Mazda maps out its eco future at the Tokyo Motor Show

The striking Kiyora concept car seems likely to get all the attention at Mazda's stand at this year's Tokyo Motor Show but at the same time the company is also releasing a wealth of detail about its future plans to make its cars more energy efficient. These include the Sky-G petrol engine, the Sky-D diesel engine, Sky-Drive automatic transmission, hybrids and hydrogen-powered rotary engines.

The Sky-G petrol engine appears to rely on a comprehensive package of refinements (for example improvements to the combustion process) rather than a single big breakthrough to achieve a 15 peer cent improvement in fuel consumption and a 15 per cent increase in torque, which should make future Mazdas quicker as well as more economical.

The Sky-D future diesel benefits from a similar programme of tweaks which are expected to produce a 20 per cent improvement in fuel consumption; the Sky-D concept extends to include a diesel particulate filter.

The Sky-Drive automatic is a six-speed transmission which is expected to yield a 5 per cent improvement in fuel consumption compared wth Mazda's current five-speeder; as well as the additional gear ratio, the future gearbox is designed to operate in locked-up mode for perhaps 80 per cent of the time instead of 50 per cent.

Mazda has also joined the rush to offer stop-start systems on its cars. It is now offering its i-stop technology on the Mazda 3; this offers a fuel saving of about 15 per cent on Japanese official fuel consumption tests.

Mazda is the only major manufacturer to persevere with the rotary (Wankel) engine, which seemed to hold out so much promise in the Seventies; now it has developed hydrogen-powered rotary-engined cars – a version of the RX-8 coupe for a Norwegian project to expand hydrogen refuelling infrastructure and a hybrid for the Japanese market.

As significant as any of these changes, however, is the continuation of Mazda's car weight reduction programme. The existing Mazda 2 caused a stir when it was introduced because it bucked the apparently inexorable trend towards heavier cars by offering a weight saving over the predecessor model of 100kg. Now Mazda plans to introduce a similar reduction on all future models from 2011 onwards, and expects to follow that with another round of 100kg reductions from 2016. More efficient structural engineering and the use of different materials are expected to be the main means by which this will be achieved.