Chapter 4 emission control
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The document discusses positive crankcase ventilation systems which draw crankcase vapors into the engine's intake manifold to be burned. It describes how PCV valves control the flow of crankcase gases and air into the engine.
Chapter 4 emission control
- 2. • The most specific AF ratio of EFI system to make a reduce emissions are 14.7:1 (14.7 – air, 1 – fuel) • AF mixture over 14.7:1 mean its was a lean mixture. • AF mixture less than 14.7:1 mean its was a rich mixture.
- 3. Type of emission gases • CO (Carbon Monoxide) CO2 • NOx (Nitrogen Oxide) N2 + O2 • SOx (Sulfur Oxide) SO2 • HC (Hydro Carbon) H2O + CO2 • Particular Matter
- 4. Catalytic Converter • The job of the catalytic converter is to convert harmful pollutants into less harmful emissions before they ever leave the car's exhaust system
- 5. • Catalytic converters are designed to reduce all three: Carbon monoxide (CO) is a poisonous gas that is colorless and odorless. Hydrocarbons are a major component of smog produced mostly from evaporated, unburned .fuel. Nitrogen oxides (NO and NO2, together called NOx) are a contributor to smog and acid rain, which also causes irritation to human mucus membranes.
- 6. How Catalytic Converters Reduce Pollution • In the catalytic converter, there are two different types of catalyst at work, a reduction catalyst and an oxidation catalyst.
- 7. reduction catalyst • The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2
- 8. oxidation catalyst • The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas.
- 9. • 2NO => N2 + O2 or 2NO2 => N2 + 2O2 • 2NO => N2 + O2 or 2NO2 => N2 + 2O2 • 2CO + O2 => 2CO2
- 12. • Allows burned exhaust gases to enter the engine intake manifold. • Reduces NOx emissions • When exhaust gases are added to the air fuel mixture, they decrease peek combustion temperatures……... ----For this reason, an exhaust gas recirculation system lowers amounts of NOx in exhaust.
- 14. The EGR valve consists of... • A vacuum diaphragm • A spring • A plunger • An exhaust gas valve • A diaphragm housing
- 15. What’s the valve designed to do? • Control the exhaust flow into the intake manifold...
- 17. Basic EGR system operation • At idle, the throttle plate in the carburetor or fuel injection throttle body is closed. This blocks off engine vacuum so it can’t act on the EGR valve. The EGR spring holds the valve shut and exhaust gases do NOT enter the intake manifold. • *****If the EGR valve were open at idle, it could upset the air-fuel mixture and the engine could stall!!!*****
- 18. • When the throttle plate is swung open to increase speed, engine vacuum is applied to the EGR hose. Vacuum pulls the EGR diaphragm up. In turn, the diaphragm pulls the valve open. • Engine exhaust can then enter the intake manifold and combustion chambers. At higher engine speeds, there is enough air flowing into the engine that the air-fuel mixture is not upset by the open EGR valve.
- 19. Some different types of EGR systems • Back-pressure EGR valve • Engine coolant temperature switch • Wide open throttle valve (WOT) • EGR jets
- 21. systems were developed to ventilate the crankcase an recirculate the vapors to the engine’s induction system so they can be burned in the cylinders.
- 23. A PCV system includes a hose from the air cleaner assembly so that filtered air can be drawn into the crankcase. This filtered air is then drawn by engine vacuum through the PCV valve and into the intake manifold where the crankcase fumes are burned in the cylinder. The PCV valve controls and limits this flow of air and fumes into the engine and the valve closes in the event of a backfire to prevent flames from entering the crankcase area.
- 24. PCV VALVES The PCV valve in most systems is a one- way valve containing a spring-operated plunger that controls valve flow rate
- 26. Air flows through the PCV valve during idle, cruising, and light-load conditions.
- 27. Air flows through the PCV valve during acceleration and when the engine is under a heavy load.
- 28. PCV valve operation in the event of a backfire.
- 29. Evaporative Emission Control System (EVAP) • The purpose of the evaporative (EVAP) emission control system is to trap and hold gasoline vapors.
- 30. VAPOR CANISTER STORAGE • The canister is located under the hood or underneath the vehicle, and is filled with activated charcoal granules that can hold up to one-third of their own weight in fuel vapors. • A vent line connects the canister to the fuel tank
- 33. • The evaporative emission control system includes all of the lines, hoses, and valves, plus the charcoal canister.
- 34. VAPOR PURGING • During engine operation, stored vapors are drawn from the canister into the engine through a hose connected to the throttle body or the air cleaner. • This “purging” process mixes HC vapors from the canister with the existing air-fuel charge.
- 35. VAPOR PURGING Computer-Controlled Purge • Canister purging on engines with electronic fuel management systems is regulated by the powertrain control module (PCM). • Control of this function is particularly important because the additional fuel vapors sent through the purge line can upset the air–fuel ratio provided by a fuel-injection system. • Since air–fuel ratio adjustments are made many times per second, it is critical that vapor purging is controlled just as precisely.
- 37. • A typical evaporative emission control system. Note that when the computer turns on the canister purge solenoid valve, manifold vacuum draws any stored vapors from the canister into the engine. Manifold vacuum also is applied to the pressure control valve. When this valve opens, fumes from the fuel tank are drawn into the charcoal canister and eventually into the engine. When the solenoid valve is turned off (or the engine stops and there is no manifold vacuum), the pressure control valve is spring-loaded shut to keep vapors inside the fuel tank from escaping to the atmosphere.
- 38. TEST 2 • Describe about 3 operations (drive, reduction & reverse) of Automatic Transmission. • With diagram, please explain how transfer case work (gear type). • please sketch the 3 standard symbol of relay and explain how a relay its work.