HR12DDR Engine

By reducing the volume of emissions and increasing general engine efficiency, the HR12DDR engine realizes improved fuel consumption compared to regular gasoline engines. However, with this technology there is a risk that driving enjoyment will also be lost, such as a driver not being able to accelerate quickly due to decreasing the level of emissions.

Accordingly, the HR12DDR uses a supercharger to attain engine power. It had previously been considered difficult to realize both good fuel efficiency and a pleasant driving experience, but the HR12DDR engine can do just this: A new type of engine with both low-fuel consumption and driving comfort.

In general, a gasoline engine vehicle can use around 20% of the vehicle’s energy gained from burning the gasoline. The HR12DDR engine, though, has succeeded in enhancing this 20% efficiency level by introducing several technologies.

Fuel efficiency is improved in the following three ways.

The engine reduces the loss resulting from friction. For example, through a special coating for the areas where metal parts come into contact with each other, or by reducing the tension from the parts moved by belts, friction is lowered by up to 10%.

A four-stroke gasoline engine creates energy through a cycle of intake, compression, combustion and exhaust. In the intake stroke, when there is difficulty in the suction of air, there is waste and reduced efficiency. In order to have air intake that is as easy as possible, the HR12DDR uses a Miller Cycle with a more delayed intake closure than a regular engine.
As in the diagram below, Miller Cycle engine's intake valve is open even during the compression stroke, when the valve in conventional four-stroke engines is closed.

The engine compression ratio was first increased in order to enhance heat efficiency. The HR12DDR realizes an extremely high 12.0:1 compression ratio with its supercharger.

Further, the system also features direct gasoline injection in the combustion chamber. The benefit of this system is how it lowers vaporization heat temperatures in the combustion chamber by directly injecting fuel. A lower temperature helps to avoid so-called "knocking" (abnormal combustion), and stabilizes fuel combustion and makes a high compression ratio possible.

The HR12DDR engine improves efficiency but when focusing only on fuel consumption, there is a risk that the driving experience will be less enjoyable. In this way, the system utilizes a 1.2-liter supercharger that provides the power equivalent to a 1.5-liter class engine. The supercharger was adopted for its high responsiveness to the accelerator pedal and excellent emission performance.

However, depending on the usage, driving with a supercharger worsens efficiency in an engine. In order to lower the loss and raise fuel consumption efficiency when the supercharger is both needed and not needed, the supercharger's own efficiency was raised by a supercharge pressure control through a bypass valve, and a release mechanism with an on-off electromagnetic clutch.

Furthermore, the new Note uses an environmentally friendly switching system to help customers drive more ecologically. When the switch is on, it controls the engine so that unnecessary operation of the accelerator pedal does not activate the supercharger and the engine torque is curbed. Only when acceleration is needed does pressing down on the accelerator pedal then produce supercharging. On the contrary, when the switch is turned off, drivers can control linear supercharging according to their use of the pedal, realizing a rapid response equivalent to a 1.5-liter vehicle.