K4N Used Fuel Injector For Excavator E305SR Square Engine Parts

Specification

Description

Advantages of MPI

Compared to single-point injection or carburetion, MPI engines have better fuel economy and lower emissions. This is because the engine can meter the amount of fuel needed for each cylinder. If too much fuel is added, there are leftover hydrocarbons, and carbon monoxide is formed from the combustion; if too little fuel is added, the mixture can explode early, leading to engine "knock." Multi-point injection, in combination with other technologies, can also improve fuel efficiency by allowing the engine to selectively disable certain cylinders during cruising operations when the engine's full power isn't needed.

How Throttle Body Injection Works

Fuel Delivery

Fuel is delivered to the throttle body injection system by an electric fuel pump located in the fuel tank. This pump supplies fuel pressure in sufficient volume to meet the engine's fuel requirement through all load conditions. Injector pressures range from 13 to 16 psi (low pressure system) or 35 to 60 psi (high pressure system), and are kept constant by the fuel pressure regulator. The fuel pressure regulator is a vacuum-operated diaphragm, so that during cold start operation maximum fuel pressure and volume are supplied. Once the engine starts and the manifold vacuum is available, the diaphragm opens a valve and allows unused fuel to return to the tank.

Air Delivery

Air is delivered to the engine through the throttle valve. This throttle valve operates like the throttle valve on a carburetor--as the throttle is opened, more air is allowed to enter the engine. Where the throttle body injector differs from the carburetor is in the area of idle control. Instead of calibrated passages, the injector system uses a motorized Idle Air Control (IAC) valve. This valve is in effect a computer-controlled vacuum leak. To increase idle speed, the valve opens to allow more air in. To lower idle speed, the valve closes to allow less air in to the engine.