AIR POLLUTION & EVAPORATIVE EMISSIONS

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AIR POLLUTION EVAPORATIVE EMISSIONS
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Hydrocarbons

• Unburned fuel vapors
• When exposed to sunlight, chemical reaction
  occurs that produces ground-level ozone O3.
• Harmful to all living things
• Vehicle emissions create 50 of this ozone

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Carbon Monoxide

• Colorless, odorless, toxic gas
• Product of incomplete combustion
• Displaces oxygen which reduces oxygen in
  bloodstream
• Vehicles produce 2/3s of co in atmosphere

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Carbon Dioxide

• Product of proper combustion
• Does not directly impair human health
• Greenhouse gas
• Traps heat
• Helping to increase global warming

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Just What is Ozone?

• Ozone is a form of oxygen with a different
  chemical property
• Ozone differs from oxygen
• Has a distinctive odor
• Contains 3 oxygen atoms
• Absorbs damaging ultraviolet (UV) radiation
• In large concentrations ozone is hazardous

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Earths Atmosphere

• Troposphere start on the surface and extends 5
  9 miles
• Air most dense
• All weather occurs is this region
• Stratosphere extends for 31 miles
• Contains the Ozone layer

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Good Ozone

• Blocks or absorbs most of the suns ultraviolet
  rays
• Approx. 3,000 million tons of ozone in atmosphere
• If concentrated at sea level, would measure only
  3 mm thick

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Bad Ozone (Smog)

• Brown haze seen on hot summer days
• Result from burning fossil fuels chemical
  reaction from heat sun light
• Health problems
• Aggravates heart, lung ailments
• Can lower immune system
• Eye nose irritations
• Environmental problems
• Inhibits plant growth, weakens plants
• Reduce yields
• Deteriorates man-made materials
• Acid rain

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Evaporative EmissionsHydrocarbons escaping
through fuel evaporation.

• Diurnal gas evaporation as daytime temps
  increase
• Running Loss vaporization from hot engine
  exhaust parts
• Hot Soak hot engines (off), vaporization can
  continue
• Refueling Vapors forced out of tank as liquid
  fuel enters

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Evap. Emission Control Systems

• Sealed fuel tank domed to allow for vapor
  expansion
• Liquid-vapor separator when tank is full fuel
  can enter vent lines
• Vent lines routes vapor to canister engine
• Activated charcoal canister absorbs fuel
  vapors, releases vapors with fresh air
• Non venting gas cap pressure/vacuum relief valve

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Carbon Canister

• Holds vapors when engine not running
• Engine fully warm off idle, canister is
  purged allowing fresh air in, fuel vapors
  routed to engine burned

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Canister Operation
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Purge Valve

• Normally closed
• Vacuum or electric solenoid
• Engine off or idling valve is closed
• Engine running valve opens allowing purge of
  canister
• Solenoids either on/off or PWM

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Basic Purge Operation
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Thermostatic Vacuum Switch (TVS)

• Installed in intake manifold coolant passage
• Valve opens _at_ 115 F, allows vacuum to flow

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Canister Venting

• Open bottom When purging fresh air enters from
  bottom of canister
• Closed bottom fresh air enters for clean side
  of air filter
• Electric vent solenoid PCM controlled, allows
  fresh air in when commanded, seals system when
  closed.