Question

1 multiple choice 1 point
most combustion slobber is produced during:
light - load operation.
the afterburn phase.
full - load operation.
idling.
2 multiple choice 1 point
at which of the following compression ratios does the efficiency of an engine begin to diminish with increasing compression ratio?
25:1
16:1
12:1
23:1
3 multiple choice 1 point
how many valves per cylinder is a centrally located fuel injector in a diesel engine most likely to have?
four
any number of valves
three

Explanation:

1. During idling, the engine runs at a low - speed and low - load condition, and due to incomplete combustion and other factors, more combustion slobber is produced.
2. Generally, for gasoline engines, as the compression ratio exceeds about 10:1 - 12:1, the efficiency may start to decrease due to issues like pre - ignition and detonation. For diesel engines, the typical compression ratio range is 16:1 - 22:1. Beyond 16:1, the efficiency may start to diminish with further increase in compression ratio due to increased heat losses and other factors.
3. A centrally located fuel injector in a diesel engine is most likely to have four valves per cylinder to ensure proper air - fuel mixing and combustion.

Answer:

1. idling
2. 16:1
3. Four