Free Exhaust System MCQ Question and Answers — Questions and Answers
Question 1: In order to __________, engine exhaust pipes are coated with insulating material.
- Increase engine efficiency
- Reduce heat transfer (Correct answer)
- Conserve heat
- Keep the exhaust pipe warm
Correct answer: Reduce heat transfer
Engine exhaust pipes are often coated with insulating material, such as exhaust wrap, primarily to reduce the transfer of heat. This insulation helps to protect surrounding engine bay components from excessive heat, which can prolong their lifespan and contribute to slightly lower under-hood temperatures.
Question 2: The use of a three-way catalytic converter
- Burn fuel vapour
- Reduce nitrogen oxide, hydrocarbon and carbon-di-oxide emission levels (Correct answer)
- Remove carbon di-oxide, hydrocarbon and nitrogen oxide from the exhaust gases passing through it
- Re-circulate exhaust gases
Correct answer: Reduce nitrogen oxide, hydrocarbon and carbon-di-oxide emission levels
A three-way catalytic converter is engineered to simultaneously reduce three major types of harmful emissions. It converts nitrogen oxides (NOx) into nitrogen and oxygen, and oxidizes unburnt hydrocarbons (HC) and carbon monoxide (CO) into less harmful carbon dioxide and water vapor.
Question 3: Recirculating exhaust gas has the disadvantage of
- Increasing HC emission (Correct answer)
- Increasing aldehydes
- Decreasing thermal efficiency (Correct answer)
- None of the above
Correct answer: Increasing HC emission
Recirculating exhaust gas (EGR) primarily aims to reduce NOx emissions by lowering combustion temperatures. However, introducing inert exhaust gases can sometimes lead to incomplete combustion, which may result in an increase in unburnt hydrocarbon (HC) emissions. Additionally, it can slightly decrease the engine's thermal efficiency as less fresh air-fuel mixture is combusted.
Question 4: When "back pressure" increases, fuel consumption will __________.
- Decreases
- Increases (Correct answer)
- Remain unaffected
- Depend on the factor
Correct answer: Increases
When back pressure in the exhaust system increases, exhaust gases face greater resistance when exiting the engine. This makes it harder for the engine to efficiently expel combustion byproducts, forcing it to work harder. Consequently, the engine's efficiency decreases, leading to an increase in fuel consumption.
Question 5: What kind of material is utilized to make exhaust manifolds?
- Aluminum alloy
- Steel
- Cast iron (Correct answer)
- Copper
Correct answer: Cast iron
Exhaust manifolds are typically manufactured from cast iron due to its exceptional properties. Cast iron possesses high heat resistance and durability, allowing it to withstand the extreme temperatures and thermal cycling experienced directly at the engine's exhaust ports without warping or cracking.
Question 6: The following emissions are not under control by the three-way catalytic converter.
- HC emission
- PM session (Correct answer)
- NOx emission
- CO emission
Correct answer: PM session
A three-way catalytic converter is highly effective at reducing nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) emissions. However, it is not designed to control particulate matter (PM) emissions, which are solid particles typically addressed by other specialized filters, especially in diesel engines.
Question 7: EGR is the best method for lowering emissions of
- CO
- NOx (Correct answer)
- CO and HC
- HC
Correct answer: NOx
Exhaust Gas Recirculation (EGR) is a highly effective method specifically designed to lower nitrogen oxide (NOx) emissions. By introducing a small amount of exhaust gas back into the combustion chamber, EGR reduces peak combustion temperatures, which is the primary factor in the formation of NOx.
Free Exhaust System MCQ Question and Answers
In order to __________, engine exhaust pipes are coated with insulating material.