Mazda recently started production of the new Mazda2 that debuted at the Geneva Motor Show and one of the new engines available in the car will be a 1.3L Miller-cycle engine which would be more accurately called an Atkinson cycle engine. The Atkinson cycle uses a longer power stroke than the compression stroke. This is achieved on modern engines by keeping the intake valve open past bottom dead center, allowing the engine to push some of the air-fuel mix back out into the intake manifold. This can result in a significant increase in fuel economy but at the cost of low end torque. The Miller cycle adapts this concept by adding a supercharger to improve the torque and was first used by Mazda on the mid-nineties Millenia.
On the new 2 Mazda gets rid of the supercharger but uses the Atkinson cycle. Nomenclature aside the new setup provides some excellent economy. The engine is mated up to Mazda's first CVT and manages 54mpg compared to the 1.3L in the old model that got 45mpg. The engine also has variable valve timing which it appears Mazda is using to adjust the use of the Atkinson cycle to maximize efficiency and while still maintaining decent performance. On top of the all the fancy powertrain stuff, Mazda also reduced the weight of the new 2 by over 200lbs compared to the old model which helps both performance and efficiency. So far their is no indication of whether we will see this engine in the US market.
[Source: Mazda] 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.