Your SlideShare is downloading. ×
0
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Ch15
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
183
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
0
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1.  
  • 2. OBJECTIVES
    • After studying Chapter 15, the reader should be able to:
        • Prepare for ASE Engine Performance (A8) certification test content area “C” (Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair).
        • 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.
  • 3. GASOLINE
    • Gasoline is a term used to describe a complex mixture of various hydrocarbons refined from crude petroleum oil for use as a fuel in engines. The word petroleum means “rock oil.”
  • 4. VOLATILITY
    • Volatility describes how easily the gasoline evaporates (forms a vapor). The definition of volatility assumes that the vapors will remain in the fuel tank or fuel line and will cause a certain pressure based on the temperature of the fuel.
    (Continued)
  • 5.
    • Reid vapor pressure (RVP) is the pressure of the vapor above the fuel when the fuel is at 100 。 F (38 。 C ). Increased vapor pressure permits the engine to start in cold weather. Gasoline without air will not burn. Gasoline must be vaporized (mixed with air) to burn in an engine.
    (Continued)
  • 6.
    • The American Society for Testing and Materials (ASTM) standards for winter-blend gasoline allow volatility of up to 15 pounds per square inch (psi) RVP.
    • At warm ambient temperatures, gasoline vaporizes easily.
    (Continued)
  • 7.
    • The volatility of summer-grade gasoline should be about 7.0 psi RVP. According to ASTM standards, the maximum RVP should be 10.5 psi for summer-blend gasoline.
    • At higher temperatures, liquid gasoline can easily vaporize, which can cause vapor lock.
    (Continued)
  • 8.
    • If winter-blend gasoline (or high-RVP fuel) is used in an engine during warm weather, the following problems may occur:
      • Rough idle
      • Stalling
      • Hesitation on acceleration
      • Surging
    • The RVP can be tested using the test kit
    (Continued)
  • 9. Figure 15-1 This gasoline testing kit includes an insulated container where water at 100 degrees F is used to heat a container holding a small sample of gasoline. The reading on the pressure gauge is the Reid vapor pressure (RVP).
  • 10. NORMAL AND ABNORMAL COMBUSTION
    • The octane rating of gasoline is the measure of its antiknock properties. Engine knock (also called detonation, spark knock, or ping) is a metallic noise an engine makes, usually during acceleration, resulting from abnormal or uncontrolled combustion inside the cylinder.
    (Continued)
  • 11.
    • Normal combustion occurs smoothly and progresses across the combustion chamber from the point of ignition.
    (Continued)
  • 12.
    • During periods of spark knock (detonation), the combustion speed increases by up to 10 times to near the speed of sound. The increased combustion speed also causes increased temperatures and pressures, which can damage pistons, gaskets, and cylinder heads.
    (Continued)
  • 13. Figure 15-2 Normal combustion is a smooth, controlled burning of the air-fuel mixture.
  • 14. Figure 15-3 Detonation is a secondary ignition of the air-fuel mixture. It is also called spark knock or pinging.
  • 15. OCTANE RATING
    • The antiknock standard or basis of comparison was the knock-resistant hydrocarbon isooctane, chemically called trimethylpentane (C8H18), also known as 2 2 4 trimethylpentane. If a gasoline tested had the exact same antiknock characteristics as isooctane, it was rated as 100-octane gasoline.
    (Continued)
  • 16.
    • If the gasoline tested had only 85% of the antiknock properties of isooctane, it was rated as 85 octane. Octane rating is only a comparison test.
    • The two basic methods used to rate gasoline for antiknock properties (octane rating) are:
      • research method
      • motor method.
    (Continued)
  • 17.
    • Each uses a model of the special cooperative fuel research (CFR) single-cylinder engine. The research method and the motor method vary as to temperature of air, spark advance, and other parameters. The research method typically results in readings that are six to ten points higher than those of the motor method.
    (Continued)
  • 18.
    • The octane rating posted on pumps in the United States is the average of the two methods and is referred to as (R + M)/2, meaning that, for the fuel used in the previous example, the rating posted on the pumps would be:
      • RON + MON = 93 + 85 = 89
      • 2 2
  • 19. GASOLINE GRADES AND OCTANE NUMBER
    • The posted octane rating on gasoline pumps is the rating achieved by the average of the research and the motor methods.
    (Continued)
  • 20.
    • Except in high-altitude areas, the grades and octane ratings are as follows:
    (Continued) 91 or higher Premium 89 Midgrade (also called Plus) 87 Regular Octane Rating Grades
  • 21. Figure 15-4 A typical fuel pump showing regular (87 octane), midgrade (89 octane), and premium (92 octane). These ratings can vary with brand as well as in different parts of the country, especially in high altitude areas where the ratings are lower.
  • 22. OCTANE IMPROVERS
    • When gasoline companies, under federal EPA regulations, removed tetraethyl lead from gasoline, other methods were developed to help maintain the antiknock properties of gasoline. Octane improvers (enhancers) can be grouped into three broad categories:
    (Continued)
  • 23.
      • Aromatic hydrocarbons (hydrocarbons containing the benzene ring) such as xylene and toluene
      • Alcohols such as ethanol (ethyl alcohol), methanol (methyl alcohol), and tertiary butyl alcohol (TBA)
      • Metallic compounds such as methylcyclopentadienyl manganese tricarbonyl (MMT)
    (Continued)
  • 24.
      • NOTE: MMT has been proven to be harmful to catalytic converters. However, MMT is currently one of the active ingredients commonly found in octane improvers available to the public and in some gasoline sold in Canada.
  • 25. OXYGENATED FUELS
    • Oxygenated fuels contain oxygen in the molecule of the fuel itself. Examples of oxygenated fuels include methanol, ethanol, methyl tertiary butyl ether (MTBE), tertiary-amyl methyl ether (TAME), and ethyl tertiary butyl ether (ETBE).
    (Continued)
  • 26.
    • Methyl Tertiary Butyl Ether (MTBE)
      • MTBE does not increase the volatility of the fuel, and is not as sensitive to water as are other alcohols. The maximum allowable volume level, according to the EPA, is 15% but is currently being phased out due to concern with MTBE contamination of drinking water if spilled from storage tanks.
    (Continued)
  • 27.
    • Tertiary-amyl Methyl Ether
      • Tertiary-amyl methyl ether (TAME) is often added to gasoline as an oxygenater.
    • Ethyl Tertiary Butyl Ether
      • ETBE is derived from ethanol. The maximum allowable volume level is 17.2%.
    (Continued)
  • 28.
    • Ethanol
      • Ethyl alcohol is drinkable alcohol made from grain. Adding 10% ethanol (ethyl alcohol or grain alcohol) increases the (R + M)/2 octane rating by three points. The alcohol added to the base gasoline, however, also raises the volatility of the fuel about 0.5 psi. Most automobile manufacturers permit up to 10% ethanol if driveability problems are not experienced.
    (Continued)
  • 29.
    • Methanol
      • Methyl alcohol is made from wood (wood alcohol), natural gas, or coal. Methanol is poisonous if ingested and tends to be more harmful to the materials in the fuel system and tends to separate when combined with gasoline unless used with a cosolvent.
    (Continued)
  • 30.
      • A cosolvent is another substance (usually another alcohol) that is soluble in both methanol and gasoline and is used to reduce the tendency of the liquids to separate.
    (Continued)
  • 31.
    • CAUTION: All alcohols can absorb water, and the alcohol-water mixture can separate from the gasoline and sink to the bottom of the fuel tank. This process is called phase separation .
    • The advantages and disadvantages of using alcohol as an additive to gasoline can be summarized in the following manner.
    (Continued)
  • 32.
      • Advantages
        • Alcohol absorbs moisture in the fuel tank.
        • Ten percent alcohol added to gasoline raises the octane rating - (R + M)/2 - by three points.
        • Alcohol cleans the fuel system.
        • Alcohol reduces CO emissions because it contains oxygen.
    (Continued)
  • 33.
      • Disadvantages
        • The use of alcohol can result in the clogging of fuel filters with dirt and other debris cleaned from the fuel tank, pump, and lines.
        • Alcohol raises the volatility of fuel about 0.5 psi; this can cause hot-weather driveability problems.
        • Alcohol reduces the heat content of the resulting fuel mixture (it has about one-half of the energy content of gasoline): 60,000 to 75,000 British thermal units (BTUs) per gallon for alcohol versus about 130,000 BTUs per gallon for gasoline.
    (Continued)
  • 34.
        • Alcohol absorbs water and then separates from the gasoline, especially as temperature drops. Separated alcohol and water on the bottom of the tank can cause hard starting during cold weather. Alcohol does not vaporize easily at low temperatures.
    (Continued)
  • 35. Figure 15-5 This fuel tank indicates that the gasoline is blended with 10% ethanol (ethyl alcohol).
  • 36. Figure 15-6 This container holds pure gasoline and water. Notice how the water separates and sinks to the bottom.
  • 37. TESTING GASOLINE FOR ALCOHOL CONTENT
    • Take the following steps when testing gasoline for alcohol content.
      • Pour suspect gasoline into a small clean beaker or glass container.
        • DO NOT SMOKE OR RUN THE TEST AROUND SOURCES OF IGNITION!
        • Carefully fill the graduated cylinder to the 10-mL mark.
    (Continued)
  • 38.
        • Add 2 mL of water to the graduated cylinder by counting the number of drops from an eyedropper. (Before performing the test, the eyedropper must be calibrated to determine how many drops equal 2.0 mL.)
        • Put the stopper in the cylinder and shake vigorously for 1 minute. Relieve built-up pressure by occasionally removing the stopper. Alcohol dissolves in water and will drop to the bottom of the cylinder.
    (Continued)
  • 39.
        • Place the cylinder on a flat surface and let it stand for 2 minutes.
        • Take a reading near the bottom of the cylinder at the boundary between the two liquids.
        • For percent of alcohol in gasoline, subtract 2 from the reading and multiply by 10. For example,
          • The reading is 3.1 mL: 3.1 - 2 = 1.1 X 10 = 11% alcohol
          • The reading is 2.0 mL: 2 - 2 = 0 X 10 = 0% alcohol (no alcohol)
        • If the increase in volume is 0.2% or less, it may be assumed that the test gasoline contains no alcohol.
    (Continued)
  • 40.
    • Stoichiometric Air-fuel Ratio
    • If the combustion process is complete, all gasoline or HCs will be completely combined with all the available oxygen. This total combination of all components of the fuel is called stoichiometric air-fuel ratio.
    (Continued)
  • 41.
    • The stoichiometric quantities for gasoline are 14.7 parts air for 1 part gasoline by weight. Different fuels have different stoichiometric proportions.
    6.4:1 About 60,000 Methanol Alcohol 9.0:1 About 76,000 Ethanol Alcohol 14.7:1 About 130,000 Gasoline Stoichiometric Ratio Heat Energy (BTU / gal) Fuel
  • 42. HIGH-ALTITUDE OCTANE REQUIREMENTS
    • As the altitude increases, atmospheric pressure drops. The air is less dense because a pound of air takes more volume. The octane rating of fuel does not need to be as high because the engine cannot intake as much air. This process will reduce the combustion (compression) pressures inside the engine.
    (Continued)
  • 43.
    • In mountainous areas, gasoline (R + M)/2 octane ratings are two or more numbers lower than normal (according to SAE, about one octane number lower per 1000 ft or 300 m in altitude).
    (Continued)
  • 44. Figure 15-7 A pump showing E-85 which contains 85.7% ethanol and 15% gasoline. This fuel can be used in flexible fuel vehicles only.
  • 45. VALVE RECESSION AND UNLEADED FUEL
    • Vehicle engines produced after 1971 for sale in the United States were required to operate on unleaded fuel. Most engine manufacturers started induction hardening of valve seats to help prevent valve recession.
  • 46. REFORMULATED GASOLINE
    • Reformulated gasoline (RFG) is manufactured by refiners to help reduce emissions. The gasoline refiners reformulate gasoline by using additives that contain at least 2% oxygen by weight and reducing the additive benzenes to a maximum of 1% by value.
    (Continued)
  • 47.
    • Two other major changes done at the refineries are as follows:
      • Reduce light compounds. Refineries eliminate butane, pentane, and propane, which have a low boiling point and evaporate easily. These unburned hydrocarbons are released into the atmosphere during refueling and through the fuel tank vent system, contributing to smog formation.
    (Continued)
  • 48.
      • Reduce heavy compounds. Refineries eliminate heavy compounds with high boiling points such as aromatics and olefins. The purpose of this reduction is to reduce the amount of unburned hydrocarbons that enter the catalytic converter. Increased use of oxygen-containing MTBE helps the combustion process to reduce emissions.
  • 49. GENERAL GASOLINE RECOMMENDATIONS
    • To help ensure proper engine operation and keep fuel costs to a minimum, follow these guidelines:
      • Purchase fuel from a busy station to help ensure that it is fresh and less likely to be contaminated with water or moisture.
    (Continued)
  • 50.
      • Keep the fuel tank above one-quarter full, especially during seasons in which the temperature rises and falls by more than 20 。 F between daytime highs and nighttime lows. This helps to reduce condensed moisture in the fuel tank and could prevent gas line freeze-up in cold weather.
      • Do not purchase fuel with a higher octane rating than is necessary.
    (Continued)
  • 51.
      • Avoid using gasoline with alcohol in warm weather, even though many alcohol blends do not affect engine driveability. If warm-engine stumble, stalling, or rough idle occurs, change brands of gasoline.
    (Continued)
  • 52.
      • Do not purchase fuel from a retail outlet when a tanker truck is filling the underground tanks. During the refilling procedure, dirt, rust, and water may be stirred up in the underground tanks. This undesirable material may be pumped into your vehicle's fuel tank.
    (Continued)
  • 53.
      • Do not overfill the gas tank. After the nozzle clicks off, add just enough fuel to round up to the next dime. Adding additional gasoline will cause the excess to be drawn into the charcoal canister. This can lead to engine flooding and excessive exhaust emissions.
      • Be careful when filling gasoline containers.
  • 54. ALWAYS FILL A GAS CAN ON THE GROUND
    • Aircraft are always filled with fuel from a tanker truck after a ground strap is attached to both the plane and the truck and then attached to ground.
    (Continued)
  • 55. Figure 15-8 Many gasoline service stations have signs posted warning customers to place plastic fuel containers on the ground while filling. If placed in a trunk or pickup truck bed equipped with a plastic liner, static electricity could build up during fueling and discharge from the container to the metal nozzle creating a spark and possible explosion. Some service stations have warning signs stating not to use cell phones while fueling to help avoid the possibility of an accidental spark creating a fire hazard.

×