Pre-ignition in SI engines results in

1. Increase in the work of compression

2. Increase in the net work of the cycles

3. Decrease in fuel efficiencies

4. Decrease in fuel loss from the engine

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ESE Mechanical 2013 Official Paper - 1
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  1. 1, 2 and 3
  2. 1, 3 and 4
  3. 1 and 3 only
  4. 2 and 4 only

Answer (Detailed Solution Below)

Option 3 : 1 and 3 only
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Detailed Solution

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Preignition is generally caused by an overheated spot which may occur at the spark plug, combustion chamber deposits or exhaust valves. Consequences of pre-ignition are:

1. Increases the time loss and hence reduces network done.

2. Vicious cycle of pre-ignition and detonation is formed leading to power loss.

3. Decrease in fuel efficiency.
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