In recent years, new electric devices have been introduced that have led to the development of automobiles such as hybrids and electric vehicles. We have entered an era in which performance delivered by the engine, transmission, body, chassis and other vehicle parts is being augmented through their combination with electrical components. Nevertheless, it is forecast that internal combustion engines will still account for a high percentage of automobile powertrains even as far ahead as 2020.
Consequently, Mazda's priority is to improvement of the base technologies that are responsible for the core performance of our cars while adopting a Building Block Strategy of gradually introducing electric devices such as regenerative braking, hybrid and other systems.This approach aims to effectively reduce total CO2 emissions with cars that offer a winning combination of driving pleasure and excellent environmental and safety performance to all our customers, without relying heavily on vehicles that are strictly dedicated to meeting environmental needs.
SKYACTIV TECHNOLOGY is a blanket term for Mazda’s innovative new-generation technologies that are being developed under the company’s long-term vision for technology development, Sustainable Zoom-Zoom. The SKYACTIV TECHNOLOGY name is intended to reflect Mazda’s desire to provide driving pleasure as well as outstanding environmental and safety performance in its vehicles. To achieve this goal, Mazda has implemented an internal Building Block Strategy to be completed by 2015. This ambitious strategy involves the comprehensive optimization of Mazda’s base technologies, which determine the core performance of its vehicles, and the progressive introduction of electric devices such as regenerative braking and a hybrid system. All the technologies that are developed based on the Building Block Strategy will fall under the SKYACTIV TECHNOLOGY umbrella.
The development of automotive mechanisms for engines has a history going back more than 120 years and has involved
the work of countless engineers. For this reason we tend to find it difficult to think that any further improvement in performance is possible. But the fact remains that 70 to 80 percent of the energy contained in fuel is lost within a vehicle’s powertrain and fails to be transferred as motive power to its wheels.
Many of today’s automakers are working on engine refinement by making engines smaller and various other methods.
One of Mazda’s recent developments towards an ideal engine configuration is the Homogenous Charge Compression Ignition (HCCI) engine, which offers the combined advantages of both gasoline and diesel engines. In commercializing the rotary engine and through other remarkable technical achievements, Mazda has a history of making the seemingly impossible possible. Now, we have taken on the challenge of pursuing ideal combustion.
Increasing the compression ratio considerably improves thermal efficiency. The compression ratio of recent gas engines is generally around 10:1 to 12:1. Theoretically, if the compression ratio is raised from 10:1 to 15:1, the thermal efficiency will improve by roughly 9%. However, one of the reasons preventing the spread of high compression ratio gas engines is the large torque drop due to knocking
Knocking is abnormal combustion in which the air-fuel mixture ignites prematurely due to exposure to high temperature and pressure, creating an unwanted high-frequency noise. When the compression ratio is increased, the temperature at compression top dead center (TDC) also rises, increasing the probability of knocking.
In order to lower the temperature at compression TDC, reducing the amount of hot exhaust gas remaining inside the combustion chamber is effective. For example, with a compression ratio of 10:1, a residual gas temperature of 750 deg. C, and an intake air temperature of 25 deg. C, if 10% of the exhaust gas remains, the temperature inside the cylinder before compression increases by roughly 70 deg. C, and the temperature at compression TDC is calculated to increase by roughly 160 deg. C. Therefore, it can be easily inferred that the amount of residual gas has an major impact on knocking.
This reduction of residual gas was focused on for SKYACTIV-G, enabling the realization of a high compression ratio gasoline engine
To improve resistance to knocking, shortening of combustion duration was also attempted. The faster the combustion, the shorter amount of time the unburned air-fuel mixture is exposed to high temperatures, allowing for normal combustion to conclude before knocking occurs. Specifically, aside from creating a more homogeneous mixture by means of intensifying air flow, increasing injection pressure, and using multi-hole injectors to enhance fuel spray characteristics, a piston cavity is used to prevent the initial combustion flame from hitting the piston and interfering with the flame’s growth.
Vehicle transmissions are not only extremely important for improving fuel economy, they also exert a major influence on driving performance. The performance demands on automatic transmissions vary greatly depending on the market, and since there is not a single transmission in existence that satisfies all these varied demands, automakers deploy a variety of systems, each matched to a particular market. Employing the world’s most commonly-used combination - a torque converter and stepped automatic transmission - as the basic structure, and by using technology that substantially reduces slip in starting devices, Mazda has brought together the benefits of each system and developed a highly efficient automatic transmission witha substantially direct drive feel that will be perfectly suited to conditions in numerous global markets.
SKYACTIV-DRIVE is the ideal AT with all the advantages of the various types of transmissions