Exhaust Exhaust Emissions & Catalytic Converters 3

Question 1

What is the purpose of Selective Catalytic Reduction (SCR) in modern diesel exhaust systems?

Accepted Answer

To reduce nitrogen oxides using a urea solution

Answer

To remove particulate matter

Answer

To increase fuel efficiency

Answer

To lower exhaust temperatures

Question 2

What is 'diesel exhaust fluid' (DEF) primarily composed of?

Accepted Answer

Urea and deionized water

Answer

Methanol and water

Answer

Ammonia and ethanol

Answer

Hydrogen peroxide and saline

Question 3

Which emission from gasoline engines is most directly associated with the formation of ground-level ozone (smog)?

Accepted Answer

Volatile organic compounds (VOCs)

Answer

Carbon dioxide (CO2)

Answer

Water vapor (H2O)

Answer

Oxygen (O2)

Question 4

What does an EGR valve do in an emissions control system?

Accepted Answer

Recirculates a portion of exhaust gases back into the intake

Answer

Filters particulate matter from exhaust

Answer

Injects urea into the exhaust stream

Answer

Controls air-fuel ratio

Question 5

Which OBD-II readiness monitor must be set before a vehicle can pass an emissions inspection?

Accepted Answer

Catalyst monitor

Answer

Fuel trim monitor

Answer

Ignition timing monitor

Answer

Coolant level monitor

Question 6

What is the term for the process by which a DPF burns off accumulated soot?

Accepted Answer

Regeneration

Answer

Oxidation cycle

Answer

Purge sequence

Answer

Flash burn