FEATURE AUDI R18 TDI
Above: Audi’s V10 R15 TDI (left) went through a redesign before the company bowed to the inevitable and introduced a closed Prototype – the V6 R18 TDI Right: Everywhere on the new car the emphasis has been on improving efficiency and reducing weight. The brakes are lightweight alloy monobloc calipers from Brembo with ventilated carbon fibre discs all round
Weight reduction Audi has worked hard on reducing the base weight of the car. Te carbon body is made in one piece, instead of upper and lower sections glued together, which makes it torsionally stiffer. Te chassis is rumoured to weigh just 72kg, lighter than the R15 chassis despite the addition of a roof, windscreen and doors, and the entire base weight of the car is a quoted 850kg. Tat is a base weight that Audi has campaigned for the ACO to adopt for non- hybrid cars, rather than a blanket 900kg limit whether an energy recovery system is run or not, though the ACO rejected that plan this year. Tis weight reduction comes at a time when Audi’s
production cars are also on a diet. Te latest A6 is 80kg lighter than its predecessor and the new A4 is also lighter, all following the race team’s belief that the best way of improving fuel consumption is by reducing weight. Te new V6 engine is, of course, lighter than the V10.
Audi’s engineers have cut around 25 per cent from the weight of the unit, plus changed to a lighter gearbox and transmission, which has to cope with less torque. Te V6 weighs approximately the same as the petrol V8 that was in the R8 racecar 12 years ago.
Efficiency drive Te engine itself has a 120-degree v angle, rather than the 90 degrees of the previous V10, with a mono turbocharger and single exhaust housed within the v angle. Tis lowers the c of g and allows for more efficient
airflow through the turbocharger, which then exits through the single exhaust housed around the mandatory fin on the engine cover. ‘We thought about the package with two turbos, but
found it extremely compromising in terms of the exhaust and the arrangement,’ says Ulrich Baretzky, Audi’s head of engine development. ‘You cannot do it in parallel, and we didn’t like that idea.
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www.racecarengineering.com • August 2011 ‘Next to the fact that we have a closed car, we have
the intake on the roof, so there is a straight line to the turbocharger, [which is] much easier with one than two. If you have a close look at the Peugeot, the air comes in and is distributed into two, and there are an awful lot of losses. We know from our Bentley years that this cannot be done well.’ With minimal losses, the car produces a quoted 397kW (540bhp) and more than 900Nm of torque. However, Audi’s production car department has produced a V6 delivering 600Nm of torque, so few believe the racecar figures are accurate. Whatever the actual output, there is still a reduction
in performance compared with the V10, leaving the drivers struggling for power to pass the production-based
“the best way of improving fuel consumption is by reducing weight”
GTE cars, and the lower powered LMP2s – a problem that is compounded by a lack of visibility, with the a-pillar obscuring their view. Te low-slung LMP1 cars are difficult for the GTE
drivers to see mid-corner, and the Prototypes do not have the torque to pass them on short straights. Tough the top speed is higher, they take longer to get there, and that is causing problems. ‘I think driver ability will be less of an issue at Le Mans than here or at Silverstone because of the length of the straights and the type of circuit it is,’ said McNish at Spa. ‘Te cars are more spread out, because you have the same number as you do at Le Mans, but on nearly one third of the track distance. In the shorter races [Imola, Silverstone, Road Atlanta and Zhuhai], it is going to be harder.’ One potential area of concern is the weight of the R18, and the measures taken to produce such a
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