Emission Control Systems
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
