250+ TOP MCQs on Valve Timing and Answers

Automotive Engine Auxiliary Systems Multiple Choice Questions on “Valve Timing”.

1. Theoretically, the inlet valve should open at what position of the piston?
a) Bottom dead centre
b) Side centre position
c) Bottom side position
d) Top dead centre
Answer: d
Clarification: Theoretically the inlet valve should open at Top dead position of the piston and the inlet valve should close at Bottom dead centre position of the piston.

2. Theoretically, the inlet valve should close at what position of the piston?
a) Bottom dead centre
b) Side centre position
c) Bottom side position
d) Top dead centre
Answer: a
Clarification: Theoretically the inlet valve should close at Bottom dead centre position of the piston.The exhaust valve opens before the piston reaches BDC in its power stroke.

3. Theoretically, the exhaust valve should open till the piston reaches which position?
a) Bottom dead centre
b) Side centre position
c) Bottom side position
d) Top dead centre
Answer: d
Clarification: Theoretically the inlet valve should open at the top dead center position of the piston and the exhaust valve should open till the piston reaches the top dead centre.

4. Due to which factor, the valves can’t open instantaneously?
a) Inertia
b) Torsional
c) Momentum
d) Point load
Answer: a
Clarification: In practice, due to inertia the valves cannot open instantaneously, and also the air-fuel mixture has its inertia. Consequently, more time has to be allowed for the intake and exhaust process to complete.

5. What is the event known as when the inlet valve is generally opened about 50° TDC is known as?
a) Valve bent
b) Valve break
c) Valve lag
d) Valve lead
Answer: d
Clarification: The inlet valve is generally opened about 50° TDC is known as valve lead and the inlet valve is generally closed after 45° of BDC is known as Valve lag.

6. What is the event known as when the inlet valve is generally closed after 45° of BDC?
a) Valve bent
b) Valve break
c) Valve lag
d) Valve lead
Answer: c
Clarification: The inlet valve is generally closed after 45° of BDC is known as Valve lag.This valve timing can increase or decrease the power of the engine. Hence, precision is required in valve timing.

7. Practically, the inlet valve opens between what range before TDC?
a) 10°-30°
b) 40°-75°
c) 20°-60°
d) 80°-150°
Answer: a
Clarification: Practically, the inlet valve opens between 10°-30° range before TDC, Exhaust valve opens at 40°-75° range before BDC, Valve overlap at 20°-60° range at TDC and Valve overlap at 80°-150°range at BDC.

8. Practically, Exhaust valve opens at what range before BDC?
a) 10°-30°
b) 40°-75°
c) 20°-60°
d) 80°-150°
Answer: b
Clarification: The exhaust valve opens before the piston reaches BDC in its power stroke. Practically, the inlet valve opens between 10°-30° range before TDC, Exhaust valve opens at 40°-75° range before BDC.

9. Practically, Valve overlap at what range at TDC?
a) 10°-30°
b) 40°-75°
c) 20°-60°
d) 80°-150°
Answer: c
Clarification: Practically, Valve overlap at 20°-60° range at TDC and Valve overlap at 80°-150° range at BDC. Valve overlap is the time during which both the inlet and exhaust valves remain open at the same time.

10. Practically, Valve overlap at what range at BDC?
a) 10°-30°
b) 40°-75°
c) 20°-60°
d) 80°-150°
Answer: d
Clarification: Practically, Valve overlap at 20°-60° range at TDC and Valve overlap at 80°-150° range at BDC. Theoretically, the valves open and close instantaneously at the dead centers.

11.The maximum valve opening depends directly on what factor?
a) Throttle position
b) Valve drop
c) Power output
d) Valve peak lift
Answer: d
Clarification: The maximum valve opening depends directly on valve peak lift and the maximum power output of the engine would generally be increased by increasing valve peak lift.

12. The maximum power output of the engine would generally be increased by increasing what?
a) Throttle position
b) Valve drop
c) Power output
d) Valve peak lift
Answer: d
Clarification: The maximum power output of the engine would generally be increased by increasing the valve peak lift. Higher the valve lift, the more the charge can enter the cylinder. Hence, more power is obtained.

13. Which of the mentioned below is not a type of valve?
a) Poppet valve
b) Sleeve valve
c) Rotary valve
d) Non-return valve
Answer: d
Clarification: The Poppet valve, sleeve valve, and rotary valve are all the types of valve used in an internal combustion engine, whereas the Non-return valve is used in the fuel pump.