12.14.6. Explain the operating principle of a simple fuel injection system.
Fuel Injection System
– Continuous flow system
– a throttle valve controls the amount of air going to make up the mixture for the engine – and therefore the power developed
– a fuel control unit senses the mass of air entering the engine and the position of the throttle and mixture controls
– from this data the pressure output of the injection pump is varied so as to meter the correct amount of fuel required for the mixture
– metered fuel passes through a flow divider or splitter and then through individula lines to the injection nozzles associated with individual cylinders
– fuel is then injected continuously into the airflow as a high presure spray to form the mixture
12.14.4(b) . difference between direct and indirect injection. Sub Topic Syllabus Item
Direct
– fuel is injected at a much higher pressure direclty into the combustion chamber of each cylinder. (normally only diesel engines)
Indirect
– fuel is injected into and mixed with the airflow in the inlet manifold at some point prior to each inlet valve
–
12.14.4(a) . function and principles of a fuel injection system;
Fuel Injection System
– Continuous flow system
– a throttle valve controls the amount of air going to make up the mixture for the engine – and therefore the power developed
– a fuel control unit senses the mass of air entering the engine and the position of the throttle and mixture controls
– from this data the pressure output f the injection pump is varied so as to meter the correct amount of fuel required for the mixture
– metered fuel passes through a flow divider or splitter and then through individula lines to the injection nozzles associated with individual cylinders
– fuel is then injected continuously into the airflow as a high presure spray to form the mixture
12.14.2. State the advantages/disadvantages of fuel injection versus carburetor systems.
Fuel Injected Systems
Advantages:
– Freedom from refrigeration ice.
– Better control and distribution of fuel mixture .
Disadvantages:
– Possibility of vapour lock when starting a hot motor.
– susceptable to contamination problems.
12.12.22. Describe the function of the inlet manifold.
Intake Manifold
– is the system of pipes which leads the mixture from the carburettor to each cylinder
Exhaust Manifold
– a system of pipes through which the burnet gasses are forced out of the cylinder to the atmosphere
12.12.20(i.e. . Remove this ref
Atmospheric Conditions
– when realtive humidity exceeds 50%
– when ambient air temperature is near to or at zero oC
Throttle Settings
– low throttle settings
12.12.20(c) . correct use of carburettor heat for de-icing, and as an anti-icing measure
Carburettor heat for de-icing
– Apply carburettor heat. The motor may run rough while the ice melts. Once the motor is running smoothly return carburettor heat to cold and normal power should be available.
Carburettor heat is used as an anti-icing measure
– during descent with a low power setting especially in high humidity
– on short final approach to land – Carburettor heat is turned to COLD – in case full power is required for a go -around
– avoid carburettor heat continuously whilst on the ground – can introduce grit and dust into the carburettor and engine
12.12.20(b) . symptoms of carburettor ice formation;
Symptoms of Carfburettor Ice:
– loss of power – drop in rpm and reduction in manifold pressure or poor performance (worse than expected)
– rough running