Fuel Injection Systems Aims and Objectives Aim To

Fuel Injection Systems Aims and Objectives Aim • To be able to describe the operation of an injection system within an internal combustion engine Objectives • • • Be able to describe the operation of an injection system within an internal combustion engine Be able to recognize a single point injection system and a multi-point injection system Identify how fuel and air is atomized within a fuel injection system

Fuel Injection Systems The role of the Injectors The injector delivers a finely atomized spray of fuel into the inlet port The injectors also vary the amount of fuel delivered to suit the engines conditions The spray is obtained by passing fuel (that is pressurised) through the nozzle of the injector It is located in the inlet manifold near the cylinder head intake port

Fuel Injection Systems Injectors The opening of the injector is controlled by the vehicles ECU The injector is supplied with the battery voltage via a relay, the earth circuit is controlled by the ECU When the circuit is completed by the ECU a solenoid operates, the injector valve opens, fuel is then able to be sprayed into the inlet manifold The valve moves roughly 1. 5 -10 milliseconds. This is known an injector duration or opening time The ECU will make amendments to the duration depending on engine temperature, loading air temperature and battery voltage

Fuel Injection Systems Fuel Atomisation During fuelling of a cylinder the fuel is pressurised which causes the fuel to become a vapour, allowing it to burn easily (compared to the fuel being delivered to the cylinder in liquid form)

Fuel Injection Systems Question How is fuel atomized in injector fuelling systems?

Fuel Injection Systems Simultaneously and Sequential Simultaneous injectors will operate all (or groups of injectors) at the same time Sequential will operate independently and open at close at different times (determined by the ECU)

Fuel Injection Systems Single point injection system Single point injection or throttle body injection system uses a single injector to spray fuel in the air intake side of the throttle butterfly (where the carburettor is situated)

Fuel Injection Systems Single point injection system Gives poor atomization of the fuel Does not give precise control of the air/fuel ratio to meet emission regulations However, it is easier to control electronically than a carburettor The fuel pressure is less then that of a multi point injection system (usually 1 bar)

Fuel Injection Systems Multi point injection system Individual injectors are used for each cylinder An injector is positioned near the inlet valve of each cylinder This system was originally used on diesel engines but is also now widely used on petrol engines

Fuel Injection Systems Multi point injection system The multi point injection system is the most common type of fuelling system that is used on modern vehicles today This is mainly due to the fact that this injection system can be controlled easily by the vehicles ECU Furthermore, this type of fuelling system provides a better method of burning the fuel without much wastage. Compared with other fuelling systems

Fuel Injection Systems Question Name three advantageous of a single point injection system ? Name three advantageous of a multi-point injection system ?

Fuel Injection Systems Types of injectors Pintle Type Injector Original injector design Offers good atomization of fuel Prone to deposit build up on the Pintle valve (deposits can reduce the amount of fuel flow, and therefore the vehicle will run leaner than recommended

Fuel Injection Systems Hole type injector Was introduced on later engine models, initially to reduce the reduce concerns with injector deposits Fuel is delivered through holes drilled in a director plate at the injector tip. Offers good fuel atomization and gives better resistance to deposit build-up.

Fuel Injection Systems High and low resistance injector windings Two different types of injector windings are used This is dependant on the type of drive circuit used, And is also dependant of weather an external resistor is being used. Low resistance injector windings High Resistance circuits Range between 2 -3Ώ at 21. 1 ◦C Range around 13. 8Ώ at 21. 1 ◦C Used with an external resistor in a voltage controlled circuit Do not require the use of an external resistor in a voltage controlled driver circuit.

Fuel Injection Systems Question What resistance should you expect a high resistance circuit to operate at ?

Fuel Injection Systems Injector driver circuits

Fuel Injection Systems Summary – have we ? Been able to describe the operation of an injection system within an internal combustion engine Been able to recognize a single point injection system and a multi-point injection system Identified how fuel and air is atomized within a fuel injection system