Abstract: Internal combustion engines are widely used in cars, trucks and buses. Among them, the spark
ignition engine with gasoline fuel is mainly employed for passenger cars. As the number of cars is extremely
increasing in the world, thermal efficiency in gasoline engines must be improved urgently with less expensive
cost-up. The homogeneous charge compression ignition (HCCI) combustion system has been attracted as
the promising and alternative combustion system to the spark ignition. Although many researchers have been
conducted to this system to solve the challenging issues, the practical usage is still unclear. This review paper
covers the technical methods examined so far, including the authors' idea of blow-down super-charged HCCI, to
introduce interesting ideas helping researchers who like to find a new way or to start investigating on the system,
leading to accelerate the practical usage of HCCI systems for the energy saving in the world.

Key words: passenger cars, energy saving, gasoline engines, homogeneous charge compression ignition
(HCCI), spark ignition (SI), exhaust gas recirculation (EGR), blow-down super charged (BDSC)