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

SIDE INTAKE/SIDE EXHAUST PORTS

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.

ENGINE PERFORMANCE

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 emissions.

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.

VARIABLE FRESH AIR DUCT (FAD)

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.

STRIAGHT EXHAUST SYSTEM

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.

LIGHT WEIGHT ROTOR, 3 INJECTORS PER ROTOR

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.

DYNAMICALLY BALANCED ROTORS

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

FUEL ECONOMY

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.

WEIGHT SAVINGS

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.

DIGITAL TECHNOLOGY

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.