Toyota has released details of the 5.0-litre V8 internal combustion engine that runs on hydrogen, developed in collaboration with Yamaha Motor.

Unlike the hydrogen fuel-cell powertrain used in the Toyota Mirai, in which hydrogen is used to generate electricity, this prototype burns hydrogen in place of petrol, leaving water as the only emissions.

The engine is based on the 5.0-litre V8 unit found in the Lexus RC F sports coupe. Yamaha says it delivers up to 450hp at 6,800rpm and a maximum 540Nm of torque of at 3,600rpm, which is only slightly less than the petrol version.

Japanese car makers are publicly committed to collaborative research to investigate alternative fuels for internal combustion engines. In November 2021, Kawasaki Heavy Industries, Subaru, Toyota, Mazda and Yamaha announced an ambition to “expand the range of fuel options for internal combustion engines in the quest for carbon neutrality”. The partners plan to experiment with biodiesel and synthetic fuels as well as hydrogen.

Yamaha Motor president Yoshihiro Hidaka is reported as saying “‘Motor’ is in our company name and we accordingly have a strong passion for and level of commitment to the internal combustion engine.”

Burning hydrogen in a combustion engine isn’t a new idea. Two decades ago BMW produced the Hydrogen 7, a 7-Series with a hydrogen-powered V-12. But the idea is seemingly being taken seriously again with Renault revealing this week that it will introduce a hydrogen internal combustion engine concept model in May.

However the chemistry of using hydrogen as a fuel for internal combustion engines is hard to stack up. Firstly a litre of liquid hydrogen provides about a quarter of the energy of a litre of petrol; and hydrogen needs to be super-cooled to remain in a liquid state.

Then there is the issue that internal combustion engines are at best 40% efficient, in contrast to an electric motor that typically turns 90% of the electricity into movement.

And from a carbon perspective, a hydrogen internal combustion engine is only carbon neutral if the hydrogen is manufactured using electrolysis powered by renewable energy sources. Currently production of so call green hydrogen is very limited and expensive.

Yamaha’s president Yoshihiro Hidaka however maintains “Hydrogen engines house the potential to be carbon-neutral while keeping our passion for the internal combustion engine alive at the same time.”