Problems with the development of Mazda’s next generation of rotary engines are delaying the launch of the new RX-7 sports car, according to sources close to the company.

The fourth-generation RX-7 was originally scheduled to be unveiled at last year’s Tokyo show and go on sale this year, but issues facing the new 16X engine forced the company to scrap that schedule. The car’s release date is now unknown.

Engineers are trying to solve the heavy oil and fuel consumption issues of the current rotary, and its lack of mid-range torque. Adding direct injection will make the unit more efficient, but extra components mean the new engine weighs more than the current 13B motor. This goes against Mazda’s strategy of cutting 100kg from all of its cars in the next five years.

The engineers have also been having problems getting the engine to reach their target for maximum revs; the current rotary revs to 9000rpm.

Development has also been hit by the economic downturn. Mazda is battling with a drop in global sales of nearly 19 per cent, and MX-5 sales are down by 26 per cent. Sales of the RX-8, the only production car with a rotary engine, are also down and workers in Japan have been laid off.

Mazda is keen to retain the rotary engine for a new generation of cars. The engine is a source of pride within the firm, and has been used in 18 models since it was launched in the Cosmo Sports in 1967.

Dan Stevens