AUSTIN, TEXAS—The World Endurance Championship's annual visit to the US is one of the hottest events in racing—figuratively and literally, given the sweltering heat and humidity that afflicts Austin in mid-September. We at Ars have made it to every Lone Star Le Mans weekend, and 2016 was no exception.

You can check out stunning images of the IMSA WeatherTech race elsewhere on the site (the first of the two double-bill headliners), but now it's time to talk prototypes. Specifically, the 1,000hp (745kW) hybrids that compete in the Le Mans Prototype 1 class. Audi, Porsche, and Toyota each enter two-car teams which compete around the world, most often over the course of six hours, although at Le Mans in June the race is obviously four times that.

Porsche

Porsche

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

For our money, nothing else in the world of racing pushes so many buttons. The LMP1 hybrids are breathtakingly fast. Sure, a Formula 1 car is faster on the same FIA Grade 1 circuits; comparing fastest qualifying and racing laps at Spa for both series' visits in 2016 shows the former to be between eight and nine seconds faster over the same 4.3 miles (7km). But the LMP1s weigh an extra 381 lbs (172 kg), and adding 2.2 lbs (1 kg) to an F1 car is commonly held to add 0.1 seconds to a lap.

The allure of LMP1 is more than speed. For one thing, cars run on (Michelin) tires that aren't designed to artificially degrade in order to spice things up. Endurance Drivers can—and indeed must—push from the moment the race starts until the checkered flag waves. And compared to F1, the rulebook is wide-open. Manufacturers simply pick how much energy they intend to deploy from the hybrid systems—currently Audi is at 6MJ per lap of Le Mans, while Toyota and Porsche are both at the maximum of 8MJ—and off they go.

Want a naturally aspirated V8? Go for it. Four-cylinder turbocharged V4? Why not. How about a V6 turbodiesel? All have or are being raced in WEC. And there's freedom with the hybrid systems as well: currently two are allowed on each car, with three being permissible from 2018 with the addition of a new 10MJ class. Oh, and we've also seen electromechanical flywheels and supercapacitors as energy stores in previous years, although by 2016 all three had coalesced around lithium-ion batteries. (You can read a more in-depth technical look at the Audi, Porsche, and Toyota in this piece from March.)

What really caps our love of the World Endurance Championship is how this technological arms-race has direct relevance for our road cars. The new direct injection turbocharged engines in Porsche's 911 and 718 road cars use a cylinder head design that's almost carried over from the 919 Hybrid's V4, and if you drive a new Toyota Prius, the control electronics that govern its hybrid system were first tested on the TS040.

2016 has been quite the year in the LMP1 class, particularly after 2015 was utterly dominated by Porsche's 919 Hybrid. A look at the results suggests a repeat performance, with Porsche winning every round bar the Spa-Francorchamps in May. Reliability woes cost Toyota's TS050 the win in Belgium (their loss being Audi's gain) and at Le Mans (where the lead car failed with three minutes left on the clock). As for Audi, where caution and conservatism have ruled in the past, this year's R18 pushes the envelope such that it's unquestionably the fastest of the three—the consequence being a level of unreliability that we've not seen from the four rings since the turn of the century.

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Elle Cayabyab Gitlin

Porsche

As far as Porsche Team Principal Andreas Seidl is concerned, there's always room to improve. He told Ars:

We're still a young team, and we can still make huge steps compared to last year. The lap times in qualifying were quite a bit quicker than last year even though per the regulations we lost quite a lot of performance on the fuel flow side and so on. So it just confirms how motorsport is—you never stand still, you're always looking for improvements on the car, there's always something to improve, and looking at us, being a young team, even the basics of the car you can still find a lot of performance improvements.

Seidl told us the decision to start the 919 Hybrid program in 2014 in the top 8MJ class wasn't without consequences, but the results the past two years appear to have borne that strategy out. He told us:

We went straight to lithium batteries plus two energy recovery systems, including the only ones using an exhaust energy recovery system. We paid our price in the first year for being so aggressive with some reliability issues, which is normal if you set something up from scratch, but obviously we benefited big time last year—we clearly had the fastest car over the entire season.

This year's 919 Hybrid keeps the same basic concept—a 2.0L turbocharged V4 gasoline engine driving the rear wheels, a motor-generator unit recovering and deploying kinetic energy at the front axle, and an exhaust energy recovery system that also sends its power to the front (via the car's lithium-ion batteries).

If you look what we did over the winter, we kept the basic concept the same, but touched nearly 80-90 percent of the parts on the car—every area. There are improvements on the engine side—efficiency, weight, performance. And the same on the hybrid side. Obviously we're working a lot on the drivability of the car; sensitivity of the aerodynamics especially during cornering, the sensitivity regarding side winds, crosswinds, and so on. We're acting on what we learned on every race last year. Even if you have dominant performances—and we had a lot of those last year—there's always a long list of things that can be done better.

Although Porsche has decades of success at the top level of endurance racing, that didn't mean the 919 Hybrid program has been simple. Aside from an aborted program in 2000 that was quickly consigned to the memory hole, the company hadn't built and raced a prototype for many years. That meant starting a team from scratch. We asked Seidl if having a hybrid system was challenging. He said with a smile: