Questions set 71

Carburettors

1.      What is the stoichiometric air-fuel ratio of diesel?
a) 50: 1
b) 14.7: 1
c) 25: 1
d) 14.5: 1
Answer: d
Explanation: The stoichiometric air-fuel ratio of diesel is 14.5: 1. The stoichiometric air-fuel ratio of petrol is 14.7: 1. The mixture which contains less air than the stoichiometric requirement is called a rich mixture.

2.      What is the purpose of the venturi in the carburetor?
a) To decrease the fuel flow
b) To increase the manifold vacuum
c) To increase the air velocity
d) To decrease the air velocity
Answer: d
Explanation: The purpose of the venturi in the carburetor is to increase the air velocity. The venturi in carburetors is used to measure airflow in an engine.

3.      When does the simple carburetor supplies rich mixture?
a) Idling
b) Cruising
c) Accelerating
d) Starting
Answer: c
Explanation: The simple carburetor supplies the rich mixture during accelerating. During acceleration, the engine requires more amount of fuel to get the high speed of the vehicle due to which there is a requirement of the rich mixture.

4.      To burn 1 kg of octane completely, how much amount of air is required?
a) 14.12 kg
b) 15.12 kg
c) 16.12 kg
d) 10.12 kg
Answer: b
Explanation: Complete combustion means all carbon in the fuel is converted to CO₂ and all hydrogen to H₂O. To burn one kg of octane (C₈H₁₈) completely 15.12 kg of air is required. Hence the correct Air Fuel ratio is 15.12: 1. Sometimes, it is approximated to 15: 1.

5.      Which type of carburetor is a constant vacuum carburetor?
a) Zenith
b) Solex
c) S. U.
d) Carter
Answer: c
Explanation: S. U. carburetor is a constant vacuum carburetor. Solex, Carter, and Zenith are a type of constant choke carburetor.

6.      A four-stroke gasoline engine of 1.9-liter capacity is to develop maximum power at 6000 revolutions per minute. The volumetric efficiency is 80%. What is the actual volume of air sucked per second?
a) 0.053 m³/s
b) 0.076 m³/s
c) 0.046 m³/s
d) 0.089 m³/s
Answer: b
Explanation: Actual volume of air sucked per second = efficiency * volume of engine *(revolution per minute / 2) * (1 / 60) = 0.8 * 1.9 * 10^-3* (6000 / 2) * (1 /60) = 0.076 m³/s.

7.      The principle of compensating jet device is to make the mixture leaner as the throttle opens progressively.
a) True
b) False
Answer: a
Explanation: Most of the times the compensating jet is incorporated in the carburetor with the main jet. The compensating jet makes the mixture leaner as the main jet makes the mixture richer.

8.      Which of the following is not the part of a carburetor?
a) Float chamber
b) Choke and throttle
c) Fuel strainer
d) Auxiliary valve
Answer: d
Explanation: A carburetor consists of fuel strainer, float chamber, choke, throttle, main fuel metering, and idling nozzles. The auxiliary valve is one of the compensating devices.

9.      Which type of carburetor the Solex is?
a) Constant choke carburetor
b) Constant vacuum carburetor
c) Multiple venturi carburetors
d) Multijet carburetor
Answer: a
Explanation: Solex carburetor is a constant vacuum carburetor. Other constant vacuum carburetors are Zenith and Carter. S. U. carburetor is a type of constant choke carburetor.

10.  In multiple venturi carburetors, the main jet discharges the fuel in a downward direction into the primary venturi against the upward air stream.
a) True
b) False
Answer: b
Explanation: In multiple venturi carburetors, the main jet discharges the fuel in an upward direction into the primary venturi against the downward air stream. The fuel atomized by the air stream.