1. Engine Design and Classification
Chapter Lesson 3
Engine Design and Classification

2. Two-Stroke-Cycle Engine
Not used for automotive applications because of high emission levels and poor fuel efficiency
Requires only one revolution of the crankshaft for a complete power-producing cycle
Two piston strokes complete the intake, compression, power, and exhaust events

3. Two-Stroke-Cycle Engine Operation
As the piston moves upward, the air-fuel mixture is compressed
Vacuum is created in the crankcase, which draws fuel and oil into the crankcase
A reed valve or rotary valve controls flow into the crankcase

4. Two-Stroke-Cycle Engine Operation

5. Two-Stroke-Cycle Engine Operation
When the piston reaches the top of the cylinder, ignition occurs
Burning gases force the piston downward
The reed valve or rotary valve closes, compressing and pressurizing the fuel mixture in the crankcase

6. Two-Stroke-Cycle Engine Operation
As the piston moves down in the cylinder, it uncovers the exhaust port
Burned gases leave the cylinder
The piston continues downward, uncovering the transfer port
Pressure in the crankcase causes a fresh fuel charge to flow through the transfer port and into the cylinder

7. Two-Stroke-Cycle Engine Operation

8. Two-Stroke-Cycle Engine Lubrication
The crankcase is used as a storage chamber for each successive fuel charge
Lubricating oil is introduced into the crankcase along with the air-fuel charge to provide lubrication
Inside the crankcase, some of the oil separates from the fuel
The oil mist lubricates and protects the moving parts inside the engine

9. Typical Automotive
Engines

10. Provides the lowest center of gravity of any piston engine
Horizontally Opposed
Provides the lowest center of gravity of any piston engine

11. Features four chain-driven camshafts and 32 valves
Overhead Cam V-8

12. Inline SOHC
This 16-valve, four-cylinder engine has a belt-driven camshaft and a balance shaft

13. This engine uses many aluminum parts
Fuel-Injected V-8
This engine uses many aluminum parts

14. Each cylinder head contains two camshafts
DOHC V-6
Each cylinder head contains two camshafts

15. Note the reciprocating assembly and the valve train
V-8 Engine
Note the reciprocating assembly and the valve train

16. Six-cylinder engine with a rear drive belt for the injection pump
Inline Diesel

17. Two roller chains drive the overhead camshafts
V-12 Engine
Two roller chains drive the overhead camshafts