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

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