Engine Design and Classofocation Chapter 12 Lesson 1 Engine Design and Classofocation

Engine Classifications Even though basic parts are the same, design differences can change the way engines operate and how they are repaired For this reason, you must be able to classify engines

Common Engine Classifications Cylinder arrangement Number of cylinders Cooling system type Valve location Camshaft location

Common Engine Classifications Combustion chamber design Type of fuel burned Type of ignition Number of strokes per cycle Number of valves per cylinder Type of aspiration

Cylinder Arrangement Refers to the position of the cylinders in relation to the crankshaft There are five basic cylinder arrangements: inline V-type slant W-type opposed

Cylinder Arrangement

Number of Cylinders Most car and truck engines have either 4, 6, or 8 cylinders Some may have 3, 5, 10, 12, or 16 cylinders Engine power and smoothness are enhanced by using more cylinders

Cylinder Numbering Engine manufacturers number each engine cylinder to help technicians make repairs Service manual illustrations are usually provided to show the number of each cylinder Cylinder numbers may be cast into the intake manifold

Firing Order Refers to the sequence in which the cylinders fire Determined by the position of the crankshaft rod journals in relation to each other May be cast into the intake manifold Service manual illustrations are usually provided to show the firing order

Cylinder Numbering and Firing Order

Cooling System Type There are two types of cooling systems: Liquid cooling system surrounds the cylinder with coolant coolant carries combustion heat out of the cylinder head and engine block Air cooling system circulates air over cooling fins on the cylinders air removes heat from the cylinders

Cooling System Type A. Air cooling B. Liquid cooling

Fuel Type Engines are classified by the type of fuel used Gasoline engines burn gasoline Diesel engines burn diesel fuel Liquefied petroleum gas (LPG), gasohol (10% alcohol, 90% gasoline), and pure alcohol can also be used to power an engine

Ignition Type Two basic methods are used to ignite the fuel in an engine combustion chamber: spark ignition (spark plug) compression ignition (compressed air)

Uses an electric arc at the spark plug to ignite the fuel Spark Ignition Engine Uses an electric arc at the spark plug to ignite the fuel

Compression Ignition Engine Squeezes the air in the combustion chamber until it is hot enough to ignite the fuel

Valve Location Engines are classified by the location of the valves: L-head engine also called a flat head engine I-head engine also called an overhead valve (OHV) engine

Both the intake and exhaust valves are in the block L-Head Engine Both the intake and exhaust valves are in the block

Both valves are in the cylinder head I-Head Engine Both valves are in the cylinder head

Camshaft Location There are two basic locations for the engine camshaft: Camshaft located in the block cam-in-block engine Camshaft located in the cylinder head overhead cam (OHC) engine

Cam-in-Block Engine Uses push rods to transfer motion to the rocker arms and valves Also called an overhead valve (OHV) engine

Camshaft is located in the top of the cylinder head Overhead Cam Engine Camshaft is located in the top of the cylinder head

Overhead Cam Engine OHC engines may use one or two camshafts per cylinder head Single overhead cam (SOHC) engine uses only one camshaft per cylinder head Dual overhead cam (DOHC) engine uses two camshafts per cylinder head one cam operates the intake valves, while the other cam operates the exhaust valves