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Automotive Service Modern Auto Tech Study Guide Chapters 20 & 21 Pages 301 ­ 339 Fuels & Fuel Systems 30 Points Automotive Service 1

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Automotive Service Modern Auto Tech Study Guide Chapters 20 & 21 Pages 301 ­ 339 Fuels & Fuel Systems 30 Points Automotive Service 1 Automotive Service Modern Auto Tech Study Guide Chapters 20 & 21 Pages 301 ­ 339 Fuels & Fuel Systems 30 Points Automotive Service 1. Gasoline, refined from _________, & is a mix of 12% _______ & 82% ______. Petroleum 12% Hydrogen & 82% Carbon Automotive Service Automotive Service 2. The ______________ rating of gasoline is a measurement of the fuel’s ability to resist knock or ping. High octane fuels burn slower than low octane fuels, so they are more resistant to violent burning. Octane Cetane Kerosene Automotive Service 3. _______ octane fuel should be used in engines with high compression ratios (11:1 & higher). Slower Burning ____ octane fuel should be used in engines with low compression ratios (8:1 up to 10.5:1). Faster Burning Automotive Service 4. The oxygenates or octane _____________ now being used in gasoline are ethanol, MBTE, & toluene. Diffusers Enhancers Destabilizers Automotive Service 5. The ___________ air/fuel mixture is the chemically correct a/f mixture. (14.7:1 by weight) (Best for CATALYST efficiency) Volumetric Photogenic Stoichiometric Automotive Service 6. A __________ a/f ratio contains lots of air. _________ a/f mixtures contains less air than stoichiometric Lean = Lots More Air… As compared to Stoichiometric Rich = Lots Less Air… As compared to Stoichiometric 14.7:1 Stoichiometric Air:Fuel Ratio Automotive Service Normal Combustion 8. _____ is abnormal burning that begins before the start of normal combustion. Pre­ignition 7. _________ is destructive, abnormal burning that begins after the start of normal combustion. Detonation Automotive Service 9. _________________, also called run­on or after­run is when the engine keeps running even after the key is turned off. It can be caused by high idle rpm, overheated engine, leaky injectors or hot carbon deposits. Detonation Damage Dieseling = Run­on w/o spark Automotive Service 10. _______ or ________ under load may be caused by pre­ignition, detonation, or advanced spark timing. Knock Sensors Ping or Knock Sting or Spock King or Crock ~~~ Automotive Service 11. Fuel systems have 3 sub systems: the ________ supply, ______ supply, & fuel ________ system Fuel Supply Air Supply Fuel Metering Automotive Service Air Fire Triangle Heat Fuel 1) Compression 2) Spark 66% or 2/3 of the Fire Triangle has to do with the Air & Fuel Delivery System Automotive Service Automotive Service 12. Fuel tanks are made of either metal or plastic and have internal _____________ (dividers) to prevent fuel sloshing. Baffles Waffles Screens Automotive Service 13. Fuel tank caps are sealed off to prevent escape of fuel __________ (HC) to the atmosphere. Vapors Odors Droplets Automotive Service 14. Fuel tank __________­_____________ units pick­up fuel & have a float to sense & send fuel level info. Sending Stickup­Sending Pickup Pickup­Sending Pickup­Spending Automotive Service 15. Fuel lines or hoses are used to route fuel from the tank to the engine where a fuel _______ distributes fuel to the injectors. The fuel rail on an EFI system may contain a schrader valve for diagnostic purposes. Rail Nail Detail Automotive Service 16. Fuel _____________ can be located in the line, on pump, in the tank, inside of the injectors or on the carburetor. Filters Pumps Injectors Automotive Service 17. _____________________ fuel pumps, driven by a cam lobe or eccentric, are used on carbureted engines. Mechanical Electric Pneumatic “Carb­a­saurus” Automotive Service 18. _____________________ fuel pumps, energized with battery power, are used on EFI engines. Mechanical Electric Pneumatic Automotive Service 19. Fuel pumps are commonly tested for their _____________ & their ______________ (capacity). Pressure & Volume Compression & Leakage Spark & Timing Fuel Pressure Gauge Automotive Service 20. Some vehicles are equipped with an ____________ (IFS) switch to shut off the fuel pump after a collision. (Used almost exclusively on Ford® products) Inertia Momentum Pendulum Inertia Fuel Shut­off Automotive Service 21. Some engines have an oil pressure switch to shut off the electric fuel ________ if oil pressure is too low. Silencer opsw Pump Filter Automotive Service 22. Changing the paper ______ ____________ is part of routine maintenance. Dirty filter can lead to a richer A/F ratio and increased CO emissions. Hair Dryer Air Filter Spare Filter Automotive Service 42 gallons in a barrel of crude Automotive Service Automotive Service Automotive Service Automotive Service Pressure Volume Automotive Service The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower­octane gas (like "regular" 87­octane gasoline) can handle the least amount of compression before igniting. Automotive Service The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high­performance engine" has a higher compression ratio and requires higher­octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight ­­ that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more. Automotive Service The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, methane, propane and butane are all hydrocarbons. Methane has a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together. Automotive Service It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well ­­ you can compress it a lot and nothing happens. Eighty­seven­octane gasoline is gasoline that contains 87­percent octane and 13­percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio. Automotive Service What is gasoline? Gasoline is known as an aliphatic hydrocarbon. In other words, gasoline is made up of molecules composed of nothing but hydrogen and carbon arranged in chains. Gasoline molecules have from seven to 11 carbons in each chain. Here are some common configurations: H H H H H H H | | | | | | | H­C­C­C­C­C­C­C­H Heptane | | | | | | | H H H H H H H H H H H H H H H | | | | | | | | H­C­C­C­C­C­C­C­C­H Octane | | | | | | | | H H H H H H H H.
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