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Q4. a) By drawing a block diagram describe how on a large 2-stroke marine diesel engine, fuel quantity and timing is controlled? (8)

b) What are disadvantages of VIT system? (4)

c) What actions are required in case of VIT system failure? (4)

Q6.a) Describe VIT of any 2-stroke marine diesel engine by Diagrammatic sketch, naming each component and its function. (8)

b) Describe following

i) What is Effective stroke and Idle stroke of a Fuel Pump? (2)

ii) What is fuel pump lead? (2)

iii) What is Super VIT? (2)

iv) What is breakpoint for VIT? (2)

Q9. a) With the help of simple diagram, explain Variable Injection Timing (VIT). (8)

b) Explain with suitable diagram, start and end of VIT points. (4)

c) Explain with graph variation of P(Max) with VIT position. (4)

Q2. A. Explain the term Variable Injection Timing (VIT) when applied to fuel pumps and state why a change in timing of fuel injection may be required.;

B. Describe, with the aid of sketches a VIT fuel pump and explain how the change in timing is achieved whilst the pump is in operation

C. Explain how it may be determined that individual fuel pumps are injecting the correct quantity of fuel with the correct timing at a particular pump setting.

Q3. A. Describe with the aid of sketches a fuel pump capable of variable injection timing;

B. State why injection timing might need to be changed;

C. State how injection timing is adjusted while the engine is running.

Q8. With respect to VIT in fuel injection give your comments on the following statements.

a) By using VIT 100% peak pressure is achieved at 85% rpm. Thus 100% power is achieved at 85% rpm. This results in fuel saving.

b) VIT is not possible nor used in alternator engines as they run at constant rpm.

c) Breakpoint is the point at which maximum break horsepower is achieved.

d) VIT system can ensure the correct Pmax is achieved irrespective of the fuel used.

e) Electronically controlled engines do not have VIT.