i. The thermal efficiency of a diesel cycle will increase with increase in cut off ratio.

Ans: False. The thermal efficiency of a diesel cycle will decrease with increase in cut off ratio.

ii. Higher the Octane numbers of a fuel, longer the ignition delay.

Ans: True, The octane number lower is possibility of detonation. This is because octane number of a fuel is percentage of iso-octane in the Primary reference fuel that gives the same knock intensity as that of the fuel.

iii. Camshafts of four strokes I.C. Engine rotate at twice the speed off crankshaft.

Ans: False. Camshafts of four strokes I.C. Engine rotate at half the speed of the crankshaft.

iv. Increasing the compression ratio of a C.I. Engine will increase the knocking tendency.

Ans: False. Increasing the compression ratio of a C.I. Engine will decrease the knocking tendency.

v. Carbon deposits in I.C. Engine cylinder results in decrease of effective compression ratio.

Ans: False. Carbon deposits in I.C. Engine cylinder results in increase of effective compression ratio.