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A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performance, combustion and exhaust-gas characteristics were analyzed experimentally and compared for operation with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. The power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and either of the two EFI methods. The exhausted unburnt fuel of the direct fuel-injection engine was lower than that for operation with a carburetor, and formaldehyde and the CO concentration were of the same level as for operation with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation.

It is important not only to increase a thermal efficiency of a spark ignition engine, but also to decrease a driving loss of auxiliary component of engine such as a cooling system. For example, there is a limitation of cooling performance when a requirement of aerodynamics design of a motorcycle or an automobile is severe. We propose an active application of ejector pump drove by exhaust energy to the cooling system. There were several applications of ejector system to the intake or exhaust system, but there was nothing for the design of it. In this report, one of the fundamental researches conducted in our laboratory, the effects of the dimensions of the ejector on the ejector performance are discussed. The results are followings: (1) The more the engine speed decreases, the more the ejector efficiency (G2/G1: G1 is the mass of charging air in the engine, G2 is the mass of entrained air by the ejector system) increases.