250+ TOP MCQs on Air Fuel Mixtures and Answers

IC Engines Multiple Choice Questions on “Air Fuel Mixtures”.

1. Air injected in IC engines refers to injection of ____________
a) air only
b) liquid fuel only
c) liquid fuel and air
d) none of the mentioned
Answer: c
Clarification: Liquid fuel and air are injected in IC engines.

2. The m.e.p. of a petrol engine first increases as the fuel air ratio is increased and then decreases on further increase in fuel air ratio. The m.e.p. is maximum in the zone of ____________
a) lean mixture
b) chemically correct mixture
c) rich mixture
d) none of the mentioned
Answer: c
Clarification: The m.e.p. is maximum in the zone of rich mixture.

3. The specific fuel consumption for a petrol engine first decreases with increase in fuel air ratio and then increases with further increase in air fuel ratio. The maximum value occurs in the range of ____________
a) lean mixture
b) chemically correct mixture
c) rich mixture
d) none of the mentioned
Answer: a
Clarification: The maximum value occurs in the range of lean mixture.

4. Auto-ignition reaction time for petrol engine first decreases with increase in fuel air ratio, reaches a minimum value and then increases with subsequent increase in fuel air ratio. The maximum value occurs in the region of ____________
a) lean mixture
b) chemically correct mixture
c) rich mixture
d) none of the mentioned
Answer: b
Clarification: The maximum value occurs in the region of chemically correct mixture.

5. Which is the most effective air cleaner in the case of diesel engines?
a) dry type
b) wet type
c) whirl type
d) oil bath type
Answer: d
Clarification: Oil bath type is the most effective air cleaner in case of diesel engines.

6. A high flame speed is obtained in diesel engine when air fuel ratio is ____________
a) uniform throughout the mixture
b) chemically correct mixture
c) about 3-5% rich mixture
d) about 10% rich mixture
Answer: d
Clarification: When air fuel ratio is about 10% rich mixture, then a high flame speed is obtained in diesel engine.

7. During idling, a petrol engine requires ______________ mixture.
a) lean
b) rich
c) chemically correct
d) none of the mentioned
Answer: b
Clarification: Rich mixture is required by a petrol engine when it is in idling condition.

8. The ___________ engines can work on very lean mixture of fuel.
a) spark ignition
b) compression ignition
c) spark & compression ignition
d) none of the mentioned
Answer: b
Clarification: Only the compression ignition engines can work on very lean mixture of fuel while spark ignition requires a richer mixture.

9. In order to mix air and petrol in the required proportion and to supply it to the engine during suction stroke, then ______________ is employed.
a) fuel pump
b) injector
c) carburetor
d) none of the mentioned
Answer: c
Clarification: None.