Engine Design and Classification Chapter 12 Lesson 3 Engine Design and Classification
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
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
Two-Stroke-Cycle Engine Operation
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
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
Two-Stroke-Cycle Engine Operation
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
Typical Automotive Engines
Provides the lowest center of gravity of any piston engine Horizontally Opposed Provides the lowest center of gravity of any piston engine
Features four chain-driven camshafts and 32 valves Overhead Cam V-8
Inline SOHC This 16-valve, four-cylinder engine has a belt-driven camshaft and a balance shaft
This engine uses many aluminum parts Fuel-Injected V-8 This engine uses many aluminum parts
Each cylinder head contains two camshafts DOHC V-6 Each cylinder head contains two camshafts
Note the reciprocating assembly and the valve train V-8 Engine Note the reciprocating assembly and the valve train
Six-cylinder engine with a rear drive belt for the injection pump Inline Diesel
Two roller chains drive the overhead camshafts V-12 Engine Two roller chains drive the overhead camshafts