Chapter 5 Principles of Engine Operation, Two- and Four-Stroke Engines
95
which the engine is intended. It cannot be said that
one type of engine is better than another without
considering every aspect of its application.
The chart in Figure 5-16 lists the differences
between two- and four-stroke engines.
Four-Stroke Engine vs.
Two-Stroke Engine
The advantages and disadvantages of any
engine are directly related to the purpose for
Characteristics Four-Cycle Engine (equal hp)
One Cylinder
Two-Cycle Engine (equal hp)
One Cylinder
1. Number of major moving parts Nine Three
2. Power strokes One every two revolutions of crankshaft One every revolution of crankshaft
3. Running temperature Cooler running Hotter running
4. Overall engine size Larger Smaller
5. Engine weight Heavier construction Lighter in weight
6. Bore size equal hp Larger Smaller
7. Fuel and oil No mixture required Must be premixed
8. Fuel consumption Fewer gallons per hour More gallons per hour
9. Oil consumption Oil recirculates and stays in engine Oil is burned with fuel
10. Sound Generally quiet Louder in operation
11. Operation Smoother More erratic
12. Acceleration Slower Very quick
13. General maintenance Greater Less
14. Initial cost Greater Less
15. Versatility of operation Limited slope operation (Receives
less lubrication when tilted)
Lubrication not affected at any
angle of operation
16. General operating efficiency
(hp/wt. ratio)
Less efficient More efficient
17. Pull starting Two crankshaft rotations required to
produce one ignition phase
One revolution produces an ignition
phase
18. Flywheel Requires heavier flywheel to carry
engine through three nonpower strokes
Lighter flywheel
Kohler Co.
Figure 5-16.
This chart lists the differences between two-stroke and four-stroke engines.
Copyright Goodheart-Willcox Co., Inc.