Automotive Engine Auxiliary Systems Multiple Choice Questions on “Variable Valve Timing”.
1. Which technology changes the timing of intake/exhaust valves when the engine is running?
a) CRDI
b) DOHC
c) TDI
d) VVT
Answer: d
Clarification: VVT is a generic term for an automobile engine technology that allows the timing os the intake/exhaust valves to be changed when the engine is working.
2. Which system can change independently the valve-event timing and valve lift?
a) Profile switching system
b) Phase changing system
c) Variable event-timing system
d) Variable lift system
Answer: a
Clarification: The profile switching system can change independently of the valve-event timing and valve lift. Variable event-timing system can change both the phase and duration of the valve event.
3. Which system can change both the phase and duration of the valve event?
a) Profile switching system
b) Phase changing system
c) Variable event-timing system
d) Variable lift system
Answer: d
Clarification: Variable event-timing system can change both the phase and duration of the valve events and can be optimized at different engine speeds and load conditions.
4. Which system reduces the pumping losses due to conventional throttle?
a) Profile switching system
b) Phase changing system
c) Variable event-timing system
d) Variable lift system
Answer: d
Clarification: Variable lift system has the main advantage of reducing the pumping losses due to conventional throttle. Variable event-timing system can change both the phase and duration of the valve events.
5. What does VTEC stands for?
a) Valve timing and lift electronic control system
b) Variable valve timing and lift electronic system
c) Variable timing electronic system
d) Variable valve timing and lift electronic control system
Answer: d
Clarification: VTEC stands for variable valve timing and lift electronic control system. This creates a large amount of overlap between the inlet and the exhaust valves, is beneficial at high speeds.
6. What results in the use of a high degree of overlap inat lower engine speed?
a) Loss of torque
b) Gain of performance
c) loss of torque and performance
d) Gain of torque and performance
Answer: c
Clarification: The use of a high degree of valve overlap results in a loss of torque and performance at lower engine speeds. Moreover, the engine idling is also unstable-the engine hunts and misses, on stall.
7. What is the value of the valve overlap, for a smooth idle and healthy low rpm torque?
a) 0
b) 40°-75°
c) 1
d) 80°-150°
Answer: a
Clarification: For a smooth idle and healthy low rpm torque we need to have zero valve overlap between the inlet and exhaust valve. Hence, 0 is the right answer.
8. Which type of valve system does the VTEC uses in Indian ‘Honda city’?
a) DOHC
b) SOHC
c) TDCI
d) CRDI
Answer: b
Clarification: The VTEC used in Indian ‘Honda city’ is a SOHC type that varies the timing and lift of only the intake valves. The DOHC type of VTEC varies valve timing and lift of both the intake and exhaust valves.
9. Which valve system varies the valve timing and lift of both intake and exhaust?
a) DOHC
b) SOHC
c) TDCI
d) CRDI
Answer: a
Clarification: The VTEC used in Indian ‘Honda city’ is a SOHC type that varies the timing and lift of only the intake valves. The DOHC type of VTEC varies valve timing and lift of both the intake and exhaust valves. – duplicate of Q8
10. What was the Fiat’s new air management technology in 2009 known as?
a) I-VTEC
b) VVTEC
c) Turbo engine
d) MultiAir
Answer: d
Clarification: Fiat unveiled its new air management technology named ‘MultiAir’ at the 2009 Geneva Motor Show. This is a real technological breakthrough and claimed to be much better than the VVT system.
11. How many valves per cylinder are used in Multi air technology?
a) 1
b) 2
c) 3
d) 4
Answer: d
Clarification: In this technology, instead of twin camshafts of four valves per cylinder engine, a single camshaft opens up all four valves and eliminates engine pumping losses.
12. By which component in a Camless engine, each engine valve is operated individually?
a) ECU
b) Cam
c) Sensor
d) Actuator
Answer: d
Clarification: In a Camless engine, each engine valve is operated individually by an actuator. There is no camshaft. So cylinder deactivation is possible.
13. Which of the mentioned bellow is a disadvantage of a poppet valve?
a) Cold start wear
b) Higher overall valve train efficiency
c) Cylinder deactivation
d) Valve stem scuffing
Answer: d
Clarification: Valve stem scuffing is due to geometrical irregularities or over-speeding. This can be corrected by bent or slanted valve, which may need replacement.