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Mazda wasn’t the sole company to explore the comically named Wankel rotary engine. Nevertheless, this power source has remained a symbol of Mazda’s technical ingenuity throughout its history. In a similar fashion, the company once assembled and put to the test a hydrogen-fueled rotary-engine vehicle, recognized as the RX-8 Hydrogen RE.
Hydrogen has been viewed as an appealing substitute for traditional fuels for various reasons. It can be generated sustainably using renewable resources, and when utilized in an internal combustion engine, it burns significantly cleaner than gasoline or diesel, producing almost zero carbon emissions. The exhaust primarily consists of water vapor, with a minor amount of nitrogen oxides still being released.
Mazda delved into the application of hydrogen as a compromise between ecological considerations and performance. Thus, in 2003, the RX-8 Hydrogen RE was born, showcasing an altered twin-rotor Wankel engine capable of operating on either gasoline or hydrogen. The Renesis R2 engine could yield 206 hp on gasoline and 107 hp on hydrogen, with acceleration times of 7.2 and 10 seconds from 0-60 mph, respectively.
The vehicle was equipped with an aluminum and carbon-fiber hydrogen tank capable of storing up to 5.3 pounds (2.4 kilograms) of the gaseous fuel, alongside the standard 16-gallon gasoline tank. The hydrogen tank added 187 pounds to the car and occupied most of the space in the already compact trunk of the RX-8. The 5.3 pounds of hydrogen offered a range of 62 miles (100 km), and the vehicle could seamlessly switch between the two fuels at the push of a button.
The rotary engine was particularly well-suited for hydrogen combustion. Unlike a conventional piston engine, the intake and combustion regions in a Wankel rotary engine are distinct, reducing issues related to premature ignition often associated with hydrogen fuel usage. This design also offered ample flexibility for injector placement, enabling Mazda to incorporate both direct and premixing injectors; this combination allowed for optimizing performance based on prevailing driving conditions.
Hydrogen has not gained popularity as a fuel for internal combustion engines due to various factors. While hydrogen engines can be calibrated to deliver similar power outputs to conventional gasoline engines, in this stoichiometric operational zone, they release significant quantities of nitrogen oxides, which are pollutants in their own right. They can be adjusted to minimize these emissions to nearly zero, albeit at the expense of generating roughly half the power of an equivalent gasoline-powered unit.
Challenges related to hydrogen production and storage are also prevalent. While it is feasible to produce hydrogen in an environmentally friendly manner, most hydrogen is currently generated using relatively polluting methods. Similar to electric vehicles, hydrogen faces the obstacle of necessitating a substantial deployment of new infrastructure to become a viable option. As of today, this transformation has yet to materialize, with only a handful of hydrogen refueling stations operational worldwide.
Mazda devoted significant resources to developing hydrogen-powered vehicles. These engines found their way into a range of Mazda models over the years, from the MX-5 to the Premacy minivan. There were even some semi-public experiments, with a number of RX-8 Hydrogen REs being leased in Japan, while 30 units heading to Norway for testing under the HyNor project.
However, due to limited demand and numerous challenges, the hydrogen rotary engine never reached production. Today, several companies are still exploring hydrogen combustion technology, including Mazda. Yet, it appears unlikely to compete directly with electric vehicles as the latter continue to gain prominence.
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