Sky magic for new Mazdas
THE magic number for Mazda’s new ‘‘Skyactiv’’ engines is 14:1.
That’s the compression ratio for their frugal petrol and diesel engines.
For a petrol engine, that’s high compression – in fact the highest in the world for a mass-produced engine – but for a diesel, it’s very low.
Mazda executive officer Kyoshi Fuziwara says the new Skyactiv engines will be produced in different capacities and configurations over the next decade, replacing theMZRengine.
He says the new internal combustion engines and other ‘‘Sky’’ manufacturing technologies will help improve fuel economy of the Mazda fleet by 30 per cent and decrease emissions by 23 per cent by 2015.
The new engines will be introduced alongside developments in electric and hybrid powertrains.
Powertrain manager Susumu Niinai says high compression means more air mixed with the fuel for a faster burn and reduced load.
Mazda brought out four technical officers from Japan headquarters to a technical briefing in Melbourne this week.
Niinai says the key point of the Skyactiv-G petrol engine is high compression without knocking or pinging by reducing residual gas in the cylinder and therefore reducing temperature.
To achieve this it uses a longer 4-2-1 exhaust manifold, direct injection and a new piston head.
In the Skyactiv-D diesel engine, lower compression allows more time for the air and fuel to mix for a cleaner and more efficient burn that reduces soot and greenhouse gases.
These engines will be mated to new Skyactiv automatic and manual transmissions that technical officer Toshiyuki Kikuchi says will further improve economy by up to 7 per cent.
Mazda has chosen to reject continuously variable and double-clutch transmissions and stay with a torque converter automatic highly modified with less clutch slip and an expanded lock-up range.
Kikuchi says this gives it a manual transmission feel.
He claims it shifts gears faster than DCT.
The Skyactiv-MT manual is lightweight and compact with a ‘‘light and crisp feel like MX-5’’.
Mazda Skyactive-D prototype diesel (front) with current model Mazda6 diesel