THE HEART OF A WINNER
Gordon Murray designed a road car that could beat the best racers – with a little help from BMW, explains Glen Waddington
During the development of the F1, Gordon Murray was in contact with every supplier as he sought to pare away grammes in the pursuit of road-car perfection. (Kenwood’s engineers no doubt remember with frustration being told to ‘just try harder’ with their CD player.) But Murray enjoyed a particularly close relationship with BMW – and specifically with the F1’s engine designer Paul Rosche, then technical manager at BMW Motorsport.
What began as a prospective adaptation of the company’s racing V12 escalated into a bespoke project for just 100 cars. Rosche asked what was really wanted and was given a list: a V12 of the biggest displacement in the smallest overall package possible, no more than 600mm in length or 250kg in weight, rigid enough to act as a load-bearing member, and with dry-sump lubrication. ‘Never use a 10mm bolt where 9mm would do; consider weight as driving the design,’ Murray commanded.
The target power output was 550bhp;
Rosche found 627bhp in the prototype. With full emissions equipment, it weighed 266kg. A 6.4% weight penalty in return for 14% more power, then. And it truly is part of the car: with a bolted-on aluminium alloy subframe, the engine is the F1’s main rear structural member. Even the exhaust silencer is suspended on cables so it can help absorb impacts.
It dictated the body shape too, as intake air is drawn through a slot on the F1’s roof via a venturi that forces it into the carbonfibre airbox at higher than atmospheric pressure.
Peak power occurs at 7500rpm, specific output is 103bhp per litre, there’s 398lb ft of torque at just 1500rpm, and at least 479lb ft spread from 4000rpm to 7000rpm. To ensure reliability, each of the 110 S70/2 V12s BMW built was subjected to 500 hours of bench testing. Perhaps that’s what made the engine so good at endurance racing. But here’s the irony: for Le Mans, the F1 GTR was detuned to 592bhp (600PS) by restricting those clever air intakes. Well, it was either that or run ballast…
The ultimate iteration of the S70/2 is found in the five F1 LMs built to celebrate the 1995 Le Mans win. Fitted with the GTR’s remapped ignition but without restrictors, it makes 680bhp. The LM found its own place in history with a 0-100mph-0 World Record run in 11.5sec while travelling a distance of only 828.4ft.