Hydrogen Vehicle

The hydrogen rotary engine is extremely eco-friendly and perfect for a society in which people can continue to enjoy Zoom-Zoom driving while caring for the Earth

Hydrogen rotary engine

Mazda's hydrogen rotary engine, based on our unique rotary engine technology but adapted to use hydrogen as its fuel, emits no CO2 and offers superb environmental performance.
Because the rotary engine required only a few design changes to allow it to operate on hydrogen, Mazda was able to build hydrogen-fueled rotary engine vehicles at low cost. Also, a dual-fuel system allows the vehicle to run on either gasoline or hydrogen. The driver does not need to be concerned about running out of hydrogen making the car convenient because it can travel long distances to areas without hydrogen stations.

Technologies of the RENESIS hydrogen rotary engine

The RENESIS hydrogen rotary engine employs direct injection, with an electronically-controlled hydrogen gas injector. This system draws in air from a side port and injects hydrogen directly into the intake chamber with an electronically-controlled hydrogen gas injector installed on the top of the rotor housing. The technology illustrated below takes full advantage of the benefits of the rotary engine in achieving hydrogen combustion.

Outline of RENESIS hydrogen rotary engine

Watch a video showing the movement of hydrogen rotary engine

1 RE features suited to hydrogen combustion - natural suppression of backfiring -

In the practical application of hydrogen internal combustion engines, avoidance of so-called backfiring (premature ignition) is a major issue. Backfiring is ignition caused by the fuel coming in contact with hot engine parts during the intake process. In reciprocal engines, the intake, compression, combustion and exhaust processes take place in the same location-within the cylinders. As a result, the ignition plugs and exhaust valves reach a high temperature due to the heat of combustion and the intake process becomes prone to backfiring.
In contrast, the RE structure has no intake and exhaust valves, and the low-temperature intake chamber and high-temperature combustion chamber are separated. This allows good combustion and helps avoid backfiring.
Further, the RE encourages thorough mixing of hydrogen and air since the duration of the intake process is longer than in reciprocal engines.

2 Combined use of direct injection and premixing

Aiming to achieve a high output in hydrogen fuel mode, a direct injection system is applied by installing an electronically-controlled hydrogen gas injector on the top of the rotor housing. Structurally, the RE has considerable freedom of injector layout, so it is well suited to direct injection.
Further, a gas injector for premixing is installed on the intake pipe enabling the combined use of direct injection and premixing depending on driving conditions. This produces optimal hydrogen combustion.
When in gasoline fuel mode, fuel is supplied from the same gasoline injector as in the standard gasoline engine.

3 Adoption of lean burn and EGR

Lean burn and exhaust gas recirculation (EGR) are adopted to reduce nitrogen oxide (NOx) emissions. NOx is primarily reduced by lean burn at low engine speeds, and by EGR and a three-way catalyst at high engine speeds. The three-way catalyst is the same as that used in the base model. Optimal and appropriate use of lean burn and EGR satisfies both goals of high output and low emissions.

4 Dual-fuel system

When the system runs out of hydrogen fuel, it automatically switches to gasoline fuel. For increased convenience, the driver can also manually switch the fuel from hydrogen to gasoline at the touch of a button.

Hydrogen Rotary Engine Vehicles

Premacy Hydrogen RE Hybrid/ Hydrogen RE Plug in Hybrid

The Premacy Hydrogen RE Hybrid combines Mazda's hydrogen rotary engine with a hybrid system for significantly improved performance and practicality

The Premacy Hydrogen RE Hybrid inherits the dual-fuel system from the Mazda RX-8 Hydrogen RE and combines it with a newly developed hybrid system for greatly enhanced driving performance and practicality. The Premacy Hydrogen RE Hybrid has been available on lease to governmental bodies and companies in Japan since March 2009.

The layout of the Premacy Hydrogen RE Hybrid

The advanced hydrogen RE power unit realizes the excitement and power of Zoom-Zoom!

The Premacy Hydrogen RE Hybrid produces approximately 40 percent more power than the Mazda RX-8 Hydrogen RE, resulting in significantly enhanced acceleration. It also improves fuel economy. The heart of the vehicle, the hydrogen rotary engine, is switched from a longitudinal to a transverse layout. The engine's reduced intake/exhaust resistance and improved combustion efficiency yields high power output across a wide range of engine speeds.
The hybrid system efficiently converts the hydrogen combustion energy to electricity, which drives the wheels via an electric motor. This setup is extremely energy efficient and provides exceptional vehicle response. As a result, drivers enjoy low fuel consumption as well as direct feel and powerful ride, and driving range of 200 kilometers on hydrogen fuel. For even greater range, the model is equipped with Mazda's dual-fuel system that allows the car run on gasoline as well as hydrogen. Being a Premacy, it is also more user-friendly than the RX-8 Hydrogen RE, offering greater cargo space and seating for five adults.

Watch a video showing how the hydrogen rotary vehicle runs

“Mazda Premacy Hydrogen RE Range Extender EV” based on “Mazda Premacy Hydrogen RE Hybrid”. It adapts plug-in-system, a larger high-voltage battery and a thermal efficiency-improved engine.

RX-8 Hydrogen RE

The ultimate “green” car, providing an unrivaled balance of fun-to-drive and eco-friendliness

The Mazda RX-8 Hydrogen RE, developed and commercialized by Mazda, is the world's first practical implementation of a hydrogen rotary engine vehicle. Without compromising the sensations of torque and acceleration nor the exhaust note unique to internal combustion engines, it emits no CO2 and almost no NOx making it the ultimate “green” car. In Japan, the vehicle has been offered for lease to local governments and enterprises since 2006, and in 2008 Mazda began to participate in the Norwegian hydrogen highway project “HyNor.”


Seating capacity of four adults has been maintained from the base vehicle, with two hydrogen tanks installed in the trunk. The tanks are pressurized to 35 Mpa, the current national standard for hydrogen fueling station. The hydrogen filler valve is the one commonly used in fuel cell vehicles, located on the opposite side of the gasoline filler valve on the base vehicle.

Vehicle layout