Mazda has announced that it is to launch new petrol and diesel-powered cars with the same fuel efficiency as, or better than, rival hybrid-powertrain vehicles. A petrol version of the Mazda2, featuring the company’s new Skyactiv G (gasoline) technology, is to become available on the Japanese market during the first half of next year. It is claimed to return a consumption figure of 3,3 litres/100 km.
Company CEO Takashi Yamanouchi pointed out in a press briefing I attended in Tokyo that petrol engines typically had an efficiency level of 30 per cent. Mazda believes that, by working smart with current technology without resorting to add-ons, it will eventually be possible to build engines that claw back much of the fuel heat capacity lost in the process of turning chemical energy from fuel into mechanical energy.
The efficiency shortfall is due to factors such as the small percentage of fuel that remains unburned, as well as cooling losses, exhaust losses, pumping losses and mechanical losses. Seita Kanai, director of research and development responsible for the Skyactiv programme, said that engineers had focused on increasing efficiency in these areas by fine-tuning normally aspirated petrol engines without the use of expensive external aids such as turbochargers or superchargers, as some other manufacturers are currently doing.
Innovations on the new petrol unit include a high 14,0 to 1 compression ratio, with kinetic knock controlled through items such as multi-hole injectors, cavities in the pistons and a 4-2-1 exhaust system. Further benefits achieved by innovative use of basic technology include reduced pumping losses, reduced weight and reduced mechanical friction. Naturally, the company’s innovative i-stop stop-start system, honoured in CAR’s annual industry awards, is part of the package. The engine can run on normal 95 RON fuel, so should be able to operate on South African petrol.
Turning to turbodiesels, Kanai-san said that his team had managed to increase eficiency by lowering the compression ratio to 14,0 to 1, optimising combustion timing, reducing the weight of components and thus reducing mechanical friction and employing two-stage turbocharging. Among the other technical innovations are multi-hole piezo injectors and a variable exhaust-valve mechanism.
Benefits included a 20 per cent improvement in fuel efficiency compared with other similar small diesels, major enhancement of low and mid-range torque, with a smoot, linear response and no need for costly NOx post-processing to meet forthcoming emission standards in the US, Japan and Europe.The engine will run on current Japanese or Euro diesel fuel, but Kanai-san was unable to say whether it would be compatible with South African diesel. Mazda does not currently sell its modern diesel cars in South Africa, though the BT-50 pick-up range uses older-tech diesel powerplants.
The Skyactiv engines will be used in conjunction with other efficiency-improving features such as new lightweight manual and automatic gerarboxes (the latter featuring a dramatically expanced lock-up range), lighter and more rigid bodyshells, lightweight suspension systems and electric power-steering.
