Engine Construction and Principles of Operation Chapter 4
Objectives Explain simple engine operation. List the qualities of gasoline that make it an efficient fuel for small engines. Explain why gasoline is atomized in the small engine. Identify the basic components of a small engine and describe the function of each part.
How does an Engine Work?
Gasoline Hydrocarbon fuel (mix of hydrogen and carbon) Gas should Ignite readily, burn cleanly, resist detonation Vaporize easily w/o vapor lock Free of dirt, water, and abrasives
Octane Number Ability to resist detonation Low Compression = Regular High Compression = Premium Video 1 Video 2
Octane Number Lead Oxygenates Ethanol
How does gasoline burn? Liquid? Vapor? Atomizing
Containing Our Explosion Minimizing Lost Energy Combustion Chamber
Questions on Page 71
Cylinder Block Keeps all parts aligned Cast Iron Aluminum Alloy
Cooling Fins Function Design
Crankshaft Major rotating part of the engine Forged or Cast Steel with precisely machined and ground bearings
Crankshaft Counterweights Crankpin or Connecting Rod Journal Throw Flywheel PTO
Crankcase Rigid and Strong Keep Parts Aligned Hold Oil and Keep Out Dirt
Piston Straight line driving member of the engine Subject to direct heat from combustion
Piston Adequate clearance to allow for expansion Piston rings Compression Ring: Scraper Ring (Compression): Oil Ring:
Piston Ring grooves Characteristics of a Piston Wrist Pin (Piston Pin): Retainers
Connecting Rod Connects piston to crankshaft Bearings Bearing Cap
Intake and Exhaust Ports Ports (Two Stroke) Poppet Valves
Poppet Valves Intake (Usually Larger): Exhaust:
Poppet Valves Valve Face Valve Seat Valve Stem
Poppet Valves Valve Guide Valve Spring Valve Rotator Retainer (Keeper) Pin Collar Keyhole
Valve Lifter or Tappet Link b/w camshaft lobe and valve stem
Camshaft Timing Gear Lobe Compression Release Position?
Flywheel Three Functions Momentum Cooling Ignition/Accessories
Objectives Explain simple engine operation. List the qualities of gasoline that make it an efficient fuel for small engines. Explain why gasoline is atomized in the small engine. Identify the basic components of a small engine and describe the function of each part.