ABM_1 - Flipbook - Page 40
FEATURE
HYDROGEN COMBUSTION
The same,
→ Dylan Robertson is a reporter
at Automotive Business Magazine
F
or decades, hydrogen powered
vehicles have been heralded
as the future of motoring.
Whether a hydrogen fuel
cell powered electric vehicle
(FCEV), or a hydrogen-fuelled
internal combustion engine
(ICE), the combination of zero
tailpipe carbon emissions and quick
refuelling has captivated both engineers
and battery electric vehicle (BEV)
sceptics alike.
Hydrogen fuel cell vehicles have already
entered series production, albeit with
limited consumer adoption, but hydrogen
combustion engines are yet to reach the
same level of maturity. Toyota has been
developing the technology for years, and
its Gazoo Racing division previewed a
hydrogen combustion-powered GR Yaris
concept at the Rally Finland round of the
World Rally Championship (WRC) at the
beginning of August.
ABM spoke to Jason Gao, technology
principal for motorsports at Mobil 1,
and Norio Aoki, head of rally engine
development at Toyota, to hear more
about this technology.
Physical differences
On the surface, hydrogen combustion
engines operate in similar ways to
traditional petrol engines, Aoki explains:
“In terms of how the internal combustion
engine works, they are very similar,
almost identical. We have an intake
system where the valve opens, air comes
in. There is a piston, we compress it
together with fuel of some kind and the
gas goes out through the exhaust valve.
From this point of view, they are like a
petrol engine.”
The hydrogen-powered GR Yaris uses
a tweaked version of the standard car’s
1.6-litre turbocharged three-cylinder
engine. However, the modifications
extend beyond simply filling the petrol
tank with hydrogen.
40
AUTOMOTIVE BUSINESS Q4 2025
Hydrogen combustion
engines explained by experts
Aoki continues: “We need to work with
different materials or components. An
injector is an injector, but maybe it needs
a different characteristic. We have a
piston, but maybe we need it to take
care of different combustion behaviour.
“For petrol engines, we have many
choices established. For a hydrogen
engine, there are not many choices that
we can go to the supermarket and buy.
“This is quite a challenge, and we need
to work with partners who are in this
field to try and develop it for the future.”
Similar to electric vehicles (EVs) built on
ICE platforms, converting a petrol engine
to run on hydrogen is possible. But this is
not the most efficient way of harnessing
the technology.
Aoki says: “Conversion is possible.
The car we run as a demonstration
today is a converted version of a Toyota
production engine.
“Ideally, though, we would wish to
come up with the best configuration for
a hydrogen combustion engine, but today
we don’t know what that is.
“We are trying to define what would
be the best kind of hydrogen engine
configuration, which would be different
from a petrol conversion.”
Engineering challenges
The changes go further than
componentry. Even in a petrol engine,
seemingly small changes in oil chemistry
can be the difference between
longevity and premature engine wear.
Hydrogen introduces additional factors
into the mix.
Gao says: “Hydrogen is a fuel which
is easy to ignite, it’s actually easier
than gasoline. So, if there are any
hotspots, you have a phenomenon called
‘preignition’. That means ignition does
not happen on schedule based on the
engine’s design.
“Lubricants could contribute to it, and
we have been looking at lubricants that
