Chapter 06

Automotive Fuel and Emissions Control Systems, 2/eBy James D. Halderman and Jim Linder 2009 Pearson Higher Education, Inc.Pearson Prentice Hall - Upper Saddle River, NJ 07458

OBJECTIVESAfter studying Chapter 6, the reader should be able to:Describe how the proper grade of gasoline affects engine performance.List gasoline purchasing hints.Discuss how volatility affects driveability.Explain how oxygenated fuels can reduce CO exhaust emissions.Discuss the advantages and disadvantages of various alternative fuels.


AIR INTAKE FILTRATIONGasoline must be mixed with air to form a combustible mixture.Air movement into an engine occurs due to low pressure (vacuum) being created in the engine.

FIGURE 6-1 Downward movement of the piston lowers the air pressure inside the combustion chamber. The pressure differential between the atmosphere and the inside of the engine forces air into the engine.


AIR INTAKE FILTRATIONFIGURE 6-2 Dust and dirt in the air are trapped in the air filter so they do not enter the engine.


AIR INTAKE FILTRATIONFilter ReplacementAir Filter ElementsRemotely Mounted Air Filters and Ducts

FIGURE 6-3 Most air filter housings are located on the side of the engine compartment and use flexible rubber hose to direct the airflow into the throttle body of the engine.


ALWAYS CHECK THE AIR FILTERFIGURE 6-4 (a) Note the discovery as the air filter housing was opened during service on a Pontiac Bonneville. The nuts were obviously deposited by squirrels (or some other animal). (b) Not only was the housing filled with nuts, but also this air filter was extremely dirty, indicating that this vehicle had not been serviced for a long time.


ENGINE AIR TEMPERATURE REQUIREMENTSSome form of thermostatic control has been used on vehicles equipped with a throttle-body fuel injection to control intake air temperature for improved driveability.An air control valve or damper permits the air intake of:Heated air from the heat stoveCooler air from the snorkel or cold-air ductA combination of both


WHAT DOES THIS TUBE DO?FIGURE 6-5 A resonance tube, called a Helmholtz resonator, is used on the intake duct between the air filter and the throttle body to reduce air intake noise during engine acceleration.


THROTTLE-BODY INJECTION INTAKE MANIFOLDSA throttle-body fuel injector forces finely divided droplets of liquid fuel into the incoming air to form a combustible airfuel mixture.

FIGURE 6-6 A throttle-body injection (TBI) unit used on a GM V-6 engine.


THROTTLE-BODY INJECTION INTAKE MANIFOLDSFIGURE 6-7 Heavy fuel droplets separate as they flow around an abrupt bend in an intake manifold.


PORT FUEL-INJECTION INTAKE MANIFOLDSThe size and shape of port fuel-injected engine intake manifolds can be optimized because the only thing in the manifold is air. The fuel injection is located in the intake manifold about 3 to 4 inches (70 to 100 mm) from the intake valve. Therefore, the runner length and shape are designed for tuning only.


PORT FUEL-INJECTION INTAKE MANIFOLDSFIGURE 6-8 The graph shows the effect of sonic tuning of the intake manifold runners. The longer runners increase the torque peak and move it to a lower RPM. The 600-mm-long intake runner is about 24 inches long.


PORT FUEL-INJECTION INTAKE MANIFOLDSFIGURE 6-9 Airflow through the large diameter upper intake manifold is distributed to smaller diameter individual runners in the lower manifold in this two-piece manifold design.


VARIABLE INTAKESMany intake manifolds are designed to provide both short runners, best for higher engine speed power, and longer runners, best for lower engine speed torque.

FIGURE 6-10 The air flowing into the engine can be directed through long or short runners for best performance and fuel economy.


PLASTIC INTAKE MANIFOLDSPlastic intake manifolds have smoother interior surfaces than do other types of manifolds, resulting in greater airflow.

FIGURE 6-11 Many plastic intake manifolds are constructed using many parts glued together to form complex passages for airflow into the engine.


PLASTIC INTAKE MANIFOLDSFIGURE 6-12 The exhaust gas recirculation system is more efficient at controlling NOX emissions if the exhaust gases are cooled. A long metal tube between the exhaust manifold and the intake manifold allows the exhaust gases to cool before entering the engine.


UPPER AND LOWER INTAKE MANIFOLDSMany intake manifolds are constructed in two parts.A lower section, usually called the plenum, attaches to the cylinder heads and includes passages from the intake ports.An upper manifold connects to the lower unit and includes the long passages needed to help provide the ram effect that helps the engine deliver maximum torque at low engine speeds. The throttle body attaches to the upper intake.


EXHAUST MANIFOLD DESIGNThe exhaust manifold is designed to collect high-temperature spent gases from the head exhaust ports.

FIGURE 6-13 The exhaust gases are pushed out of the cylinder by the piston on the exhaust stroke.


EXHAUST MANIFOLD DESIGNFIGURE 6-14 This exhaust manifold has a heat shield to help retain the heat and help reduce exhaust emissions.FIGURE 6-15 Many exhaust manifolds are constructed of pressed steel and are free flowing to improve engine performance.


HOW CAN A CRACKED EXHAUST MANIFOLD AFFECT ENGINE PERFORMANCE?FIGURE 6-16 A crack in an exhaust manifold is often not this visible. A crack in the exhaust manifold upstream of the oxygen sensor can fool the sensor and affect engine operation.


EXHAUST MANIFOLD GASKETSGaskets are used on new engines with tubing- or header-type exhaust manifolds. The gaskets often include heat shields to keep exhaust heat from the spark plugs and spark plug cables. They may have several layers of steel for high-temperature sealing.

FIGURE 6-17 Typical exhaust manifold gaskets. Note how they are laminated to allow the exhaust manifold to expand and contract due to heating and cooling.


THE CORRECT TOOLS SAVE TIMEFIGURE 6-18 An exhaust manifold spreader tool is a tool that is absolutely necessary to use when reinstalling exhaust manifolds. When they are removed from the engine, they tend to warp slightly even though the engine is allowed to cool before being removed. The spreader tool allows the technician to line up the bolt holes without doing any harm to the manifold.


MUFFLERSSound is air vibration. When the vibrations are large, the sound is loud. The muffler catches the large bursts of high-pressure exhaust gas from the cylinder, smoothing out the pressure pulses and allowing them to be released at an even and constant rate.

FIGURE 6-19 Exhaust gases expand and cool as they travel through the passages in the muffler.


WHY IS THERE A HOLE IN MY MUFFLER?FIGURE 6-20 A hole in the muffler allows condensed water to escape.


MORE AIRFLOW MORE POWERFIGURE 6-21 A high-performance aftermarket air filter often can increase airflow into the engine for more power.


SUMMARYAll air entering an engine must be filtered.Engines that use throttle-body injection units are equipped with intake manifolds that keep the airflow speed through the manifold at 50 to 300 feet per second.Most intake manifolds have an EGR valve that regulates the amount of recirculated exhaust that enters the engine to reduce NOX emissions.Exhaust manifolds can be made from cast iron or stainless steel.The exhaust system also contains a catalytic converter, exhaust pipes, and muffler. The entire exhaust system is supported by rubber hangers that isolate the noise and vibration of the exhaust from the rest of the vehicle.


REVIEW QUESTIONSWhy is it necessary to have intake charge velocities of about 50 feet per second?Why can fuel-injected engines use larger (and longer) intake manifolds and still operate at low engine speed?What is a tuned runner in an intake manifold?How does a muffler quiet exhaust noise?


CHAPTER QUIZIntake charge velocity has to be _____ to prevent fuel droplet separation.25 feet per second50 feet per second100 feet per second300 feet per second


CHAPTER QUIZIntake charge velocity has to be _____ to prevent fuel droplet separation.25 feet per second50 feet per second100 feet per second300 feet per second


CHAPTER QUIZ2.The intake manifold of a port fuel-injected engine _____.Uses a dual heat riserContains a leaner airfuel mixture than does the intake manifold of a TBI systemContains only fuel (gasoline)Contains only air


CHAPTER QUIZ2.The intake manifold of a port fuel-injected engine _____.Uses a dual heat riserContains a leaner airfuel mixture than does the intake manifold of a TBI systemContains only fuel (gasoline)Contains only air


CHAPTER QUIZ3.Why are the EGR gases cooled before entering the engine on some engines?Cool exhaust gas is more effective at controlling NOX emissionsTo help prevent the exhaust from slowing downTo prevent damage to the intake valveTo prevent heating the airfuel mixture in the cylinder


CHAPTER QUIZ3.Why are the EGR gases cooled before entering the engine on some engines?Cool exhaust gas is more effective at controlling NOX emissionsTo help prevent the exhaust from slowing downTo prevent damage to the intake valveTo prevent heating the airfuel mixture in the cylinder


CHAPTER QUIZ4.A heated air intake system is usually necessary for proper cold-engine driveability on _____.Port fuel-injection systemsThrottle-body fuel-injection systemsBoth a port-injected and throttle-body injected engineAny fuel-injected engine


CHAPTER QUIZ4.A heated air intake system is usually necessary for proper cold-engine driveability on _____.Port fuel-injection systemsThrottle-body fuel-injection systemsBoth a port-injected and throttle-body injected engineAny fuel-injected engine


CHAPTER QUIZ5.Air filters can remove particles and dirt as small as _____.5 to 10 microns10 to 25 microns30 to 40 microns40 to 50 microns


CHAPTER QUIZ5.Air filters can remove particles and dirt as small as _____.5 to 10 microns10 to 25 microns30 to 40 microns40 to 50 microns


CHAPTER QUIZ6.Why do many port fuel-injected engines use long intake manifold runners?To reduce exhaust emissionsTo heat the incoming airTo increase high-RPM powerTo increase low-RPM torque


CHAPTER QUIZ6.Why do many port fuel-injected engines use long intake manifold runners?To reduce exhaust emissionsTo heat the incoming airTo increase high-RPM powerTo increase low-RPM torque


CHAPTER QUIZ7.Exhaust passages are included in some intake manifolds. Technician A says that the exhaust passages are used for exhaust gas recirculation (EGR) systems. Technician B says that the exhaust heat is used to warm the intake charge on some engines equipped with a throttle-body-type fuel-injection system. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ7.Exhaust passages are included in some intake manifolds. Technician A says that the exhaust passages are used for exhaust gas recirculation (EGR) systems. Technician B says that the exhaust heat is used to warm the intake charge on some engines equipped with a throttle-body-type fuel-injection system. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ8.The lower portion of a two-part intake manifold is often called the _____.HousingLower partPlenumVacuum chamber


CHAPTER QUIZ8.The lower portion of a two-part intake manifold is often called the _____.HousingLower partPlenumVacuum chamber


CHAPTER QUIZ9.Technician A says that a cracked exhaust manifold can affect engine operation. Technician B says that a leaking lower intake manifold gasket could cause a vacuum leak. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ9.Technician A says that a cracked exhaust manifold can affect engine operation. Technician B says that a leaking lower intake manifold gasket could cause a vacuum leak. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ10.Technician A says that some intake manifolds are plastic. Technician B says that some intake manifolds are constructed in two parts or sections: upper and lower. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ10.Technician A says that some intake manifolds are plastic. Technician B says that some intake manifolds are constructed in two parts or sections: upper and lower. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B

Chapter 06

Documents

air pressure

air movement

heated air

air filterfigure

air control valve

engine forces air

intake air temperature

air intake filtrationfigure