Mazda5 Hydrogen RE Hybrid Concept

At the British Motor Show, Mazda is showing its "green" side with the Mazda5 Hydrogen RE Concept. The 5-seat MPV (Mazda calls it an MAV - Multi Activity Vehicle) is fitted with Mazda's dual-fuel Hydrogen/gasoline RENESIS rotary engine. It, in turn, is supplemented by a 30kW/40PS electric motor, which allows for torque assistance, stop/start functionality, and regenerative braking. Both units fit underhood thanks to the RENESIS' compact size.

The Mazda5's FWD configuration allowed engineers to locate the gasoline tank and lithium-ion batteries beneath the second row of seats. The hydrogen tank resides where one would normally find the third row of seats. This still leaves storage space for luggage in back, and a storage shelf was placed atop the hydrogen tank.

The driver can control whether the engine runs in gasoline or hydrogen mode via a control in the cockpit. Furthermore, if the car runs out of fuel in hydrogen mode, it will seamlessly transition to gasoline operation. Maximum power in hydrogen mode is 109 horsepower, while in gasoline mode it makes 210. Curiously, fuel economy and emissions stats were not provided. With a "green" vehicle, these are the numbers people are most interested in.

In any case, a hybrid powertrain in a package like the Mazda5 would likely be attractive to people who are looking for greater utility than a Civic or Prius can provide, but aren't interested in an SUV like the Highlander, Lexus RX or Escape/Mariner/Tribute. The Mazda5 Hydrogen RE concept is an interesting study that blends different alternative fuel technologies in a practical vehicle. Furthermore, the use of RENESIS engine emphasizes the car's "Mazda-ness."

(Additional info and more photos after the jump)

[Source: Mazda]

Mazda5 Hydrogen RE Hybrid ConceptMazda5 Hydrogen RE Hybrid Concept


Mazda5 Hydrogen RE Hybrid Concept

Zoom-Zoom Performance with Low Emissions

Also on stage at The British International Motor Show is an ecofriendly concept vehicle, the Mazda5 Hydrogen RE Hybrid, which employs Mazda's unique hydrogen rotary engine technology with an electric motor.

This concept combines Zoom-Zoom performance with very low emissions, and is a further example of the flexibility and
environmental potential of Mazda's rotary-engine technology. Placed in a transverse, front-wheel drive layout, the hybrid engine allows optimal packaging for a Mazda5 concept that seats five people without sacrificing comfort.

Mazda Motor Corporation has consistently applied its engineering expertise to develop viable hydrogen-fuel rotary engines with the goal of reducing harmful emissions without sacrificing Mazda Zoom-Zoom driving fun.

After introducing the rear-wheel drive Mazda RX-8 Hydrogen RE concept two years ago in Geneva, Mazda now introduces a frontwheel drive hydrogen rotary engine concept in its roomy, compact multi-activity vehicle (MAV), Mazda5, combined this time with hybrid technology. This concept is the latest test vehicle from over 15 years of Mazda alternative fuel development that began with the Mazda HR-X in 1991 and includes an experimental MX-5 hydrogen rotary vehicle, and fuel-cell electric vehicles.

A turning point in Mazda's eco-friendly engine development, however, came with the launch of Mazda RX-8's revolutionary RENESIS rotary engine in 2003, which won a total of four International Engine of the Year awards in 2003 and 2004.

This naturally-aspirated petrol rotary engine delivers a marked improvement in both emissions (achieving Euro Stage IV compliance) and fuel consumption compared to Mazda's previous generation of turbocharged rotary engines, while retaining and even improving the traditional strengths of the rotary engine concept – smooth, high-rev performance and power delivery in a very compact size. Over 15 years of developing hydrogen-fuel rotary engines was applied to this new rotary generation and Mazda engineers quickly developed and built a dual-fuel hydrogen/petrol version of RENESIS.

This version of the RX-8 has been introduced for fleet leasing this year. With the Mazda5 Hydrogen RE Hybrid, all three of these technologies – petrol, hydrogen and electric – come together in one concept vehicle. Onboard is RENESIS rotary engine performance using either hydrogen or petrol as fuel, and the advantages of a 30 kW/40 PS electric motor, which enhances torque and further lowers fuel consumption by facilitating idle-stop.

Comfort and Interior Space

The Mazda5 Hydrogen RE Hybrid concept vehicle is the next step in Mazda's eco-friendly 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 layout – 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 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 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 engine – 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.

Mazda5 Hydrogen RE Hybrid Concept Specifications

Seating capacity: 5
Overall length (mm): 4505
Overall width (mm): 1745
Overall height (mm): 1615
Wheelbase (mm): 2750

RENESIS hydrogen rotary engine with dual-fuel system
Maximum output* (kW/PS)
Hydrogen mode: 80 / 109
Petrol mode: 154 / 210
Maximum torque* (Nm / kgm)
Hydrogen mode: 140 / 14.3
Petrol mode: 222 / 22.6
Fuel: Hydrogen and petrol

Type: AC synchronous
Maximum output: (kW/PS) 30 / 40
Battery: Nickel hydride

Front/rear: 195/65R15

* Output from the Mazda RX-8 Hydrogen RE vehicle

All photos courtesy of Mazda

Share This Photo X