Questions set 79

Ignition System

1.      Which instrument is used for adjusting the ignition timing?
a) Accurate clock
b) Tachometer
c) Stopwatch
d) Stroboscopic light
Answer: d
Explanation: Stroboscope is used for adjusting the ignition timing. It is the light-emitting device which is connected to the spark plug of the cylinder for setting the ignition timing.

2.      Which of the following firing order is commonly used for the four-cylinder vertical engine?
a) 1-2-3-4
b) 3-4-1-2
c) 4-3-2-1
d) 1-3-4-2
Answer: d
Explanation: 1-3-4-2 firing order is commonly used for a four-cylinder engine. For the four-cylinder engine, the firing order is decided such that a power stroke occurs every 180 degrees.

3.      What is the dwell time?
a) It is the time for which the contact breaker points remain closed
b) It is the time for which the contact breaker points remain open
c) The time during which inlet and exhaust valves open
d) The time during which inlet and exhaust valves close
Answer: a
Explanation: The dwell time is the time for which the contact breaker points remain closed. Dwell is the time for which the coil turned on.

4.      Which of the following is not considered while deciding the optimum firing order of the engine?
a) Engine vibration
b) Engine cooling
c) Development of the backpressure
d) Engine configuration
Answer: d
Explanation: Engine vibration, engine cooling, and development of back pressure are considered while deciding the optimum firing order of the engine. The reduced vibration is required for optimum firing order of the engine.

5.      Why is the Dwell meter used?
a) To set the spark plug gap
b) To set the ignition advance
c) To set the contact breaker gap
d) To set ignition timing
Answer: c
Explanation: The dwell meter used for setting the contact breaker gap. It uses the dwell angle as the parameter to set the contact breaker gap. To set the ignition timing stroboscope is used.

6.      Which of the following is the disadvantage of the magneto ignition system?
a) Magneto ignition system has a poor quality of spark during starting
b) Magneto ignition system occupies more space
c) Magneto ignition system has more maintenance problems
d) Magneto ignition system is used largely in four wheels
Answer: a
Explanation: During starting, the quality of the spark is poor due to low speed. Magneto ignition system is mainly used in racing cars and two-wheelers. The main advantage is that it does not require a battery.

7.      For how many times the contact breaker must make and break the circuit for a four-cylinder engine operating at N rpm?
a) N times
b) 1.5N times
c) N/2 times
d) 2N times
Answer: d
Explanation: The cam is having the same number of lobes as there are engine cylinders. They are used with two contact breakers in parallel.

8.      Which of the following is the wrong statement?
a) In the exhaust, retarded timing causes burning of the hydrocarbons
b) The retarded timing improves fuel economy
c) The retarded timing requires the small opening for correct burning of the fuel
d) The exhaust gas temperature becomes higher due to retarded time
Answer: b
Explanation: The retarded timing reduces fuel economy. Due to spark retardation, the fuel burns slowly and after some time than it should be burned.

9.      On which condition does the vacuum advance mechanism shift the ignition point?
a) Under part-load operation
b) Under full load operation
c) Under no-load operation
d) Under sudden acceleration
Answer: a
Explanation: The vacuum advance mechanism shifts the ignition point under part-load operation. The adjustment system is designed so that its operation results in the part-load advance curve.

10.  The optimum spark timing must be retarded for the engine operating with a rich mixture.
a) True
b) False
Answer: b
Explanation: The optimum spark timing must be advanced for the engine operating with a rich mixture. The larger throttle opening size means better mixing and combustion.