TECHNOLOGY - KERS The Flybrid Systems CFT installed on an Xtrac gearbox in the ORECA chassis. The engine will then connect to the CFT


the engine’s vibrations at idle speeds caused a resonance in one component in the CFT, which led to a failure. That part has since been re-designed, and such


of those things cause the system to do something you were not expecting. We know it works perfectly at full power on the test bench but we cannot put it to full


It’s like a mountain bike,


with three gears on the front and six on the back


are accepted as simply teething problems on what is still a new technology in racing. ‘The biggest problem we have


had is getting all of the systems working together before we can turn it up to a significant level of performance. The challenge is that it is capable of delivering 100kw in either storage or recovery and, if it did that at some poor moment on track, you can cause the car to crash. So you have to be a bit circumspect about running it flat out at first. You have start and make sure everything is working with it turned down to a very low level. So we had it on at the Le Mans test day but at very low power levels, just 10kw or some tiny number. We did that to test all the things you can think of and cannot do on the rig, like running a high kerb or with the sharp torque spikes that result when the driver locks a wheel and you get some unusual speed sensor readings. You have to prove none


52 www.racecar-engineering.com • Le Mans


power in the car until we know all those control systems work. ‘During the running we


have done we have had a lot of electronic communication problems. We found that the Bosch ECU and the ACO logger both use the same CAN channel, but for different information, and neither supplier wants to move off that channel. That channel is the throttle pedal signal from the Bosch unit, which we need, and the ACO information messes that up. It required engineers from the team, Flybrid, Cosworth and Bosch to work together to resolve the problem, as without a clean throttle pedal signal we can’t get the system to work reliably. And we cannot just add an extra sensor and loom because the signal the Bosch unit puts out has already been processed for safety, so this means that if the driver presses the brakes and throttle at the same time they send us a signal that says idle throttle rather than


what the pedal says. All of that safety software is in the Bosch ECU and we intended to use that, but it’s the processed signal that goes to the engine not the raw throttle position data.’


PIT LANE TEST Another unique challenge with the Le Mans hybrids is the so-called ‘pit lane test’. The regulations require all hybrids running in the race to be able to drive the length of the pit lane (400m) at Le Mans on its hybrid system only at 60kph. It was thought this test would involve a car leaving the pits, doing an out lap, then driving through the pits on hybrid power alone, the system fully charged from the out lap. At the test day both hybrids present were summoned to a straight on the infield circuit at Le Mans and told to do the 400m from a standing start. ‘The pit lane test was not


what we expected. With an electric hybrid system you can arrive fully charged after


capable


of delivering 100kw in either storage or recovery


plugging it in in the pits, but you can’t do that with a mechanical system. Even if you could spin it up in the garage, it would slow down by the time you have pushed it to where it needs to be tested. It’s the case for our system as well that the amount of storage you need to work well on the track is not that much – maybe 300kJ – but that is not enough to pass the pit lane test, so the flywheel is sized for the pit lane test and is only just big enough to do that. Any bigger and it is just dead weight, as it is already oversized. It is not the same problem for a battery car because they are power limited rather than energy limited. So the battery is sized by the power requirement and the capacity is many times bigger than required.’ Even before this discovery, the pit lane test had thrown up another issue, as Hilton reveals: ‘This is where the devil is, in all of this detail. The first time we tried to run the pit lane test, when the driver hit the engine kill switch it turned the Bosch ECU off and, in turn, the throttle pedal signal, so the KERS didn’t work! It’s these small simple things that you need to resolve. You can’t just put one of these systems on the car and have it working in 10 minutes. It’s not plug and play, it’s not easy, it’s hard-won data and proper engineering, and it’s not free!’ It is for all these reasons that


hybrid racecars are genuinely difficult to develop, claims Hilton. And what happened at Le Mans this year bears this out. Of the three hybrids scheduled to run at the test day, only the Flybrid-equipped ORECA took to the track. Zytek’s petrol / electric hybrid did not leave its garage and Peugeot Sport’s diesel electric 908 was withdrawn ahead of the event.


The Hope Racing-run Hybrid ORECA 01 took part during the test day and completed 22 laps, the first time a hybrid has taken part in official running at Le Mans since the Zytek- developed Panoz Q9 in 1998. It was also the first public run for a car equipped with KERS developed by Flybrid but, with the development work that has gone into it, it’s looking likely not to be the last.


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