Questions set 63

Engine Valves and their Mechanisms

1.      In a four stroke engine each cylinder has
a) One valve
b) Two valves
c) Three valves
d) Four valves
Answer: b
Explanation: A four stroke engine cylinder has one intake and one exhaust valve.

2.      In a diesel engine the fuel injection pressure is in the range
a) 100 to 170 atm
b) 60 to 70 atm
c) 30 to 40 atm
d) 20 to 25 atm
Answer: a
Explanation: The pressure of fuel injection is very high for a diesel engine.

3.      The valve is opened as the cam lobe on the cam raises the
a) Bearing
b) Piston
c) Valve lifter
d) Valve seat
Answer: c
Explanation: Valve opens when valve lifter is raised.

4.      Exhaust valve temperature is about
a) 35 degree celsius
b) 100 degree celsius
c) 150 degree celsius
d) 500 degree celsius
Answer: d
Explanation: The temperature of the exhaust valve is of the order of 500 degree celsius.

5.      The size of the engine intake valve is
a) Same as that of exhaust valve
b) Smaller than that of exhaust valve
c) Larger than that of exhaust valve
d) Does not depend upon the size of exhaust valve
Answer: b
Explanation: The exhaust valve is made bigger in size than the intake valve.

6.      The device used to measure the clearance between the valve and tappet of an IC Engine is
a) Feeler gauge
b) Snap gauge
c) Slip gauge
d) Micrometer
Answer: a
Explanation: A Feeler gauge is used to measure the clearance.

7.      The purpose of valve clearance is to
a) Allow the valve to expand
b) Allow the sliding of valve in the guide
c) Ensure that the valve closes fully
d) Ensure that the crankshaft is free to rotate
Answer: c
Explanation: Valve clearance ensures that valve closes completely.

8.      The opening and closing of a valve is respectively done by
a) A cam and a spring
b) A spring and a cam
c) Gas pressure and cam
d) Cylinder vacuum and spring
Answer: a
Explanation: An engine valve is opened by a cam and closed by a spring.

9.      On modern four stroke engines the exhaust valve opens just
a) Before TDC
b) After TDC
c) Before BDC
d) After BDC
Answer: c
Explanation: Exhaust valve opens before the piston reaches Bottom Dead Centre.

10.  On modern four stroke engines the inlet valve opens just
a) Before TDC
b) After TDC
c) Before BDC
d) After BDC
Answer: a
Explanation: Inlet valve opens before the piston reaches Top Dead Centre.

11. A relief valve is fitted to the main oil gallery of an engine. The purpose of this valve is to
a) Limit the maximum oil pressure
b) Open when the oil is hot
c) Maintain the supply if the gallery becomes blocked
d) Stop the oil flow to the bearings
Answer: A

         relief valve limits the maximum oil pressure.