Toyota has been a vocal, if sometimes solitary, advocate of hydrogen combustion since Toyoda climbed behind the wheel of that prototype Corolla race car. Over the past year, he has driven the hydrogen-burning Corolla, and more recently a hydrogen-powered Yaris, in numerous races.

But Toyoda's message that carbon,not combustion, is the ememy has gained little traction in a global industry that's plowing hundreds of billions of dollars into pluggable EVs.

Hydrogen combustion is actually carbon free. And it has the added benefit of piggybacking on existing engine technologies and the sprawling worldwide network of suppliers and workers that develop and deliver them. For companies vested in internal combustion products, such as BorgWarner or Riken, hydrogen promises a more seamless transition to a  carbon-neutral future.

"The problem is not the internal combustion engine," said Hans Hardam, country manager and chief engineer for fuel systems at BorgWarner Japan Ltd. "The problem is carbon."

His sentiment echoes Toyoda's almost to the letter. As head of the world's biggest automaker, Toyoda misses no opportunity to espouse his company's philosophy that clean-burning combustion is just as viable in the carbon neutral gambit as EVs and fuel cell vehicles.

Meanwhile, other automotive players are delving into hydrogen combustion, including Daimler, MAN Truck and Bus, engine maker Cummins and powertrain specialist AVL. In Japan, Yamaha Motor is looking at it for potential use in motorcycles and all-terrain runabouts. Earlier this year, Yamaha worked up a 5.0-liter V-8 hydrogen engine based on the Toyota powertrain used in the Lexus RC F sport coupe.

Aiming even higher, Rolls-Royce is teaming with easyJet to put hydrogen engines in planes.

On the ground, hydrogen combustion proponents see the potential for early commercialization in trucks and other heavy vehicles in construction, agriculture or marine applications. Hydrogen's density makes it a better substitute for diesel than electric batteries. Machines that work long hours with heavy loads would need impractical heavy and expensive battery packs, the thinking goes.

BorgWarner expects initial deployment in heavy vehicles, but it also sees use in SUVs and pickups — vehicles that are heavy in their own right and often used to haul hefty cargo. But the company also believe there is an opportunity for hydrogen combustion in niche markets for sports cars and off-roaders.

BorgWarner has been working on hydrogen combustion for a decade and has two development centers for it in Europe, one in Blois, France, the other in Gillingham, UK. But discussions with customers have picked up only in recent years, Hardam said.

For old-school combustion specialists like BorgWarner and Riken, the prospect for hydrogen combustion cushions what might otherwise be a jarring shift to an all-electric future.

"The auto parts industry is also facing a 'once-in-a-century period of great change,' and is required to undergo major changes and reforms," Riken said of its hydrogen initiative. "We will make maximum use of the engine knowledge that we have accumulated over 90 years and focus on developing hydrogen engines as next-generation engines that will achieve decarbonization."

Suppliers are under pressure. BorgWarner has committed to going carbon neutral in its operations by 2035 and sees hydrogen combustion as a way to ease into the future by tweaking today's technologies.

"With 5.5 million people working in Japan's auto industry, we want to avoid too quick of an industry structural change," said Kunihiko Mishima, general manager of BorgWarner Morse Systems Japan, one of the company's local subsidiaries. "That's why Japanese manufacturers are thinking about alternative fuels and so on. Japanese OEMs are very, very serious about carbon neutrality."

But BorgWarner, which reached just under $14 billion in original equipment parts sales last year, wants to go carbon neutral by building on its existing expertise in turbochargers, injectors, fuel rails, temperature sensors and EGR systems. It also sees potential in hydrogen engine control units and software modules to regulate the pressure of hydrogen from the tank.

Turbochargers, in particular, are required for hydrogen engines in order to deliver the optimum balance of power and emissions, the company says. Hydrogen needs more air than gasoline in the combustion equation and needs to operate on the lean side to tamp down temperatures. Hydrogen also has the potential for higher thermal efficiency than gasoline, BorgWarner predicts.

While the systems are virtually carbon free — they emit only trace amounts from burned-off lubricant — they are not emissions free. As with diesel, nitrogen oxide is the main challenge.

But BorgWarner sees hydrogen combustion as an important tool in reaching its corporate goal of carbon neutrality by 2035. And like Toyota, which champions hydrogen as just one path forward, BorgWarner also sees the systems as part of a mixed-cocktail approach for a greener tomorrow.

Small passenger cars will likely gravitate toward pure battery electrics, while hydrogen fuel cells will eventually emerge as a more mainstream option across the board.

But hydrogen combustion will fill certain gaps.

The technology adds as much as 30 percent to the cost of existing engines. But because it builds on proven technology, hydrogen combustion is still cheaper than battery electrics and fuel cells.

And because the supply chain already exists, hydrogen combustion can be brought to market more quickly than next-generation batteries and fuel cell stacks. Compared with fuel cells, hydrogen combustion is less costly, more reliable and more durable, proponents say. But it also lags fuel cell technology a little in efficiency. And compared with pure battery electric systems, hydrogen combustion performs better in cold and hot environments and under heavy loads.

Because hydrogen combustion is such a nascent and niche technology, there is little in the way of a forecast of its long-term market penetration. But BorgWarner predicts hydrogen combustion could eventually comprise 20 percent to 30 percent of the heavy-duty vehicle and equipment sector.

"There are still a lot of unknowns," Hardam said. "But there is high potential in this market."

Leveraging existing combustion technologies is key for old-school suppliers such as BorgWarner. But even as it seeks to modernize its portfolio, it isn't ignoring the migration to EVs. The company got just under 3 percent of its global revenue from EV-related products last year. It wants that to increase to 25 percent or more in 2025, and then to 45 percent in 2030. It has a long checklist of new products to target, including electric drive motors, inverters, on-board chargers, DC-DC converters and battery pack controllers.

"You will see much more diversity in powertrains," Hardam said. "It will be a cocktail mix of solutions depending on the market, the region, company policies and government policies."

BorgWarner has a big presence in Japan, with two factories and a network of technical centers and engineering offices that serve almost all of Japan's big automakers. It also has a joint venture with Japanese steering and ball-and-bearing maker NSK Corp.

In Japan, it started making engine and transmission chains and now makes all-manner of engine-related components, including timing chains, sprockets and variable cam timing systems.

But BorgWarner isn't delving into hydrogen combustion simply as a play for business with Toyota. It seeks merits in the technology in its own right. Its main research centers are in Europe, and it is casting for customers not only in Japan but in South Korea, Europe, China and the U.S.

Explains Hardam: "It's not just a Japanese or a Toyota-only activity."