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Chapter 1
Internal Combustion Engines
Engine Classification • Small Engine
Development • Energy Conservation
Principles • Small Engine History
Chapter 1 — Internal Combustion Engines
Competencies
 Explain the classification “small engine” and discuss the
main small engine types.
 Describe types of cylinder design and cooling systems.
 Explain small engine development history.
 Explain energy conversion principles that apply to small
engines.
 Explain heat transfer.
 List the common energy conversion calculations.
 Explain the chemistry of fuel combustion in small engines.
 Describe the small engine industry.
Chapter 1 — Internal Combustion Engines
Small Engines
 internal combustion engine
 converts heat energy from the
combustion of fuel into mechanical energy
 rated up to 25 horsepower (HP)
 spark ignition or compression
 four-stroke or two-stroke cycle
Chapter 1 — Internal Combustion Engines
Engine Design
 one, two, or four cylinders
 cylinder orientation

vertical, horizontal, or slanted
 cylinder configuration

V, horizontally-opposed, or in-line
 air-cooled or liquid-cooled
Chapter 1 — Internal Combustion Engines
Development History
 gunpowder engine
 steam engine
 coal gas
 internal
combustion
 gasoline power
 diesel engine
Chapter 1 — Internal Combustion Engines
Energy Conversion Principles
 small engines convert potential energy
into kinetic energy
 all internal combustion engines operate
utilizing basic principles of heat, force,
pressure, torque, work, power, and
chemistry
Chapter 1 — Internal Combustion Engines
Heat Transfer
 conduction is heat transfer from atom to
atom via molecules in direct contact
 convection is heat transfer by currents in
a fluid
 radiation is heat transfer that occurs as
radiant energy without a material carrier
Chapter 1 — Internal Combustion Engines
Energy Conversion
Calculations
 temperature is the intensity of heat


°C = (°F – 32) ÷ 1.8
°F = (1.8 × °C) + 32
 pressure is a force acting on a unit of
area

pressure = force ÷ area
Chapter 1 — Internal Combustion Engines
Energy Conversion
Calculations
 torque is a force acting on a
perpendicular radial distance from a
point of rotation

torque = force × radius
 work is the movement of an object by a
constant force

work = force × distance
Chapter 1 — Internal Combustion Engines
Energy Conversion
Calculations
 power is the rate at which work is done

power = work ÷ time
 horsepower (HP) is a measure of power
equal to 76 watts or 33,000 lb-ft per min

HP = work ÷ (time × 33,000)
Chapter 1 — Internal Combustion Engines
Combustion Chemistry
 combining of hydrocarbon fuel with
oxygen
 a chemical reaction between the
hydrocarbon molecule and atmospheric
oxygen combining at ignition temperature
causes an exchange of elements that
releases heat energy
Chapter 1 — Internal Combustion Engines
Small Engine Industry
 outdoor power
equipment
manufacturers
 service
technicians
 Briggs & Stratton
MST program
Chapter 1 — Internal Combustion Engines
Chapter 1 Review
In a typical small engine, approximately
what percent of the energy released is
converted into useful work?

Approximately 30% of the energy is
converted into useful work.
What is horsepower?

Horsepower is a unit of power equal to
33,000 lb-ft per min.