1 / 26

Emission Control Systems

Emission Control Systems. Vehicle Pollution Sources. 3 areas of a vehicle that can pollute… tailpipe emissions fuel tank vapors (and carburetor vapors) crankcase blow-by gases. Major Engine Pollutants.

Download Presentation

Emission Control Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Emission Control Systems

  2. Vehicle Pollution Sources • 3 areas of a vehicle that can pollute… • tailpipe emissions • fuel tank vapors (and carburetor vapors) • crankcase blow-by gases

  3. Major Engine Pollutants • hydrocarbons: produced when some or all of the fuel does not get burned during combustion, or from raw gasoline vapors • tailpipe emission • fuel tank & carburetor emission • carbon monoxide: produced when there is insufficient oxygen to support combustion • tailpipe emission • oxides of nitrogen: produced when combustion temperatures exceed 1400°C / 2500°F • tailpipe emission

  4. Blow-by Emission Control • crankcase ventilation system handles blow-by gases • hydrocarbon emissions • road-draft tube used until 1962

  5. Blow-by Emission Control • Positive Crankcase Ventilation system (PCV system) in use since 1963

  6. Checking PCV System • replace the Positive Crankcase Ventilation valve and check its hose (inexpensive)… • Tech Tip: • pull the PCV valve out of the engine while it’s running • place your finger under the valve • you should feel and hear suction & the valve should click

  7. Fixed Orifice Tube PCV Systems • a precisely determined hole size acts as the valve • no need for a spring and valve assembly

  8. Evaporative Emission Control System • prevents raw HC’s (from gasoline) from being vented into the atmosphere • (in use since 1971) • charcoal canister absorbs fuel vapors when the engine is off & sends them to the intake manifold so they can be burned when the engine is running

  9. Evaporative Emission Control Systems • on 1996 & newer vehicles, PCM… • purges canister vapors via a purge solenoid • monitors vapor flow • monitors the system for leaks • vehicle may use a separate pump to pressurize system to see if pressure can be maintained • if PCM detects a leak, check engine light will illuminate

  10. Reducing NOx Tailpipe Emissions • Exhaust Gas Recirculation valve (EGR) allows some exhaust gas back into the intake air stream • used on most engines since mid-1970’s but not all • EGR dilutes/displaces fresh, incoming AFM which drops combustion temperature = < NOx

  11. EGR typically operates under light throttle, cruising conditions on a warmed up engine • during warm up, WOT & at idle, it does not operate EGR Valve EGR Pipe

  12. EGR Valve Styles • 1) mechanical EGR operated by engine vacuum • vacuum acts on a diaphragm to open the valve (fig. a) • some EGR valves use a computer controlled solenoid to modulate the vacuum signal to the diaphragm (fig. b) • others use an exhaust pressure sensor to help determine rate of exhaust gas flow (fig. c) fig. c fig. b fig. a

  13. EGR Valve Styles • 2) digital or electronic EGR valve • PCM controls 1 or more solenoids to modulate EGR flow • no vacuum diaphragm is used • each solenoid has an integral pintle position sensor • this sensor “tells” the PCM the position of the pintle valve • the solenoids are pulsed on & off by the PCM many times/second when needed

  14. EGR Service • Inoperative EGR systems can lead to… • excessive NoX emissions (possible failure at AirCare) • detonation (knocking & pinging) • caused by… • defective diaphragm • weak vacuum signal • defective or incorrectly routed vacuum hoses • shorted or open solenoid • exhaust passage blocked with carbon

  15. EGR Service • Excessive EGR operation can lead to… • rough idle • stalling • caused by… • improperly routed vacuum hoses • carbon on pintle valve seat • faulty EGR valve

  16. Reducing Tailpipe Emissions • catalytic converters reduce HC, CO & possibly NOx • used on all vehicles since mid-1970’s • HC & CO in the exhaust is oxidized by the catalyst which can contains platinum, palladium & rhodium • HC + O2 = CO2 & H20 • CO + 02 = CO2 • this is a two-way catalyst • needs ≈ 315°C / 600°F to operate

  17. Three Way Catalysts • reduces HC, CO and NOx levels • NOx is converted to nitrogen & CO2 • front ½ controls NOx & back ½ reduces HC & CO • contains cerium – has the ability to store oxygen • the oxygen is used to oxidize HC & CO • in use in Canada since 1988

  18. Reducing Tailpipe Emissions • air injection systems • used on some engines, but not all • cold engine: air is injected into the exhaust manifold to oxidize HC & CO • warm engine: air is injected into the converter to oxidize HC & CO

  19. Air Injection Systems

  20. Causes of excessive hydrocarbons…

  21. Causes of Excessive Carbon Monoxide… • plugged air filter • high float level • choke not opening • faulty fuel injector • higher than normal fuel pressure • faulty EFI sensor

  22. Causes of Excessive NOx… • carbon deposits • inoperative EGR valve • some valves are vacuum operated • others are electronically activated • higher than normal coolant temperatures

  23. Pollution Sources & What Controls Them – a Recap… • 3 areas of a vehicle that can pollute… • tailpipe emissions • fuel tank vapors (and carburetor vapors) • crankcase blow-by gases

More Related