FEATURE PEUGEOT 908
Short travel suspension
R
acecar Engineering’s chassis expert, Mark Ortiz, on the 908’s rear suspension: ‘It appears
to have torsion bars for the main ride springs, with rotary dampers. There is a ride-only third spring mechanism with a compression coil and a rubber snubber. The small device on top of the bellhousing forward of that appears to be an anti-
the tyres, and the tyres to the car.’ Peugeot is not alone though. Audi
is facing a similar problem, and it is undoubtedly a worry for both teams. Temperatures at Le Mans can vary by up to 25degC between the day and night,
“The ACO has to be very careful to give a bonus to new technologies”
and the car needs to be able to cope with this. It also needs to work in very different conditions around the world, from the undulating Road Atlanta circuit to the fl at track at Zhuhai in November.
Hybrid thinking Peugeot has said that it expects to have to run a hybrid system in the 908 before the end of the year. With the PSA group shortly putting on sale battery hybrid cars to the general public, the race team has also developed a 908 with batteries instead of a fl ywheel, partly because that
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www.racecarengineering.com • August 2011
roll bar, presumably with a compound torsion bar extending down into the bellhousing. From the size of the links, it appears to be a small portion of the roll resistance, and does not appear to be adjustable for rate, except by changing bars? As for the third spring not being coplanar with the rockers, they usually aren’t as normally
the rockers aren’t coplanar with each other, so nothing else can be coplanar with both of them. The layout shouldn’t cause any bad behaviour, unless the spherical rod ends run out of misalignment capacity and bind. The system does seems designed for very short travel indeed but, up to a point, that’s normal for this type of car.
technology is a step too far at this stage. ‘To integrate a fl ywheel is very diffi cult,’
says Peugeot’s technical director, Bruno Famin. ‘Mechanically speaking, the fl ywheel is quite a big issue. As a fi rst step, it was quicker and easier to go with batteries, and the decision was already made to do that at the beginning in 2008.’ The regulations demand that the
power is delivered back to the wheels from which the energy is collected, and Peugeot has opted to keep things simple and concentrate everything on the rear of the car. ‘You need more batteries, a bigger electrical machine, and everything is more diffi cult,’ says Famin, explaining the reasoning behind not collecting and delivering power to the front wheels. ‘[besides] we think we can collect all the energy that we need from the rear wheels.’ The French manufacturer was instrumental in reducing the amount of stored energy from 1MJ to 0.5MJ, which also helps to keep control of the costs, needing less capacity storage and regeneration of energy to recharge the battery. ‘The bigger the energy you have to store, the more the
cost, and it is not linear.’ The weakness of the new 908 appears
to be its operating window, which is narrower than the old car. That means the three cars have to work on set up in practice and qualifying, and share the information between them to achieve the optimum race set up.
In conclusion With all the work concentrated on the rear axle, the system is lighter and less complicated than Porsche’s GT3 fl ywheel hybrid, for example. Peugeot’s system, which will weigh around 35kg, is expected to deliver a further 80bhp to the rear wheels between braking zones, and will meet the ACO’s condition that it can run the entire length of the pit lane on battery power alone. There seems to be little doubt that the
Hybrid will be given a performance break, and that it should be capable of delivering more performance than the standard engine. The ACO has mandated that the system be used only for improving economy, hence the smaller fuel tank.
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