Mazda Goes Miller Cycle With Demio for Japan

Watch out, diesel. Mazda says it's developed a Miller-cycle engine for the new Demio (Mazda2) in Japan that gets around 54 miles per gallon. The new JDM gas sipper goes on sale in July, sporting a 20 percent improvement in mileage over the current model, in combination with a continuously variable transmission. So what's this Miller cycle we speak of? Let's ask Wikipedia:

"In the Miller cycle, the intake valve is left open longer than it would be in an Otto cycle engine. In effect, the compression stroke is two discrete cycles: the initial portion when the intake valve is open and final portion when the intake valve is closed. This two-stage intake stroke creates the so called "fifth" cycle that the Miller cycle introduces. As the piston initially moves upwards in what is traditionally the compression stroke, the charge is partially expelled back out the still-open intake valve."
That's lovely. Problem is, the engines trade power for efficiency, which is usually compensated with a supercharger or electric motor (in the case of hybrids). Mazda's new Miller is naturally aspirated. Maybe the whole Zoom-Zoom thing accounts not stopping for gas. It's more of a net benefit thing.

Press Release:

Mazda Develops New Naturally-Aspirated MZR 1.3L Miller-cycle Engine
- The new MZR 1.3L engine powers the all-new Mazda Demio to achieve a fuel economy of 23.0 km/L and qualify for Japan's Green Tax exemptions -

HIROSHIMA, Japan—Mazda Motor Corporation has developed a new, naturally aspirated MZR 1.3L Miller-cycle engine, which will power the all-new Demio (known as the all-new Mazda2 in overseas markets) when it goes on sale in Japan in July 2007. In combination with Mazda's first continuously variable transmission (CVT), the engine will assist the new Demio to achieve a 10-15 mode fuel economy of 23.0 km/L, an improvement of approximately 20 percent over the 19.2 km/L rating of the current model.

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 conjunction with the CVT, which transfers torque at low speeds without power loss and eliminates gear-shift shock, the setup achieves excellent fuel efficiency as well as a smooth and exhilarating ride.

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.

Related:
Geneva Pre-Show: The New Mazda2 [internal]