Question 1

Which of the following is an in-cylinder method used by manufacturers to prevent emission formation?

Accepted Answer

EGR (exhaust gas recirculation) is an in-cylinder method that reduces nitrogen oxide emissions by recirculating a portion of the engine's exhaust back to the engine cylinders, lowering combustion temperatures and thus reducing NOx formation.

Question 2

How many distinct stages of exhaust aftertreatment systems are used based on the progressively more restrictive Environmental Protection Agency (EPA) emission standards?

Accepted Answer

The answer of How many distinct stages of exhaust aftertreatment...

Question 3

The alternative to SCR (selective catalyst reduction)-liquid (SCR-L) systems using DEF was to manufacture:

Accepted Answer

SCR systems using DEF (Diesel Exhaust Fluid) rely on ammonia to reduce NOx emissions. An alternative is to produce ammonia onboard in exhaust catalysts, eliminating the need for DEF.

Question 4

Diesel particulate filters, which trap soot emissions, became mandatory in:

Accepted Answer

Diesel particulate filters became mandatory in 2007 for new diesel vehicles in the United States to meet stricter emissions standards.

Question 5

Which of the following is NOT a common exhaust catalyst element in the exhaust aftertreatment systems being used on contemporary diesel engines?

Accepted Answer

The answer of Which of the following is NOT a...

Question 6

Technician A says the problem with using automobile catalysts in the exhaust system of diesel engines is the system's excess air and cool temperatures. Technician B says diesel exhaust catalysts need to be designed to withstand the higher exhaust temperatures of a diesel engine and its exhaust's lower oxygen content. Who is correct?

Accepted Answer

The answer of Technician A says the problem with using...

Question 7

When comparing types of catalytic technology used by diesel engines and spark-ignition engines, which of the following catalyst technologies reduces just NOx (oxides of nitrogen)?

Accepted Answer

Selective catalytic reduction using liquid (SCR-L) is specifically designed to reduce NOx emissions in diesel engines by injecting a reductant, such as urea, into the exhaust stream.

Question 8

A conventional oxidation catalytic converter found on a gasoline-fueled vehicle requires exhaust temperatures as high as ____ for catalysts to operate effectively.

Accepted Answer

The answer of A conventional oxidation catalytic converter found on...

Question 9

What are chemical reactions called where oxygen is removed from NOx?

Accepted Answer

Reduction is the process where oxygen is removed from a compound, such as NOx.

Question 10

Which of the following causes oxygen to chemically combine with HC (hydrocarbons) and CO (carbon monoxide) at lower temperatures with the result of HC and CO being converted to carbon dioxide and water?

Accepted Answer

An oxidation catalytic converter facilitates the reaction of oxygen with hydrocarbons (HC) and carbon monoxide (CO) at lower temperatures, converting them into carbon dioxide and water.

Question 11

Which strategy will most likely be used to passively regenerate a catalyzed DPF?

Accepted Answer

Passive regeneration of a Diesel Particulate Filter (DPF) typically occurs when the vehicle is driven at higher speeds, allowing the exhaust temperature to rise sufficiently to burn off the accumulated soot naturally.

Question 12

Dosing the exhaust system of a 2007 diesel engine with fuel is necessary to do which of the following?

Accepted Answer

Dosing the exhaust system with fuel is necessary to actively regenerate a catalyzed Diesel Particulate Filter (DPF) by increasing the exhaust temperature to burn off accumulated soot.

Question 13

Technician A says that without the pressure differential sensor (delta P sensor), the exhaust DPF would not regenerate, because the amount of soot loading would not be able to be properly calculated. Technician B says that the amount of soot loading is only estimated, and not accurately measured, using the delta P sensor. Who is correct?

Accepted Answer

The delta P sensor only estimates the amount of soot loading, it does not accurately measure it.

Question 14

A fully loaded DPF (diesel particulate filter) may contain ____ of soot per liter of volume capacity.

Accepted Answer

A fully loaded DPF typically contains about 4-6 grams of soot per liter of volume capacity.

Question 15

Trapped soot and other trapped particles collected on the walls of the DPF (diesel particulate filter) will eventually plug the filter and produce:

Accepted Answer

Trapped soot and particles in the DPF increase resistance to exhaust flow, leading to high exhaust backpressure.

Question 16

Which process is used to clean ash from a DPF?

Accepted Answer

Ash in a Diesel Particulate Filter (DPF) is typically removed by physically cleaning the filter, such as removal and back-flushing with compressed air, rather than through regeneration processes.

Question 17

Which of the following particles that cannot be regenerated does NOT end up in the DPF (diesel particulate filter)?

Accepted Answer

The answer of Which of the following particles that cannot...

Question 18

OEM rebuilders have observed a relationship between increased ash loading in DPF (diesel particulate filter) and the likelihood for a DPF to:

Accepted Answer

The answer of OEM rebuilders have observed a relationship between...

Question 19

To extend DPF (diesel particulate filter) life caused by compacted ash and cracking, some fleets make it part of routine maintenance to remove and clean DPFs on a regular basis, more frequently than what is required by the:

Accepted Answer

OEM recommendations typically provide guidelines for maintenance intervals, including DPF cleaning. Fleets may choose to clean DPFs more frequently than these recommendations to prevent issues and extend the filter's life.

Question 20

Which of the following will MOST LIKELY restrict gas flow through the DPF (diesel particulate filter)?

Accepted Answer

Hardened ash is a byproduct of the combustion process that can accumulate in the DPF over time, leading to blockages and restricted gas flow.

Quiz 18: Exhaust Aftertreatment Systems