Mazda pumps up SkyActiv engines

MAZDA is predicting its future engine technology will deliver up to 30 per cent in fuel savings – even before factoring in weight-gain savings from its SkyActiv program.

The Japanese car-maker has hinted at future engine technology that will result in it developing a high-compression petrol engine that will act like a diesel powertrain at low revs, and a conventional spark-ignition petrol powerplant higher in the rev range.

The target for the car-maker is a staggeringly high 18:1 compression ratio that will force the engine into a state known as homogenous charge compression ignition (HCCI), where the compression alone is sufficient for the petrol to self-combust without the need for a spark plug.

That compares with a current compression ratios of about 10:1 in most vehicles, although motorcycles are generally up around 12:1.

Speaking in Tokyo at an Australia-first preview of a Mazda2 electric vehicle featuring a rotary-powered, petrol-fuelled range extender, Mazda general manager of product strategy, Hidetoshi Kudo, said the next generation of HCCI-enabled engines to roll out the technology was only a few years away.

“We’d like to introduce that strategy at an appropriate time,” Mr Kudo said.

“For the SkyActiv-G or -D (petrol and diesel engines) in 2006 we began engineering and in 2011 we began mass production.

“So in about five years we were able to mass-produce those technologies after studying the engineering.

“It (engineering engines) is difficult, so maybe you can imagine the sort of timing you could expect. It’s not a commitment it’s the image you can get for the timing.”

One of the keys of the next generation of SkyActiv engines is that the diesel-like performance will expand the engine’s low fuel-use characteristics over a wider rev range, doing away with the need for expensive turbochargers to help reduce emissions.

More importantly, though, the car-maker could stick with a traditional six-speed gearbox when other brands needed to develop more expensive – and complicated – gearboxes with up to 10 ratios, Mr Kudo said.

Ichiro Hirose, the vice-president of Mazda’s European research and development unit, said the car-maker would build its new SkyActiv technology, including a high-compression head, on top of its existing 2.0-litre four-cylinder petrol engine.

“The basic concept is carried over as that technology story is on top like a building block strategy,” Mr Hirose said.

“The current consideration for (SkyActiv) generation 2 is something around 16:1 to 18:1 (compression ratio) that we are aiming for.”

The figure of about 18:1 was “an appropriate limit”, he said.

Mr Hirose said reducing engine performance losses using special low-friction cylinder coatings would contribute towards further fuel use improvements for generation three of SkyActiv.