Mazda plans rotary-engine club

Mazda is expected to bring back the RX-7 as a high-performance two-seater sports car - if the upcoming RX-8 is a sales success.

Work has already begun on the RX-7, although overseas reports say the project has not yet been signed off.

Mazda engineers are said to be working to ensure that the RX-7 body weighs around 1000kg, in an effort to ensure nimble handling and potent performance.

The next generation RX-7 is expected to share its platform with the RX-8 and the all-new MX -5, due in 2005.

The return of the RX-7, expected to be more expensive than the RX-8, would give Mazda a family of rotary-engine sports cars.

The RX-7 would likely be powered by a larger-capacity version of the RX-8 Renesis engine, providing better performance while retaining the compact packaging advantages of the twin-rotor layout.

Mazda has apparently decided against turbocharging the rotary engine because it would add weight and could cause problems in meeting future emission regulations. Similarly, a triple-rotary arrangement would increase the engine's bulk.

The RX-8 was widely regarded as a successor to the RX-7, which sold for 20 years. But Mazda insists that the four-door RX-8 is more of a sports tourer than a performance machine.

Production of the RX-8 has begun in Japan but only a limited number will make it to New Zealand this year, says Mazda New Zealand sales and marketing chief Andrew Clearwater.

"The outstanding reviews from media have fuelled demand even further and unfortunately for New Zealand this means we will be limited to about 60 vehicles," he said.

"We expect all of them to be pre-sold before the New Zealand launch of the RX-8 in June."

Two models will be available in New Zealand, a four-speed automatic at about $66,500 and a more powerful six-speed manual at about $68,500. The rotary engine was invented in 1934 by German engineer Felix Wankel. Its advantages are compact size, light weight and high power because unlike a conventional engine it does not need to convert the forward and back motion of the pistons into rotary motion. Conventional engines have distinct cycles or strokes but the rotary engine draws in air and fuel, compresses it and ignites it in a continuous motion. Unlike piston engines the rotary engine has no valves. The spinning rotor itself closes or opens the inlet and exhaust ports as it turns through its cycle. The RX-8 Renesis engine has relocated exhaust ports for more effective burning of fuel.