Le Mans Hybrids

Sports car racing could be on the verge of something that Formula 1 has so far failed to do: offering engineers a fascinatingly open-ended platform to explore the new generation of fuel-efficient technologies

The future has finally arrived. The Audi and Toyota LMP1 prototypes that grace the entry list for this year’s 80th running of the Le Mans 24 Hours offer a glimpse of a high-tech future in which the cars at the sharp end of the grid for the sports car blue-riband are bristling with avant-garde technology.

That future takes the form of Audi’s R18 e-tron quattro and the Toyota TS030 Hybrid. These factory machines, underpinned by multi-year and multi-million dollar development programmes, are much more than the bit players ielded by previous contenders running what in Formula 1 parlance are called Kinetic Energy Recovery Systems (KERS).

The Audi and Toyota hybrids are genuine contenders at Le Mans. The hybrid Audi and Toyota LMP1s signal the start of an era for Le Mans, as the big race and the series that run to the same rulebook, including the new-for-2012 FIA World Endurance Championship, seek a new relevance. Long-distance sports car racing is aiming to re-establish itself as a true laboratory for future developments that could revolutionise the automotive world. That process should only accelerate when a new LMP1 rulebook, designed to encourage new and environmentally friendly technologies, comes into force in 2014. The amount of recovered energy that can be released back through the wheels will be approximately doubled and the scope of the systems allowed will be widened. The aim is that the next generation of Le Mans front-runner will achieve similar levels of performance to today’s cars but using 35 per cent less fuel.

Hybrids are not entirely new to the scene, of course. The world’s irst hybrid racing car, the Panoz Q9, nicknamed ‘Old Sparky’ by marque boss Don Panoz, attempted to pre-qualify for Le Mans way back in 1998. It didn’t make the cut, but it did race in that year’s Petit Le Mans 1000-mile enduro at Road Atlanta.

Toyota, which has been selling Prius hybrid road cars since 1997, has even won a 24-hour race with this technology, triumphing with a modified Super GT Supra at the minor Tokachi event back in 2007. More recently, a distant descendant of the system developed by Zytek for ‘Old Sparky’ contested ive American Le Mans Series races in 2009 in one of Zytek’s LMP1 chassis ielded by the US Corsa Motorsports squad. And last year, a hybrid inally raced at Le Mans when the British-developed Flybrid system ran in the Swiss Hope Racing team’s Lehmannpowered ORECA 01 chassis (pictured below).

But 2012 truly is the watershed year for hybrid technology in long-distance sports car racing, because after unfeasibly long gestation periods, it is the manufacturers who are now taking the lead in development.

The term hybrid isn’t a technical one. It simply means that a car is driven by a combination of powerplants. The Toyota is a petrol-electric hybrid, the Audi a diesel-electric, while the privateer Hope ORECA that ran the fully mechanical Flybrid system should perhaps be correctly called a petrol-mechanical hybrid.

Formula 1, predictably, found it necessary to re-invent the terminology and came up with a catchy acronym in the form of KERS when it announced that it would be going down the hybrid route from 2009. The men in blazers who rule sports car racing have come up with Rechargeable Energy Storage System (along with a counter-intuitive acronym, STSY), which doesn’t quite trip off the tongue in the same way, but between them the two terms just about describe what hybrid technology is designed to achieve.

A hybrid racer turns braking energy that would otherwise be wasted in heating up the brakes into kinetic energy, which in the majority of systems drives a motor-generator unit. Put simply, the braking resistance slowing down the car is converted into electrical energy that can then be stored, whether it be in a battery pack, a series of super-capacitors or a flywheel.

This energy is later recycled back through the wheels to give extra power. That’s the explanation for the current breed of hybrids, but that could and should change when the new rules come into force. There’s also the somewhat less catchy term ERS, which will feature in both the F1 and P1 rulebooks from 2014. Not all energy that will be retrieved on the future breed of P1 sports car will be of the kinetic variety harvested from the braking system. Heat recovery from elsewhere is just one of the areas that F1 teams and sports car manufacturers are known to be investigating.

The way the stored energy is returned to the track is not the same in sports car racing as in F1. Recovered energy in F1 is used to spice up the racing along with another technology with a snazzy acronym, DRS (Drag Reduction System), in a push-to-pass scenario. The hybrid systems on P1 prototypes are not activated by the driver because the sports car rulemakers, a combination of the FIA and the Automobile Club de l’Ouest at Le Mans, have an altogether more altruistic motivation: to save fuel.

There are also subtle differences in the rules governing energy release for hybrids between F1 and LMP1. F1 limits the release of energy to 400kJ per lap; in prototypes the igure is 500kJ between what are known as two ‘braking events’, so around the 8.47-mile Circuit de la Sarthe that means seven or eight times a lap. The F1 regulations limit the power delivery to 6.6 seconds through a motor-generator unit rated at 60kW, the equivalent of 81bhp.

There is no limit on the power of the motors in P1 for the moment. Audi has revealed that its e-tron quattro has two 75kW motors, the equivalent of 200bhp. If used at full power, they would use up the allowable 500kJ in a shade over three seconds, though it is likely that the Audi will spread its power burst over ive or six.

Toyota has yet to state a power output for its single motor, while Peugeot published an 80kW figure for the hybrid 908 (pictured far left), and Zytek’s off-the-shelf system, used in the privateer P1 car ielded by MIK Corse in the Le Mans Series last year, is rated at 50kW (67bhp).

The racing hybrids that have hit the track so far have stored energy in one of three ways. Zytek, which is a world leader in electric car technology, has always used batteries, a choice Peugeot followed on its stillborn 908 HYbrid4. Toyota has opted for super-capacitors, while Audi’s storage system is a flywheel, which it calls an accumulator but is probably best described as a mechanical battery. Electrical energy is converted into mechanical energy to spin up the flywheel and back to electrical energy to drive the motor-generator unit.

The Flybrid system also stores its energy in a high-speed flywheel, but unlike the Audi system it shouldn’t be called a battery because there is a direct mechanical link, via a system of gears and clutches, through the gearbox to the wheels.

There are question marks over the suitability of batteries in racing. They have the capability to store a lot of energy, which makes them the best option for electric road vehicles, but have disadvantages in the rate at which that energy can be stored and released. Or that’s what the proponents of the alternatives claim.

Battery detractors also argue that the constant use at Le Mans – Audi has come up with a igure of about 4000 energy cycles – means that a battery of a suitable size for racing would lose eficiency over the race distance. They also claim that there are substantial cooling issues with batteries.

“In F1, the batteries lose about 10 per cent in performance over the race, so at Le Mans the degradation would be enormous,” says Flybrid boss Jon Hilton, who investigated the options when he was working for the Renault F1 team. “A battery of a suitable size would not do the distance at Le Mans.”

Doubts about the suitability of batteries have been fuelled by a change in the rules from those originally proposed for 2012. Early drafts allowed for a one-megajoule energy release, but after lobbying from one manufacturer, almost certainly Peugeot, this was halved to 500kJ. The suggestion is that the French manufacturer had doubts that it could make its battery last at the higher power level.

Zytek founder Bill Gibson counters the arguments that batteries, lithium-ion in the case of his system, are not the way forward.

“Then why is every F1 system based on batteries?” he says. “It is all a question of how you control it. That’s what determines the life of the battery. It’s no different to the battery in your phone: never let it go flat and always charge it properly. Batteries need a bit of TLC.”

He claims that the arguments put forward for flywheels are because “racing cars are designed by mechanical engineers and they don’t understand electronics”. And that is why they have sought a mechanical solution.

The super-capacitor can store less energy than a battery, but offers a big punch of power. Think of the flash on a camera, which is typically driven by a capacitor.

“Racing means a big power delivery in a short time,” says Hisatake Murata, Toyota’s hybrid project leader. “A lithium battery has a big storage capacity, but the power ratio is very low. A capacitor has a small storage capacity but a high power ratio.”

Some of the disadvantages of batteries also apply to super-capacitors. Weight is one, though Toyota has not disclosed the weight of the pack of super-capacitors that
sit alongside the driver in the TS030; and another is cooling, which can have a substantial impact on aerodynamics.

A flywheel spinning at high speed in a vacuum offers the same advantage as a super-capacitor:
a rapid surge of power.

“The reason lywheels are being chosen is that they are the lightest system for the required power density,” says the boss of the company building the flywheel for the Audi, Williams Hybrid Power managing director Ian Foley. “If you need more than 100kW and to cycle that many times over a lap, which means multiple cycles over the course of a 24-hour race, then a lywheel is a lighter way of doing it than either a battery or a super-capacitor. I am sure that if we tried to make a capacitor with the same power as our flywheel, it would be bigger and heavier.”

The increase in power for 2014 will only further increase the advantages of a flywheel, according to Foley. There have been inevitable questions about the reliability of a lywheel that spins at 45,000rpm, but the Williams system built for Porsche’s 911 GT3-R Hybrid has come close to winning the 24-hour race at the Nürburgring in 2010 (engine failure put it out with two hours to go), and inished the race in 2011.

The rhetoric from Audi suggests that the primary reason for its decision to go the flywheel route was based on reliability and sustained performance.

“In our opinion it offers the most stable platform at the moment,” says Christopher Reinke, technical project leader for the LMP at Audi Sport. “We believe it is the best way to achieve full performance for 24 hours.”

The Flybrid system used in the Hope Racing ORECA last year and which will be used by another LMP1 privateer at some point this year has several key advantages, according to Flybrid’s Jon Hilton. He has no doubts that it is the best system out there.

“It is the lightest and offers the most power for the weight,” he says of his system, which hits the scales at 38kg and gives 100kW or approximately 135bhp. Hilton believes his system is substantially lighter than that in the Audi.

Hilton claims that the Flybrid system achieves 64 per cent efficiency, or in layman’s terms the percentage of the energy retrieved under braking to be retransmitted to the wheels. He
suggests that’s a higher number than the Audi system because of the conversion losses, though that’s something disputed by Foley at Williams.

The existing Flybrid system can only work on the rear wheels (it sits in the bell-housing between the engine and gearbox), but the company is already working on a system for the front axle for 2014.

The Le Mans rules, as they stand, allow energy recovery on the front or rear axle, but not both, although that is going to change for 2014. There are clearly advantages to each approach.

Harvesting power from the front axle is more efficient as a result of the high braking loads. There could be beneits for overall tyre wear, too, by putting the regenerated energy through the front wheels.

The other advantage is in terms of traction, as indicated by the use of the quattro monicker on the hybrid R18, though the significance has been reduced by another rule change, also believed to have been driven by Peugeot, which means that energy release is not allowed to the front wheels until the car has reached 120km/h (75mph).

There are clearly weight and packaging advantages to be had in using the rear axle. There is no need for additional driveshafts, which could also impinge on the front aerodynamics, and the motor-generator unit can be sited in the bell-housing as on the Toyota system.

These are the reasons cited by Toyota for opting to retrieve power from the rear wheels, though it clearly sees the merits of both. It was experimenting with two systems (with motor units supplied by different companies) in January and February.

Audi’s reasons for opting for front drive are complex, according to Reinke. Despite the marketing hype around the revival of the quattro name in racing, he says the traction benefit was never the primary reason for its choice. He says it went from “priority number two or three” to “priority four or ive” in the wake of the rule change.

A key reason for its decision (though Reinke stops short of saying it was the primary reason) is Audi’s strategy of splitting its Le Mans attack between two e-tron quattros and two non-hybrid turbo-diesels, known as ultras.

“The two types of car will be identical apart from the hybrid systems,” he explains. “Using the front axle allowed us to take this flexible, modular approach. We can change the car
overnight from hybrid to non-hybrid.”

Reinke says that balance also came into the equation. “It is definitely beneficial for weight distribution,” he says, “especially with a diesel car having more weight at the rear.”

The intention is that recovered energy is used to save fuel, hence a fuel tank capacity reduced by two litres for hybrids, but it is clear that an extra 200bhp on each straight could offer a significant beneit in lap time. Of course, it could also offer a signiicant fuel saving because the conventional engine could be backed off when the recovered energy is being released.

Many believe that Toyota will use its extra electrical horses for sheer performance, a suspicion backed up by the stated targets of the Japanese manufacturer for its irst Le Mans since 1999.

“We think it is realistic to be the fastest hybrid,” says Toyota Motorsport technical director Pascal Vasselon. “As racers we will go to Le Mans to win. That is passion talking, but when reason is talking it may not be realistic to last 24 hours at the first attempt.”

That’s the big question. The hybrid R18s and TS030s should be quicker, over one lap and over a stint, but no one can be sure of their reliability, Audi and Toyota included. Audi didn’t race the e-tron quattro at Sebring, the first round of the WEC, instead relying on a revised 2011 R18 TDI. The quattro and the conventional version of the 2012 car were present at the Florida track, both taking part in a four-day endurance test that was interrupted by a major shunt for one of the ultras.

Toyota’s preparations have also been hit by a major accident. The irst TS030 was badly damaged ahead of what should have been Toyota’s second endurance run at Paul Ricard in April. With the second car not yet ready, the accident forced Toyota to withdraw from the Spa WEC round, meaning the TS030 will be making its race debut at Le Mans.

It’s looking much less bold than originally envisaged. The new LMP1 rulebook is based on giving each car an energy allocation for each racing lap, measured in megajoule content rather than volume or litres, and then allowing the engineers, team and drivers to make the best of that. Recovered energy, kinetic or otherwise, was not going to be part of that allocation because it was, in effect, ‘free’ energy.

That’s changed since the rule-making process for 2014 began in earnest last summer. The original plan to leave a way open for privateers to be competitive was to allow them to build an ultra-lightweight non-hybrid car tipping the scales at just 750kg, or 150kg under the existing minimum. That’s all changed.

The draft version of the 2014 regulations distributed to competitors now allows independents running without any kind of energy recovery a larger allocation of fuel or energy. In fact, the rules make a distinction between “intermediate ERS” and “large ERS”, the former being a car running one recovery system, the latter a car running a maximum of two. Then there’s the so-called “no ERS” subclass open only to P1 privateers.

The shift in philosophy of the rules has been designed to protect the privateers. The ACO has stated that it wants private teams to be able to still “compete at a high level”.

The change of direction appears unpopular with the manufacturers, or at least with Audi. Ulrich Baretzky, the head of engine technology at Audi Sport, reckons it will stile innovation.

“The question I am asking is, do you want to have efficiency in motorsport?” he says. “We should be given the opportunity to showcase what we can really do. If you screw everything down, it will make Le Mans uninteresting for manufacturers like Audi.”

For the moment, the challenge for Audi, Toyota and anyone else choosing to run a hybrid this season is immense. But that’s why they are part of the future, not just for racing but also for the road, as an accelerator for the kind of technologies we may come to take for granted tomorrow.

Gary Watkins