Abstract: In an internal combustion engine having an air intake passage containing a throttle valve, and provided with passages to the outside from points upstream and downstream of the throttle valve, an auxiliary air regulator comprising a mounting block within which is formed a bypass passage, one end of which is matably connected with a passage in said air intake passage upstream of the throttle valve, and the other end of which is matably connected with a passage in said air intake passage downstream of the throttle valve. A movable shutter means is disposed within said bypass passage so as to control the effective cross-sectional area of said bypass passage. A bimetallic coil is enclosed within an air tight chamber annd being selectively heated. Engaging means connects the outer end of said bimetallic coil with said shutter means so that a movement of the bimetallic coil in response to a temperature change is transmitted mechanically to the shutter means.

Abstract: Engine suction is applied for controlling admission of atmospheric air into a vacuum chamber of an EGR control valve so as to reduce the degree of opening of the EGR control valve during low load running of the engine, and concurrently the vacuum in a venturi of a carburetor is applied for controlling the admission of atmospheric air into the vacuum chamber so as to increase the degree of opening of the EGR control valve during high load running of the engine.

Abstract: Two spark plugs are disposed in each combustion chamber of an internal combustion engine to ignite the air-fuel mixture mixed with a considerably large proportion of the exhaust gases. The wall surface of the combustion chamber is formed so that only one spark plug can not be excessively cooled down by the stream of the cool air-fuel mixture inducted through the intake port of the engine.

Abstract: Passage means is provided to feed atmospheric air into the vacuum chamber of a vacuum actuator of a breaker plate and a control valve is provided to control the amount of atmospheric air fed into the vacuum chamber to make the vacuum in the vacuum chamber equal to the intake manifold vacuum during engine operation below a predetermined speed and above a predetermined load and to reduce the vacuum in the vacuum chamber to a predetermined level lower than the intake manifold vacuum during engine operation above the predetermined speed and below the predetermined load so that the ignition timing of the engine is adequately retarded during running of the engine at low load and at low speed and medium load and the engine ignition timing is not retarded or is slightly retarded during running of the engine at high load and at high speed and medium load.

Abstract: Each combustion chamber of an internal combustion engine is divided into four generally equal imaginary parts by a longitudinal vertical imaginary plane parallel with the longitudinal axis of the cylinder head of the engine and a lateral vertical imaginary plane perpendicular to the longitudinal vertical imaginary plane. Two spark plugs, and intake and exhaust valves are disposed on the cylinder head wall surface defining the upper part of the combustion chamber, and located at the four generally equal imaginary parts, respectively.

Abstract: A fuel vaporizer for internal combustion engines employs a chamber exposed to and directly below the underside of the engine carburetor and a heater wall at the bottom of the chamber to receive drops of fuel released from the engine carburetor into the intake manifold. It also includes an apertured wall having an upperside forming the bottom of the intake manifold riser and an underside forming the top of the chamber. The heater wall may be heated by exhaust gases or bypassed water from the cooling system of the engine. The chamber is shallow so that surface of the heater wall of volume of the chamber will be high enough for rapid evaporation of fuel. The drops of fuel released from the engine carburetor drop down directly onto the heater wall and fuel vapor flows out of the chamber into the intake manifold. The apertured wall is not formed with holes in the peripheral area thereof to prevent the drops of fuel from splashing and/or spilling out of the chamber into the intake manifold.

Abstract: Two bimetallic leaf valves having thermal hysteresis characteristics different from each other are provided to permit or inhibit transmission of engine induction passage vacuum to a distributor motor to advance or retard the ignition timing in accordance with engine temperature of the time of start of the engine and within a predetermined temperature range after starting the engine.

Abstract: A pressure control valve for venting excess air pressure in a secondary air supply conduit opening to an exhaust system of an internal combustion engine has a relief valve member to close a vent port through which excess air pressure in the secondary air supply conduit is vented. The valve member is directly operable in response to excess pressure in the secondary air supply conduit. This valve member is fixedly secured to one end of a stem slidably extending through a spring seat. The stem has at its opposite end a flange and a coil spring is compressed between the spring seat and the flange to urge the relief valve to its vent port closing position. The spring seat is spring biased in a direction toward the flange to increase compression of the coil spring and it is also moved in the opposite direction in response to intake manifold vacuum by means of a vacuum servo to reduce compression of the coil spring.