Mazda brings in the changes

The facelifted Mazda3 will come with a range of technological improvements. Photo / Supplied

Mazda New Zealand is next month expected to introduce the first of its new fuel-saving SkyActiv petrol engines under the bonnet of the facelifted Mazda3.

Nothing official has come from the carmaker's NZ office yet, other than that the car will arrive here before Christmas. But the new-look model has gone on sale in Japan and Australia with the SkyActiv engine and six-speed gearbox technology.

The new drivetrain will probably appear in only one Mazda3 model in New Zealand. Again, nothing official from Mazda NZ, but it will almost certainly follow Mazda Australia, which has equipped only its 2-litre SP20 model with SkyActiv.

The rest of the new Mazda3 line-up picks up upgrades on existing technology, including styling enhancements, plus a range of suspension and body changes to improve ride and reduce road noise.

Ultimately, the SkyActiv technology will find its way into every Mazda petrol and diesel vehicle and across chassis designs, starting with the Mazda CX-5 compact SUV, due in New Zealand next year.

Mazda says the direct-injection 2-litre SkyActiv-G (petrol) drivetrain has improved fuel efficiency over the existing four-pot MZR unit and five-speed auto 'box by 25 per cent.

The carmaker claims town and around consumption of 6.1 litres/100km, which would make the SkyActivc-G the most fuel-efficient 2-litre petrol unit on the market.

Power and torque have increased by 4.6 and 6.6 per cent respectively over the MZR engine, it says.

SkyActiv is at the centre of Mazda's aim to cut fuel consumption across its range by 30 per cent by 2015. It believes the vast majority of vehicles will still be using internal-combustion engines in 2020 and beyond.

The new-look Mazda3 shows off the first SkyActiv-G petrol unit and Sky-Drive transmission, a six-speeder that Mazda says has the best characteristics of conventional, dual-clutch and CVT transmissions. The first SkyActiv-D direct-injection diesel engine will be under the bonnet of next year's CX-5.

The SkyActiv-G engine is a high-compression unit. Mazda says it has been able to increase the petrol engine's compression ratio to a diesel-like 12-1, thanks to a range of new technologies, including multi-jet direct fuel injectors and a piston with a small cavity in the top to suppress knocking.

The multi-jet injectors provide finer atomisation of petrol, and the small cup-like cavity promotes a uniform spread of flame immediately after ignition.

Mazda engineers redesigned the pistons, conrods and gudgeon pins to shave 127 grams from the weight of components in each cylinder, plus 690g from the redesigned crankshaft.

Light-load valve springs, a new plastic water pump impeller, low-resistance water and oil paths through the engine, smaller oil pump and a low-tension serpentine belt drive were among the measures adopted to reduce the drag on the engine for greater efficiency.

In a first for Mazda, SkyActiv has start-stop to further reduce the engine's thirst. Thrifty driving is also helped by bigger underbody streamlining panels to reduce aerodynamic drag at highway speeds.

The Mazda3 was the best-selling car in New Zealand and Australia in August. It racked up 28,736 sales across the ditch, ending the Holden Commodore's 15-year reign as Australia's number-one seller.