Mazda2 Gets Miller-cycle Technology

Motoring Channel Staff - 1/June/2007

Hiroshima, Japan — The highly anticipated and thoroughly modern-looking Mazda2 will makes its debut in Japan in July (where it's known as the Demio) and the range will include a new version of the 1.3-litre MZR engine.

Mazda has revealed that it has developed a new, naturally aspirated 1.3-litre Miller-cycle engine for its compact car which, in combination with the company's first continuously variable transmission (CVT), will provide the new model with a 20 per cent fuel efficiency improvement.

Mainstream Miller-cycle engines - seen in models like the Eunos 800 here in Australia - use a supercharger to ostensibly increase the displacement of the engine to improve the efficiency of the compression phase of a four-stroke engine. Sometimes it's even referred to as the '5th stroke', and reduces fuel use and increases power.

The intake valves are left open far longer than normal, but the way the system works in the new 1.3-litre naturally aspirated engine without a supercharger is intriguing. The new MZR engine delays the closing of the intake valves like other Miller-cycle engines, which it claims reduces pumping losses due to a "higher expansion ratio".

The standard 1.3-litre MZR engine makes 62kW, though it's unclear just how much more power - if any - the naturally aspirated Miller-cycle version of the powerplant will make. Gains are not likely to be significant because forced induction is not part of the process.

Logic suggests that you need a pump of some sort to achieve gains with a Miller-cycle engine, but because the engine is relatively small it's not so much of an issue. Mazda's primary intention with this engine is to lower emissions, not to attain more power.

Here's the official line: Newly developed from the current MZR 1.3L DOHC aluminum engine, the naturally-aspirated MZR 1.3L Miller-cycle engine employs delayed closing of the intake valves in order to reduce pumping losses and improve thermal efficiency through a higher expansion ratio. Intake valve timing is optimized by the Sequential Valve Timing System to provide improved fuel efficiency over the current MZR 1.3L engine when cruising and accelerating.

In addition to this new, highly efficient powertrain, the all-new Demio has been made approximately 100 kg lighter than its predecessor through weight reduction techniques, which have resulted in nimble handling and significantly improved fuel economy.

The Demio model with the naturally aspirated MZR 1.3L Miller-cycle engine combined with the CVT transmission achieves a fuel economy that is rated as 20 percent or better than the level specified by Japan’s 2010 fuel economy standards. Exhaust emissions are also at least 75 percent lower than 2005 standards, which conforms to Japan’s Super Ultra-Low Emissions Vehicle (SU-LEV) standard and qualifies the Demio for Green Tax exemptions.

Through its Sustainable Zoom-Zoom plan that was announced in March 2007, Mazda declared its intention to pursue the harmony felt between driving pleasure and environmental and safety features, and its quest for an advanced Zoom-Zoom world. This includes the ongoing desire to create captivating design, to provide our customers with continual driving pleasure and to develop improved safety and environmental technologies. 

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