The Lone Star Le Mans Part 1: Hybrid hypercars

AUSTIN, Texas—Texas' Lone Star Le Mans might be one of the best-kept secrets in motorsport. Now in its third year, it takes place at the Circuit of the Americas—COTA to its friends—just to the east of Austin's airport. The track is state of the art, built to host Formula 1 on its return to the US in 2012. But that event takes place later in the year. COTA in September is all about sports cars, a headlining double bill of the Tudor United Sportscar Championship (TUSC) during the day and the World Endurance Championship (WEC) racing into the night. It's Ars' favorite race to visit, in part because it's the only time the US gets to see the 1100-horsepower hybrids from Audi, Porsche, and Toyota.

Those three companies have been battling for supremacy for the last several years with three very different approaches to the complicated questions asked in the WEC's technical rulebook. Those rules stretch for many pages, but essentially they equalize performance for different fuels and energy storage systems using a lap of the Le Mans circuit as a reference (Le Mans is the centerpiece of the WEC season, for the other races the formula is adjusted based on the length of the track).

Hybrid systems are allowed to deploy between 2MJ and 8MJ of energy during a single lap of Le Mans, augmenting the power from an internal combustion engine. Energy can be recovered from up to two motor/generator units (MGUs); usually this means recapturing kinetic energy from the front and rear wheels under braking. To balance things out, cars that recover and deploy 8MJ carry less fuel, and the flow rate at which they can feed it to the engine decreases.

Audi's R18, with its mix of turbo diesel and flywheel hybrid technology, was king of the hill for several years, but the hybrid systems were much less powerful. Last year, Toyota's gasoline V8 and supercapacitor-powered TS040 was the car to beat. But 2015 is the year of the Porsche 919 Hybrid. Porsche chose lithium-ion batteries to hybridize the 919's turbocharged gasoline V4, and this year is able to capture and deploy the full 8MJ (Toyota is in the 6MJ class and Audi 4MJ).

It's a vivid illustration of just how much development work is happening in the field battery technology, thanks to massive investment from both the automotive and consumer electronics industries. The batteries in the Porsche–made by A123 Systems—are a significant improvement compared to 2014's car, and neither Audi's flywheel technology or Toyota's supercapacitors have been able to match that development curve.

Toyota has been having a rough year in the WEC. In 2014 the TS040 dominated the series, but Audi and Porsche—both of which have programs with at least least double Toyota's budget—found much more speed over the winter. As a result the Cologne-based team has had to rely on problems befalling their competitors to finish better than 5th and 6th. The team was sanguine about the situation when we spoke with them at COTA, telling Ars that the frustration is part and parcel of racing.

But Toyota is committed to its WEC program for at least the next several years. Work in Germany and Japan is focused on next year's hybrid prototype, the TS050. That car will stick with gasoline, but the naturally aspirated V8—now quite long in the tooth—will be replaced with a smaller capacity turbocharged unit. And 2015 is the last year for the supercapacitor hybrid, as Toyota are joining Porsche in the lithium-ion battery club.

Audi's 2015 season has been better, winning the first two rounds in the UK and Belgium. And in almost every event, the fastest lap of the race has gone to one of the R18s. But as Dr. Wolfgang Ullrich, head of Audi Motorsport, puts it, "at Le Mans you don't win the fastest car," you have to have the fewest problems and the least time stationary in the pits. We were able to speak at length to Ullrich and his colleague, Chris Reinke (who heads the Le Mans prototype program) about the Audi's 2015 WEC season and the R18.

Were they finding the competition tougher than ever this year?

"If you look at the first races it was such a close and intense fight for tenths of a second, and you don't get that very often," Ullrich said. "The first two races of the season, and especially Le Mans, the first five or six hours it was such close racing that you can say competitiveness this year is on a very high level. For whatever reason Toyota hasn't been on the same level as Porsche and us, but last year they were the ones to beat, which shows how important it is to make the right decisions year to year to remain competitive."

Reinke told us that the level of competition in 2015 has been much more intense: "For all the years that Audi has done sports car racing there was usually only one other team that was a serious competitor. Now this year there are two. It's us battling against Porsche at the moment, but we know if we set one foot wrong, Toyota has a reliable package that will let them jump in there." We wondered if that level of competition made the effort more rewarding? "Yes, absolutely," Reinke said. "We're here to race, to fight, to challenge, and that's what's happening."

Ullrich and Reinke also explained some of the development the team has made to the car during the year. "It's crucial to have a competitive car in the second half of the season," Ullrich said. "We worked to make the best of the car we prepared from Le Mans, using that car as a base. The tracks after Le Mans have quite different demands, and we knew that in this period of the championship we'd have much races with higher ambient temperatures. We needed a hot country specification, but the basic car is the same. If you want more cooling, you have to be careful you don't run into more aero losses [from cutting holes and vents into the bodywork that add drag]," he said. At COTA, cooling would certainly need to be taken into account by the drivers, engineers, and even the fans in attendance. Even as the rest of the country started to cool in late September, Austin treated us to a day in the mid-90s (mid-30s C for you SI fans) with 65 percent humidity.

After the first race of the year, Audi revised the bodywork on the R18, ready for the Le Mans race. In days gone by, race teams would optimize their cars to be as low-drag as possible in order to maximize speeds on the French circuit's long straights. These days it's a bit different. "The idea that you have low drag configuration for Le Mans is old school. You have to have a more efficient bodywork. You have the Porsche Curves, where you need downforce, so [aerodynamic] efficiency matters. It's the key thing," Reinke says. "We would never give up downforce," Ullrich adds.