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					Emissions
         Air is made up of :
   21%O2
   78%N
   1% other gasses (mostly argon)
    Fuel is primarily made up of :
   HC
        Perfect combustion =
   HC, O2, N2 in
   Heat, H2O, CO2 and N2 out
       Imperfect combustion
   Adds HC, CO, NOx and O2 to exhaust
            Stoichiometric
   Much of our emissions are related
    directly to A/F mixtures
   Theoretical best a/f ratio for
    emissions, economy, performance is
    14.7:1
   14.7 pounds of air to 1 pound of fuel
              Think about it
   Gasoline weighs 6 pounds per gallon
   Air weighs 1 pound per 100 gallons
   At 15:1 it takes 9000 gallons of air to
    burn 1 gallon of fuel
    – 9000 Gallons of air is equal to a single
      car garage
               Think about it
   1 gallon of water equals 8.33 lbs.
   1 gallon of gasoline equals 5.8 to 6.5 lbs.
   1 gallon of ethanol equals 6.59 lbs.
   1 gallon of Diesel equals about 7.1 lbs.
         HC - Hydrocarbons
   Unburned fuel
   Currently measured in parts per
    million (ppm)
    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
    Not so common causes of HC
   Quench areas in combustion
    chamber
    – Carbon
    – Poor combustion chamber design
   Cam profiles too aggressive
       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
          Causes of high CO
   Hard to use as an A/F guide over 15:1
    due to flattening out of curve
   Must use O2 above stoichiometric
              O2 - Oxygen
   Currently measured in %
   Unused air in exhaust
   O2 directly related to A/F
   Can also come from dilution
    – Air pump, exhaust leaks
   Misfires will raise O2
   If O2 is > 5% and vehicle running OK
    then it must be from dilution
       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
      NOx - Oxides of nitrogen
   Created when peak combustion
    temps. exceed 2500F
         Causes of high NOx
   Advanced timing
   Inoperative EGR
   Carbon build up
   Anything that overheats combustion
    chamber
           Smog, what is it?
   Ground level ozone - O3
   Three ingredients; HC, NOx and
    sunlight
   CO is a pollutant all by itself
        State emissions testing
   Attainment areas vs. non-attainment
    areas
    – Ozone and/or CO
   Centralized vs. non-centralized
    testing
               IM240 test
   Varying load test with a constant
    volume sampler
   Idle test
   Evaporative emissions test
   Testing all three gases
   Visual inspection
                ASM test
   Loaded test with constant load with a
    CVS
   Idle test
   With or without an evaporative
    emissions test
   Test all three gasses
        Washington State test
   Variation of a ASM test
   Loaded cruise test except special
    vehicles
   Idle test
   No NOx measuring in effect yet
        Remote sensing device
   Like photo radar
   Used in California
Emission Controls
PCV systems
           Purpose of PCV
   Control of blowbye gasses (HC)
   Reducing moisture and acids
    extending oil life
             PCV history
   Road draft tube was responsible for
    20-25% of vehicles emissions
   Completely sealed systems on all
    domestics since 1968
         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
        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
    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
Inspect / replace at tune up
          intervals
Evaporative emissions system
         Evap system purpose
   To control HC during fuel
    evaporation
      Evap system components
   Gas cap
    – Important seal of system
    – Easily over looked
    – Allows air in but pressure out only if >1
      psi
   Vapor liquid separator
      Evap system components
   Canister
    – Stores evaporating vapors
    – Approx. 1.5 Lbs. Activated charcoal
    – Can hold twice it’s 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
       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
       Evap system operation
             (purging)
   Demand system
    – None at idle
    – Uses ported vacuum as control
    – Manifold vacuum does purging
    – Needs TVS
   Computer controls
   OBDII diagnostics
       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
Early fuel evaporation systems
         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
         EFE system purpose
   Warms intake to prevent
    condensation of fuel
   Prevents icing in carbs (temps can
    drop 66f when fuel vaporizes)
          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
          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
          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)
           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
        EFE grid components
   Electrical heater
    – Usually only, on carburetors and only
      on primary bore(s)
   Commonly ceramic
         EFE grid operation
   Heats and mixes a/f mixture
   Controlled by switches or relay
    – Usually powered up cold only
         EFE grid problems
   Grids melt
   Switches stick on
   Heater element opens
           Coolant passages
   Primarily icing controls
   Also helps warm intakes
      Heat riser valve purpose
   Directs exhaust to underside of
    intake manifold
   Prevents condensation
   Improves vaporization
   Not necessary on PFI engines
    Heat riser valve components
   Vacuum with rod
    – Uses TVS
   Bimetal spring
   On V engines valve will plug off one
    side of exhaust when cold
         Heat riser problems
   Binding on shaft
   Stuck in cold mode causing ping and
    NOx by overheating incoming a/f
    mixture
   Valve disintegrating
         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
Two types - air pump and air
     suction (pulseair)
Air pump system
                 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
      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
             Check valve
   Purpose: to prevent exhaust from
    coming up into AIR system
   Failed valves can cause melted
    hoses and diverter valves
       Air manifolds and pipes
   Rotting out causing backfire /
    exhaust leaks
           Air on CCC cars
   Computer controls routing of AIR
    system
   Upstream cold vs. downstream warm
   Still diverts totally away during decel
            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
      Pulseair system problems
   Back firing on decel if reed valves
    leak
   Melted stuff is melted if valves leak
   Can stick upstream
EGR systems
  Purpose : flows exhaust gas
into intake to lower combustion
    temps which lowers NOx
             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
    Three methods to obtain EGR
   Floor jets
    – Egr at all times
   Cam grinds
    – Egr at all times
   Egr valves
     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
      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
     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
          Electronic controls
   Can use vsv’s to control EGR via
    ECU
   Electric valves
    – Using solenoids to control operation
   Sensors
    – Position (EVP)
    – Exhaust pressure (PFE)
    – Temperature switch
               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
              EGR testing
   Egr movement under load
    – Some need to see VSS input
   Vacuum present at valve
   Lift up at idle to check passages
Catalytic converters
      Two types of converters
   Oxidizing
   Reducing
              Oxidizing
   Converts HC and CO to H2O, CO2
    and heat
       Monolith construction
          (honeycomb)
   Ceramic coated with p&p
   Lots of surface area
          Pellet construction
   Aluminum oxide pellets coated with
    p&p
   Not as much surface area
         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
              Reducing cat
   Converts NOX into N2, CO2, O2
   Needs lack of oxygen and some CO
    to work
    – Likes richer mix
   Uses rhodium
Three way or dual bed
      First part (bed) reducing
   Gives off O2 to help second bed
   Needs CO which second bed
    eliminates
     Second part oxidizing bed
   Uses O2 from first part
   Can use air into cat behind first bed
         Needs to be close to
       stoichiometric to work
   Only found on cars with closed loop
    fuel
                  Problems
   Plugging
    – Abuse
    – If not abuse must find cause before
      replacing
       Rich

       Leaded  fuel
       Missfire

       Air system
       Symptoms of plugging:
   Lack of power
   No start in extreme cases
        Testing backpressure
   Vacuum test not always accurate
   Back pressure reading of > 3psi is
    excessive
   Test at back pressure transducer, O2
    sensor, AIR fitting, EGR
             Efficiency loss
   Loss can be due to lead, coolant, oil,
    miles
   Aftermarket not as effective
              Symptoms:
   Excessive HC or CO or both
DO NOT USE USED CATS
OBDII efficiency monitor
           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
  Using the bible sticker
underhood to id components

				
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posted:8/26/2012
language:English
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