Halderman ch024 lecture

Objectives The student should be able to: Prepare for ASE Engine Performance (A8) certification test content area “C” (Air Induction and Exhaust Systems Diagnosis and Repair). Discuss the purpose and function of intake air system components.

Objectives The student should be able to: Explain the differences between throttle-body fuel-injection manifolds and port fuel-injection manifolds. List the materials used in exhaust manifolds and exhaust systems. Describe the purpose and function of the exhaust system components.

Air Intake Filtration Need for Air Filtering Gasoline must be mixed with air for combustion Air movement into engine occurs due to vacuum created in engine

Figure 24-1 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 Filtration Need for Air Filtering Dirt in air cannot reach engine Air filter and cleaner remove contaminants

Air Intake Filtration Need for Air Filtering Three jobs of air cleaner and filter Clean air before it is mixed with fuel Silence intake noise

Air Intake Filtration Need for Air Filtering Three jobs of air cleaner and filter Act as flame arrester in case of backfire

Air Intake Filtration Need for Air Filtering Automotive engine uses 9,000 gallons (34,000 liters) of air per gallon of gasoline in air-fuel ratio of 14.7:1 by weight Abrasive particles cause wear inside engine

Air Intake Filtration Need for Air Filtering Filter is in air cleaner housing Stamped steel Composite (usually nylon reinforced plastic)

Air Intake Filtration Air Filter Elements Paper air filter element most common Paper stock contains tiny passages in fibers

Air Intake Filtration Air Filter Elements Airflow passes through several fiber surfaces Fiber surfaces trap microscopic particles

Air Intake Filtration Air Filter Elements Most air filters trap particles larger than 10 to 25 microns NOTE: A person can see objects 40 microns or larger in size. Human hair is about 50 microns in diameter.

Figure 24-2 Dust and dirt in the air are trapped in the air filter so they do not enter the engine.

Air Intake Filtration Filter Replacement Manufacturers recommend cleaning or replacing air filter elements at periodic intervals Replace filter before it becomes too dirty to be effective

Air Intake Filtration Remotely Mounted Air Filters and Ducts Air cleaner and duct design depend on size, shape, location, and vehicle body construction Port fuel-injection systems generally use horizontally mounted throttle body

Air Intake Filtration Remotely Mounted Air Filters and Ducts Some systems have mass airflow (MAF) sensor between throttle body and air cleaner Design issues make it is more efficient to use remote air cleaner placement

Figure 24-3 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.

Air Intake Filtration Remotely Mounted Air Filters and Ducts Turbocharged engines require remote air filter placement Air filter connects to air inlet elbow on turbocharger

Air Intake Filtration Remotely Mounted Air Filters and Ducts Heat generated by turbocharger requires remote placement of air filter Air filter connected to turbocharger by composite ducting

Air Intake Filtration Air Filter Restriction Indicator Connections must be airtight Vehicles driven in dusty conditions often have air filter restriction indicators

Air Intake Filtration Air Filter Restriction Indicator Device warns if filter is restricted and needs replacement Device operates by detecting drop in air pressure

Air Intake Filtration Air Filter Restriction Indicator Typical calibration of indicator 15 to 20 in. of water (in. H 2 O) for gasoline engines

Air Intake Filtration Air Filter Restriction Indicator Typical calibration of indicator 20 to 30 in. of water (in. H 2 O) for diesel engines

Air Intake Filtration Air Filter Restriction Indicator Unit of inches of water measures difference in air pressure before and after air filter

Air Intake Filtration Air Filter Restriction Indicator 28 in. of water equals pound per square inch (PSI) Some air filter restriction indicators use electrical switch to light dash-mounted warning light ?

Figure 24-4 A typical air filter restriction indicator used on a General Motors truck engine. The indicator turns red when it detects enough restriction to require a filter replacement.

Figure 24-5 (a) Note the discovery as the air filter housing was opened during service on a Pontiac. The nuts were obviously deposited by squirrels (or some other animal).

Figure 24-5 (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.

Figure 24-6 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 MANIFOLDS

Throttle-Body Injection Intake Manifolds Terminology Intake manifold also called inlet manifold Smooth engine operation occurs only when each combustion chamber produces same pressure

Throttle-Body Injection Intake Manifolds Terminology All cylinders must receive exactly same quality and quantity of charge Charges must have same physical properties and air-fuel mixture

Throttle-Body Injection Intake Manifolds Terminology Throttle-body fuel injector forces tiny droplets of liquid fuel into incoming air to form combustible air-fuel mixture

Figure 24-7 A throttle-body injection (TBI) unit used on a GM V-6 engine.

Throttle-Body Injection Intake Manifolds Intake Air Speeds Droplets begin to evaporate when they leave throttle-body injector nozzles Droplets stay in the charge as long as charge flows at high velocities

Throttle-Body Injection Intake Manifolds Intake Air Speeds At maximum engine speed, velocity may reach 330 ft per second Separation of droplets from charge as it passes through manifold occurs when velocity drops below 50 ft per second

Throttle-Body Injection Intake Manifolds Intake Air Speeds At idle speed, intake charge velocities may drop below 50 ft per second

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Cross section large enough for maximum power

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Cross section small enough so equal mixtures reach each cylinder

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Racing manifolds must be large enough to reach maximum horsepower

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Large size allows charge to move slowly

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Fuel separation occurs at low engine speeds

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifold sizes and shapes represent compromise Fuel separation leads to poor accelerator response

Figure 24-8 Heavy fuel droplets separate as they flow around an abrupt bend in an intake manifold.

Throttle-Body Injection Intake Manifolds Intake Air Speeds Standard passenger vehicle engines designed for economy under light load, partial-throttle operation

Throttle-Body Injection Intake Manifolds Intake Air Speeds Manifolds have smaller cross-sectional area than racing engines Small sizes keep flow velocities high through normal operating speeds

PORT FUEL-INJECTION INTAKE MANIFOLDS

Port Fuel-Injection Intake Manifolds Terminology Size and shape of port fuel-injected engine intake manifolds can be optimized because only air is in the manifold

Port Fuel-Injection Intake Manifolds Terminology Fuel injector located in intake manifold 3 to 4 in (70 to 100 mm) from intake valve

Port Fuel-Injection Intake Manifolds Terminology Runner length and shape designed for tuning only No need to keep air-fuel mixture homogenized

Port Fuel-Injection Intake Manifolds Terminology Intake manifolds tuned to improve performance Long runners build low-RPM torque

Port Fuel-Injection Intake Manifolds Terminology Intake manifolds tuned to improve performance Shorter runners provide maximum high-RPM power

Figure 24-9 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 intake runner is about 24 in. long.

Figure 24-10 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.

Throttle-Body Injection Intake Manifolds Variable Intakes Some engines with four valve heads use dual or variable intake runners At low engine speeds, long intake runners give low-speed torque

Throttle-Body Injection Intake Manifolds Variable Intakes At high engine speeds, shorter intake runners increase high-speed power Many intake manifolds have both long and short intake runners Valves that control air flow are computer controlled

Figure 24-11 The air flowing into the engine can be directed through long or short runners for best performance and fuel economy.

Throttle-Body Injection Intake Manifolds Plastic Intake Manifolds Most intake manifolds are made from thermoplastic molded Some manifolds are molded in two parts and bonded together

Throttle-Body Injection Intake Manifolds Plastic Intake Manifolds Plastic intake manifolds have smoother interior surfaces for greater airflow

Figure 24-12 Many plastic intake manifolds are constructed using many parts glued together to form complex passages for airflow into the engine.

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Many intake manifolds are constructed in two parts Lower section attaches to cylinder heads and have passages from intake ports

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Many intake manifolds are constructed in two parts Upper manifold, called plenum, connects to lower unit

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Many intake manifolds are constructed in two parts Upper manifold includes long passages

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Many intake manifolds are constructed in two parts Throttle body attaches to upper intake

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Two-part intake manifolds allow easier manufacturing and assembly Two-part intake manifold create additional locations for leaks

Throttle-Body Injection Intake Manifolds Upper and Lower Intake Manifolds Leak in lower intake manifold can affect operation of engine Leak in upper intake manifold results in vacuum leak only

EXHAUST GAS RECIRCULATION PASSAGE

Exhaust Gas Recirculation Passages Purpose and Function To reduce emission of oxides of nitrogen (NOx), engines have exhaust gas recirculation (EGR) valves

Exhaust Gas Recirculation Passages Purpose and Function Most EGR valves are mounted on intake manifold Some newer engines do not require EGR system

Exhaust Gas Recirculation Passages Purpose and Function EGR valve opens at speeds above idle EGR valve allows small portion of exhaust gas (5% to 10%) to enter intake manifold

Exhaust Gas Recirculation Passages Purpose and Function EGR system interconnects exhaust and intake manifolds EGR valve controls gas flow through passages On V-type engines, intake manifold crossover provides exhaust gas

Exhaust Gas Recirculation Passages Purpose and Function EGR valve controls gas flow through passages On inline-type engines, external tube carries exhaust gas to EGR valve

Exhaust Gas Recirculation Passages Exhaust Gas Coolers Exhaust gases are more effective in reducing NOx emissions if exhaust is cooled before entering cylinders Tube is long so exhaust gas is cooled before entering EGR valve

Figure 24-13 A typical long exhaust gas line used to cool the exhaust gases before being recirculated back into the intake manifold.

Exhaust Manifolds Purpose and Function Exhaust manifold collects high-temperature spend gases from head exhaust ports and connects them to exhaust system

Figure 24-14 The exhaust gases are pushed out of the cylinder by the piston on the exhaust stroke.

Exhaust Manifolds Purpose and Function Hot gases are sent to exhaust pipe, catalytic converter, muffler, resonator, and tailpipe

Exhaust Manifolds Purpose and Function Exhaust system designed to meet these needs Provide least possible restriction or backpressure

Exhaust Manifolds Purpose and Function Exhaust system designed to meet these needs Keep exhaust noise to minimum

Exhaust Manifolds Purpose and Function Exhaust gas temperature varies

Exhaust Manifolds Purpose and Function Manifold must operate at engine idle and full power

Exhaust Manifolds Purpose and Function Temperature of exhaust manifold can exceed 1,500°F (815°C)

Exhaust Manifolds Construction Most exhaust manifolds are made from the following Cast iron Steel tubing

Exhaust Manifolds Construction Manifold temperature usually reaches high-temperature extremes Manifold is bolted to head to allow expansion and contraction

Exhaust Manifolds Construction Many manifolds have heat shields to protect spark plug wires and improve emissions

Figure 24-16 Many exhaust manifolds are constructed of steel tubing and are free flowing to improve engine performance.

Exhaust Manifolds Exhaust Manifold Gaskets Exhaust heat expands manifold more than head Heat causes exhaust manifold to slide on sealing surface of head

Exhaust Manifolds Exhaust Manifold Gaskets Heat causes thermal stress Removing manifold for service may cause manifold to warp

Exhaust Manifolds Exhaust Manifold Gaskets Manifold gaskets seal slightly warped manifolds If gasket has facing on one side only, put facing against head

Exhaust Manifolds Exhaust Manifold Gaskets Gaskets are used on new engines with tubing- or header-type exhaust manifolds Gaskets may have several layers of steel for high-temperature sealing ?

Figure 24-18 Typical exhaust manifold gaskets. Note how they are laminated to allow the exhaust manifold to expand and contract due to heating and cooling.

Figure 24-19 An exhaust manifold spreader tool is absolutely necessary when reinstalling exhaust manifolds. When they are removed from the engine, the manifolds 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 harming the manifold.

Exhaust Manifolds Exhaust Manifold Gaskets Many new engines do not use gaskets with cast exhaust manifolds

Mufflers Purpose and Function When the exhaust valve opens, it releases a strong air pressure The air pressure produces an explosion

Mufflers Purpose and Function Muffler catches bursts of high-pressure exhaust in perforated tubes Smoothing out bursts of pressure quiets exhaust

Figure 24-20 Exhaust gases expand and cool as they travel through passages in the muffler.

Mufflers Construction Most mufflers have larger inlet diameter than outlet diameter Cooler exhaust is denser and requires less volume

Mufflers Construction Resonators and catalytic converters also functions as mufflers Tailpipe releases exhaust gases away from vehicle

Mufflers Construction Muffler and tailpipe are supported by hangers Hangers isolate exhaust noise from vehicle

Mufflers Construction Types of exhaust system hangers Rubberized fabric with metal ends Rubber materials that look like rubber bands ?

Figure 24-21 A hole in the muffler allows condensed water to escape.

Figure 24-22 A high-performance aftermarket air filter often can increase airflow into the engine for more power.

TECH TIP Always Check the Air Filter Always inspect the air filter and the air intake system carefully during routine service. Debris or objects deposited by animals can cause a restriction to the airflow and can reduce engine performance. BACK TO PRESENTATION Figure 24-5 (a) Note the discovery as the air filter housing was opened during service on a Pontiac. The nuts were obviously deposited by squirrels (or some other animal). Figure 24-5 (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.

FREQUENTLY ASKED QUESTION What Does This Tube Do? What is the purpose of the odd-shape tube attached to the inlet duct between the air filter and the throttle body, as seen in FIGURE 24–6? ? BACK TO PRESENTATION The tube shape is designed to dampen out certain resonant frequencies that can occur at specific engine speeds. The length and shape of this tube are designed to absorb shock waves that are created in the air intake system and to provide a reservoir for the air that will then be released into the airstream during cycles of lower pressure. This resonance tube is often called a Helmholtz resonator, named for the discoverer of the relationship between shape and value of frequency, Herman L. F. von Helmholtz (1821–1894) of the University of Hönizsberg in East Prussia. The overall effect of these resonance tubes is to reduce the noise of the air entering the engine. Figure 24-6 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.

FREQUENTLY ASKED QUESTION How Can a Cracked Exhaust Manifold Affect Engine Performance? Cracks in an exhaust manifold will not only allow exhaust gases to escape and cause noise, but also allow air to enter the exhaust manifold. SEE FIGURE 24–17. ? BACK TO PRESENTATION Exhaust flows from the cylinders as individual puffs or pressure pulses. Behind each of these pressure pulses, a low pressure (below atmospheric pressure) is created. Outside air at atmospheric pressure is then drawn into the exhaust manifold through the crack. This outside air contains 21% oxygen and is measured by the oxygen sensor (O 2 S). The air passing the O 2 S signals the engine computer that the engine is operating too lean (excess oxygen) and the computer, not knowing that the lean indicator is false, adds additional fuel to the engine. The result is that the engine will be operating richer (more fuel than normal) and spark plugs could become fouled by fuel, causing poor engine operation. Figure 24-17 A crack in an exhaust manifold is often not visible because a heat shield usually covers the area. A crack in the exhaust manifold upstream of the oxygen sensor can fool the sensor and affect engine operation.

TECH TIP Using the Correct Tool Saves Time When cast-iron exhaust manifolds are removed, the stresses built up in the manifolds often cause the manifolds to twist or bend. This distortion even occurs when the exhaust manifolds have been allowed to cool before removal. Attempting to reinstall distorted exhaust manifolds is often a time-consuming and frustrating exercise. BACK TO PRESENTATION However, special spreading jacks can be used to force the manifold back into position so that the fasteners can be lined up with the cylinder head. Figure 24-19 An exhaust manifold spreader tool is absolutely necessary when reinstalling exhaust manifolds. When they are removed from the engine, the manifolds 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 harming the manifold.

FREQUENTLY ASKED QUESTION Why Is There a Hole in My Muffler? Many mufflers are equipped with a small hole in the lower rear part to drain accumulated water. About 1 gallon of water is produced in the form of steam for each gallon of gasoline burned. The water is formed when gasoline is burned in the cylinder. Water consists of two molecules of hydrogen and one of oxygen (H 2 O). ? BACK TO PRESENTATION The hydrogen (H) comes from the fuel and the oxygen (O) comes from the air. During combustion, the hydrogen from the fuel combines with some of the oxygen in the air to form water vapor. The water vapor condenses on the cooler surfaces of the exhaust system, especially in the muffler, until the vehicle has been driven long enough to fully warm the exhaust above the boiling point of water (212°F [100°C]). Figure 24-21 A hole in the muffler allows condensed water to escape.

HIGH PERFORMANCE TIP More Airflow = More Power One of the most popular high-performance modifications is to replace the factory exhaust system with a low-restriction design and to replace the original air filter and air filter housing with a low-restriction unit, as shown in FIGURE 24–22. BACK TO PRESENTATION The installation of an aftermarket air filter not only increases power, but also increases air induction noise, which many drivers prefer. The aftermarket filter housing, however, may not be able to effectively prevent water from being drawn into the engine if the vehicle is traveling through deep water. Almost every modification that increases performance has a negative effect on some other part of the vehicle, or else the manufacturer would include the change at the factory. Figure 24-22 A high-performance aftermarket air filter often can increase airflow into the engine for more power.

Halderman ch024 lecture

More Related Content

What's hot (20)

Viewers also liked (7)

Similar to Halderman ch024 lecture (20)

More from mcfalltj (20)

Recently uploaded (20)

Halderman ch024 lecture

Editor's Notes