Automobile Engineering Questions and Answers – Engine Emissions

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This set of Automobile Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Engine Emissions”.

1. Which of the following is one of the major exhaust emissions from CI engines compared to SI engines?
a) Oxides of nitrogen
b) Particulates
c) CO and CO2
d) Unburnt hydrocarbon
View Answer

Answer: b
Explanation: Unburnt hydrocarbons are one of the major exhaust emissions from CI engines. The components in diesel fuel have higher molecular weight.
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2. Which of the following causes the photochemical smog?
a) Excess O2
b) CO and CO2
c) Soot and particulate matter
d) NOx and HC
View Answer

Answer: d
Explanation: NOx is one of the primary causes of photochemical smog. This smog is formed by the photochemical reaction of automobile exhaust and atmospheric air in the presence of sunlight.

3. What does the blue smoke in diesel engine indicate?
a) Unburnt oil
b) HC
c) NOx
d) CO
View Answer

Answer: a
Explanation: Blue smoke comes out from the exhaust when there is unburnt oil in the diesel engine. A very thin layer of the oil gets deposited on the cylinder wall to provide the lubrication between the walls and the moving piston.

4. During which condition of the vehicle does NOx emission in SI engine will be lowest?
a) Cruising
b) Idling
c) Accelerating
d) Decelerating
View Answer

Answer: b
Explanation: NOx emissions are lowest in SI engine during idling. NOx is created from nitrogen in the air. Nitrogen can also be found in fuel blends.

5. For what purpose is the Rhodium used?
a) To reduce CO and HC
b) To reduce NOx
c) To reduce CO
d) To reduce HC
View Answer

Answer: b
Explanation: Rhodium is used to reduce NOx. It is used to clean vehicle emission. It is mixed with the other two metals – platinum and palladium.
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6. Why is the fumigation technique used?
a) To control HC
b) To control NOx
c) To control CO
d) To control smoke
View Answer

Answer: d
Explanation: The fumigation technique is used to control smoke. Fumigation is injecting gaseous or liquid fuel into the intake of air steam of CI engines. There are two types of smoke: hot smoke and cold smoke.

7. Why are lead compounds added in petrol?
a) Reduce knocking
b) Reduce HC emission
c) Reduce exhaust temperature
d) Increase power output
View Answer

Answer: b
Explanation: The lead compounds are added in petrol to reduce the HC emission. The additive TEL (Tetraethyl Lead) was added to increase the octane number. The resulting lead in the engine exhaust was a poisonous pollutant.

8. Which of the following cannot be reduced by thermal converters?
a) CO
b) HC
c) Soot
d) NOx
View Answer

Answer: d
Explanation: NOx emission cannot be reduced using a thermal converter. Thermal converters are high-temperature chambers through which the exhaust gas flows.

9. What can be reduced by using exhaust gas recirculation (EGR) effectively?
a) CO
b) NOx
c) HC
d) CO and HC
View Answer

Answer: b
Explanation: The most effective way of reducing NOx emission is to hold combustion chamber temperatures down. Using this also reduces the thermal efficiency of the engine.
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10. Three-way catalytic converters reduce the emission of CO, HC, and soot.
a) True
b) False
View Answer

Answer: b
Explanation: Three-way catalytic converters reduce the emission of CO, NOx, and HC. They are chambers contain catalytic material. It promotes the oxidation of the emission contained in the exhaust flow.

Sanfoundry Global Education & Learning Series – Automobile Engineering.

To practice all areas of Automobile Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn