The engine runs on the Miller cycle, a variant of the Atkinson cycle used on hybrid vehicles. Miller cycle engines close the intake valve late (after bottom dead center on the intake stroke) which gives an effective power stroke that is longer than the compression stroke. This cycle is more efficient but produces less torque, a deficiency that is alleviated by the supercharger.
The new triple is equipped with automatic start-stop and internal friction is reduced by 30 percent through special coatings on the piston rings and a variable displacement oil pump. Nissan claims the new engine will have power similar to a 1.5-liter inline-four (100-105 horsepower) with CO2 emissions of about 95 grams / kilometer on the EU drive cycle.
Nissan Announces a New 3-Cylinder 1.2L DIG Supercharger Engine
- Aims for Lowest level of Fuel Consumption in the World with a Power Output Equivalent to that of a 1.5L Engine -
YOKOHAMA (July 16, 2010)-Nissan Motor Co., Ltd. today announced its newly developed HR12DDR, a 1.2 liter engine, aiming to achieve the lowest level of fuel consumption in the world for gasoline-powered cars, with an engine power output equivalent to that of a 1.5L engine(s) and CO2 emission of 95 grams per kilometer (New European Drive Cycle).
The engine will be mounted on the new "Micra (also known as March in other markets)" in the European market in the first half of 2011. The engine is based on the HR12DE, the 1.2L 3-cylinder engine mounted on the new Nissan MARCH. High engine performance and low fuel consumption levels have been achieved through the adoption of the Miller cycle, gasoline direct injection system (DIG), and a highly efficient supercharger, in combination with an Idling Stop system.
Here are details of the technologies:
By adopting the Miller cycle, in which the power stroke is enhanced by the compression stroke as a result of delaying the closing timing of the intake valve, the thermal energy of the fuel is converted to kinetic energy much more efficiently than it is with regular 4-stroke cycle engines, and pumping loss caused by intake manifold negative pressure has been reduced.
Moreover, the highly compressed and high-temperature air-fuel mixture is cooled by the latent heat of the vaporization of fuel directly injected into the cylinder, and the temperature of the combustion chamber is lowered by adopting a piston-cooling channel and sodium-filled valves to control detonation. These technologies have enabled a compression ratio of 13*1 for improved combustion efficiency.
The supercharger*2 is equipped with an automatic on/off clutch, which means that both high fuel efficiency and high engine performance can be achieved by automatically switching off supercharging while driving at low speeds, such as on city roads.
Moreover, adoption of a hydrogen-free diamond-like carbon (DLC) coating for the piston rings and a variable displacement oil pump helps to reduce friction by up to 30%, compared with conventional 4-cylinder engines with similar performance levels.
These technologies are the culmination of the company's research and development efforts based on the Nissan Green Program 2010 (NGP 2010) - Nissan's mid-term environmental action plan that includes initiatives to reduce CO2 emissions and introduce truly effective technologies, products and services into the market.
1. *1 Volume ratio of top dead center (TDC) and bottom dead center (BDC). With a higher ratio, higher efficiency (i.e. high performance) can be expected, although it becomes prone to detonation, such as engine knocking. In the case of gasoline-powered engines, the compression ratio is around 10, even for high-performance engines.
2. *2 A system in which a pump engine powered by the output shaft forcibly sends compressed air to the cylinder to gain a similar effect to that of engine displacement.