A two-stage combustion is one of the GDI™ technologies for a quick catalyst warm-up on cold-start. However, when the combustion is continued for a long time, increase of the fuel consumption is a considerable problem. To solve the problem, two emission control technologies are newly proposed. The combustion has a potential to maintain thermal reaction at out of a cylinder. However, the burning gas has hardly an opportunity to meet with the unburned gas. A reactive exhaust manifold promotes mixing and reaction of these gases. The fuel economy is improved because the manifold strengthens the catalyst warm-up and reduces HC emissions. A stratified slight-lean combustion, which is locally prepared rich mixture in cylinder, supplies simultaneously substantial CO and surplus O2 to a catalyst and induces catalyst reaction. CO oxidation warms up the catalyst and promotes HC oxidation. The fuel consumption is greatly less than the two-stage combustion. Consequently, when warm-up time of the two-stage combustion is shortened by introduction of the stratified slight-lean combustion, the fuel economy is improved while maintaining low emission level. To avoid soot generation and fouling of a spark plug, fuel vaporization and diffusion are facilitated by adjustment of an interval between a fuel injection and a spark ignition. These are realized by excellent robustness based on wide spacing concept.