Hydrogen Motor

Mazda Premacy Hydrogen RE Hybrid

Mazda Premacy Hydrogen RE Hybrid (2007)

The Mazda5 Hydrogen RE Hybrid concept vehicle is the next step in Mazda's ecofriendly engine technology, and proves once again the flexibility of the rotary engine. By virtue of its compact size, RENESIS could be redesigned for a Mazda5 in an east-west, frontwheel drive layout in the RX-8, it has a front engine, rear-wheel drive layou leaving enough room in the engine compartment for the electric motor. The batteries of the electric motor and the petrol fuel tank could be located under the second row seats where they do not take away space in the interior. This in turn allowed engineers to place the high-pressure hydrogen fuel tank where Mazda5's third row of seats would normally be, with space behind the tank for luggage. They also added a tray on top of the tank to transport smaller items. The Mazda5 Hydrogen RE Hybrid, then, is a five-seat compact MAV that retains interior comfort, despite having three different power sources.

The concept not only delivers the comfort expected of a five-seat Mazda5, its low emissions and fuel consumption would mean additional benefits for buyers whenever it would eventually go into production. And since the petrol-only version of the RENESIS rotary powerplant requires just minor engine changes to use hydrogen, it would be inexpensive to adapt and produce.

Mazda Premacy Hydrogen RE Hybrid Mazda Premacy Hydrogen RE Hybrid Mazda Hybrid Technology The Advantages of Electric Motor Support

The Mazda5 Hydrogen RE Hybrid concept employs a dual-fuel system that is supported by a 30 kW/40 PS electric motor. The hybrid electric motor system is an especially eco-friendly aspect of this aggregate, since it stops the engine in some driving situations (standing at a traffic light, for instance) to save fuel, then restarts the engine when the driver is ready to pull away again. The electric motor also helps to ensure superior engine response during acceleration by supplementing the engine's torque. During deceleration the motor functions as a generator, recovering braking energy and using it to charge the battery.

Mazda Premacy Hydrogen RE Hybrid Mazda Premacy Hydrogen RE Hybrid Mazda Hydrogen Rotary Engine Technology

Working in conjunction with the electric motor of the Mazda5 Hydrogen RE Hybrid concept is the RENESIS dual-fuel hydrogen/petrol rotary engine.

This system is designed to be especially easy and practical to use in real world driving and features "on the fly" fuel selection, which allows the driver to switch from hydrogen to petrol mode without stopping the car. This is useful on long journeys or when driving through areas where there is no hydrogen infrastructure. The selection switch is located on the instrument panel in front of the driver. If the concept vehicle runs out of hydrogen during hydrogen-mode operation, it automatically switches to petrol mode.

The Mazda5 Hydrogen RE Hybrid engine is supplied with hydrogen gas by an electronically controlled direct-injection system. With each of the engine's two rotor housings, air is drawn through a side port and hydrogen is injected directly into the induction chamber by an electronically controlled gas injector on the top of the rotor housing. There are several engine technologies employed to maximize the benefits of the rotary engine in hydrogencombustion mode, including:

Backfire Suppression

Unlike a reciprocating engine, a rotary engine has separate lowtemperature induction chambers and high-temperature combustion chambers. With the RENESIS hydrogen rotary engine, therefore, there is no risk of ignition in the part of the operating cycle in which hydrogen is injected. In other words, the Mazda5 Hydrogen RE Hybrid concept's rotary engine realizes superior combustion without ever backfiring.

Direct Injection + Exhaust-gas Recirculation (EGR)

The concept's rotary engine, with its separate induction and combustion chambers, ensures a safer temperature compared to the higher temperatures here of a conventional piston engin for fitting the hydrogen injectors with their rubber seals. This allows the gas injectors to be mounted directly on the rotor housings beside the induction chambers for direct-injection.

In accordance with driving conditions, the direct-injection arrangement is optimally combined with a system that injects fuel into the intake manifold. An EGR system complements the fuelsupply arrangement to further enhance the engine's combination of high power and low exhaust emissions.

Excellent Mixing of Hydrogen and Air

A rotary engine also has a more vigorous intake flow and a longer operating cycle than a piston engine. This allows for an optimal mixing of the hydrogen-air intake charge and contributes to a uniform mixture, which is critical for hydrogen combustion.


The Mazda5 Hydrogen RE Hybrid is equipped with sensors to detect leakage of hydrogen gas and prevent accidents. These sensors are located in the engine compartment, cabin and fuel tank. Warning of gas leakage is indicated by these sensors and they close the safety valve installed in the hydrogen tank.