• Jul 19th 2006 at 3:18PM
  • 12
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

I'm reporting this comment as:

Reported comments and users are reviewed by Autoblog staff 24 hours a day, seven days a week to determine whether they violate Community Guideline. Accounts are penalized for Community Guidelines violations and serious or repeated violations can lead to account termination.

    • 1 Second Ago
      • 8 Months Ago
      Fuel economy figures were not provided because rotaries suck fuel in a huge way.
      • 8 Months Ago
      So I'm guessing this vehicle is based on the hybrid architecture in the Escape/Tribute. Which means the vehicle is not a standard shift type of driving experience. Blah. Also, why is the detuned 210hp (automatic) Renesis version used for this vehicle? If you're going to build a concept vehicle, you might as well go all out, especially with something better easily available. Maybe the rev limit on the hybrid transmission can't handle the 9K redline of the high performance Renesis version... Kudos to Mazda for building a hybrid rotary though. The high torque electric and high hp, lightweight rotary ought to be a match made in sportscar heaven. Package it with RWD and a manual shifter and I might be convinced to part with my money. H2 would be nice, can anyone say "electrolyzer fillups at home?". Rotarys will definitely whip up on the piston pumpers when it comes to H2 combustion.
        • 8 Months Ago
        Mazda didn't "detune" the engine, note that it gets the full 210 HP when running on petrol. It is the bulky nature of H2 fuel that cuts the power so dramatically when running on H2.

        It is not clear whether Mazda plans to use a Ford style "power split" hybrid transmission, or if they plan a simple "assist" hybrid instead. In either case, the hybrid system can easily be adapted to the characteristics of the Renesis engine. BTW, many electric motors redline at over 10,000 rpms, the Tesla Roadster motor redlines at 13,500 rpm!

        As for "fillups at home", I'd rather go with a plug-in battery. Consider that the combination of charger, battery, and electric motor is about 80% efficient, but the combination of electrolyzer, compressor (for storage), and Wankel engine is only 7% efficient - it would take 11 times more electricity, and would be more costly than running on $5 per gallon gasoline! Then when you add in the high cost for that electrolyzer and H2 compressor, and the higher cost for H2 storage tanks, and the reduced performance, and I say "No Thanks".
      • 8 Months Ago
      AMcA: Rotaries are not significantly more thirsty than an average 3L v6, which is comparable to the output of the Renesis. Just like any engine, you have to burn fuel to make power. You can't have your cake and eat it too. On long distance highway trips averaging 75-80 I routinely got 27mpg with my '86 and 25mpg with my '90GTUs 2nd generation RX7s.

      Go rain on someone else's parade with false blanket statements.
        • 8 Months Ago
        Actually, Wankel engines get worse fuel economy than piston engines of equivalent power. The reason is the odd shaped combustion chamber, which has a much higher surface area to volume ratio than in a piston engine. That in turn means more heat loss through the chamber walls, and that lost heat represents lost energy.

        But that reduction in fuel economy is small, and in some instances the Wankel advantages of compact size and light weight might outweight the disadvantages of a slightly reduced fuel economy. For example, it might be well suited for use as as a rarely used range extender in a plug-in hybrid.
      • 8 Months Ago
      This is great, the only reason I didn't buy a Mazda 5 this last time around was because of its fuel economy. I went out and got a Honda Fit instead, and I'm extrememly happy with it on many levels. However, when child number 4 comes out, I'm hoping they have a hybrid version of the Mazda 5 ready.
      • 8 Months Ago
      i am asisten engenerig to make and developer cars since
      1968 i see the first wankel rotative motor the mazda spaider
      1964 or 65 sinse then i develop my qwn rotative motor ( i don' t make this because i don't have money but i all ready kown
      at that time fuel cars whit hidrogen fuel like the laboratory flame
      use hidrogen fuell since them i am craisy for the rotative motors
      t have in the time 17 years old now i have 62
      because the big interest for the oil companis i don't see nothing
      that batyifull like this car include the electrical motor
      wath hell the humans do to keep this tecnologie deat for so many years .
      i see the firs microway owens too
      great good we have this greate cars
      cars i love the engenier who make mazda.
      same times we need to waite to many years to see the future
      this is the time after more the 40 years waiting
      why i am so happy you know
      • 8 Months Ago
      Oh my God, this will be the holy grail...in fifteen years.

      another case where "we have the technology, now we just need to make it economically feasable"

      I can imagine everybody riding in one of these RENESIS cars in the near future as we make the transition from gasoline to hydrogen.

      kudos to Mazda and their engineers!
      • 8 Months Ago
      This is fantastic!!! I have long been a fan of hydrogen as a replacement for petrol. It is my considered opinion that we should have (extra) nuclear power plants for the sole purpose of generating electricity to use to separate the H out the H2O. I remember back around 1985(?)that good old (well, younger then :0) Jack Nicholson had a Chevy (I think) converted to burn hydrogen and was touting way back then for this clean source for vehicles......... I can't help but wonder about the size, if it would be small/light enough to use in my light sport plane (see www.SeastarHawaii.com) It currently uses a Rotax 912S which only kicks out 100 ponies and I believe the RENESIS does 109 horsepower in hydrogen mode.........
      • 8 Months Ago
      Interesting to note how both power and torque are dramatically reduced, cut almost in half, when running on H2 fuel. The reason is quite simple - H2 is an extremely bulky fuel, it is difficult to pack enough H2 and air into the combustion chamber to produce a reasonable amount of power.

      Of course, that bulk means that even with a very large very high pressure tank, the driving range on H2 is short, thus a petrol backup is needed.

      Then you add the high cost of H2 fuel and the high cost of H2 storage, and it is quite clear - H2 is a poor choice for automotive fuel.
      • 8 Months Ago
      RE "Fuel economy figures were not provided because rotaries suck fuel in a huge way."

      Totally incorrect. And that's from someone who's had their fair share of V8 cars and big twin V2 bikes.
      • 8 Months Ago
      I have a mazda 5 and I love it. I can't wait for this new vehicle to come out, I will definitely check it out.
    Share This Photo X