INTERNAL COMBUSTION ENGINE

Four-Stroke Cycle

A four-stroke cycle experiences four piston movements over two engine revolutions for each cycle.

Fuel injector

A pressurized nozzle that sprays fuel into the incoming air on SI engines or into the cylinder on CI engines. On SI engines, fuel injectors are located at the intake valve ports on multipoint port injector systems and upstream at the intake manifold inlet on throttle body injector systems. In a few SI engines, injectors spray directly into the combustion chamber.

Two-Stroke Cycle

A two-stroke cycle has two piston movements over one revolution for each cycle.

Internal combustion engines can be classified in Type of Cooling

Air Cooled. Liquid Cooled, Water Cooled.

Supercharged.

Air Intake Process, Intake air pressure increased with the compressor driven off of the engine crankshaft.

Naturally Aspirated.

Air Intake Process, No intake air pressure boost system.

Spark Ignition (SI).

An SI engine starts the combustion process in each cycle by use of a spark plug. The spark plug gives a high-voltage electrical discharge between two electrodes which ignites the air-fuel mixture in the combustion chamber surrounding the plug.

Spark Ignition

An engine in which the combustion process in each cycle is started by use of a spark plug.

Compression Ignition (CI)

An engine in which the combustion process starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression. ________ are often called Diesel engines, especially in the non-technical community.

Internal combustion engines can be classified in Application

Automobile, Truck, Bus. Locomotive. Stationary. Marine. Aircraft. Small Portable, Chain Saw, Model Airplane.

Connecting rod bearing

Bearing where connecting rod fastens to crankshaft.

Block

Body of engine containing the cylinders, made of cast iron or aluminum. In many older engines, the valves and valve ports were contained in the block. Camshaft Rotating shaft used to push open valves at the proper time in the engine cycle, either directly or through mechanical or hydraulic linkage (push rods,The block of water-cooled engines includes a water jacket cast around the cylinders. On air-cooled engines, the exterior surface of the block has cooling fins.

Throttle

Butterfly valve mounted at the upstream end of the intake system, used to control the amount of air flow into an SI engine. Some small engines and stationary constant-speed engines have no throttle.

Overhead Cam (aRC)

Camshaft mounted in engine head, giving more direct control Block Body of engine containing the cylinders, made of cast iron or aluminum. In many older engines, the valves and valve ports were contained in the block. The block of water-cooled engines includes a water jacket cast around the cylinders. On air-cooled engines, the exterior surface of the block has cooling fins.of valves which are also mounted in engine head.

Method of Fuel Input for SI Engines

Carbureted. Multipoint Port Fuel Injection. Throttle Body Fuel Injection.

Catalytic converter

Chamber mounted in exhaust flow containing catalytic material that promotes reduction of emissions by chemical reaction.

Gasohol.

Common fuel consisting of 90% gasoline and 10% alcohol.

Engine Management System

Computer and electronics used to control smart engine.

In-Line

Cylinders are positioned in a straight line, one behind the other along the length of the crankshaft. They can consist of 2 to 11 cylinders or possibly more. In-line four-cylinder engines are very common for automobile and other applications. ________ engines are sometimes called straight (e.g., straight six or straight eight).

Exhaust system

Flow system for removing exhaust gases from the cylinders, treating them, and exhausting them to the surroundings. It consists of an exhaust manifold which carries the exhaust gases away from the engine, a thermal or catalytic converter to reduce emissions, a muffler to reduce engine noise, and a tailpipe to carry the exhaust gases away from the passenger compartment.

Direct Injection (DI)

Fuel injection into the main combustion chamber of an engine. Engines have either one main combustion chamber (open chamber) or a divided combustion chamber made up of a main chamber and a smaller connected secondary chamber.

Indirect Injection (IDI)

Fuel injection into the secondary chamber of an engine with a divided combustion chamber.

Head gasket

Gasket which serves as a sealant between the engine block and head where they bolt together. They are usually made in sandwich construction of metal and composite materials. Some engines use liquid head gaskets.

Internal combustion engines can be classified in Fuel Used

Gasoline. Diesel Oil or Fuel Oil. Gas, Natural Gas, Methane. LPG. Alcohol-Ethyl, Methyl. Dual Fuel. Gasohol.

Piston rings

Metal rings that fit into circumferential grooves around the piston and form a sliding surface against the cylinder walls.

Clearance Volume

Minimum volume in the combustion chamber with piston at TDC.

Fan

Most engines have an engine-driven fan to increase air flow through the radiator and through the engine compartment, which increases waste heat removal from the engine. Fans can be driven mechanically or electrically, and can run continuously or be used only when needed.

Stroke

Movement distance of the piston from one extreme position to the other: TDC to BDC or BDC to TDC.

Oil pan

Oil reservoir usually bolted to the bottom of the engine block, making up part of the crankcase. Acts as the oil sump for most engines.

Water pump

Pump used to circulate engine coolant through the engine and radiator. It is usually mechanically run off of the engine.

Oil pump

Pump used to distribute oil from the oil sump to required lubrication points. The oil pump can be electrically driven, but is most commonly mechanically driven by the engine. Some small engines do not have an oil pump and are lubricated by splash distribution.

Air-Fuel Ratio (AF)

Ratio of mass of air to mass of fuel input into engine.

Fuel-Air Ratio (FA)

Ratio of mass of fuel to mass of air input into engine.

Oil sump

Reservoir for the oil system of the engine, commonly part of the crankcase. Some engines (aircraft) have a separate closed reservoir called a dry sump.

Connecting rod

Rod connecting the piston with the rotating crankshaft, usually made of steel or alloy forging in most engines but may be aluminum in some small engines.

Flywheel

Rotating mass with a large moment of inertia connected to the crankshaft of the engine. The purpose of the flywheel is to store energy and furnish a large angular momentum that keeps the engine rotating between power strokes and smooths out engine operation. On some aircraft engines the propeller serves as the flywheel, as does the rotating blade on many lawn mowers.

Crankshaft

Rotating shaft through which engine work output is supplied to external systems.

Camshaft

Rotating shaft used to push open valves at the proper time in the engine cycle, either directly or through mechanical or hydraulic linkage (push rods, rocker arms, tappets).

W Engine.

Same as a V engine except with three banks of cylinders on the same crankshaft. Not common, but some have been developed for racing automobiles, both modern and historic. Usually 12 cylinders with about a 60° angle between each bank.

starter

Several methods are used to start IC engines. Most are started by use of an electric motor (starter) geared to the engine flywheel. Energy is supplied from an electric battery.

Glow plug

Small electrical resistance heater mounted inside the combustion chamber of many CI engines, used to preheat the chamber enough so that combustion will occur when first starting a cold engine. The glow plug is turned off after the engine is started.

T Head engines.

Some historic engines with valves in block had the intake valve on one side of the cylinder and the exhaust valve on the other side. These were called

Brake Maximum Torque (BMT)

Speed at which maximum torque occurs.

Speed control-cruise control

Speed control-cruise control Automatic electric-mechanical control system that keeps the automobile operating at a constant speed by controlling engine speed.

Water jacket

System of liquid flow passages surrounding the cylinders, usually constructed as part of the engine block and head. Engine coolant flows through the water jacket and keeps the cylinder walls from overheating. The coolant is usually a water-ethylene glycol mixture.

Main bearing

The bearings connected to the engine block in which the crankshaft rotates. The maximum number of main bearings would be equal to the number of pistons plus one, or one between each set of pistons plus the two ends. On some less powerful engines, the number of main bearings is less than this maximum.

Cylinders

The circular cylinders in the engine block in which the pistons reciprocate back and forth. The walls of the cylinder have highly polished hard surfaces. Cylinders may be machined directly in the engine block, or a hard metal (drawn steel) sleeve may be pressed into the softer metal block.

Compression Ignition (CI).

The combustion process in a CI engine starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression.

Piston

The cylindrical-shaped mass that reciprocates back and forth in the cylinder, transmitting the pressure forces in the combustion chamber to the rotating crankshaft.

Ignition Delay (ID)

Time interval between ignition initiation and the actual start of combustion.

Turbocharger

Turbine-compressor used to compress incoming air into the engine. The turbine is powered by the exhaust flow of the engine and thus takes very little useful work from the engine.

V Engine

Two banks of cylinders at an angle with each other along a single crankshaft. The angle between the banks of cylinders can be anywhere from 15° to 120°, with 60°-90° being common.

Opposed Cylinder Engine.

Two banks of cylinders opposite each other on a single crankshaft (a V engine with a 180°V). These are common on small aircraft and some automobiles with an even number of cylinders from two to eight or more. These engines are often called flat engines (e.g., flat four).

Opposed Piston Engine.

Two pistons in each cylinder with the combustion chamber in the center between the pistons. A single-combustion process causes two power strokes at the same time, with each piston being pushed away from the center and delivering power to a separate crankshaft at each end of the cylinder. Engine output is either on two rotating crankshafts or on one crankshaft incorporating complex mechanical linkage.

Crankcase Compressed.

Two-stroke cycle engine which uses the crankcase as the intake air compressor. Limited development work has also been done on design and construction of four-stroke cycle engines with crankcase compression.

Valves

Valves Used to allow flow into and out of the cylinder at the proper time in the cycle.

Overhead Valve (ORV)

Valves mounted in engine head.

Carburetor

Venturi flow device which meters the proper amount of fuel into the air flow by means of a pressure differential. For many decades it was the basic fuel metering system on all automobile (and other) engines. It is still used on lowcost small engines like lawn mowers, but is uncommon on new automobiles.

Displacement or Displacement Volume

Volume displaced by the piston as it travels through one stroke. Displacement can be given for one cylinder or for the entire engine (one cylinder times number of cylinders). Some literature calls this swept volume.

clearance volume.

When the piston is at TDC, the volume in the cylinder is a minimum called the __________.

Valves in head (overhead valve)

also called I Head engine.

Valves in block (flat head)

also called L Head engine.

internal combustion engine

is a heat engine that converts chemical energy in a fuel into mechanical energy, usually made available on a rotating output shaft.

Bore

Diameter of the cylinder or diameter of the piston face, which is the same minus a very small clearance.

Spark plug

Electrical device used to initiate combustion in an SI engine by creating a high-voltage discharge across an electrode gap. Spark plugs are usually made of metal surrounded with ceramic insulation. Some modern spark plugs have built-in pressure sensors which supply one of the inputs into engine control.

Fuel pump

Electrically or mechanically driven pump to supply fuel from the fuel tank (reservoir) to the engine. Many modern automobiles have an electric fuel pump mounted submerged in the fuel tank. Some small engines and early automobiles had no fuel pump, relying on gravity feed.

Single Cylinder

Engine has one cylinder and piston connected to the crankshaft.

Reciprocating

Engine has one or more cylinders in which pistons reciprocate back and forth. The combustion chamber is located in the closed end of each cylinder. Power is delivered to a rotating output crankshaft by mechanical linkage with the pistons.

Rotary

Engine is made of a block (stator) built around a large non-concentric rotor and crankshaft. The combustion chambers are built into the nonrotating block.

Wide-Open Throttle (WOT)

Engine operated with throttle valve fully open when maximun power and/or speed is desired.

Smart Engine

Engine with computer controls that regulate operating characteristics such as air-fuel ratio, ignition timing, valve timing, exhaust control, intake tuning, etc. Computer inputs come from electronic, mechanical, thermal, and chemical sensors located throughout the engine.

Radial Engine.

Engine with pistons positioned in a circular plane around the central crankshaft. The connecting rods of the pistons are connected to a master rod which, in turn, is connected to the crankshaft. A bank of cylinders on a radial engine always has an odd number of cylinders ranging from 3 to 13 or more.

Throttle Body Fuel Injection.

Injectors upstream in intake manifold.

Turbocharged.

Intake air pressure increased with the turbine-compressor driven by the engine exhaust gases

Radiator

Liquid-to-air heat exchanger of honeycomb construction used to remove heat from the engine coolant after the engine has been cooled. The radiator is usually mounted in front of the engine in the flow of air as the automobile moves forward. An engine-driven fan is often used to increase air flow through the radiator.

Supercharge

Mechanical compressor powered off of the crankshaft, used to compress incoming air of the engine.

Push rods

Mechanical linkage between the camshaft and valves on overhead valve engines with the camshaft in the crankcase. Many push rods have oil passages through their length as part of a pressurized lubrication system.

Cooling fins

Metal fins on the outside surfaces of cylinders and head of an aircooled engine. These extended surfaces cool the cylinders by conduction and convection.

Multipoint Port Fuel Injection.

One or more injectors at each cylinder intake.

F Head engine

One valve in head (usually intake) and one in block, also called

Crankcase

Part of the engine block surrounding the rotating crankshaft. In many engines, the oil pan makes up part of the crankcase housing.

Wrist pin

Pin fastening the connecting rod to the piston (also called the piston pin).

Exhaust manifold

Piping system which carries exhaust gases away from the engine cylinders, usually made of cast iron.

Exhaust manifold

Piping system which carries exhaust gases away from the enginecylinders, usually made of cast iron.

Intake manifold

Piping system which delivers incoming air to the cylinders, usually made of cast metal, plastic, or composite material. In most SI engines, fuel is added to the air in the intake manifold system either by fuel injectors or with a carburetor. Some intake manifolds are heated to enhance fuel evaporation. The individual pipe to a single cylinder is called a runner.

Top-Dead-Center (TDC)

Position of the piston when it stops at the furthest point away from the crankshaft.

Bottom-Dead-Center (BDC)

Position of the piston when it stops at the point closest to the crankshaft.

Combustion chamber

The end of the cylinder between the head and the piston face where combustion occurs. The size of the combustion chamber continuously changes from a minimum volume when the piston is at TDC to a maximum when the piston is at BDC.

Head

The piece which closes the end of the cylinders, usually containing part of the clearance volume of the combustion chamber. The head is usually cast iron or aluminum, and bolts to the engine block. In some less common engines, the head is one piece with the block. The head contains the spark plugs in SI engines and the fuel injectors in CI engines and some SI engines. Most modern engines have the valves in the head, and many have the camshaft(s) positioned there also (overhead valves and overhead cam).