The Mazda way to improve relations between
people, the automobile and the planet
Mazda is committed to creating better relations
between the motorized society and the global environment
of the 21st century, while, at the same time, maintaining
and advancing the company's characteristic
Zoom-Zoom spirit. Thoughtful, innovative products
developed by Mazda can balance the dual needs of
both the environment and the driving enthusiast.
One example of Mazda's most recent efforts--the
RENESIS Hydrogen Rotary Engine--is being showcased
at the 2003 Tokyo Motor Show.
As the world's only manufacturer of rotary engines,
Mazda continues to develop and explore all the potential
and possibilities of this unique internal combustion
engine. The RENESIS is Mazda’s next-generation rotary
engine that was launched in early 2003 in the all-new
Mazda RX-8. By virtue of its smooth performance,
compact size and unique driving characteristics,
RENESIS was named International Engine of the Year
in June 2003. It delivers high power output for a naturally
aspirated engine of its size and demonstrates significantly
improved fuel economy and reduced emissions
compared with previous generation rotary engines.
Now, as the auto industry’s attention turns to hydrogen
as a potential source of power for fuel cell vehicles,
Mazda confidently presents a realistic example
of its hydrogen-power technology, embodied in the
hydrogen-powered version of the RENESIS.
Fun to drive and environmentally sound, the
RENESIS Hydrogen Rotary Engine is a Mazda-unique
alternative-fuel vehicle. It is the ultimate demonstration
of the flexibility of the unique rotary engine, maintaining
a traditional driving feel, yet realizing extremely
clean emissions through the use of hydrogen.
The RENESIS Hydrogen Rotary Engine capitalizes on
the advantages of the rotary engine to assure the same
ease-of-operation and reliability whether the engine is
running on gasoline or hydrogen fuel. Moreover, since
the engine requires modifications to run on hydrogen,
it could enable production of a relatively low-cost
hydrogen-powered alternative-fuel vehicle.
The engine has been developed with a dual-fuel
system, allowing it to run on either gasoline or hydrogen,
as Mazda believes desirable, flexible automotive
choices will help effectively promote the usage of
hydrogen fuel and the development of a supporting
The fruit of over ten years of research and
development of hydrogen power
The RENESIS Hydrogen Rotary Engine is not
Mazda’s first effort in this area of advanced R&D. In
1991, Mazda developed and tested its first hydrogen
rotary-powered prototype vehicle, known as the
Mazda HR-X. Concurrent with the development of the
HR-X2, the engineering team also developed an
experimental version of the MX-5 roadster in 1993,
powered by a hydrogen rotary.
Two years later, in 1995, Mazda was granted
approval by Japan’s then Ministry of Transport to
conduct on-road tests of two hydrogen rotarypowered
Capella Cargos. At this time, Mazda also
began to experiment with fuel cell electric vehicles
(FC-EV) alongside its hydrogen rotary engine program.
In 1992, Mazda developed a prototype vehicle
with fuel cell electric battery, and in 1997, created a
Mazda Demio FC-EV.
In 2001, Mazda began conducting public road
tests of the methanol-reforming type Premacy
FC-EV. Data on driving performance, fuel consumption,
exhaust emissions and other parameters were
collected during on-road tests to advance studies
aimed at commercialization.
The RENESIS Hydrogen Rotary Engine, as presented
at the 2003 Tokyo Motor Show, is another step forward
in these ongoing efforts to experiment and develop
Mazda RENESIS Hydrogen Rotary Engine
The RENESIS Hydrogen Rotary Engine incorporates
an electronically-controlled hydrogen injector system
(the hydrogen is injected in a gaseous state). The
system draws air from the side port during the induction
cycle and uses dual hydrogen injectors in each
of the engine’s twin rotor housings to directly inject
hydrogen into the intake chambers. The following
technologies have been introduced to help maximize
the benefits of the rotary engine in hydrogen combustion
The RENESIS Hydrogen Rotary Engine is currently
undergoing running tests in a special-edition Mazda
RX-8 Hydrogen RE test vehicle. The test vehicle is
equipped with a dual-fuel system that consists of a
high-pressure hydrogen tank and separate gasoline
tank, and can run on either hydrogen or gasoline. It is
as reliable and easy to operate when running on
hydrogen as on gasoline.
In addition to the revolutionary RENESIS rotary
engine, the Mazda RX-8 Hydrogen RE test vehicle
benefits from improved aerodynamics, optimised tires
and weight-saving measures, as well as a host of technologies
for exceptional environmental compatibility.
- Direct injection system
By virtue of its construction—with separate chambers
for induction and combustion—the rotary engine is
ideally suited to burn hydrogen without inviting the
backfiring that can occur when hydrogen is burned in
a traditional piston engine. The separate induction
chamber also provides a safer temperature for fitting
the dual hydrogen injectors with their rubber seals,
which are susceptible to the high temperatures
encountered in a conventional reciprocating engine.
- Twin hydrogen injectors
Because hydrogen has an extremely low density, a
much greater injection volume is required compared
with gasoline. This demands the use of more than one
injector, which can be difficult to achieve with a
conventional reciprocating engine because of the
structural constraints that prevent directly mounting
injectors in the combustion chamber. In contrast, the
rotary engine provides adequate space for installation
of two injectors per induction chamber. With its twin
hydrogen injectors, Mazda’s hydrogen rotary engine
is both practicable and able to deliver sufficient power.
- Excellent mixing of hydrogen intake charge
In a reciprocating engine, the output shaft turns
through 180 degrees in one cycle, whereas the rotary
engine’s output shaft covers a greater angle of 270
degrees, enabling a more vigorous intake flow for
ample mixing of the hydrogen-air intake charge. This
promotes production of a uniform mixture, which is
critical for hydrogen combustion.
At the 2003 Tokyo Motor Show, Mazda is also presenting
a number of technologies currently being
developed that could help support the potential for a
futuristic hydrogen rotary system.
These next-generation technologies are being
refined to help achieve the dual goals of drivability
comparable with gasoline cars and excellent efficiency
derived from the practical use of energy. An example
of these technologies includes an electric-motorassisted
turbocharger to enhance the efficiency of
hydrogen combustion and regeneration of energy
from the car’s exhaust. Additionally, in an effort to
capitalize on existing hybrid technology, Mazda continues
to refine the idle-stop system; regenerative
braking systems; electric acceleration assistance
systems; and other means of improving the efficiency
of the entire vehicle. By combining these various
technologies, Mazda is aiming to achieve advanced
clean-running vehicles that also deliver an exceptional
driving experience in line with the company’s Zoom-
An electric-motor-assist turbocharger is used to maximize
the effectiveness of forced induction throughout
the rev range. At low rpm, beginning at approximately
1000 rpm, an electric motor operates to assist the
turbocharger and increase induction efficiency. At
high rpm, the turbocharger is driven in a traditional
fashion, by the flow of exhaust gas alone.
Mazda Hybrid System
The Mazda Hybrid System is composed of a motor,
inverter and a 144-volt battery. When the vehicle is
stationary—for example, when waiting at traffic
signals—the system normally stops the engine to
reduce fuel consumption and exhaust gas emissions,
and restarts it automatically with the electric motor
when the driver is ready to accelerate.
Additionally, when the engine is running at low rpm,
the electric motor is used to boost engine torque and
effectively improve response. During deceleration,
the motor operates as an electrical generator, recovering
the braking energy and using this energy to
recharge the battery.
- Three layer wet-on paint: This water-based paint
dramatically reduces emission of organic solvents,
saves energy by shortening the drying process and
- Plant-based plastic for interior parts: Plant-based
plastic is an attractive alternative to plastics derived
from fossil fuels such as petroleum. Plant-based plastic
fiber-reinforced extrusion-molded plastic employing
cellulose extracted from timber is used for quarter
panels, and reduces CO2 emission.
- Low-resistance brakes: Use of a fast-fill tandem
master cylinder reduces brake drag.
- Low-resistance hub carriers: Reduced friction hub
carriers help cut power losses.
- Hydrogen fuel: From stationary to moving on
The engine is normally stopped automatically when the
vehicle is stationary (the engine is not stopped when
battery recharging is required). The engine is automatically
restarted by electric hybrid motor when moving off.
- Hydrogen fuel: Accelerating from standing position
The electric hybrid motor provides torque assist for initial
acceleration when the engine is running at low rpm.
Further assist is provided by the electric-motor-assist
turbocharger, which begins operating at approximately
- Hydrogen fuel: During steady running
Running on hydrogen fuel. Lean combustion promotes
NOx emission levels as low as just a few parts per million.
- Hydrogen fuel: During acceleration or running under
high speed and load conditions.
The electric-motor-assist turbocharger boosts induction
to assure ample power with lean combustion.
- Hydrogen fuel: During deceleration
Fuel cut-off by electronic throttle control. In addition, the
motor/generator recovers electric power through battery
- Gasoline fuel
A gasoline and air mixture is introduced through the side
ports of the rotor housing as with a conventional RENESIS
rotary engine. The engine is normally stopped when the
vehicle is stationary, and restarted automatically by the
motor when moving off. Changing between gasoline and
hydrogen fuel is achieved by a simple switch operation
from the driver’s seat.