Emissions

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Emissions
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Air is made up of

• 21O2
• 78N
• 1 other gasses (mostly argon)

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Fuel is primarily made up of

• Hydrocarbons (HC)

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Perfect combustion

• HC, O2, N2 in
• Heat, H2O, CO2 and N2 out

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Imperfect combustion

• Adds HC, CO, NOx and O2 to exhaust

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Stoichiometric

• Much of our emissions are related directly to A/F
  mixtures
• Theoretical best A/F ratio for emissions,
  economy, performance is 14.71
• 14.7 pounds of air to 1 pound of fuel

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Think about it

• Gasoline weighs 6 pounds per gallon
• Air weighs 1 pound per 100 gallons
• At 151 it takes 9000 gallons of air to burn 1
  gallon of fuel
• 9000 Gallons of air is equal to a single car
  garage

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HC - Hydrocarbons

• Unburned fuel
• Currently measured in parts per million (ppm)

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Common causes of high HC

• Missfiring will cause HCs
• Ignition
• Mechanical
• Lean
• A/f ratios off either way
• Timing too advanced
• Cools exhaust and cylinder walls

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Not so common causes of HC

• Quench areas in combustion chamber
• Carbon
• Poor combustion chamber design
• Cam profiles too aggressive

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CO - Carbon monoxide

• Currently measured in
• EXTREMELY deadly gas!!!
• Partially burned fuel
• Too much fuel or too little O2
• Combustion process ran out of air
• CO directly related to a/f ratios

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Causes of high CO

• Any thing that will cause a rich fuel mixture
• Sensor malfunction
• Carburetor or injector failures
• Diluted oil
• Hard to use as an A/F guide over 151 due to
  flattening out of curve
• Must use O2 above stoichiometric

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O2 - Oxygen

• Currently measured in
• Unused air in exhaust
• O2 directly related to A/F
• Can also come from dilution
• Air pump, exhaust leaks
• Missfires will raise O2
• If O2 is gt 5 and vehicle running OK then it must
  be from dilution

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CO2 - Carbon dioxide

• Currently measured in
• Byproduct of complete combustion
• Peak indicates good A/F
• Any problems pull CO2 away from peak
• Used by Washington State to determine exhaust
  system integrity

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NOx - Oxides of nitrogen

• Created when peak combustion temps. exceed 2500F

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Causes of high NOx

• Advanced timing
• Inoperative EGR
• Carbon build up
• Anything that overheats combustion chamber

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Smog, what is it?

• Ground level ozone - O3
• Three ingredients HC, NOx and sunlight
• CO is a pollutant all by itself

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State emissions testing

• Attainment areas vs. non-attainment areas
• Ozone and/or CO
• Centralized vs. non-centralized testing

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ASM test

• Loaded test with constant load with a CVS
• Idle test
• With or without an evaporative emissions test
• Test all three gasses

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Washington State test

• Variation of a ASM test
• Loaded cruise test except special vehicles
• Idle test
• No NOx measuring in effect yet

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IM240 test

• Varying load test with a constant volume sampler
• Idle test
• Evaporative emissions test
• Testing all three gases
• Visual inspection

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Remote sensing devices

• Like photo radar
• Used in California / Colorado

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Emission Controls
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PCV systems
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Purpose of PCV

• Control of blowbye gasses (HC)
• Reducing moisture and acids extending oil life

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PCV history

• Road draft tube was responsible for 20-25 of
  vehicles emissions
• Completely sealed systems on all domestics since
  1968

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Components of PCV

• Breather to filter incoming air
• PCV valve
• Calibrated vacuum leak to intake manifold
• Controls flow rates based on strength of vacuum
• Eliminates backfiring path to crankcase
• Bleed orifice type / dual bleed type

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PCV system problems

• Can flow up to 20 of the total a/f mixture at
  idle
• Plugged system could cause high CO at idle
• Stuck open valve could cause lean or high idle
  speed

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PCV system diagnosis / testing

• Valve should snap back at idle
• Rattle test
• Cheap valves pass both tests but could flow wrong
• Inspect breathers for plugging
• Oil dilution
• 1 Change too much dilution or blowbye

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Inspect / replace at tune up intervals
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Evaporative emissions system
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Evap system purpose

• To control HC during fuel evaporation

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Evap system components

• Gas cap
• Important seal of system
• Easily over looked
• Allows air in but pressure out only if gt1 psi
• Vapor liquid separator

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Evap system components

• Canister
• Stores evaporating vapors
• Approx. 1.5 Lbs. Activated charcoal
• Can hold twice its own weight in fuel
• Chrysler used the crankcase in 1971
• Vapor line(s) from tank(s)
• Carb bowl venting
• Electronic solenoids
• Switching with purge valve

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Evap system operation (purging)

• Uses stored fuel vapors in canister
• Variable type-hose to air cleaner snorkel
• Constant purge type-vacuum to manifold
• Uses TVS and orifice

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Evap system operation (purging)

• Demand system
• None at idle
• Uses ported vacuum as control
• Manifold vacuum does purging
• Needs TVS
• Computer controls
• OBDII diagnostics

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Evap system problems

• Failed purge valves / diaphragms rupturing
• Plugged filters
• Failing TVS can cause cold flooding
• Loaded canister due to over full tanks
• Charcoal in carb. bowl indicates defective
  canister

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Early fuel evaporation systems
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EFE system purpose

• Helps a/f mixture vaporize on cold engine
• Provide good cold driveability (cold air too
  dense and leans out mixture)
• Improve cold emissions

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EFE system purpose

• Warms intake to prevent condensation of fuel
• Prevents icing in carbs (temps can drop 66f when
  fuel vaporizes)

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Four types of EFE

• 1. T.A.C. (thermostatic air cleaner)
• 2. EFE grid
• 3. Coolant heated intakes and throttle bodies
• 4. Heat riser valve

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T.A.C. components

• Mode door
• Cold air position for warm eng.
• Warm air position for cold eng.
• Uses manifold vacuum and vacuum motor to move
  mode door
• Heat stove and pipe
• Primary failure of emission tests

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T.A.C. components

• Sensor
• Bleeds off vacuum at 100 - 120f
• Must bleed off vacuum - can not trap it
• Wax bulb type
• Manual movement (older asians)

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T.A.C. problems

• Stuck in hot air position will cause ping / NOx
• Often caused by a plugged bleed off hole
• Any missing piece can cause cold driveability
  problems
• Cracked manifold sucks exhaust into air cleaner

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EFE grid components

• Electrical heater
• Usually only, on carburetors and only on primary
  bore(s)
• Commonly ceramic

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EFE grid operation

• Heats and mixes a/f mixture
• Controlled by switches or relay
• Usually powered up cold only

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EFE grid problems

• Grids melt
• Switches stick on
• Heater element opens

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Coolant passages

• Primarily icing controls
• Also helps warm intakes

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Heat riser valve purpose

• Directs exhaust to underside of intake manifold
• Prevents condensation
• Improves vaporization
• Not necessary on PFI engines

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Heat riser valve components

• Vacuum with rod
• Uses TVS
• Bimetal spring
• On V engines valve will plug off one side of
  exhaust when cold

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Heat riser problems

• Binding on shaft
• Stuck in cold mode causing ping and NOx by
  overheating incoming a/f mixture
• Valve disintegrating

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Air systems purpose

• To pump or allow air to be sucked into exhaust
  system
• Completes combustion
• Dilutes exhaust gasses
• Gives O2 to cats
• Heats O2 sensor

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Two types - air pump and air suction (pulseair)
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Air pump system
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Air pump

• Belt driven vane and rotor pump
• Some use electric air pumps
• Some means of filtered air intake
• Often using a centrifugal filter
• 1/2 Hp draw on engine

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Diverter and gulp valves

• Purpose divert AIR away from exhaust on decel to
  prevent backfire
• Gulp dumps AIR to intake
• Similar to a decel valve / mixture control valve
• Vacuum or electric controlled

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Check valve

• Purpose to prevent exhaust from coming up into
  AIR system
• Failed valves can cause melted hoses and diverter
  valves

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Air manifolds and pipes

• Rotting out causing backfire / exhaust leaks

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Air on CCC cars

• Computer controls routing of AIR system
• Upstream cold vs. downstream warm
• Still diverts totally away during decel

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Pulseair system

• No pump
• Uses negative exhaust pulses
• Reed valves
• Can still divert or block off AIR
• Can be computer controlled
• Often mounted to air cleaner

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Pulseair system problems

• Back firing on decel if reed valves leak
• Melted stuff is melted if valves leak
• Can stick upstream

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EGR systems
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Purpose flows exhaust gas into intake to lower
combustion temps which lowers NOx
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EGR details

• Exhaust supports no combustion
• Dilutes a/f mix and slows combustion slightly
• First used on Buicks in 1972, common in 1973
• Does not affect a/f ratios

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Three methods to obtain EGR

• Floor jets
• Egr at all times
• Cam grinds
• Egr at all times
• Egr valves

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Control of EGR needed for three reasons

• Idle can not support dilution and little NOx
• Cold poor driveability, no NOx, not all engines
• WOT limits power and less NOx due to richer a/f

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EGR valve is a means of controlling EGR flow

• Basic systems use ported vacuum to control and
  limit operation and a TVS to eliminate cold
  operation
• Some use a vacuum amplifier
• Works like vacuum relay
• Often will have delay orifices and valves

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Backpressure Transducer

• Limits with exhaust pressures
• Exhaust pressures good load indicator
• Can modulate valve
• Many valves have built in transducers
• Positive valves vs. Negative valves

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Electronic controls

• Can use vsvs to control EGR via ECU
• Electric valves
• Using solenoids to control operation
• Sensors
• Position (EVP)
• Exhaust pressure (PFE)
• Temperature switch

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Problems

• Inop valves cause high combustion temps pinging
  NOx
• Plugged EGR passages common
• Too much EGR lack of power, surge
• Stuck open at idle causes rough idle due to
  excessive dilution

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EGR testing

• Egr movement under load
• Some need to see VSS input
• Vacuum present at valve
• Lift up at idle to check passages

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Catalytic converters
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Two types of converters

• Oxidizing
• Reducing
• May be in one case

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Oxidizing

• First in 1975
• Converts HC and CO to H2O, CO2 and heat
• Uses precious metals platinum and palladium

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Monolith construction (honeycomb)

• Ceramic coated with pp
• Lots of surface area
• Very brittle
• Most common

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Pellet construction

• Aluminum oxide pellets coated with pp
• Not as much surface area
• Very heavy
• Not easily damaged

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Oxidizing operation

• Needs O2 to convert HC and CO to H2O AND CO2
• Gets O2 from lean a/f ratios, AIR systems,
  missfires
• Light off at 500f, average temps 1400f inside,
  700f outside
• Abbreviated OC

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Reducing cat

• Converts NOX into N2, CO2, O2
• Needs lack of oxygen and some CO to work
• Likes richer mix
• Missfires provide too much o2
• Uses rhodium

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Three way or dual bed
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First part or bed reducing

• Gives off O2 to help second bed
• Needs CO which second bed eliminates

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Second part oxidizing bed

• Uses O2 from first part
• Can use air into cat behind first bed

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Needs to be close to stoichiometric to work

• Only found on cars with closed loop fuel

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Problems and testing all types

• Plugging
• Abuse
• If not abuse must find cause before replacing
• Rich
• Leaded fuel
• Missfire
• Air system

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• Symptoms
• Vacuum not always accurate
• Back pressure reading of gt 3psi is excessive
• Test at back pressure transducer, O2 sensor, AIR
  fitting, EGR

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Efficiency loss

• Symptoms
• Loss can be due to lead, coolant, oil, miles
• Aftermarket not as effective
• DO NOT USE USED CATS
• OBDII efficiency monitor

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Efficiency testing

• Temps 100-200f increase across cat
• Intrusive method
• Egr, AIR pipes (must seal), drilling hole
• Need thin probe
• Rivet holes up
• Not at O2 sensor

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Using the bible sticker underhood to id components