The McLaren MP4-12C is a mid-engined two seat sports car. This is not unique but the packaging of the 12C is based upon this layout for very good, historical reasons.
Almost all racing cars up until the late 1950s had a traditional bonnet housing the engine in front of the driver. In a revolutionary move, Cooper Cars, who were to be Bruce McLaren’s first British employer and Ron Dennis’ first racing employer, placed the engine behind the driver and within three years all other Formula 1 cars had moved to a mid-engined layout. Sporting road cars followed this lead towards the end of the 1960s and most cars claiming a sporting intent since have stayed true to this pattern.
The fundamental advantages for a sports car lie in the physics of the moment of inertia, weight distribution, the division of steering and drive, grip, traction and handling.
The moment of inertia describes how easy or difficult it is to turn an object. In the case of a car, the more weight that is located near to the centre between the axles, rather than towards the front or rear, then the easier it will be to change direction. This reduces the polar moment of inertia, or the tendency of heavy items at the front or rear to act as a pendulum. In short the polar moment of a car determines its agility, therefore weight distribution is crucial to balanced handling.
The natural starting point for weight distribution is 50:50 on the front and rear axles in order to have an equal weight acting on all four wheels, which in turn affects the level of grip each can provide. Determining a preferred level of understeer or oversteer alters the 50:50 displacement and then gives a car its own personality.
A 43:57 ratio was preferred by McLaren Automotive to offer better traction and a neutral balance.
The 12C also has as much weight as close to the road as possible in order to lower the centre of gravity, and these objectives of positioning weight where it can best help the car to react positively to the driver’s commands provide the safest and soundest foundation for an agile, fine handling performance sports car.
Driving the rear wheels and steering with the front then helps retain a purity in which drive is delivered to the rear axle, allowing the front axle to concentrate on steering without being polluted by torque.
This is why McLaren chose the classic rear, mid-engined layout as the basis for the 12C and from this basic principle all the other elements of the car were developed. Reducing weight throughout then became an almost obsessive goal across all engineering disciplines, starting with the core of the car, the carbon MonoCell.
Weight is the enemy of performance in every area of car design. It affects acceleration, speed, handling, fuel consumption and CO2 emissions – everything. Whilst the MonoCell offers huge weight savings (and performance gains) over competitors, it has not been the sole focus of attention. McLaren Automotive’s engineers have pursued saving weight in every single aspect of the car.
Packaging was fundamental to support the MP4-12C’s low weight targets. Externally, the car had to be compact, yet internally it had to offer an unparalleled driver and passenger environment where space, comfort and driving enjoyment at all levels were not compromised.
At 4509mm long, 1895mm wide at the front axle (1908mm rear), and 1199mm high, the 12C is compact externally, smaller in all dimensions than for example, the Ferrari 458 Italia, yet the interior is spacious, being designed to accommodate 98th percentile adults in comfort.
The McLaren MP4-12C has been designed around a demanding mechanical package that puts emphasis on aerodynamics, compact dimensions, performance and efficiency, practicality and comfort. The design of the 12C was driven by aerodynamics and engineering innovation; the reason why McLaren Automotive believes it will remain contemporary and elegant throughout its lifetime as well as distinctive among its peers.
Aerodynamic efficiency defined the 12C’s design. It has smooth upper body surfaces to yield a highly effective drag coefficient and generate very high levels of balanced downforce at high speed. This helps to maintain traction, cornering ability and stability while low drag aids top speed and acceleration.
A completely flat underbody helps to smooth out and speed up air flow under the car, as faster air pulled from the rear of the car increases downforce at the rear. A removable nose splitter gives more downforce at the front.
Aerodynamics also plays a major part in the cooling of the car and in reducing its CO2 emissions. Air flow through, over and under the car has been honed through Computational Fluid Dynamics (CFD) and real-world testing programmes. Managing engine temperatures has been a key focus for the development team, driven by the ground-breaking combination of a small capacity, high power engine that sits very low in the chassis and as close as possible to the cabin.
Source: McLaren press