Alpine's hydrogen V6 hypercar could make production

Racers at the 24 Hours of Le Mans – which will include a hydrogen-combustion class for the first time in 2027 – typically complete 10 to 20 laps of the nearly-8.5-mile circuit before they pit for fuel.

Alpine also plans for the V6 to put out more power than the Hy4’s turbocharged 2.0-litre unit, which makes 335bhp.

Although the V6 is being developed with a view to eventually go racing, it’s possible that it could also be deployed on a road car, thanks to user-friendly power delivery.

“It’s not going to be an F1 engine revving very very high,” said François Champod, Alpine’s director of racing vehicles. He added that it would drive comparably to existing petrol engines.

But that isn't to say that it would drive identically. Pierre-Jean Tardy, Alpine’s chief hydrogen engineer, told Autocar that the nature of hydrogen would bring some key differences.

He explained: “From the passion point of view, it’s almost the same sound, almost the same response. However, there could be some elements that could bring a difference to the response.

“Running clean on hydrogen means that you have to make sure that your NOx emissions will be low. Low NOx emissions – and also for efficiency – you want to run lean, and leaner than for gasoline.

“Running lean with hydrogen produces lower-temperature exhaust gas, which means that for a turbocharger, [you have to work the compressor harder] with less energy available on the turbine. There’s a sort of imbalance between the turbine and the compressor, which is even higher than on a diesel engine. This could cause some lag time problems that you will have to get around by other means.”

Tardy added that mitigating engine knock is also a big challenge for hydrogen engines, because hydrogen is flammable over a wider range of fuel-to-air concentrations than petrol is. Hydrogen burns at concentrations from 4% to 76%, whereas petrol vapour ignites from 1.4% to 7.6%. This means that – within a single combustion chamber – the mix of hydrogen and air can simultaneously be lean and rich.

“We will learn from this engine how that works, how to improve the combustion process and how to improve the mixture preparation,” said Tardy.

He explained: “It’s much more difficult to properly mix a gas like hydrogen with a gas like air – gas-to-gas – than with gas droplets [vapour] in air. This isn't easy to figure out, but it’s the truth. Especially when hydrogen comes out of the injector: it comes with a massive velocity, and that makes it more difficult to mix properly with air.

“The more you increase the speed of the engine, the less time you have to inject. The more you increase the power, the more thermal load you have. So you also have more risk of abnormal combustions [knock].”

This creates issues not only in cooling the engine but in ensuring that you manage temperatures “homogeneously” in each combustion chamber.

Several Alpine executives conceded that the hydrogen-combustion project was still at an early stage. The new V6 recently entered dynamometer testing, and the brand has committed to it powering the Alpenglow by the end of this year. 

Alpine is expected to enter a hydrogen-combustion car into the 24 Hours of Le Mans in 2027, but it has yet to make a firm commitment to the event. It said in a statement that it's “paying close attention to changes in competition regulations”.

As for when a hydrogen-burning road car could be ready, Champod said: “It’s early days, it’s going to be research years. For the road, it’s not all in our hands. It’s all about infrastructure and these kinds of things. So I can’t really say how far it’s going to progress.”