Small Gasoline Engines Engine Define Engine: Are these engines? A. YES: An engine or motor is a machine designed to convert energy into useful mechanical motion Engine Define Engine: What is the primary difference between these engines and modern engines? Heat Engine How does modern engines use heat? Two general categories based on how the heat is used. External combustion engine Internal combustion engine Internal Combustion Engines Small Engine Development Year Engine Designer/developer 1680 Gunpowder Christian Huygens 1698 Savery Pump Thomas Saverly 1712 Newcomen Steam Thomas Newcomen 1763 Watt Double-acting steam James Watt 1801 Coal gas/electric ignition Eugene Lebon 1802 High pressure steam Richard Trevithick 1859 Pre-mixed fuel and air Etienne Lenoir 1862 Gasoline Nikolaus Otto 1876 Four cycle gasoline Nikolaus Otto 1892 Diesel Rudolf Diesel 1953 Die-cast aluminum B&S Internal Combustion--Intro Engine designs can be classified by: 1. Size 2. Ignition system 3. Strokes per cycle 4. Cylinder orientation 5. Crankshaft orientation 6. Control system 7. Cooling system 1. Engine Size Engines are available in a wide range of sizes. Industry definition: “A small engine is an internal combustion engine rated up to 25 horsepower.” 1. Size - Largest The Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine is the most powerful and most efficient prime-mover in the world today. The cylinder bore is just under 38" and the stroke is just over 98". Each cylinder displaces 111,143 cubic inches (1,820 liters) and produces 7,780 horsepower. Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the fourteen cylinder version. 1. Size - Smallest • Not much bigger than a stack of pennies, the "mini engine" is the first engine of its size to deliver power on a continuous basis. • Currently will produce 2.5 watts of electricity (0.00335 hp). • Uses 1/2 fluid ounce of fuel per hour 3. Cycles Four stroke Two stroke Name one common use for each type. 4. - Cylinder Orientation There is no limit on the number of cylinders that a small engines can have, but it is usually 1 or 2. Four common cylinder orientations for small engines Vertical Slanted Horizontal Multi position Give an example of a use for each. 4. - Cylinder Orientation—cont. Three common cylinder configuration in multiple cylinder engines: V Horizontally opposed In-line Can you identify one application for each of these types? 5. Crankshaft Orientation Small gas engines use three crankshaft orientations: Multi-position Horizontal Vertical Identify a use for each one. 6. Controls Traditionally engines are controlled by mechanical means. Governor Throttle Choke Etc. Honda has an engine with an electronic control unit (ECU). ECU - Electronic Control Unit – Monitors and controls engine functions including Throttle, Choke, Ignition Timing, Oil Alert – Offers programmable governor and throttle modes for unprecedented flexibility and diagnostic LED for trouble shooting – Stepper motors precisely control throttle and choke position 7. Cooling System Small engines use two types of cooling systems: – Air – Water Why does an internal combustion engine need a cooling system? Why what are the advantages and disadvantages of both systems? 7. Cooling system—cont. Convection – Transfer of heat via transfer from one material in contact with another (Water boiling in a pan) Conduction – Transfer of heat via movement within the material being heated Radiation – Transfer of heat through the air 7. Cooling System—cont. How is excess heat moved within and removed from the engine? 7. Cooling system—cont. Q. Why is it important to understand the transfer of heat in a small engine? A. Heat is one of the single biggest hazards to an engine. Why? Internal Temperatures can reach 3600 Degrees F Exhaust Manifolds can reach 1800 Degrees F ***Aluminum melts at around 1200 Degrees F*** ***Cast Iron melts at around 2300 Degree F*** The cooling system of an Aluminum Engine is critical to its efficient operation and life. Cooling System So how does a Small Engine Cool? Conduction/Convection/Radiation? A. All of the above, and all three methods must be maintained for efficient operation. Fuel/Air Ignition by Convection heats the engine, The Cylinder (mostly) transfers heat to cooling fins by Conduction and the flywheel/shroud transfer heat by Radiation. Example of a cooling system failure include scared cylinder walls, valve warpage, broken crank, connecting rod or cam, and engine seizure. Cooling System Servicing Air-Cooled Engines Most small, single-cylinder engines are cooled by a stream of air developed by fan blades on the flywheel. The air stream is deflected around the cylinder and cylinder head by a metal or plastic cover called a shroud. Additional engine heat is dissipated through cooling fins around the cylinder. Servicing air-cooled systems is generally very easy but often overlooked. Here's how to service an air-cooled system: Step 1: Periodically (annual inspection) remove the shroud from around the engine flywheel and inspect the inside for debris. Step 2: With the shroud removed, visually inspect the flywheel blades for debris and damage. NOTE: Broken Flywheel Blades DO NOT move air! Step 3: Visually inspect cooling fins on the cylinder and cylinder head. Use a wooden stick or clean paintbrush to clear away any debris. When the engine is cool, wipe the surfaces of the cooling fins, cylinder, and cylinder head with a cloth. Remember that even the tip of a cooling fin can have a surface temperature of over 100 degrees Farenheit (38 degrees Celsius). NOTE: Broken cooling fins CAN NOT transfer heat. Oil and grease on a cooling fins WILL PREVENT efficient transfer of heat. Step 4: Replace the shroud over the flywheel and cylinder. Make sure the flywheel blades aren't striking the shroud. Liquid Cooling Systems Circulating fluid (coolant) assists in removing heat of combustion Coolant is usually a mixture of antifreeze and water Coolant must be changed periodically to remove corrosion and replace additives UT Extension Antifreeze Types Ethylene glycol (green) Propylene glycol (green) Long-Life ethylene glycol (orange) UT Extension Replacing Antifreeze* Regular antifreeze – Drain, flush and replace every one to two years Long life antifreeze – Drain, flush, replace every 5 years or 100,000 to 150,000 miles * Additives include corrosion inhibitors, sealers, water pump lubricant, heat transfer compounds UT Extension Toxicity Ethylene glycol – very toxic Propylene glycol – non toxic* * Will be slightly toxic after use in cooling system – picks up contaminants such as lead, mercury UT Extension Freeze Protection Pure antifreeze – minus 9 F 50% water + 50% antifreeze – minus 34 F 30% water + 70% antifreeze – minus 84 F UT Extension Boil-Over Protection Pure antifreeze – 98 degrees F 50% water + 50% antifreeze – 265 F 30% water + 70% antifreeze – 282 F UT Extension Mixing Anti-Freezes Regular antifreeze (green) and Long-life antifreeze (orange) cannot be mixed !!!!!!! Regular antifreeze contains alkaline corrosion inhibitors Long life antifreeze contains organic acid corrosion inhibitors UT Extension Physical Principles of Engines Energy Energy is the capacity for doing work. What are the two forms of energy? Which form are these? Physical Principles of Engines Intake Compression Power Exhaust Physical Principles of Engines Intake System • Air Intake • Fuel Intake Main Causes of Premature Small Engine Failure (Short Engine Life) UT Extension Dirt 60% to 70% of all failures are caused by dirt* getting into engine *Dust, insects, bits of grass, etc. UT Extension Service air filter on a regular basis (usually once a season) Service more often under dusty or adverse conditions UT Extension For every gallon of gasoline used, the air filter must clean 10,000 to 11,000 gallons of air UT Extension Air Filter – Paper Type UT Extension Carburetor UT Extension Failure to use clean, fresh fuel Dirty fuel tank Dirty fuel can Dirty funnel Trash/dirt around fuel cap UT Extension Install a fuel filter on fuel line if not factory equipped UT Extension Fuel Filter UT Extension Use a suitable fuel container to prevent fuel contamination and insure safety Metal cans will eventually rust inside Plastic containers will not rust Use a funnel with mesh filter UT Extension Can Good Plastic Fuel UT Extension Failure to use proper fuel Unleaded fuel is cleaner burning Choose proper fuel octane level Do not use fuel containing alcohol Use lead substitutes if 1974 or older UT Extension Operating tips to extend engine life Let engine idle for two minutes before stopping Never stop under load Avoid stalls and sudden impacts UT Extension Small Engines Ignition System Ignition-Power Stroke Spark ignition Compression ignition What is the primary difference? 2. Ignition Spark ignition Compression ignition What is the primary difference? Ignition System Function Ignite the fuel and air mixture at the proper time. Advance and retard the ignition timing as needed. “Ground-out” the ignition system so the engine will stop running. Ignition Parts Battery type Battery Ignition coil Ignition switch Low voltage wires (battery volts) Ignition Pick-up ( points or electronic) High Voltage wire(s) Spark Plug Ignition Principles Electromagnetic Induction How does the Ignition Coil work? Primary winding: creates a magnetic field by running current through it. When we open the circuit current stops, and the electromagnetic field collapses. Ignition Coil Parts Primary Winding Secondary Winding Iron Core Switching current in Primary Breaker Points and condenser Points: Mechanical switch Condenser: makes the switch last longer so the points don’t “ burn out” Self Induction When you run current through a coil of wire, you create a magnetic field. When you “open” the current flow through that coil of wire you collapse that magnetic field into itself. Coil output You produce about 1 volt per turn of wire Example: 225 turns of coil wire can produce up to 225 volts, however your current output drops at the same rate that you voltage increases.