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Difficulty: EasyExhaust and Emissions Systems

When servicing automotive exhaust and emission systems, technicians must identify what each component regulates. Match each emission control device on the left with the specific gas or vapor stream it manages on the right.

  • Catalytic ConverterConverts carbon monoxide (CO\text{CO}) and hydrocarbons (HC\text{HC}) in the exhaust stream into carbon dioxide (CO2\text{CO}_2) and water (H2O\text{H}_2\text{O})
  • Exhaust Gas Recirculation (EGR) ValveMeters inert exhaust gas back into the intake charge to reduce combustion temperatures and oxides of nitrogen (NOx\text{NO}_x)
  • Positive Crankcase Ventilation (PCV) ValveDraws blow-by gases and moisture out of the engine crankcase and routes them back into the intake manifold
  • Evaporative Emission Control (EVAP) CanisterTraps and temporarily stores raw fuel vapors evaporating from the fuel tank until they can be purged into the cylinders

Answer

Catalytic Converter matches converting exhaust CO and HC into carbon dioxide and water; EGR Valve matches metering inert exhaust gas into the intake to lower combustion temperatures and reduce NOx; PCV Valve matches drawing blow-by gases from the crankcase into the intake manifold; EVAP Canister matches trapping raw fuel vapors evaporating from the fuel tank.
Each match correctly associates the specific automotive emission device with the exact fluid or vapor stream it is designed to manage: the catalytic converter processes tailpipe exhaust gases; the EGR valve regulates exhaust gas recirculation for temperature control; the PCV valve purges internal crankcase blow-by; and the EVAP canister stores evaporative fuel vapors from the fuel tank.

Step-by-Step Solution

1
Identify the exhaust treatment component that chemically alters tailpipe emissions
The Catalytic Converter is paired with converting exhaust carbon monoxide and hydrocarbons into carbon dioxide and water.
Catalytic converters use noble metals in the exhaust pipe to promote chemical oxidation and reduction of tailpipe pollutants.
2
Identify the valve responsible for controlling combustion chamber temperature
The EGR Valve is paired with introducing inert exhaust gas to lower combustion temperatures and reduce oxides of nitrogen.
Oxides of nitrogen (NOx) form at temperatures exceeding approximately 2,500°F (1,370°C); recirculating inert exhaust lowers the peak temperature.
3
Identify the component that vents engine crankcase pressure and oil vapors
The PCV Valve is paired with drawing blow-by gases from the crankcase into the intake manifold.
Combustion gases leaking past piston rings must be cleared from the crankcase to prevent pressure buildup and sludge formation.
4
Identify the storage device for evaporative fuel tank vapors
The EVAP Canister is paired with trapping and storing evaporating fuel vapors from the fuel tank.
Charcoal canisters store raw gasoline vapors when the vehicle is parked and purge them into the engine during operation.

Key Concept

Functions and target emission streams of primary automotive emission control components

Alternative Method

Group the components by their physical location on the vehicle: crankcase (PCV), fuel tank vapor line (EVAP), exhaust manifold/intake junction (EGR), and exhaust pipe/underbody (Catalytic Converter).
Estimated Time:45s
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Topics

Exhaust and Emissions Systems

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