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Emission Devices

Emission Devices. PCV systems. Purpose of PCV . Control of blowbye gasses (HC) Reducing moisture and acids extending oil life. Components of PCV. Breather to filter incoming air PCV valve Calibrated vacuum leak to intake manifold Controls flow rates based on strength of vacuum

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Emission Devices

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  1. Emission Devices

  2. PCV systems

  3. Purpose of PCV • Control of blowbye gasses (HC) • Reducing moisture and acids extending oil life

  4. 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

  5. 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

  6. Evaporative emissions system

  7. Evap system purpose • To control HC during fuel evaporation

  8. 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

  9. 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)

  10. Evap system operation (purging) • Typical operation • None at idle • May use ported vacuum for purging • May have manifold vacuum purge but be controlled by ported • Needs TVS to eliminate cold operation • Computer controls common • OBDII must have diagnostics for system

  11. EGR systems

  12. Purpose : flows exhaust gas into intake to lower combustion temps which lowers NOx

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. END ------------ OF IT ALL

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