See inside a working DISI engine
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The MZR 2.0L DISI engine was developed to improve fuel efficiency, one of the key values of family cars, and to offer exhilarating driving.
*DISI, the abbreviation of Direct Injection Spark Ignition, is Mazda's term for our direct injection technology for gasoline engines.
In developing the DISI engine, we aimed to cool the interior of the cylinder as much as possible by promoting fuel vaporization and uniform mixing of atomized fuel and air. This produces a high charging efficiency of the air-fuel mixture and a high compression ratio, which results in significant improvements in both torque and fuel efficiency.
Characteristics of the direct injection engine:
- Fuel is injected from a tiny nozzle into a relatively large cylinder, so it has a high latent heat of vaporization, which efficiently cools the air within (in-cylinder cooling effect).
- The air temperature in the cylinder decreases, which means:
- (1) more air may be charged into the combustion chamber, which produces increased torque.
- (2) the engine is less prone to knocking. This contributes to increased torque, and enables a higher compression ratio that also contributes to good fuel efficiency.
- Realization of excellent fuel efficiency
The Mazda5 (known as the Mazda Premacy in Japan) with the MZR 2.0L DISI engine achieves a fuel economy of 15.0 km/L, seven percent better than with the conventional 2.0L port injection engine (14 km/L), and easily exceeds Japan's Green Tax standard of 14.3 km/L.
- Clean emissions
The MZR 2.0L DISI meets Japan's strictest SU-LEV (Super Ultra Low Emission Vehicle) standards. SU-LEV standards require that nitrogen oxide (NOx) and non-methane hydrocarbon (NMHC) levels are at least 75 percent lower than Japan's 2005 exhaust emissions standards. To achieve such low emissions, the ignition timing is delayed when the engine is cold in order to heat the exhaust gas. Mazda's DISI technology provides higher combustion stability which enables the delayed ignition timing.
- High torque and response
The in-cylinder cooling effect of the DISI engine increases torque by 7 to 10 percent at normal engine speeds for a responsive and lively ride.
- High-pressure stoichiometric combustion
To meet stricter exhaust emissions regulations, a three-way catalyst is employed. Stoichiometric combustion is required for best results with a three-way catalyst, and once this was decided, we were able to focus on uniform mixing of the atomized fuel and further improved the in-cylinder cooling effect. We achieved compression ratios as high as 11.2 with regular gasoline.
- Swirler injectors
Atomized fuel injection was made possible by the swirler injector. To ensure the fuel is injected in a hollow conical spray (upper right figure), an intricate and highly precise design is required for the top end of the injector (upper left figure).
- Tumble swirl control valve (TSCV)
Under conditions unfavorable to combustion, such as low engine temperatures, the TSCV installed on the intake manifold closes one port to increase the flow velocity of intake air and create an in-cylinder flow (tumble swirl) as the arrows below indicate. This enhanced in-cylinder flow pattern improves the fuel mixing, increases combustion speed and ensures higher combustion stability.
- Variable fuel pressure system
When the engine is idling, this system reduces the fuel pressure to as low as 3 MPa in order to reduce mechanical resistance and improve fuel efficiency. With the throttle fully open, the fuel pressure rises to as high as 11.5 MPa, exhibiting improved atomization and increased power output. The maximum fuel pressure of 11.5 MPa is thirty to forty times as high as in conventional port injection engines.
