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Emission Control SystemsEmission Control Systems

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Vehicle Pollution SourcesVehicle Pollution Sources

• 3 areas of a vehicle that can pollute…3 areas of a vehicle that can pollute… tailpipe emissionstailpipe emissions fuel tank vapors (and carburetor vapors)fuel tank vapors (and carburetor vapors) crankcase blow-by gasescrankcase blow-by gases

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Major Engine PollutantsMajor Engine Pollutants

1)1) hydrocarbonshydrocarbons: produced when some or all of the fuel does not get burned during : produced when some or all of the fuel does not get burned during combustion, or from raw gasoline vaporscombustion, or from raw gasoline vapors tailpipe emissiontailpipe emission fuel tank & carburetor emissionfuel tank & carburetor emission

2)2) carbon monoxidecarbon monoxide: produced when there is insufficient oxygen to support combustion: produced when there is insufficient oxygen to support combustion tailpipe emissiontailpipe emission

3)3) oxides of nitrogenoxides of nitrogen: produced when combustion temperatures exceed 1400°C / 2500°F: produced when combustion temperatures exceed 1400°C / 2500°F tailpipe emissiontailpipe emission

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Blow-by Emission ControlBlow-by Emission Control

• crankcase ventilation system crankcase ventilation system handles blow-by gaseshandles blow-by gases hydrocarbon emissionshydrocarbon emissions

• road-draft tube used until 1962road-draft tube used until 1962

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Blow-by Emission ControlBlow-by Emission Control

• PPositive ositive CCrankcase rankcase VVentilation system (entilation system (PCVPCV system) in use since 1963 system) in use since 1963

• replace the replace the PPositive ositive CCrankcase rankcase VVentilation valve and check its hose (inexpensive)…entilation valve and check its hose (inexpensive)…

• Tech TipTech Tip: : pull the PCV valve out of the engine while it’s running pull the PCV valve out of the engine while it’s running place your finger under the valve place your finger under the valve you should feel and hear suction & the valve should clickyou should feel and hear suction & the valve should click

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Checking PCV SystemChecking PCV System

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Fixed Orifice Tube PCV SystemsFixed Orifice Tube PCV Systems

• a precisely determined hole size acts as the valvea precisely determined hole size acts as the valve• no need for a spring and valve assemblyno need for a spring and valve assembly

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Evaporative Emission Control SystemEvaporative Emission Control System• prevents raw HC’s (from gasoline) from being vented into the atmosphere prevents raw HC’s (from gasoline) from being vented into the atmosphere

(in use since 1971)(in use since 1971)

• charcoal canistercharcoal canister absorbs fuel vapors when the engine is off & sends them to the intake manifold so absorbs fuel vapors when the engine is off & sends them to the intake manifold so they can be burned when the engine is runningthey can be burned when the engine is running

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Evaporative Emission Control SystemsEvaporative Emission Control Systems

• on 1996 & newer vehicles, PCM…on 1996 & newer vehicles, PCM… purges canister vapors via a purge solenoidpurges canister vapors via a purge solenoid monitors vapor flowmonitors vapor flow monitors the system for leaksmonitors the system for leaks

vehicle may use a separate pump to pressurize system to see if pressure can be vehicle may use a separate pump to pressurize system to see if pressure can be maintainedmaintained

if PCM detects a leak, if PCM detects a leak, check engine light check engine light will illuminatewill illuminate

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Reducing NOx Tailpipe EmissionsReducing NOx Tailpipe Emissions

• EExhaust xhaust GGas as RRecirculation ecirculation vvalve (alve (EGREGR) allows some exhaust gas back into the intake air ) allows some exhaust gas back into the intake air streamstream used on mostused on most engines since mid-1970’s engines since mid-1970’s but not allbut not all

• EGR dilutes/displaces fresh, incoming AFM which drops combustion temperature = < NOxEGR dilutes/displaces fresh, incoming AFM which drops combustion temperature = < NOx

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• EGR typically operates under light throttle, cruising conditions on a warmed up EGR typically operates under light throttle, cruising conditions on a warmed up engineengine

• during warm up, WOT & at idle, it does not operateduring warm up, WOT & at idle, it does not operate

EGR Valve

EGR Pipe

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EGR Valve StylesEGR Valve Styles

• 1) 1) mechanical EGRmechanical EGR operated by engine vacuum operated by engine vacuum

vacuum acts on a diaphragm to open the valve vacuum acts on a diaphragm to open the valve (fig. a)(fig. a)

some EGR valves use a some EGR valves use a computer controlled solenoidcomputer controlled solenoid to modulate the vacuum to modulate the vacuum signal to the diaphragm signal to the diaphragm (fig. b)(fig. b)

others use an exhaust pressure sensor to help determine rate of exhaust gas others use an exhaust pressure sensor to help determine rate of exhaust gas flow flow (fig. c)(fig. c)

fig. afig. a

fig. bfig. b

fig. cfig. c

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EGR Valve StylesEGR Valve Styles

• 2) 2) digitaldigital or or electronic EGRelectronic EGR valve valve PCM controls 1 or more solenoids to modulate EGR flowPCM controls 1 or more solenoids to modulate EGR flow no vacuum diaphragm is usedno vacuum diaphragm is used each solenoid has an integral pintle position sensoreach solenoid has an integral pintle position sensor

this sensor “tells” the PCM the position of the pintle valvethis sensor “tells” the PCM the position of the pintle valve the solenoids are pulsed on & off by the PCM many times/second when neededthe solenoids are pulsed on & off by the PCM many times/second when needed

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EGR ServiceEGR Service• InoperativeInoperative EGR systems can lead to… EGR systems can lead to…

excessive NoX emissions (possible failure at AirCare)excessive NoX emissions (possible failure at AirCare) detonation (knocking & pinging)detonation (knocking & pinging)

• caused by…caused by… defective diaphragmdefective diaphragm weak vacuum signalweak vacuum signal

defective or incorrectly routed vacuum hosesdefective or incorrectly routed vacuum hoses shorted or open solenoidshorted or open solenoid exhaust passage blocked with carbonexhaust passage blocked with carbon

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EGR ServiceEGR Service• ExcessiveExcessive EGR operation can lead to… EGR operation can lead to…

rough idlerough idle stallingstalling

• caused by…caused by… improperly routed vacuum hosesimproperly routed vacuum hoses carbon on pintle valve seat carbon on pintle valve seat faulty EGR valvefaulty EGR valve

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Reducing Tailpipe EmissionsReducing Tailpipe Emissions

• catalytic converterscatalytic converters reduce HC, CO & possibly NOx reduce HC, CO & possibly NOx used on all vehicles since mid-1970’sused on all vehicles since mid-1970’s

• HC & COHC & CO in the exhaust is in the exhaust is oxidizedoxidized by the catalyst which can contains platinum, by the catalyst which can contains platinum, palladium & rhodiumpalladium & rhodium

• HC + OHC + O22 = CO = CO22 & H & H2200

• CO + 0CO + 022 = CO2 = CO2

• this is a two-way catalystthis is a two-way catalyst

• needs ≈ 315°C / 600°F to operateneeds ≈ 315°C / 600°F to operate

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Three Way CatalystsThree Way Catalysts• reduces HC, CO reduces HC, CO and NOxand NOx levels levels

• NOx is converted to nitrogen & CONOx is converted to nitrogen & CO22

• front ½ controls NOx & back ½ reduces HC & COfront ½ controls NOx & back ½ reduces HC & CO contains cerium – has the ability to store oxygencontains cerium – has the ability to store oxygen the oxygen is used to oxidize HC & COthe oxygen is used to oxidize HC & CO

• in use in Canada since 1988in use in Canada since 1988

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Reducing Tailpipe EmissionsReducing Tailpipe Emissions

• air injection systemsair injection systems used on some engines, but not allused on some engines, but not all

• cold enginecold engine: air is injected into the exhaust manifold to oxidize HC & CO: air is injected into the exhaust manifold to oxidize HC & CO

• warm enginewarm engine: air is injected into the converter to oxidize HC & CO: air is injected into the converter to oxidize HC & CO

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Air Injection SystemsAir Injection Systems

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Causes of excessive hydrocarbons…Causes of excessive hydrocarbons…

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Causes of Excessive Carbon Monoxide…Causes of Excessive Carbon Monoxide…

• plugged air filterplugged air filter• high float levelhigh float level• choke not openingchoke not opening• faulty fuel injectorfaulty fuel injector• higher than normal fuel pressurehigher than normal fuel pressure• faulty EFI sensorfaulty EFI sensor

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Causes of Excessive NOx…Causes of Excessive NOx…

• carbon depositscarbon deposits

• inoperative EGR valveinoperative EGR valve

some valves are vacuum operatedsome valves are vacuum operated

others are electronically activatedothers are electronically activated

• higher than normal coolant temperatureshigher than normal coolant temperatures

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Pollution Sources & What Controls Them – a Recap…Pollution Sources & What Controls Them – a Recap…• 3 areas of a vehicle that can pollute…3 areas of a vehicle that can pollute…

tailpipe emissionstailpipe emissions fuel tank vapors (and carburetor vapors)fuel tank vapors (and carburetor vapors) crankcase blow-by gasescrankcase blow-by gases