Presentation on theme: "Small Engine Theory What is the purpose of a Small Engine?"— Presentation transcript:
1Small Engine Theory What is the purpose of a Small Engine? When does a small engine Get classified into a large engine?
2Internal Combustion Engine Internal: To happen insideCombustion: Burning of some sort of fuel and air.Engine: Converts heat energy into a useful mechanical energy.
3Four Main PartsPistonConnecting RodCylinderCrankshaft
4PistonA plunger that slides in the cylinder converting heat energy into mechanical energyLight weight material (Aluminum alloy) so it can spin at high revolutions per minute.Must withstand pressures up to 2,000PSIMust withstand heat up to 1,200 FMust not expand
5Connecting Rod Used to connect the piston to the crankshaft I-Beam construction, saves weight and makes the rod stronger.Connecting rod cap is bolted to the end with the use of two hardened bolts.Piston pin connects piston to the connecting rod
6Cylinder Made from Aluminum alloy or Cast iron TWO PARTS OF THE CYLINDER ARE:Cylinder HeadCylinder Block
7Cylinder Head Houses the combustion chamber and the spark plug. I-Head (OHV) Houses:all the above plus valves, seats, valve guides, intake and exhaust ports, rocker stud, pushrod guide plate.
8Cylinder Block The foundation for all moving parts. Houses the cylinder: the area the piston moves up and down in.Houses the crankshaftMakes-up the crankcase, area where the crankshaft rotates.Houses the following in a L-head engine;
9ValvesValve SeatsIntake and Exhaust PortsValve Springs and RetainersTappetsCamshaft
10Crankshaft Made of nodular steel. Changes Reciprocating motion into rotary motion.PartsPTO JOURNALROD JOURNALMAGNETO JOURNALCOUNTER-WEIGHTS
11FLYWHEELCarries the crankshaft through the three non power producing strokes.A heavy weight; takes a lot of energy to start and stopProvides the crankshaft with inertia.
12COMBUSTION CHAMBERArea in the cylinder head where fuel and air are burned.Spark plug is always located in the combustion chamber.
13FuelA combustible that will burn effectively in the combustion chamberTypesGasoline (petro)DieselPropaneCompressed natural gas
14Fuel Stages Liquid Atomized Vaporized Purchased and delivered to the carburetor in this state.AtomizedCarburetor mixes with air in this state. To the proper stochiometric ratio of 14:1 air to fuelVaporizedFuel becomes a gas in the combustion chamber on the compression stroke
15Valve trainAll components that allow for the transfer of fuel and air both fresh and burnt.
16Valves Open and close the combustion chamber. Seals the combustion chamber.Allows for the transfer of fuel and air.
17Valve seatsInserts in the block or head that allow the valves face to rest on, and to cool and seal the combustion chamber.Made from high carbon steel to withstand high heat and pressure.
18Valve guideTube like structure in the head or block that guides the valve, and is concentric with the valve seat.
20Valve RetainersUsed to retain the valve spring onto the valve.
21CamshaftUsed to open and close the valves at the proper time (phasing), for a specific length of time (duration).Driven by the crankshaft.Gear, chain or belt driven
22Tappets/ LiftersUsed to transfer the motion of the camshaft to the valve (L-head) or the push-rod (ohv)
23Passageways Fuel and Air must pass into and out of the combustion chamber. Fresh fuel and air is called INTAKE Burnt fuel and air is called EXHAUST Cylinder head passageways are called PORTS MANIFOLD passageways are called RUNNERS
24Four stroke cycle Intake Compression Power Exhaust
25Intake stroke Piston moves down from TDC to BDC Intake stroke Piston moves down from TDC to BDC. Cylinder creates a vacuum. Fuel and Air rush into the cylinder when the Intake Valve opens. Cylinder is now filled with the fresh fuel and air charge. Exhaust valve stays closed.
26Compression Piston moves from BDC to TDC Compression Piston moves from BDC to TDC. Fuel and Air is squeezed so tight that heat is generated. Fuel becomes Vaporized. Intake and Exhaust valves are closed.
27Power Piston moves from TDC to BDC Power Piston moves from TDC to BDC. Fuel and air is Ignited by the spark plug. Fast burning of the fuel creates a tremendous heat and pressure increase. Pressure forces the piston down with 2000 PSI of Force. Both the Intake and Exhaust valves are closed.
28Exhaust Piston moves from BDC to TDC Exhaust valve opens, Intake stays closedBurnt fuel and air is forced out of the exhaust Ports and exhaust manifold Runners.