automotive chapter definitions Engine

inline engine

In an inline design the cylinders are placed in a single row. There is one crankshaft and one cylinder head for all of the cylinders. the block is cast so that all cylinders are located in an upright position. Inline engine design have certain advantages and disadvantages. They are easy to manufacture and service. However, because the cylinder are positioned vertically, the front of the vehicle must be higher. This affects the aerodynamic design of the car.

opposed cylinder engine

In this design two rows of cylinders are located opposite the crankshaft. These engines have a common crankshaft and a cylinder head on each bank of cylinders. Porsche and Subaru use this style of engine, commonly called a boxer engine. Boxer engines have low center of gravity and tend to run smoothly during all operating conditions.

mid engine transverse

In this design, the engine and drivetrain are positioned between the passenger compartment and rear axle. The mid engine location is found in rear wheel drive, high performance sports cars. The central location of heavy compartments results in a center of gravity very near the center of the vehicle, which vastly improves steering and handling. Since the engine is not under the hood, the hood can be sloped downward, improving aerodynamic and increasing the drivers field of vision. However, engine access and cooling efficiently are reduced. A barrier is also required to reduce the transfer of noise, heat, and vibration into the passenger compartment.

valve train type

Valve trains can be either the overhead camshaft (OHC) or the camshaft in block overhead valve (OHV) design. Some engines have separate camshafts for the intake and exhaust valves. These are based on the OHC design and are called DOUBLE OVERHEAD CAMSHAFT (DOHC) engines. V-types DOHC engines have four camshafts two on each side.

dual mode HCCI

during most driving modes, the engine operates in the HCCI mode. However, the engine does switch to spark ignition at high speeds, heavy acceleration and loads, and cold starting. The latter is necessary because heat is required to cause ignition and when the engine is cold, there is little initial heat. The ability to switch from compression ignition to spark ignition must be done smoothly. This requires precise control of valve timing, air and fuel metering, and ignition timing.

hybrid

most hybrid vehicles have atkinson cycle engine. the low power out put from the engine is supplemented by the power from the electric motors. This combination offers good fuel economy, low emissions, and normal acceleration.

V types

A V type engine design has two rows of cylinders located 60 to 90 degree away from each other. A V type engine uses one crankshaft, which is connected to the piston on both sides of the V. This type of engine has two cylinder heads, one over each row of cylinders. One advantage of using V configuration is that the engine is not as high or long as one with an inline configuration. If eight cylinders are needed for power, a V configuration makes the engine much shorter, lighter, and more compact. Many years ago, some vehicles had an inline eight cylinder engine. The engine was very and its long crankshaft also caused increased torsional vibration in the engine. A variation of v type engine is the w type engine. These engines are basically two v type engines joined together at the crankshaft. This design makes the engine more compact. They are commonly found in the late models Volkswagen, Bentley, and Bugatti Veyron.

battery operated electric vehicle

A battery operated electric vehicle, sometimes referred to as an EV, uses one or more electric motors to turn its drive wheels. The electricity for the motors is stored in batteries that must be recharge by external electrical power source. Normally they are recharge by plugging them into an outlet at home or are recharge by plugging them into an outlet at home or other locations. The recharging time varies with the type of charger, the size and types of battery, and other factors. Normal recharge time is 4 to 8 hours. An electric motor is quiet and has few moving parts. It starts well in the cold, is simple to maintain, and does not burn petroleum products to run. The disadvantages of an EV are limited speed, power, and range as well as the need for heavy, costly batteries. However, an EV is much more efficient than a conventional gasoline-fueled vehicle. EVs are considered zero emissions vehicles because they do not directly pollute the air. The only associated with them is the result of creating the electricity to charge their batteries.

benefits of HCCI

A gasoline HCCI engine could deliver almost the same fuel economy as diesel engine and at a much lower cost. GM estimates that HCCI could improve gasoline engine fuel efficiency by 15 percent, while emitting near zero amounts of NOx and particulate matter. However, a gasoline engine running in the HCCI mode produces more noise and vibrations than a coventional engine. Also, they tend to experience incomplete combustion, which leads to hydrocarbon and carbon monoxide emissions. To rectify this, HCCI engines are fitted with typical emission control systems, including an oxidizing catalytic converter.

four stroke cycle

A stroke is the full travel of the piston either up or down in a cylinder's bore. It takes two full revolutions of the crankshaft to complete the four stroke cycle. One complete rotation of the crankshaft is equal to 360 degrees; therefore, it takes 720 degrees to complete the four stroke cycle. During one piston stroke, the crankshaft rotates 180 degrees. The piston moves down by the pressure produced during combustion, but this moves the piston only enough to complete one stroke. In order to keep the engine running, the piston must travel through the other three strokes. The inertia of a fly wheel attached to the end of the crankshaft keeps the crankshaft rotating and allows the piston complete the rest of the four stroke cycle.

overhead cam OHC

An OHC engine also has the intake and exhaust valves located in the cylinder head. But as the name implies, the camshaft is located in the cylinder head. In an OCH engine, the valves are operated directly by the camshaft or through cam followers or tappets. Engine with one camshaft above a cylinder are often referred to as single overhead SOHC engines. Those with two camshafts per cylinder bank are called dual overhead camshaft DOHC engines.

miller cycle engine

An atkinson cycle engine with forced introduction ( supercharge ) is called a miller cycle engine. The decrease of intake air and resulting low power is compensated for by the supercharger. the

slant cylinder engine

Another way of arranging the cylinders is in a slant configuration. This arrangement is much like an inline engine, except the entire block has been placed at a slant. The slant engine was designed to reduce the distance from top to the bottom of the engine allowing for more aerodynamic vehicle designs.

overhead valve OHV

As the name implies, the intake and exhaust valves in an OHV engine are mounted in the cylinder head and are operated by a camshaft located in the cylinder block. This arrangement requires the use of valve lifters, pushrods, and rocker arms to transfer camshaft rotation to valve movement.

lobe

Cams are raised section of a shaft that have high spots called lobes. Cam lobes are oval shaped. The placement of the lobe on the shaft determines when the valve will open. The height and shape of the lobe determines how far the valve will open and how long it will remain open in relation to piston movement.

basic operation HCCI

During the intake stroke, fuel is injected directly into each cylinder's combustion chamber. Intake air arrives in the cylinder at the same time as the fuel; however, the resulting mixture is very lean ( much more air than fuel ). Near the end of the intake stroke, the cylinder is filled with the air and fuel mixture. Heat begins to build as the piston begins its compression stroke. when the piston has reached TDC, there is enough heat to spontaneously ignite the mixture. The result of this combustion is a low temperature and flameless release of energy. The resulting release of energy and increase in pressure pushes the piston down on its power stroke. When the power stroke is completed, the piston moves back up the cylinder to begin the exhaust stroke. In contrast to the convertional exhaust stroke, the goal is not to empty the cylinder of all of its gases, Rather the exhaust valve closes before the end of the stroke to trap some of the hot gases in the cylinder. Before the next intake stroke begins, a small amount of fuel is injected into the trapped exhaust gases. This pre-charge helps control combustion temperatures and exhaust emission.

front engine transverse

Engines that are mounted transversely in the front of a vehicle sit sideways in the engine compartment.They are used with transaxles that combine transmission and differential gearing into a single compact housing, fastened directly to the engine. Transversely mounted engines reduce the size of the engine compartment and overall vehicle weight. Transversely mounted front engines allow for downsized, lighter vehicles with increased interior space. However, most of the vehicle weight is toward the front of the vehicle. While this increases the traction of the front suspension and brakes.

mechanical efficiency

Mechanical efficiency is measure of how much power is available once it leaves the engine compared to the amount of power that was exerted on the piston during the power stroke. Power losses occur because of friction generated by the moving parts. Minimizing friction increases mechanical efficiency.

engine construction

Modern engines are design to meet the performance and fuel efficiency demands of the public. Most are made of lightweight, non-iron materials (for example, aluminum, magnesium, fiber reinforced plastic); and fewer and smaller fasteners to hold things together.

operational cycle

Most technician will come in contact with only four stroke cycle engines. A fewer older cars have used, and some in the future may use, a two stroke engine.

bore

The bore of a cylinder is simply its diameter measured in inches or millimeters. The stroke is the distance the piston travels TDC and BDC. The bore and stroke determine the displacement of cylinders. When the bore and stroke are of equal size, the engine is called square engine.

compression ratio

The compression ratio is a statement of how much the air fuel mixture will be compressed during the compression stroke. It is important to keep in mind that this ratio can change through wear and carbon and dirt buildup in the cylinders.

compression stroke

The compression stroke begins as the piston starts to move from BDC. With the intake valve closed, the air in the cylinder is trapped. The upward movement of the piston compresses the air, thus heating it up. The amount of pressure and heat formed by the compression stroke depends on the amount of air in the cylinder and the compression ratio of the engine. The volume of the cylinder with the piston at BDC compared to the volume of the cylinder with the piston at TDC determines the compression ratio of the engine. In most modern engines, fuel is injected into the cylinder sometime during the compression stroke.

cylinder arrangement

The cylinders of an engine can be arranged inline with each other, i a "V" with an equal number of cylinders on each side, or arranged directly across from each other, these are called HORIZONTALLY OPPOSED.

exhaust stroke

The exhaust valve opens just before the piston reaches BDC on the power stroke. Pressure within the cylinder cause the exhaust gas to rush past the open valve and into the exhaust system. Movement of the piston from BDC pushes most of the remaining exhaust gas from the cylinder. As the piston nears TDC, the exhaust valve begins to close as the intake valve starts to open. The exhaust stroke completes the four stroke cycle. T he opening of the intake valve begins the cycle again. This occurs in each cylinder and is repeated over and over, as long as the engine is running.

intake stroke

The first stroke of the cycle is the intake stroke. As the piston moves away from top dead center TDC, the intake valve opens. The downward movement of the piston increases the volume of the cylinder above it, reducing the pressure in the cylinder. This reduce pressure, commonly referred to as engine vacuum, cause the atmospheric pressure to push air through the open intake valve. Sometimes engines are equipped with a super or turbo charger that pushes more air past the valve. air continues to enter the cylinder until the intake valve is closed. In most engines, the intake valve closes after the piston has reached bottom dead center BDC. This delay closing of the valve increase the volumetric efficiency of the cylinder by packing as much air into it as possible.

fuel type

The fuels currently used in automobiles include gasoline, natural gas, methanol, diesel, ethanol, and propane. the most commonly used is gasoline although most gasoline is blended with ethanol.

power stroke

The power stroke begins as the compressed fuel mixture is ignited. With both valves closed,an electrical spark across the electrodes of a spark plugs ignites the air fuel mixture. The burning mixture rapidly expands, creating a very high pressure against the top of the piston. This drives the piston down toward BDC. The downward movement of the piston is transmitted through the connecting rod to the crankshaft.

valves

There are at least two valves at the top of each cylinder. The air fuel mixture enters the combustion chamber through an intake valve and leaves (after having been burned) through an exhaust valve. A valve is said to be seated or closed when it rest in its opening or seat.

cooling system

There are both air cooled and liquid cooled engines in use. All current engines have liquid cooling systems.

ignition type

There are two types of ignition systems: spark and compression. Gasoline engine use a spark ignition system. In a spark ignition system, the air fuel mixture is ignited by electrical spark. - diesel engine relies on the heat generated as air is compressed in the cylinder to ignite the fuel.

thermal efficiency

Thermal efficiency is measure of how much of the heat formed during combustion is available as power from the engine. Normally only one fourth of the heat is used to power the vehicle. The rest is lost to the surrounding air and engine parts and to the engines coolant obviously, when less heat is lost, the engine is more efficient.

homogeneous charge compression ignition HCCI engine

These are four stroke cycle engines and relynon a combination of spark ignition and compression ignition technologies. In fact, they can run as spark or compression ignited engines. The term Homogeneous charge mean the fuel is thoroughly mixed with the intake air. In gasoline engines, the air and fuel are mixed homogenized before ignition and ignition is caused by a spark. In a diesel engine, the air and fuel are never mixed. The air is compressed and ignition occurs when fuel is sprayed into the high temperature air.

emission

This has been an obstacle for diesel cars and new stricter emission standards go into effect shortly. Cleaner, low sulfur, diesel fuel has been available in the united states since 2007. With new technologies and the cleaner fuel, a diesel engine is able to run as clean as most gasoline engines. Many diesel vehicles have an assortment of traps and filters to clean the exhaust before it enters the atmosphere. Also diesel engines produce very little co because they run with an abundance.

engine rotation

To meet the standards set by the SAE, engine rotate in a counterclockwise direction. The standards are based on the rotation of the flywheel, which is at the rear of the engine, and there the engine rotates counterclockwise.

volumetric efficiency

Volumetric efficiency describes the engine's ability to fill its cylinders with air and fuel. If the engines cylinder can be filled during its intake stroke, the engine has volumetric efficiency of 100 percent. Typically, engines have a volumetric efficiency of 80 percent to 100 percent if they are not equip with a turbo or supercharge. Basically, an engine becomes more efficient as its volumetric efficiency is increased. Turbocharger and supercharge force more air into the cylinders and therefore increase the volumetric efficiency of the engine. In fact, anything that is done to an engine to increase the intake air volume will increase its volumetric efficiency.

front engine longitudinal

With this arrangement, the engine, transmission, front suspension, and steering system are located in the front of the vehicle, and the differential and rear suspension are in the rear. Most front engine longitudinal vehicles are rear wheel drive. Some front wheel drive cars with a transaxle have this configuration, and many four wheel drive vehicles equipped with a transfer case have the engine mounted longitudinally. Total vehicle weight can be evenly distribute between the front and rear wheel with this configuration. This lightens the steering force and equalizes the braking load. Longitudinally mounted engines require large engine compartments. The need for a rear drive propeller shaft and differential also reduces passenger compartment space.

sound

a characteristic of a diesel engine is its sound. This noise, knocks or clatter, is caused by the sudden ignition of fuel as it is injected into the combustion chamber. Through the use of electronically controlled common rail injector systems, this noise has been reduced.

oversquare engine

can be fit with larger valves in the combustion chamber and longer connecting rods, which means these engine are capable of running at higher engine speeds. But due to size of the bore, these engines tend to be physically larger than under square engines.

atkinson cycle

engine is a four stroke cycle engine in which the valve is held open longer than normal during compression stroke. As the piston is moving up, the mixture is being compressed and some of of it pushed back into the intake manifold. As a result, the amount of mixture in the cylinder and the engines effective displacement and compression ratio are reduce. Often the atkinson cycle is referred to as a five stroke cycle because there are two distinct cycles during the compression stroke.

auto ignition

gasoline occurs when the temperature of the mixture reaches 1,430f to 1,520f ( 777c to 827c ). To control timing of ignition, the engine's control unit must supply the correct amount of fuel mixed with the correct amount of air. In addition, the control unit must provide a mixture that is hot enough to be able to auto ignite at the end of the compression stroke. Therefore, it must be able to vary the compression ratio, the temperature of the intake air, the pressure of the intake air, or the amount of retained or reinducted exhaust gas.

ignition system

has the responsibility for beginning and maintaining combustion. Obviously when combustion does not occur in any of the cylinder, the engine will not run. If combustion occurs in all but one or two cylinders, the engine may start but will run poorly. Poor combustion is not always caused by the ignition system, it can also be caused by problems in the engine, air fuel system, or exhaust system.

undersquare engine

have short connecting rods that allow for more power at low engine speeds. A square engine is a compromise between the two designs.

glow plugs

help ignite the fuel during cold start. These small electrical heaters are place inside the cylinder and are only used when the engine is cold. Other diesel have a resistive grid heater in the intakes manifold to warm to warm the air until the engine reaches operating temperature.

efficiency

is simply a measure of relationship between the amount of energy put into an engine and the amount available from the engine.

combustion chamber

is the area where the air fuel mixture is compressed and burned. The cylinder head also contains ports through which the air fuel mixture enters and burned gases exit the cylinders and bores for the spark plugs.

crank throw

is the distance from the crankshafts main bearing centerline to the connecting rod journal centerline. An engines stroke is twice the crank throw.

horse power

is the rate at which torque is produce.

Combustion Chamber

is the space between the top of the piston and the cylinder head. It is an enclosed area in which the fuel and air mixture is burned. If all of the fuel in the chamber is burned, complete combustion has taken place. -In order to have complete combustion, the right amount of air.This mixture must be compressed in a sealed container, then shocked by the right amount of heat (spark) at the right time.

torque

is twisting or turning force.

introduction to engines

provides them power to drive the vehicles. All automobile engines, both gasoline and diesel, are classified as internal combustion engines because the combustion or burning that creates energy takes place inside the engine. The block house or holds the major engine parts.

diesel

rely on compression ignition.

firing order

states the sequence in which an engine's piston are on their power stroke and therefore the order in which the cylinder's spark plugs fire.

selective catalytic reduction SCR

systems to reduce NOx emissions. Is a system that has a substance injected into the exhaust stream and then absorbed in the catalyst. This breaks down the exhausts NOx to form H2O and N2. Other will USE NOx TRAPS.

HCCI mode

the temperature of the mixture is greatly increased during the compression stroke. the air and fuel are mixed and heat builds as the mixture is compressed. This heat ignites the mixture without the need for a spark plug. To develop the heat necessary for ignition, these engines have a very high compression ratio and a very lean air/fuel mixture. To make all of this work, the mixture must get hot enough to auto ignite. When the mixture ignites, combustion immediately and simultaneously begin at several points within the mixture. The combustion process occurs rapidly and controlled by the quality and temperature of the compressed mixture. This spontaneous combustion produces a flameless release of energy to drive the piston down. The temperature of the mixture at the beginning of the compression stroke must be increase to auto ignition temperatures at the end of the compression stroke. This fact makes it hard to control the ignition timing of an HCCI engine.

fuel cell electric vehicles

these vehicles are powered solely by electric motors, but the energy for the motors is produce by fuel cells. Fuel cells rely on hydrogen to produce the electricity. A fuel cell generates electrical power through a chemical reaction. A fuel cell ev uses the electricity produced by the fuel cell to power motors that drive the vehicle's. The batteries in these vehicles do not need to be charge by external source. Fuel cells convert chemical energy to electrical energy by combining hydrogen with oxygen. The hydrogen can be supplied directly as pure hydrogen gas or through a "fuel reformer" that pulls hydrogen from hydrocarbon fuels such as methanol, natural gas, or gasoline. Simply put, a fuel cell is comprised of two electrodes ( the anode and the cathode ) located on either side of an electrolyte. As the hydrogen enters the fuel cell, the hydrogen atoms give up electrons at the anode and become hydrogen ions in the electrolyte. The electrons that were released at the anode move move through an external circuit to the cathode. As the electrons move through an external circuit to the cathode. As the electrons move toward cathode, they can be diverted and used to power the vehicle. When the electrons and hydrogen ions combine with oxygen molecules at the cathode, water, and heat are formed. There are no smog producing or greenhouse gases produced. Although vehicles equipped with reformers emit some pollutants, those that run on pure hydrogen are true zero emission vehicles.

two stroke engine

two strokes of the piston to complete all four operations: intake, compression, power, and exhaust.

hybrid

vehicle has at least two different types of power or propulsion systems. Today's hybrid vehicles have an internal combustion engine and an electric motor ( some vehicles have more than one electric motor ). A hybrid's electric motor is power by batteries and/or ultracapacitors, which are recharge by a generator that is driven by the engine. They are also recharged through regenerative braking. The engine may use gasoline, diesel, or an alternative fuel. Complex electronic controls monitor the operation of the vehicle. Based on the current operating conditions, electronics control the engine, electric motor, and generator. Depending on the design of the hybrid vehicle, the engine may power the vehicle, assist the hybrid vehicle, the engine may power the vehicle, assist the electric motor while it is propelling the vehicle,or drive a generator to charge the vehicle's batteries. The electric motor may propel the vehicle by itself, assist the engine while it is propelling the vehicle, or act as a generator to charge the batteries. Many hybrid rely exclusively on the electric motors during slow speed operation, on the engine at higher speeds, and on both during certain conditions. The engines used in hybrid are specially designed for fuel economy and low emissions. The engine tend to be small displacement engines that uses variable valve timing and the Atkinson cycle to provide low fuel consumption.

diesel engine

were invented by Dr. Rudolph Diesel, a German engineer, and first marketed in 1897.