans to further decrease the pressure under the car. A "high downforce mode" can be turned on and off by the driver. At the top of the vehicle there is an air intake to direct high pressure air to the engine with a low pressure exit point at the top of the very rear. Under each door is a small air intake to provide cooling for the oil tank and some of the electronics. The airflow created by the electric fans not only increase downforce, but the airflow that is created is further exploited through design, by being directed through the engine bay to provide additional cooling for the engine and the ECU. At the front, there are ducts assisted by an electric suction fan for cooling of the front brakes.

There is a small rear spoiler on the tail of the vehicle, which is dynamic, the device will adjust dynamically and automatically attempt to balance the center of gravity of the car under braking - which will be shifted forward when the brakes are applied. Upon activation of the spoiler a high pressure zone is obviously created in front of the flap, this high pressure zone is exploited—two air intakes are revealed upon application that will allow the high pressure airflow to enter ducts that route air to aid in cooling the rear brakes. The spoiler increases the overae engine bay with a highly efficient heat-reflector: gold foil. Approximately 25 g (0.8 ounce) of gold was used in each car.

The road version used a compression ratio of 11:1 to produce 627 hp (468 kW; 636 PS) at 7400 rpm—considerably more than Murray's specification of 550 horsepower (404 kW). Torque output of 480 ft·lb (651 N·m) at 5600 rpm. The engine has a redline rev limiter set at 7500 rpm.