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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

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

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Common Engine Classifications

1. Cylinder arrangement

2. Number of cylinders

3. Cooling system type

4. Valve location

5. Camshaft location

6. Type of fuel burned

7. Type of aspiration

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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

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Cylinder Arrangement

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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

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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

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A. Air cooling

B. Liquid cooling

Cooling System Type

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Fuel Type

Engines are classified by the type of fuel used: Gasoline Diesel Liquefied petroleum gas (LPG), gasohol (10% alcohol, 90% gasoline),

and pure alcohol may also be used

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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

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L-Head Engine

Both the intake and exhaust valves are in

the block

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I-Head Engine

Both valves are in the cylinder head

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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

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Cam-in-Block Engine Uses push rods

to transfer motion to the rocker arms and valves

Also called an overhead valve (OHV) engine

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Overhead Cam

EngineCamshaft is located in the top of the cylinder

head

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Overhead Cam Engine Single overhead cam

(SOHC) engine uses only one camshaft

per cylinder head Dual overhead cam

(DOHC) engine uses two camshafts per

cylinder head One operates the intake

valves, while the other operates the exhaust

Animation Link

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Type of Aspiration

Supercharger – Pump driven by crankshaft forces air into engine.

Turbocharger – Pump driven by exhaust gases forces air into engine.

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Vehicles generally use internal combustion, 4-stroke cycle, reciprocating piston engines

Alternative engines include all other engine types that may be used to power a vehicle

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Rotary Engine

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Rotary Engine Operation

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Steam Engine

Used on some of the first automobiles

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Gas Turbine

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Horizontally Opposed

Provides the lowest center of gravity of any piston engine

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Overhead Cam V-8

Features four chain-driven camshaftsand 32 valves

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Inline SOHC

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

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Fuel-Injected V-8

This engine uses many aluminum parts

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DOHC V-6

Each cylinder head contains two camshafts

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V-8 Engine

Note the reciprocating assemblyand the valve train

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Inline Diesel

Six-cylinder engine with a rear drive belt for the injection pump

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V-12 Engine

Two roller chains drive the overhead

camshafts

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The End