Fuel & Timing

Question 1

State 2 ancillary equipment which can be driven via the timing chain

Answer 1

• L.O Pump
• Water Pump

Question 2

State the purpose of the camshaft

Answer 2

• The camshaft is used to operate the timing of valves and fuel pumps which control the engines cycles.
• The profile and shape for each cam is designed to give the correct timing, speed and height of lift to its corresponding follower.

Question 3

State 2 methods of driving a camshaft

Answer 3

• Chain Drive
• Gear Drive

Question 4

State the speed of the Camshaft relative to the Crankshaft

Answer 4

4 Stroke = 2 to 1
2 Stroke = 1 to 1

Question 5

Describe 3 methods of reversing an engine

Answer 5

Axial Moving Cams - Uses two sets of cams (Ahead & Astern) these cams are engaged by sliding the camshaft axially but can only be achieved by gear driven camshafts

Moving the Cam Follower - this is done by shifting the cam follower on top of a negative cam profile altering pump timings

Lost Motion - uses a servomotor to rotate the camshaft relative to the crankshaft, altering valve and injection timing for reversal

Question 6

Explain what is meant by lost motion

Answer 6

Lost motion is the motion lost when rotating the camshaft as the engine is stopped.