In late May, a special Toyota Corolla entered the track at Fuji Speedway in Japan to take part in a 24-hour race. Unlike the other cars in the race, this one was hydrogen-powered. But it didn’t use a fuel cell like the Mirai sedan; instead, this car’s three-cylinder engine was converted to burn the gas instead of burning gas(oline). The driver line-up for the car showed why. Among the racers listed was a “Morizo,” better known to the world as Akio Toyoda, Toyota Motor Company’s president.
No pressure, then.
“The reason for competing in a 24-hour endurance race is that simply lasting three or five hours is not enough. You have to have done the preparation to last for 24 hours,” Toyoda said in the weeks before the race. There’s no doubt about it—completing a 24-hour race is no easy thing, and the crucible of racing will often reveal problems that engineers don’t encounter on the test bench.
But Toyoda had another reason for strapping into the Corolla instead of the GR Yaris that he and his Rookie Racing teammates used to contest the first two rounds of the Super Taikyu endurance racing series. “Many people in Japan associate hydrogen with explosions. So I want to show that it is safe by driving in a race myself,” he explained.
Three months to get ready
Getting the OK from the accountants for a new racing program is easier when the boss is one of the driving forces behind the idea. But there still wasn’t much time to get everything ready. “We started to build the Corolla in February, so only three months ago,” said Naoyuki Sakamoto, chief engineer of Hydrogen Engine Corolla.
That meant using plenty of off-the-shelf components. The turbocharged 1.6 L, three-cylinder engine was borrowed from the GR Yaris. “We revised some parts, such as the fuel delivery system, fuel injection and ignition systems to convert it into hydrogen engine,” Sakamoto told me.
“The fuel tank, delivery system, and the fuel management system was already developed for Toyota’s fuel cell EV Mirai. So the safety is already confirmed,” Sakamoto explained. The car features four H2 tanks—two medium-sized ones from the Mirai and another pair that were slightly shorter—surrounded by carbon fiber reinforced plastic to protect them in the event of a crash. In total, the four tanks have a capacity of 180 L at 70 MPa (700 bar), about 27 percent more than a Mirai.
“The combustion speed of hydrogen is very fast, and that’s the biggest advantage over petrol engines, but it’s difficult to control. So our biggest challenge of developing the hydrogen engine was combustion management,” Sakamoto said. To that end, his team converted the engine to direct injection, with an injector system developed by Denso. Toyota wouldn’t talk specifics, but Teru Ogawa, group manager of the Advanced Powertrain Engineering Division Number 2, told me that the injection system runs at comparable pressure to a gasoline direct injection system. In terms of power, “compared to the gasoline engine, there’s not too much of a loss right now,” Ogawa said.
During the race, the H2 Corolla required much longer refueling stops than the conventionally fueled race cars. Fuji Speedway does not have a hydrogen infrastructure, so Toyota arranged for a mobile H2 filling station to be parked in the paddock. “The refilling stations are also using support and grants from the [Japanese] government right now, So you can only use it on off days. But the qualifying day was actually on a weekday, so we had a lot of discussions and negotiations to allow that to happen,” Ogawa said. (The H2 itself was produced by electrolysis of water using renewable electricity at a site in Fukushima Prefecture.)
After completing any servicing in the pit lane (like changing tires or swapping drivers), the H2 Corolla drove into the paddock, where there were two H2 refueling stations. “Refueling speed is proportional to the pressure difference between the station and the vehicle’s pressure tanks,” explained Sakamoto, so it proved quicker to partially refuel from one station and then disconnect and complete fueling from a second. Even so, a refueling stop still took between six and seven minutes, and the H2 Corolla needed 35 stops to complete 358 laps.
Race one was a success
“The first and foremost goal of entering this race was to complete a complete 24-hour race, and so we’re very happy with that accomplishment,” said Ogawa, despite losing a total of eight hours during the race to repair work. And it was a learning experience for the engineers, who were able to identify some pre-ignition and abnormal combustion issues that had not appeared in bench testing. “The occurrences changed according to how the driver was operating the vehicle, and so our first job is to analyze the data and figure out why,” Ogawa said.
“Now we are taking apart the engine and checking if any parts are damaged. After that, we will probably change the combustion management system,” Sakamoto told me. The H2 Corolla’s next outing will be at a five-hour race at Autopolis on July 31 through August 1.
Listing image by Toyota