chapter 4

1. Emission Control
System

2. • The most specific AF ratio of EFI system
to make a reduce emissions are 14.7:1
(14.7 – air, 1 – fuel)
• AF mixture over 14.7:1 mean its was a
lean mixture.
• AF mixture less than 14.7:1 mean its was
a rich mixture.

3. Type of emission gases
• CO (Carbon Monoxide)  CO2
• NOx (Nitrogen Oxide)  N2 + O2
• SOx (Sulfur Oxide)  SO2
• HC (Hydro Carbon)  H2O + CO2
• Particular Matter

4. Catalytic Converter
• The job of the catalytic converter is to
convert harmful pollutants into less
harmful emissions before they ever leave
the car's­ exhaust system

5. • Catalytic converters are designed to
reduce all three:
 Carbon monoxide (CO) is a poisonous gas that is
colorless and odorless.
 Hydrocarbons are a major component of smog
produced mostly from evaporated, unburned .fuel.
 Nitrogen oxides (NO and NO2, together called NOx)
are a contributor to smog and acid rain, which also
causes irritation to human mucus membranes.

6. How Catalytic Converters
Reduce Pollution
• In the catalytic converter, there are two different types of
catalyst at work, a reduction catalyst and an oxidation
catalyst.

7. reduction catalyst
• The reduction catalyst is the first stage of the
catalytic converter. It uses platinum and rhodium
to help reduce the NOx emissions. When an NO
or NO2 molecule contacts the catalyst, the
catalyst rips the nitrogen atom out of the
molecule and holds on to it, freeing the oxygen
in the form of O2. The nitrogen atoms bond with
other nitrogen atoms that are also stuck to the
catalyst, forming N2

8. oxidation catalyst
• The oxidation catalyst is the second
stage of the catalytic converter. It reduces
the unburned hydrocarbons and carbon
monoxide by burning (oxidizing) them over
a platinum and palladium catalyst. This
catalyst aids the reaction of the CO and
hydrocarbons with the remaining oxygen
in the exhaust gas.

9. • 2NO => N2 + O2 or 2NO2 => N2 + 2O2
• 2NO => N2 + O2 or 2NO2 => N2 + 2O2
• 2CO + O2 => 2CO2

11. Exhaust Gas
Recirculation
(EGR)

12. • Allows burned exhaust gases to enter the
engine intake manifold.
• Reduces NOx emissions
• When exhaust gases are added to the air
fuel mixture, they decrease peek
combustion temperatures……...
----For this reason, an exhaust gas
recirculation system lowers amounts of NOx in
exhaust.

14. The EGR valve consists of...
• A vacuum diaphragm
• A spring
• A plunger
• An exhaust gas valve
• A diaphragm housing

15. What’s the valve designed to
do?
• Control the exhaust flow into the intake
manifold...

17. Basic EGR system operation
• At idle, the throttle plate in the carburetor
or fuel injection throttle body is closed.
This blocks off engine vacuum so it can’t
act on the EGR valve. The EGR spring
holds the valve shut and exhaust gases do
NOT enter the intake manifold.
• *****If the EGR valve were open at idle,
it could upset the air-fuel mixture and the
engine could stall!!!*****

18. • When the throttle plate is swung open to
increase speed, engine vacuum is applied to the
EGR hose. Vacuum pulls the EGR diaphragm
up. In turn, the diaphragm pulls the valve open.
• Engine exhaust can then enter the intake
manifold and combustion chambers. At higher
engine speeds, there is enough air flowing into
the engine that the air-fuel mixture is not upset
by the open EGR valve.

19. Some different types of EGR
systems
• Back-pressure EGR valve
• Engine coolant temperature switch
• Wide open throttle valve (WOT)
• EGR jets

20. Positive crankcase
ventilation (PCV)

21. systems were developed to ventilate the
crankcase an recirculate the vapors to the
engine’s induction system so they can be
burned in the cylinders.

23. A PCV system includes a hose from the air cleaner
assembly so that filtered air can be drawn into the
crankcase. This filtered air is then drawn by engine
vacuum through the PCV valve and into the intake
manifold where the crankcase fumes are burned in the
cylinder. The PCV valve controls and limits this flow of
air and fumes into the engine and the valve closes in the
event of a backfire to prevent flames from entering the
crankcase area.

24. PCV VALVES
The PCV valve in most systems is a one-
way valve containing a spring-operated
plunger that controls valve flow rate

26. Air flows through the PCV valve during
idle, cruising, and light-load conditions.

27. Air flows through the PCV valve during
acceleration and when the engine is under a
heavy load.

28. PCV valve operation in the event of
a backfire.

29. Evaporative Emission Control
System (EVAP)
• The purpose of the evaporative (EVAP)
emission control system is to trap and
hold gasoline vapors.

30. VAPOR CANISTER STORAGE
• The canister is located under the hood or
underneath the vehicle, and is filled with
activated charcoal granules that can hold
up to one-third of their own weight in fuel
vapors.
• A vent line connects the canister to the
fuel tank

33. • The evaporative emission control system
includes all of the lines, hoses, and valves,
plus the charcoal canister.

34. VAPOR PURGING
• During engine operation, stored vapors
are drawn from the canister into the
engine through a hose connected to the
throttle body or the air cleaner.
• This “purging” process mixes HC vapors
from the canister with the existing air-fuel
charge.

35. VAPOR PURGING
Computer-Controlled Purge
• Canister purging on engines with electronic fuel
management systems is regulated by the
powertrain control module (PCM).
• Control of this function is particularly important
because the additional fuel vapors sent through
the purge line can upset the air–fuel ratio
provided by a fuel-injection system.
• Since air–fuel ratio adjustments are made many
times per second, it is critical that vapor purging
is controlled just as precisely.

37. • A typical evaporative emission control system. Note that
when the computer turns on the canister purge solenoid
valve, manifold vacuum draws any stored vapors from
the canister into the engine. Manifold vacuum also is
applied to the pressure control valve. When this valve
opens, fumes from the fuel tank are drawn into the
charcoal canister and eventually into the engine. When
the solenoid valve is turned off (or the engine stops and
there is no manifold vacuum), the pressure control valve
is spring-loaded shut to keep vapors inside the fuel tank
from escaping to the atmosphere.

38. TEST 2
• Describe about 3 operations (drive,
reduction & reverse) of Automatic
Transmission.
• With diagram, please explain how transfer
case work (gear type).
• please sketch the 3 standard symbol of
relay and explain how a relay its work.