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RENESIS in Depth
Submitted by SuperUser on Wednesday, May 14, 2003 - 4:48pm

Mazda began developing rotary technology in 1961, and since the late
seventies has been the world's only rotary engine manufacturer to
depend entirely on manufacturing technology and equipment developed in
house. A good example is the Mazda Digital Innovation (MDI) project
which allows the company to conduct virtual simulations of RENESIS
manufacturing, maximizing the potential performance of the engine by
enabling high precision and quality production engineering.

In 1994, Mazda introduced Total Productive Maintenance (TPM), the
brainchild of the Japan Plant Maintenance Association, to its
production lines. Thanks to TPM, Mazda has raised the efficiency of
its production department and advanced the organization of its quality
assurance and other key aspects of the manufacturing process.

Since 1996, the company has been pursuing what it calls the Mazda
Digital Innovation (MDI) project, which involves integration of
CAD/CAM systems from design through production. By employing the most
advanced 3-D information systems, Mazda has revolutionized its entire
research and development organization. In the case of the RENESIS
project, Mazda used MDI to implement virtual simulations of machining
processes in production engineering.

RENESIS is a naturally aspirated engine. It is both smaller and
lighter in weight than the already compact 13B-REW. Owing to its
reduced size and elimination of auxiliary equipment, the new power
unit has a height of approximately 338 mm (13.3 in). In addition, the
height of the oil pan is reduced to about half of that of a
conventional design (approx 40 mm deep [1.6 in]),

Mazda engineers also used a supercomputer to conduct
structural analyses aimed at reducing rib thickness in the
engine's side housing and other locations without sacrificing rigidity.

WHAT'S IN A NAME? The RENESIS engine powering the Mazda RX-8 has its
origins in the MSP-RE that was unveiled at the 1995 Tokyo Motor Show
as the power unit for the RX-01 concept sports car. The name RENESIS
was given to the engine in the 1999 iteration of the
RX-EVOLV. Thereafter, RENE SIS, which stands for "the rotary engine's
GENESIS," was carefully prepared for series production as the
powerplant for the RX-8

RENESIS­an engine replete with innovative technologies such as side
intake/side exhaust porting­is a 654 cc x two rotor unit. Because it
has a new side-intake and side exhaust layout, the engine delivers 250
horsepower at 8,500 rpm and 162 lb-ft of torque at 7,500 rpm without
the weight and complexity of a turbo- or supercharger, while achieving
improved fuel efficiency and cleaner emissions.

* Figures are for the High Power version. Maximum power output is the
specification for Japan and North America. 4-Port and European versions vary


The key technology of RENESIS is its side exhaust port configuration,
with the exhaust ports relocated to the ro tary chamber side housing,
where the intake ports are also located.

The chief advantage of this layout is that it allows elimina tion of
intake/exhaust port timing overlap. This measure ensures that exhaust
gas is not retained and carried over to the next intake cycle, thereby
promoting more stable combustion and better fuel economy. The engine
also has two exhaust ports per rotor chamber, giving RENESIS almost
twice the exhaust port area of its predecessor. With ample exhaust
port area assured, delaying the open ing of the exhaust ports affords
RENESIS a longer expan sion cycle, for improved thermal efficiency,
power output and fuel economy.

Another major advantage of the side exhaust port is that it allows
engineers more freedom to optimize port profiles. With RENESIS, both
the six-port High Power version and four-port Standard Power version
have almost 30% more intake port cross-sectional area than the
previous engine. Additionally, the intake port close timing has been
ex tended, resulting in increased charging volume and more power.


With the previous engine, unburned gases (hydrocarbons) were voided
from the combustion chamber via the peripheral port. With the
sideexhaust ports of the RENESIS, unburned gases are retained for
burning in the next combustion cycle, further reducing regulated

The side-intake/side-exhaust port RENESIS gains 30% in intake port
area over the previous engine, and this, combined with the delayed
intake port close timing, makes for a sizable increase in charging
volume resulting in greater power output. The engine also incorporates
innovative technology designed to boost filling efficiency.

The High Power specification engine has three intake ports per rotor
chamber: primary, secondary and auxiliary (giving a total of six
intake ports for the twin rotor RENESIS engine), with each subject to
different timing. The variable intake control system operates
opening/closing of the secondary and auxiliary intake ports. RENESIS
also takes full advantage of the incoming air's dynamic charge effect
to boost charging for more substantial low-to-mid range torque, as
well as increased torque and power output at higher engine speeds. The
intake system on the Standard Power unit, which is tuned for the
superb drivability at regular rpm, has two intake ports per rotor, for
a total of four intake ports are controlled by the opening/closing of
a variable intake valve governing use of the secondary intake
port. For even more accurate control, RENESIS incorporates an
electronic throttle control system that optimizes intake control in
response to feedback of sensors monitoring the degree and speed of
accelerator pedal operation.


The High Power specification engine incorporates a variable fresh air
duct in addition to a large, low resistance air cleaner. At around
7250 rpm, a shutter valve opens to shorten the intake manifold
upstream of the air cleaner. The shutter valve works in tandem with
the variable intake valve to boost torque and power at high engine
speeds. The fresh air duct is partially inserted into the air cleaner
and enables an optimal length intake system by valve opening/closing.


To achieve a smooth flow of exhaust gases, the RENESIS exhaust system,
including the exhaust manifold, was made as straight as possible. The
system employs large diameter exhaust pipes and a high capacity main
silencer with the inlet pipe located straight through the center of
the silencer body to reduce flow resistance. These measures contribute
to the engine's high power output.


The previous 13B-REW engine generated its maximum power output at 6500
rpm, whereas the RENESIS power peak comes in at 8500 rpm. This step-up
to a higher revving engine was achieved by virtue of an 11 percent
reduction in rotor weight. Additionally, the flywheel weight has been
reduced by some 20 percent compared with the previous
engine. Combined, these weight-saving measures reduce inertia to
assure the quick response befitting a genuine sports car engine.

RENESIS also features three injectors per rotor chamber for improved
fuel atomization and employs an electronically controlled throttle and
32-bit PCM (Powertrain Control Module) for more precise control of
air-fuel metering and sharper throttle response. Additionally, the
engine uses a long span engine mount system with extremely long
members extending laterally from the rotors' center of rotation. The
mounts are effective in suppressing engine vibration, allowing more
direct transmission of power to the drive system and contributing to
the vehicle's fast response and improved NVH.


To further refine the superior balance of the twin-rotor
configuration, Mazda shifted from the previous static balance setting,
and instead adopted dynamic balance calculated from the mass of oil
entering the rotors

With the previous rotary engine, the direction of rotation of
the fixed gear locating the rotors in the front and rear
housing was the same for both rotors. With RENESIS, the
direction is reversed for front and rear rotors, achieving
smoother rotation and reduced gear noise


In addition to more stable combustion afforded by the side
exhaust ports, as well as improved breathing efficiency,
RENESIS also shows a significant gain in fuel-efficiency
through the use of the following new technologies.

Newly designed seals: RENESIS employs a new cut-off seal located
between the rotor's dual oil seals and side seal. This sealing
arrangement eliminates blow-by between intake and exhaust ports and
prevents carry-over of exhaust gas to the next intake cycle. Side
seals are a new keystone-type with wedge-shaped section. Exhaust gas
build-up against the side seal can easily cause carbonization, but
with the wedge-shaped or cuneiform side seal, the seal shape is
optimized to remove carbon. The shape is also more congruent to its
opposed frictional surface, achieving much better sealing proficiency.

Jet air-fuel mixing system: This system is installed in intake ports
to promote spray, atomization and mixing of air and fuel. The system
emits a jet of air from a constricted tube in the intake port that
effectively speeds the flow of fuel over the intake port walls and
boosts atomization of fuel particles adhering to the walls. The lower
end of the intake port is also shape-optimized to induce transport of
atomized fuel along the air stream towards the spark plug.

Micro-electrode spark plugs: The last technology employed in aid of
fuel economy for the RENESIS engine is the micro-electrode spark
plug. This spark plug uses a small side electrode and thick gauge
central electrode with an extremely fine tip that promotes stable
ignition of lean air-fuel mixtures. Also, by maintaining a lower
temperature for side and central electrodes, the plug achieves high
heat-resistance. The tip of the central electrode, which was
previously of platinum, is now made of longer lasting iridium.

The RENESIS engine retains unburned hydrocarbons from one cycle for
combustion in the next ­ a process that vastly reduces emission of
unburned gases in the exhaust. In addition, on starting the engine,
secondary air is supplied to the exhaust port by an electric
pump. Delivering secondary air in the gap between the dual exhaust
ports promotes mixing of exhaust gas with secondary air to promote
re-burning. Furthermore, RENESIS has a dual skin exhaust manifold that
maintains the temperature of burned gases and ensures that exhaust
temperature rises sharply on starting, for faster activation of the
high performance catalytic converter and consequently lower emissions.

The fuel metering system for the RENESIS engine is also new. Firstly,
the previous intake manifold pressuresensing system for metering air
intake volume has been replaced with the hot wire air-flow meter type
for more precise metering. Also, the single-loop air-fuel ratio
feedback control employing an O2 sensor located upstream of the
catalytic converter has been replaced with a doubleloop system
featuring O2 sensors upstream and downstream of the catalytic
converter. The upstream O2 sensor is a linear type achieving
straight-line response to a widerange of air-fuel ratios, promoting
precise fuel control from idling to high engine speeds. Combined with
the exhaust gas re-burning system (mentioned previously) this reduces
exhaust emissions to one tenth the amount recorded for the previous
rotary engine.


Mazda employed supercomputer analyses to reduce the thickness of
supporting ribs for the engine side housing and other areas while
maintaining high rigidity. Additionally, approximately half the length
of the long intake manifold is now made of plastic. Mazda also cut
weight by eliminating the mounting bracket for the air conditioner's
condenser, replacing it with a direct-mount arrangement. Measures such
as these, combined with further downsizing of equipment helped reduce
overall engine weight. RENESIS also has a wet sump lubrication system
with oil pan depth reduced by about 40 mm (1.6 in) to approximately
half that of the previous RE. Taken together, the inherently compact
size of the naturally aspirated RENESIS engine, plus these extensive
downsizing and lightening measures, have yielded an engine weight on a
par with the all-aluminum in-line four cylinder engine.


An example of Mazda's advanced use of digital technology can be found
in the machining of the engine's rotors. Three dimensional design data
is received from the engine development team and employed to create
3-D data for a metal die for casting. Based on this 3-D data, computer
simulations are used to analyze and check the precision, quality and
efficiency in the rotor casting and machining. Also, with regard to
cutting and other machining processes, 3-D simulations are used to
optimize the design of cutting tools and jigs throughout the entire
manufacturing process.

To achieve the critical finish quality of side seals, cut-off seals
and related components of the rotary chamber, the unique skills of
Mazda, honed through years of experience in rotary engine building, is
used to painstakingly check each and every item throughout the
manufacturing process.

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No Rotor
December 31, 1969 - 4:00pm
WOW! I didn't know there was that big of a technology leap between the RENESIS, and that last 13Bs!
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No Rotor
December 31, 1969 - 4:00pm
Do they mean the fixed gears are not straight cut?
The fixed gears are just that..fixed..they do not rotate.
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No Rotor
December 31, 1969 - 4:00pm
"Renesis in depth".
There is nothing here of any more value than the Mazda press release.

Again it states BOTH the four port and six port engines have 30% more intake cross-sectional AREA. AGAIN, this is better put by saying the ports are open 30% longer.

Again, again, in one place it says "elimination of intake/exhaust port timing overlap. This measure ensures that the exhaust gas is NOT retained and carried over to the next intake cycle" Later, on the SAME page no less it says "With the side exhaust ports of the Renesis unburned gases are retained for burning in the next combustion cycle" Now give your heads a shake either it does or it does not. This explaination is just copied from the press release by someone that does not know what he/she is talking about. Yes the engine does do both but the press release doesn't explain that. The zero overlap does prevent exhaust from continuing into the intake cycle AND some of the exhaust from outside the engine is redirected, via a passage into the intake, like it was in the '79, '80 RX-7 engines, to drop the NoX. By the way the Renesis engine also has a two chamber exhaust manifold like the '79, '80 RX-7. Yes, I know this thermo-reactor dates back to the first 1970 emission R100 but for explaination sake I am just staying withthe RX-7.
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No title supplied
No Rotor
December 31, 1969 - 4:00pm
No no... The overlap insures no INTAKE gases go out the exhaust. There is no conflict.

As the rotor comes up from the exhaust, a tiny portion of the exhaust gases are carried up, once the exhaust port is closed, and before the intake has opened. The rotor moves more, opening the intake, and with the carried over exhaust gases still there, mixes with the new mixture, and not going out the exhaust like perif port exhausts.
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RENESIS in Depth
No Rotor
December 31, 1969 - 4:00pm
Weight we are talking....that alone will do wonders...good work mazda
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