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Automotive Fuels

Automotive Fuels. Gasoline (C 8 H 15 ). Gasoline is refined from crude oil Performance characteristics of gasoline Anti-knock quality Volatility Sulfur content Deposit control. Anti-knock Quality. Measured by the octane number Research octane number (RON) Motor octane number (MON)

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Automotive Fuels

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  1. Automotive Fuels

  2. Gasoline (C8H15) • Gasoline is refined from crude oil • Performance characteristics of gasoline • Anti-knock quality • Volatility • Sulfur content • Deposit control

  3. Anti-knock Quality • Measured by the octane number • Research octane number (RON) • Motor octane number (MON) • Unknown fuel is compared to a mixture of isooctane and heptane • Isooctane has an octane number of 100 • Heptane has an octane number of 0 • If a mixture of 87% isooctane and 13% heptane is burned in a test engine, and create the same knock intensity as the unknown fuel, the octane number of the unknown fuel is 87

  4. RON vs. MON • MON and RON are determined at different preset rpm, and air inlet temperature settings - The average of these two are what you see on the gas pump

  5. Factors Affecting Octane Requirements • Compression ratio • Ignition timing • Air to fuel ratio • Combustion temperature • Inlet air temperature • EGR rate (exhaust gas recirculation) • Combustion chamber design • Barometric pressure • Ambient temperature • Humidity • Combustion chamber deposits

  6. Cetane Number • Cetane is the rating system used for diesel • Similar to the octane ratings of gasoline • The higher the cetane number, the shorter the lag time between fuel injection and ignition • The higher the cetane number the quicker and more easily the diesel fuel burns

  7. Volatility • Volatility describes how easily various fuels will evaporate • Measured by Reid vapor pressure • The higher the RVP the more volatile the fuel, which means it will vaporize more easily

  8. Reid Vapor Pressure 0 0 Fuel A Fuel B 70 F 70 F 100 F Water

  9. Reid Vapor Pressure 7 5 Fuel A Fuel B 100 F 100 F 100 F Water

  10. Volatility • During the summer fuel manufacturer’s blend fuels with lower RVP • This prevents problems such as vapor lock • During the winter fuel manufacturer’s blend fuels with higher RVP • This aids in cold startup

  11. Gasoline Additives • Tetraethyl lead • Alcohol • Methyl tertiary butyl ether (MTBE) • Ethyl tertiary butyl ether (ETBE) • Tertiary amyl methyl ether (TAME) • Deposit control additives

  12. Tetraethyl Lead • Used to lubricate valve stems • And upper cylinder walls • Restricted in 1973 and completely phased out in 1996 • Still used in aviation and some racing applications • Used in some foreign countries • Coats the surface of catalytic converters and renders them inoperative

  13. Alcohol • Used as an oxygenator • Used to reduce CO emissions • Absorbs moisture (hydroscopic) • Increases the octane rating

  14. Methyl Tertiary Butyl Ether (MTBE) • Increases octane by 2.5 to 3.0 • Used as an oxygenator to reduce CO emissions • Will not affect RVP • Carcinogen • Studies have shown groundwater containing excessive amounts of MTBE in areas using it as a fuel additive

  15. Ethyl Tertiary Butyl Ether (ETBE) • Increases octane number up to 3 points • Lowers RVP

  16. Tertiary amyl methyl ether (TAME) • Performance similar to ETBE

  17. Deposit Control Additives • Required in gasoline year round as of 1995 • Used to control deposits on or in: • Port fuel injectors • Intake valves • Combustion chambers

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