emission controls. before beginning to understand emission controls you should know the reason why...

Emission Controls

Emission Controls

Before beginning to understand emission controls you should know the reason why emission controls were installed into the automobile. 1. To reduce the amount of pollutants

entering the atmosphere .

Emission Controls

Smog is a term developed from smoke and fog

Smog is form when airborne pollutants is formed with oxygen and other atmospheric gasses to produce a grayish yellow smoke. The resulting smoke is called photochemical smog.

Smog

Smog is can be a major problem in larger cities (New York and LA)

Smog can be harmful to A. Humans B. Plants C. Animals and even effect paint rubber

and other materials.

Smog

One of largest producer of photochemical smog is the automotive internal combustion engine.

The EPA (environmental protection agency) begin putting restriction on automotive manufactories in the mid 60.

Motor Vehicle Emissions

Motor vehicle emission are emission produce by motor vehicles. They include A. Hydrocarbons (HC) Carbon monoxide (CO) Oxides of nitrogen (NOx)

Exhaust Gasses

Hydrocarbons (HC) are emission of unburned petroleum products being released into the atmosphere.

All petroleum products and made of hydrocarbons (hydrogen and carbon compounds) this includes: Gasoline LP-gas. Diesel motor oil.

Exhaust Gasses

Hydrocarbons are produced because of incomplete fuel combustion or fuel evaporation.

Hydrocarbons emission is considered a hazardous form of air pollution because of. Eye. Throat. Lung irritation. And possibility cancer.

Exhaust Gasses

In north Carolina a vehicle must not exceed 220 ppm of hydrocarbons emissions.

High hydrocarbon emission are the results of a: cylinder misfire. Improper ignition timing Worn cylinder rings (pumping oil into the

combustion chamber

Exhaust Gasses

Carbon monoxide emission are exhaust emission that is the result of partially burned fuel.

A high carbon monoxide emission can be caused by a: Restricted or dirty air cleaner. Advance ignition timing. Clogged fuel injectors.

Exhaust Gasses

Oxides of nitrogen, (NOx) are emission produced by extreme heat.

Air consist of approximately 79% nitrogen and 21% oxygen

When combustion chamber temperature reaches 2500 degrees F or 1370 degrees C nitrogen and oxygen combine to produce oxide of nitrogen (NOx)

In North Carolina the standard for Carbon Monoxide is 1.2 % of the total exhaust output.

Muffler

Exhaust output

HC 220 ppm

CO 1.2%

Exhaust Gasses

Oxides of nitrogen is responsible for the dirty brown color is SMOG.

NOx is a eye and respiratory irritant. Newer high compression, learn air

fuel mixture and hotter running engine produces more NOx than earlier engine.

Exhaust Gasses

The same factors that increases NOx will tend to improve fuel mileage and lower HC and CO2 production.

This means that to increase fuel economy and lower HC and CO2 production NOx will increase.

For this reason emission controls have beedn added to lower all form of emissions

Exhaust Gasses

14.7 – 1 AFRRicher Leaner

HC increases

NOx decreases

NOx increases

Hc and Co decreases

Exhaust Gasses

Before understanding emission controls we need to first understand where they come from.

Particulates: are solid particle of carbon soot and fuel additives that blow out the tail pipe.

Engine crank case blow by. Caused by heating of oil and unburned fuel vapors that blow past the engine rings.

Exhaust Gasses

Fuel vapors: different chemicals that enter the atmosphere as fuel evaporates.

Engine exhaust gasses: are harmful chemical that are produced inside the combustion chamber and are blow out the tail pipe.

Fuel

Air

Exhaust manifold

Catalytic Converter

Fuel Tank

Fuel Pump

HC

CO

Solid particulate

FuelFuel

Vapors

Exhaust Gasses

Automotive manufactures agree the best way to lower exhaust emission is to burn all the fuel entering the combustion chamber.

Modern engine have introduced several modification to ensure all fuel entering the combustion chamber is burned.

Exhaust Gasses

Some engine modification are: Lower compression ratio, by lowering

compression ratio vehicle can burn unleaded fuel. The use of unleaded fuel allows for catalytic converters that help reduce HC and CO emissions.

Lower compression ratio also lower combustion temperature reducing NOx emission.

Exhaust Gasses

Smaller combustion chambers, allows for more heat to remain inside the combustion chamber that can aid in the burning of fuel.

Reduce quench areas, the areas between the piston and the cylinder head is the quench area. If this areas is to close fuel will not burn completely increasing HC and CO emissions. Modern engine are design to reduce high quench areas.

Exhaust Gasses

Quench area

Exhaust Gasses

Decrease valve overlap, is used to decrease exhaust emission. A larger valve overlap increases power but dilutes incoming fuel mixture and requires a richer air fuel mixture at lower engine speed therefore increasing HC and CO emissions.

Exhaust Gasses

Overlap

Intake Exhaust

Exhaust Gasses

Higher combustion chamber temperature, are used to reduce HC and CO emissions. Today vehicles used hot thermostats than earlier

model helping to increase combustion chamber temperature.

Leaner air-fuel mixtures help fuel burn better lower HC and CO emissions.

Wider spark plug gaps, are used to burn the leaner fuel mixture and helps prevent spark plug fouling.

Exhaust Gasses

Wider spark plug gap

Some are .080 thousands

Thermostats are now 190 degrees

Learning Quiz

1. When is photochemical smog formed?

A. when airborne pollutants is formed with oxygen and other atmospheric gasses

B. When Oxygen is mixed water inside the catalytic converter.

C. When exhaust gasses is heated to over 2500 degrees

D. All the above

Learning Quiz

2. Smog can be harmful to: A. Humans B. Plants C. Rubber and medals All the above

Learning Quiz

3.Technician A says CO is a hazardous exhaust emission. Technician B says HC is a hazardous exhaust emission. Who is correct? A. Technician A only B. Technician B only C. Both technician A and B D. Neither technician A nor B

Learning Quiz

4. Oxides of Nitrogen is produced when: A. Combustion chamber temperature is

to cold. B. Combustion chamber temperature is

too hot. C. Atmospheric condition is humid. D. all the above

Learning Quiz

5. High hydrocarbon are caused by: A. Cylinder misfire B. Dirty air filter C. Low fuel pressure D. Defective air filter.

Learning Quiz

6. A rich fuel mixture will cause and increase in: A. Hydrocarbons B. Oxides of Nitrogen's NOx C. Both a and B D. Neither A nor B

Learning Quiz

7. In North Carolina the maximum amount of Hydrocarbon emission allowed by a vehicle is: A. 1000 ppm B. 1.2% by exhaust volume C. 220 ppm D. 1% by exhaust volume

Learning Quiz

8. Technician A says Oxides of Nitrogen emission increases when combustion chamber temperature decreases. Technician B says Hydrocarbon emission is the result of a cylinder misfire. Who is correct? A Technician A only B. Technician B

only C. A and B D. Neither A nor B

Learning Quiz

9. The best way to decrease exhaust emission is to: A. Increase valve overlap. B. Increase compression Ratios. C. Increase combustion chamber size. D. Burn all fuel enter the combustion

chamber.

Learning Quiz

10. Technician A says crankcase blowby is not a source of vehicle emission. Technician B says modern vehicle use unleaded fuel to increase emissions and allow for the use of catlic converters. Who is correct?

A. Technician A only B. Technician B only C. A and B D. Neither A nor B

Vehicle Emission Control Systems

There are several different types of emission control system used on modern vehicles. Positive crankcase ventilation

system (PCV) is used to recalculate engine crankcase fumes back into the combustion chamber.

Vehicle Emission Control

A PCV valve uses manifold vacuum to draw blow-by gasses from the engine into the intake manifold for reburying by the engine.

In earlier years automotive manufactories uses road draft tubes to remove crankcase blowby gasses.


The uses of road drift tube allowed for blowby gasses containing HC, CO, particulates, sulfur and small amounts of water to be vented in the atmosphere.

At idle when there is high engine vacuum the PCV value is pulled open to remove blow-by gasses from inside the engine.


At part throttle when vacuum is lower a spring inside the PCV valve forces the valve partially closed. But still allows for some blowby gasses to be vented back into the intake manifold for burning by the engine.


When engine Vacuum is High PCV valve plunger is nearly closed

When engine vacuum is low plunger Opens. Allowing exhaust gasses into Engine.PCV

Plunger

Typical PCV valve

Evaporative Emissions Control SystemsEVAP

The EVAP system prevents Hydrocarbons in the form of fuel vapors from entering the atmosphere even when the vehicle is not running.

An EVAP system is considered a closed system.

Fuel vapor are stored in a charcoal canister when the engine is off.

Evaporative Emissions Control SystemsEVAP

When the engine is started vacuum pulls fuel vapors into the engine for burning.

EVAP system different from per emission vehicle because no fuel or vapor is vented into the atmosphere.

Unvented Fuel Cap

Rollover Valve

Charcoal CanisterFuel Tank

Intake Manifold Vacuum

A rollover valve is uses to prevent fuel spillage in case of a rollover.

A liquid-vapor separator is sometime used to prevent liquid fuel from entering the charcoal canister.

A charcoal canister is used to store fuel vapor when the engine is not operating.

Most modern vehicles electrically control the EVAP system to ensure a cleaner burning engine.

The EVAP system uses purge lines to connect the fuel tank to the charcoal canister and the intake manifold.

Fuel Tank

EVAP Solenoid

12 Volts with engine on

Charcoal Canister

PCM

Rollover Valve

Enhanced EVAP system An enhanced EVAP system has the

following additional components. Fuel tank pressure sensor: This sensor

monitor internal fuel tank pressure Canister Vent Solenoid: An electrically

operated solenoid that replaces the Fresh air valve on earlier systems

Service Port: is a test point located in the engine compartment and is used for testing the EVAP system

Enhanced EVAP system

A normally open purge solenoid allows fresh air to enter the charcoal when in purge mode.

An enhanced EVAP system requires the uses of a bi-directional scan tool for several diagnostic procedures.

Fuel Tank

PCM

Engine

12 Volts When ignition is on

Test port

EVAP Solenoid

Rollover Valve

Charcoal Canister

Fuel Tank Pressure Sensor

Exhaust Gas Recirculation System (EGR)

An EGR system has two important jobs 1. The recirculation system is used

to burn un-burns gasses (HC and CO) By recirculation of un-burn gasses lower emissions can be achieved.

2.By Lowering combustion chamber temperature. By lowering combustion chamber temperature NOx emission can be lowered.


EGR Valve

EGR Control Solenoid PCM Controlled

Vacuum Line

Vacuum source

Exhaust GassesTo EGR valve

Exhaust Gasses

Exhaust Gasses to Engine

Vacuum off throttle

0 Vacuum Gauge


Later model vehicles use an electronic EGR value.

The PCM is used to control the flow of vacuum to the EGR valve.

By controlling vacuum to the EGR valve better exhaust gas metering can be obtained.

Electronic EGR Valve

PCMEGR Solenoid

Throttle Position Sensor

Intake

Vacuum present when Solenoid open by PCM

EGR Valve Charcoal Canister

To better control EGR flow later model vehicles Have begin using digital EGR valves.

A digital EGR valve is constructed using 3 EGR valve and 3 Electrical solenoid

Top of Digital EGR Valve

12 from ignition

PCM

Ports to Intake manifold

Bottom of Digital EGR valve

Emission Quiz

1.Two important job or the EGR valve is to: A. Increases ignition timing and lower

compression ratio. B. Increase HC and CO emissions C. Decrease HC emission and increase

ignition timing. D. Recirculation of unburned gasses and

lower combustion chamber temperature.

Emission Quiz

2.Technician A says that a PCV valve is used to remove blow-by from the crankcase. Technician B says the PCV valve is used to prevent HC from being vented into the atmosphere. Who is correct?

A Both A and B B. Neither A nor BC. A only D. B only

Emission Quiz

3. Technician A says that the EGR valve should operate at idle with the engine cold. Technician A says the EGR flow should increase combustion chamber temperature. Who is correct?

A. Technician A only B. Technician B Only C. Both A and B D. Neither A nor B

Emission Quiz 4.Technician A says lower combustion

chamber temperature will increase NOx. Technician B says increasing combustion chamber temperature will lower HC. Who is correct.

A. Technician A only B. Technician B only C. Both A and B D. Neither A nor B

Emission Quiz

5.Technician A says NOx is not a harmful exhaust emission. Technician A says that O2 is not a harmful exhaust emission. Who is correct?

Technician A only Technician B only Both Technician A and B Neither A nor B

Emission Quiz

6. A says a lean misfire can be caused by stuck closed EGR valve. A. True B. False

Emission Quiz

7. Photochemical SMOG is harmful to: A. Humans B. Plants C. Rubber and plastic D. All the Above

Emission Quiz 8. Technician A says the charcoal

canister is used to store fuel vapors. Technician B says the charcoal canister vents fuel vapor into the intake manifold. Who is correct?

A. Technician A only B. Technician B only C. Both A and B D. Neither A nor B

Emission Quiz

9. Digital EGR valves are controlled. A. Mechanically B. By the PCM C. Both A and B D. Neither A nor B

Emission Quiz

10. Technician A says fuel vapor from the fuel tank should be vented into the atmosphere. Technician B says a defective PCV valve can cause engine oil to become diluted. Who is correct? A. Technician A only B. Technician B

only C. Both A and B D. Neither A nor B

Catalytic Converters

In the mid 70s automotive manufacture begin installing catalytic converters to assist in meeting tougher emission standards.

A Catalytic is a material that can speed-up chemical action without changing itself.


Automotive catalytic converter are made of platinum, palladium and rhodium or a combination of these materials.

Platinum and palladium are used to change HC and CO into CO2 and Water.

Rhodium acts to reduce NOx emissions


Due to enhance emissions standard later model catalytic converters now use cerium to attract and release oxygen inside the converter to aid in the process of changing HC and CO to CO2 and H2o

Catalytic Converters The catalyst agent inside a catalytic

converter is either ceramic beads or a honeycomb-shaped blocks.

All catalytic converters are encased in a stainless steal housing.

NOTE: stainless steal is used on newer vehicle with catalytic converters because the production of water will rust traditional exhaust system medals in only a few years


HC and COCO2 H2o

Catalytic Converter

Engine

Exhaust Flow from engine through converter


Stainless steal catalytic converter housing are design to resist heat.

Before the catalytic converter can operate an operating temperature of around 300 degrees F must be reached.

Catalytic Converters This is a honey-comb block type catalytic

converter. Exhaust gasses flow thru the honey-comb

block


There are a few different types catalytic converters. Monolithic Converter Two way converter Three way converter Dual bed converter


Monolithic converter uses a ceramic honey-comb catalytic

Small ceramic beads converter are referred to as a pellet type catalytic converter


Two way catalytic converters only convert HC and CO

With a two way converter NOx is not converted

Two way converter are coated with platinum only

Two way converter are sometime referred to as oxidation converters


Three way catalytic converters can convert all three exhaust gasses HC CO NOx


A three way catalytic converter is usually plated with rhodium and platinum

Three way converter are also called reduction converters.


Dual bed catalytic converter is an oxidation and reduction converter built into one unit.

Mixing Chamber

CO, HC and NOx

CO2 and H20


Dual bed catalytic converters must be at an operating temperature of 130 degrees F

When the engine is cold additional air is forced into the exhaust manifold to aid in the burning and reduction of HC and CO

Catalytic Converters On a warn engine air is forced into the

converter to aid in burning exhaust gasses. As exhaust gasses flows iinto the front part

of the converter HC,CO and NOx is reduced. As exhaust flow into the mixing chamber

additional air is added to continue the burning process.

Exhaust gasses is the passed into the rear part of the converter to reduce HC,CO2 and NOx ever more.

emission controls. before beginning to understand emission controls you should know the reason why...

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