Abstract: An intermittent fuel-injection method for two-stroke engine, which is done by means of an injection nozzle mounted under a cylinder head or on cylinder wall so as to have fuel directly injected into a cylinder to mix the air inside the cylinder into a homogeneous mixture; a controller is used for controlling the fuel-injection timing and quantity; the controller determines the injection timing and quantity in accordance with the engine intake air flow quantity and engine rpm; under idle running or low-load running condition, an intermittent fuel-injection control method is used so as to enable an engine to perform one, two, three, four or five scavenging and exhaust cycles after one fuel-injection cycle in order to obtain a steady and high combustion efficiency.

Abstract: This invention is directed to an exhaust fume sampling apparatus for a two-stroke gasoline engine with a closed loop engine control unit. The novel exhaust fume sampling apparatus has a fume duct, a sampling valve, and a sensor. The fume duct is connected at one end thereof with a fume inlet disposed in the wall of combustion chamber and is in communication at other end thereof with the exhaust pipe of the engine. The sampling valve is disposed on the fume duct and is capable of being opened up at the moment shortly after the combustion has taken place so as to permit the exhaust fume so produced to pass therethrough to enter the sampling apparatus. The sensor can measure the oxygen content of the exhaust fume introduced into the sampling apparatus and transmit the information in reference to the measured oxygen content to the engine control unit, which regulates the supply of fuel to engine in accordance with the information it has received from the sensor so that an optimum air-fuel ratio is attained.