A throttle body fuel injection system and method that is arranged to easily replace four-barrel carburetors includes a throttle body assembly with four main bores, each with a throttle plate and an associated fuel injector. Each injector feeds fuel into a circular fuel distribution ring via a fuel injection conduit, which introduces pressurized fuel into the air stream. The fuel distribution rings and bores have profiles that avoid constrictions for to prevent low pressure zones according to the Venturi effect. The throttle body includes an idle air control circuit having a port opening into main intake bores downstream of the point of fuel distribution into the air stream, thereby reducing the tendency for a lean fuel mixture at idle. An ECU “feed forward” algorithm controls fuel injection as a function of the position of the idle air control valve.

A method of predicting manifold air pressure in an internal combustion engine during idle comprising the steps of receiving an idle air control (IAC) duty cycle value from an idle air controller, receiving an atmospheric pressure, and predicting a manifold pressure in an engine control unit based on the IAC duty cycle value and the atmospheric pressure.

An air intake system for a marine engine has a throttle body and a throttle plate that is rotatably supported within the throttle body. The throttle plate is rotatable to regulate air flow through the throttle body from a first region on a first side of the throttle plate to a second region on a second side of the throttle plate. An air conduit has an air conduit inlet and an air conduit outlet. A noise cancelling device comprises a pass-though chamber. The pass-through chamber has a chamber inlet that receives the air flow from the air conduit, a chamber outlet that discharges the air flow to the idle air control valve, and a pass-through interior between the chamber inlet and chamber outlet. The pass-though chamber is configured to cancel noise emanating from the idle air control valve.

A spark ignition type engine enabling engine startability to be favorable is provided. The spark ignition type engine includes a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve, in which when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve.

Cross-port air flow that improves engine fuel economy and reduces pumping losses during part-throttle operation can be implemented in various types of internal combustion engine systems using ports that interconnect the intake ports of different cylinders, thus allowing different cylinders to share combustion air. Cross-port air flow is commenced during part-throttle engine operation to disrupt the primary combustion air flow from each throttle to its associated cylinder, which reduces charge density and engine power. The engine compensates for the reduced power by incrementally opening the throttles, thus increasing the primary combustion air flow, reducing pumping losses and improving fuel economy.

A system and method of operating the same includes an engine speed sensor determining an engine speed, an exhaust gas bypass valve, an exhaust gas bypass valve actuator coupled to the exhaust gas bypass valve and a controller. The controller partially opens the exhaust gas bypass valve with a first predetermined effective area greater than fully closed when the engine speed is at idle. The controller determines an acceleration event, holding the exhaust gas bypass valve open at least a second predetermined effective area greater than fully closed in response to the acceleration event.

Cross-port air flow that improves engine fuel economy and reduces pumping losses during part-throttle operation can be implemented in various types of internal combustion engine systems using ports that interconnect the intake ports of different cylinders, thus allowing different cylinders to share combustion air. Cross-port air flow is commenced during part-throttle engine operation to disrupt the primary combustion air flow from each throttle to its associated cylinder, which reduces charge density and engine power. The engine compensates for the reduced power by incrementally opening the throttles, thus increasing the primary combustion air flow, reducing pumping losses and improving fuel economy.

Disclosed is an engine drive system that uses an open-type regulator as a regulator that rectifies an output and adjusts a voltage of a magneto AC generator driven by an engine. A means is provided that performs a process of increasing an opening degree of an ISC valve for a limited amount of time when a load of the generator is applied, while the engine is idling. Temporarily increasing an output torque of the engine prevents a rotational speed of the engine from dramatically decreasing, or the engine from stalling, during idling.

Disclosed is an engine drive system that uses an open-type regulator as a regulator that rectifies an output and adjusts a voltage of a magneto AC generator driven by an engine. A means is provided that performs a process of increasing an opening degree of an ISC valve for a limited amount of time when a load of the generator is applied, while the engine is idling. Temporarily increasing an output torque of the engine prevents a rotational speed of the engine from dramatically decreasing, or the engine from stalling, during idling.

Cross-port air flow that improves engine fuel economy and reduces pumping losses during part-throttle operation can be implemented in various types of internal combustion engine systems using ports that interconnect the intake ports of different cylinders, thus allowing different cylinders to share combustion air. Cross-port air flow is commenced during part-throttle engine operation to disrupt the primary combustion air flow from each throttle to its associated cylinder, which reduces charge density and engine power. The engine compensates for the reduced power by incrementally opening the throttles, thus increasing the primary combustion air flow, reducing pumping losses and improving fuel economy.