The Mazda RX-8

The Mazda Motor Corporation has unveiled at the North American International Auto Show a revolutionary high-performance, four-door sports car. Based on Mazda's RX-EVOLV concept car introduced at the October 1999 Tokyo Motor Show, RX-8 is much closer to an actual production sports car than its predecessor

The hints of an imminent release are broad - "With its four-door freestyle door system, four-passenger comfort and 250-horsepower (187kW) RENESIS rotary engine, Mazda RX-8 is the next big thing in sports cars," said Mazda President Mark Fields. "I wouldn't be surprised if you see this car - or something very close -- on some of the world's most scenic, most fun-to-drive highways in the not-so-distant future."

Claimed highlights of the car include:

• Mazda's new RENESIS rotary engine
• Central mid-ship engine layout and 50:50 front/rear weight distribution
• Freestyle door system, with front-hinged and rear-hinged doors and no centre pillar
• Comfortable seating for four adults
• A unique interior design that mixes the traditional with new contemporary material that appears to "wrap around" the passengers

Overall the RX-8 has a compact-looking body, while providing enough interior room to seat four adults comfortably. The use of a compact rotary engine allows for the low bonnet line, short overhangs, and overall sports car look while providing interior room on par with a sports sedan.

Body

With the design of the RX-8, Mazda wanted to create a new sports car that would remain attractive over time, and the company wanted to imbue it with Mazda's design heritage. In a word, Mazda wanted to create a car with a timeless appeal like that of the RX-7 and the MX-5 Miata. Since the RX-8 will be powered by a rotary engine, Mazda wanted to adopt a design that no other carmaker could match. The result is a silhouette that unmistakably says "sports car" with enough interior space to seat four adults comfortably. Mazda believes this new four-door sports car is poised to become a Mazda brand icon. One of the most revolutionary features of the RX-8 is the "freestyle doors" with no centre pillars, which Mazda first employed in the RX-EVOLV concept. They make the rear seats easier to get into and out of while improving convenience and safety.

The RX-8 inherits the basic concept of the RX-EVOLV with design changes that bring it one step closer to mass production. To accomplish this, Mazda design studios in Japan, the United States, and Europe each proposed a number of possible designs and competing ideas. Mazda located the large 19-inch wheels and tyres at the four corners of the body to provide a sense of stability, and used the extremely short front overhang to create an impression of swiftness and agility.

To reflect the compact layout of the rotary engine, Mazda moved the front pillar more forward than usual and tilted it. This design places most of the appearance of mass toward the back, resulting in a look that suggests that the car's centre of gravity is in the rear.

The front styling features a low bonnet that sets the RX-8 apart from a typical sports sedan. There is also a "power bulge" in the centre of the bonnet representing the rotors of the rotary engine. The five-point grill, the common feature among the Mazda family of vehicles, functions as the air intake, as in the RX-7 and the MX-5 Miata. Also, the front fenders swoop sharply upward above the centre of the bonnet to emphasize the sense of power. The side profile provides a sense of flow from nose to tail while still emphasizing sharp, strong lines. The "double bubble" roof is a distinguishing feature borrowed from the RX-7. The rear pillars have a cantilevered Z-configuration. The rear window is similar to that of the Cosmo Sport and the RX-7.

The rear silhouette, very important in any sports car, maintains the flavour of the MX-5 Miata and early generations of Mazda RX-7. The rear combination lights feature two round brake lamps, one with backup light and one with turn signal. Combined with the large, bold rear bumper, these elements will leave a strong impression on anyone who sees the RX-8 drive by.

Overall the RX-8 has a compact-looking body, while providing enough interior room to seat four adults comfortably. The use of a compact rotary engine allows for the low bonnet, short overhangs, and overall sports car look while providing ample interior space for four adults.

Interior

In designing the interior of the RX-8, Mazda followed the theme of "a futuristic blend of the traditional and the modern." The cockpit aims to be "an interior space that is comfortably snug and offers the pleasurable excitement of feeling at one with the car," the traditional ideal at Mazda. The instrument panel features large independent speedometer and tachometer gauges based on chronographs. The meter bonnet is topped by a "heads-up" display including a shift position indicator. The tachometer needle starts at the 6 o'clock position as is appropriate for a high-rev engine. The entire surface of the centre console is covered by an aluminium plate.

The lightweight sports mesh seats provide excellent support while contributing to less weight overall. The thin seatbacks free up room and provide extra space to seat four comfortably. Additionally, the seat sides, covered with nubuck canvas, and the shoulder and sides have been shaped forward for a hugging fit.

RENESIS Engine

The RX-8 is built to accommodate Mazda's RENESIS rotary engine. "RENESIS," derived from the word "genesis," suggests the beginning of a new type of rotary engine. Mazda's work on rotary engines began in 1961 and, six years later, Mazda introduced the Cosmo Sport, powered by a two-rotor engine. Over the years, Mazda made countless improvements. Today the rotary engine is used in the turbocharged RX-7 that Mazda sell in Japan. Through to the end of 2000, Mazda has sold about 1.8 million rotary engine-powered cars.

The RENESIS is an advanced version of the MSP-RE concept rotary engine featured in the RX-01 concept sports car exhibited at the 1995 Tokyo Motor Show. This new-generation rotary engine was employed in the RX-EVOLV four-passenger sports car shown first at the 1999 Tokyo Motor Show. When developing the RENESIS, Mazda aimed to retain power output on a par with the turbocharged 13B-REW, the rotary engine that powers the RX-7, while offering improved fuel economy and reduced emissions.

• Side Intake and Exhaust Ports

Unlike previous mass-production rotary engines, which employed peripheral exhaust ports and side intake ports,the naturally aspirated RENESIS has intake and exhaust ports in the side housings. This configuration eliminates overlap between the opening of the intake and exhaust ports, enhancing combustion efficiency. The intake ports are 30% larger and their timing has been changed to make them open sooner than in previous designs. Moreover, the exhaust ports open later, resulting in a longer power (expansion) stroke and providing radically improved heat efficiency.

At the same time, the RENESIS uses a six-port induction (6PI) design, in which each rotor employs three intake ports, and a variable intake timing mechanism. Under this system, dedicated high-speed intake ports begin to operate when the engine operates at high-rev levels. This makes it possible to use the intake's dynamic effect at high and low speeds to maximize compression efficiency.

Unlike the single peripheral port per rotor of previous designs, the RENESIS uses two exhaust ports per rotor. This produces a combined exhaust port opening area nearly twice as large and results in a substantial reduction in exhaust resistance.

The rotors have also been made lighter for better performance at high-rev levels. The rotors used in the RENESIS weigh approximately 14% less than those used in the engine that powers the RX-7, which we sell in Japan. These enhancements provide high output rivalling the power of turbocharged rotary engines with linear power characteristics from the low- to the high-rev range.

• Fuel Efficiency

The increased heat efficiency resulting from zero overlap between the opening of the intake and exhaust ports makes it possible for the RENESIS to run on a leaner fuel mixture than conventional rotary engines. When idling, the RENESIS consumes 40% less fuel than the current production rotary engine.

Reciprocating piston engines generally use a richer fuel mixture under high-speed and high-load conditions to prevent knocking. In contrast, rotary engines do not require a particularly rich fuel mixture under these conditions due to their special combustion characteristics. In addition, the RENESIS achieves nearly complete combustion over the entire speed range thanks to its high compression ratio and the use of new fuel injectors designed for improved fuel atomisation. These enhancements allow the RENESIS to run on a leaner fuel mixture than conventional rotary engines from the low to the high-rev range. The result is the power and performance of a sports car engine and reduced fuel consumption.

• Low Emissions

Due to their configurations, rotary engines produce less oxides of nitrogen (NOx) than reciprocating piston engines, but they also tend to produce large amounts of unburned hydrocarbons. The side exhaust layout used in the RENESIS prevents unburned hydrocarbons of the combustion chamber housing from escaping to the exhaust ports. Instead, they are carried over and burned in the next combustion cycle, dramatically reducing emissions. In addition, air injection directed into the combustion chamber increases the efficiency of the exhaust reaction, significantly over Mazda's existing system during engine startup. Together with the double-skin exhaust manifold, the new layout makes the exhaust much hotter when it reaches the catalytic converter, speeding the converter reaction for clean emissions from the moment the engine is started.

• Reduced Oil Consumption

In a rotary engine, oil is supplied directly to the interior walls of the combustion chamber to lubricate the apex and corner seals. Mazda has kept the paths which supply oil in the RENESIS as small as possible, and has redesigned the oil supply nozzles to improve their efficiency. With these enhancements, the RENESIS consumes about half as much oil as a conventional rotary engine.

Tech Highlights

• Body Packaging

RENESIS is a naturally-aspirated engine. It is 30% lighter and more compact than the turbocharged rotary engine (13B-REW) used in the current Mazda RX-7. Its light weight and its positioning in the vehicle help give the car excellent manoeuvrability and high-end performance. Even with its supplemental parts, the height of the RENESIS is about same as inline 4-cylinder engine. The engine block itself is only 338 mm high - about the same height as the transmission. Since the engine is so compact, Mazda were able to mount the RENESIS close to the centre of the body, resulting in a central front mid-ship layout. Compared with RX-7's front mid-ship layout, the engine in the RX-8 is 60 mm closer to the centre of the body. This central mid-ship layout enables the achievement of an ideal 50:50 weight distribution. The thickness of the RENESIS engine's oil pan is only 40mm, half the thickness of the oil pan on the current turbocharged engine that powers the RX-7. This makes it possible to mount the overall powertrain lower to give the car a lower centre of gravity.

• High Mount Backbone Frame & one-piece carbon propeller shaft

By positioning the powertrain lower, Mazda were able to improve rigidity by locating a high mount backbone frame on the upper part of the tunnel. This frame connects the front and rear bulkheads through the inner centre and strengthens body rigidity. This frame also plays a role as a main body frame to reduce thickness of the body panels, resulting in a 30kg weight reduction. The higher rigidity also enhances safety in front, offset or rear collisions. Like Roadster and RX-7, the RX-8 employs a closed section power plant frame to enhance rigidity. The wheelbase is 2700 mm. While most front-engine, rear-wheel-drive cars require two propeller shafts with a centre bearing for rigidity, the short distance between transmission and the differential gear makes it possible for only one, made of lightweight carbon composite material. This reduces weight by 3kg.

• Suspension

Mazda adopted double wishbone suspension that delivers excellent grip on road. The upper and lower arms in both front and rear are much longer compared with RX-7, keeping the tyres gripping the road against changes of roll and camber, providing smooth roll centre and excellent cornering performance. Optimally set up roll centre height and improved camber rigidity enhance control by reducing slower handling reaction. Damper is the mono-tube type that has higher tracking capability. Cornering performance is enhanced by improved lever ratio that prevents excessive roll.

• Interior & Luggage Space

With its 2,700mm long wheel base, the RX-8 provides comfortable interior space for four adults. For rear seat passengers, the centre pillar-less "new free style doors" provide large door openings for better convenience and rear seat accessibility. The RX-8 also has much larger luggage space than a conventional sports car. Rear suspension springs are positioned lower, close to lower arms, and the rear side frame is located farther out than usual to provide larger, deeper luggage space. The result is more than 300 litres of luggage space.

• Safety

The compact RENESIS engine also helps improve collision safety. The central mid-ship layout enables a sufficient crushable zone between engine and bumper, and eases the impact of frontal and offset collision. The RX-8's bonnet is much lower than that of sports sedan, and there is more than 100 mm space between the upper part of the engine and bonnet. The lower bonnet also improves front visibility. Safety features attached include smart airbags, head-protection curtain airbags for side collisions, and a non-retreated brake pedal mechanism for frontal and offset collision.

RX8 Preliminary US Specifications

Dimensions
Length		170.3 inches
Width		70.1 inches
Height		52.4 inches
Wheel Base		106.3 inches
Track	Front	58.7 inches
	Rear	59.1 inches
Curb Weight		-
Capacities
Weight Distribution % f/r		50 / 50
Passenger Seating		4 Full-Size Adults
Cargo Volume		10.6 cu.ft.
Suspension
Front		Double Wishbone
Rear		Double Wishbone
Tires and Wheels
Tires	Front	225/50ZR19
	Rear	245/45ZR19
Wheels		5-spoke, 19-inch
Engine
Type		Water-cooled, serial, 2-rotor
Displacement(CC)		654 x 2
Output(SAE hp @rpm)		250 @8,500
Torque(SAE ft-lbs @rpm)		152.7 @7,500
Transmission
Type		Rear-Wheel Drive
Transmission		6-speed with auto/manual shift
Steering and Brakes
Steering Type		Electronically-controlled, rack-and-pinion, motor-assisted power steering
Brakes		4-weel ABS, Dynamic stability Control
	Front	14inch(356mm) ventilated disc, 6-piston caliper
	Rear	14.2inch(361mm) ventilated disc, 4-piston caliper