System Flashcards

In order to __________, engine exhaust pipes are coated with insulating material.

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.

The use of a three-way catalytic converter

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.

Recirculating exhaust gas has the disadvantage of

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.

When "back pressure" increases, fuel consumption will __________.

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.

What kind of material is utilized to make exhaust manifolds?

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.

The following emissions are not under control by the three-way catalytic converter.

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.

EGR is the best method for lowering emissions of

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.