Emission Control Systems

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What types of system(s) might be used to warm the incoming air?

Exhaust crossover, preheat grid, thermostatic air cleaner

EGR systems are used to mainly reduce what pollutant?

NOx

What two vacuum sources are mainly used to control a vacuum operated EGR valve?

Ported (lifts valve) and Venturi (signal)

On a computer controlled (pulse width modulated) EGR valve, how is the strength of the vacuum signal controlled?

by electronical pulses. length (width) of pulse determines strength of vacuum signal

Why is crankcase ventilation control required?

cleans oil by removing fuel vapors, oil can be contaminated and sludge will form

What vehicle condition needs to exist before a catalytic converter can reduce emissions?

closed loop, temperature warm, fuel control is normal

Why do manufacturers use a purge valve?

controls volume of canister fumes purged

What typica basic computer inputs are needed to control the operation of a digital EGR valve?

coolant temp, throttle position, mass air flow

Why is a diverter valve used?

diverts air to different locations, prevents exhaust system backfire during high speed deceleration

When does maximum PCV flow rate occur?

during cruise

What is the main purpose of a spark control system?

ensure fuel/air mixture undergoes combustion at right time

All EGR valves can be tested by applying vacuum (via a hand pump) to the valve and watching for the engine to run rough or stall. true or false?

false

What are the main components of a typical evaporative control system?

fuel cap, fuel tank, thermal expansion tank, vapor separator, vent line, charcoal canister, purge line

Air injection is designed to reduce what two pollutants?

hydrocarbon (HC) and carbon monoxide (CO)

What pollutant will be increased without an evaporative emission system?

hydrocarbons

What are the two basic types of air injection systems?

injection pump and pulse air system

What type of vacuum operates the diverter valve?

manifold and electronically assisted

Name the two types of backpressure EGR valves that might be used?

negative and positive

What is the purpose of the coolant temperature override (CTO) switch?

provides manifold vacuum to distributor during cold operation and full manifold vacuum when engine is hot. improve cold drivability and reduce temp of overheated engine

What is the purpose of rhodium in a TWC

reduces NOx

What two types of check valves does a pulse air system use?

reed valve and spring loaded diaphragm

What two diagnostic tests can be performed on a PCV system?

rpm drop test and vacuum test

The correct spark advanced is proportional to what two factors?

speed (crank rpm) and load (MAP, MAF, TPS)

What is eventually done with the vapors that are collected by the evaporative system?

stored in the charcoal canister, rerouted back into the intake system and reburned in the engine

Where is the preheating grid located?

underneath carburetor

What is the normal internal operating temperature of a catalytic converter?

1300-1400 degrees fahrenheit

Approximately how much exhaust gas is recirculated back into the intake manifold

14%

What percentage of fuel vapor emissions were vented to the atmosphere from the fuel tank and carburetor before the initiation of evaporative emission control system?

20%

What percentage of the emissions are produced from the crankcase of an uncontrolled vehicle?

20%

At what combustion temperature are high/unacceptable levels of NOx emissions created?

2500 degrees fahrenheit

A two way catalytic converter reduces what pollutants?

HC and CO

A three way catalytic converter reduces what pollutants?

HC, CO, and NOx

What is the purpose of connecting the air injection system to the catalytic converter?

air injection system forces air into the catalytic converter to reduce HC and CO

What is the purpose of the check valve?

allows one way flow. prevents exhaust gases from entering air injection systems

What is the main purpose of pre-heating the incoming air on an air induction system?

assist with better fuel vaporization

What is the purpose of the TAC systems?

assist with fuel vaporization

What is the purpose of manifold heating?

assists with fuel vaporization


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