The world population will increase from 6 billion in 2000 to 8 billion in 2030. The number of cars will increase from 400 million in 1980 to 1 billion in 2010. This is far-reaching for Japan, a country with a technologically advanced auto industry. However, the development of the automotive industry has also brought about some global problems. From the perspective of automobiles, the status of gas emissions, global warming (increased CO2 concentration), and energy issues are analyzed. The future of gasoline engines is forecasted.

Reducing exhaust emissions, large output power, compact size, low noise, and low cost are the sources of competitiveness for Japanese automobiles. It is imperative to reduce CO2 emissions, in other words, to improve fuel economy. However, the fact that the thermal efficiency of gasoline engines is much lower than that of diesel engines is an indisputable fact. Regarding fuel economy, a comparison was made between a diesel engine with high thermal efficiency and a gasoline engine, and the differences in the three aspects of pump loss, compression ratio, and equal volume were clearly defined.

Pump loss 1 uses in-cylinder direct injection and other lean combustion and improves EGR rate; 2 uses cylinder rest system; 3 uses Atkinson cycle and so on. The core technology supporting these technologies is the variable valve system.

Knocking suppression technology to improve the compression ratio The use of in-cylinder direct injection and Atkinson cycle is an effective measure, and the combination of lean combustion and supercharging is also an effective means.

Raising the isobaricity While direct injection has a certain effect, it requires significant improvements in the control of the flame propagation profile, and there are still some difficulties. Of note is the homogeneous compression ignition (HCCI) technology.

For the future of gasoline engine technology, the following two specific issues should be solved.

1. Although the popularity of direct-injection engines has been accelerating, the cost has also been significantly lower than in the early days. However, compared with injectors used for port injection, prices are still several times higher, and costs should be further reduced. In addition, there is a need for improvement in terms of suppressing durability such as deposit formation, and it is desirable to increase the dynamic range from low flow rate to high flow rate.

2. For the most promising HCCI engines in the future, the proof-of-principle of the theoretical research phase has been completed, and the research and development for practical application is fiercely competitive. However, the goal of practical application has not yet been determined. The reason for this is that effective ignition control methods have not yet been established.