How Car Engines Work ( Internal Combustion )

The principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are:

Intake stroke

Compression stroke

Combustion stroke

Exhaust stroke

You can see in the figure that a device called a piston replaces the potato in the potato cannon. The piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves, it has the effect of "resetting the cannon." Here's what happens as the engine goes through its cycle:

The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. (Part 1 of the figure)

Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. (Part 2 of the figure)

When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. (Part 3 of the figure)

Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. (Part 4 of the figure)

Now the engine is ready for the next cycle, so it intakes another charge of air and gas.

Notice that the motion that comes out of an internal combustion engine is rotational, while the motion produced by a potato cannon is linear (straight line). In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn (rotate) the car's wheels with it anyway.

Now let's look at all the parts that work together to make this happen, starting with the cylinders.

Basic Engine Parts

Spark plug
The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.

Valves
The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Piston
A piston is a cylindrical piece of metal that moves up and down inside the cylinder.

Piston rings
Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

• They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
• They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

Most cars that "burn oil" and have to have a quart added every 1,000 miles are burning it because the engine is old and the rings no longer seal things properly.

Connecting rod
The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Crankshaft
The crankshaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.

Sump
The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).

Engine Problems

So you go out one morning and your engine will turn over but it won't start... What could be wrong? Now that you know how an engine works, you can understand the basic things that can keep an engine from running. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the "big three." Based on the simple engine we have been discussing, here is a quick rundown on how these problems affect your engine:

Bad fuel mix - A bad fuel mix can occur in several ways:

• You are out of gas, so the engine is getting air but no fuel.
• The air intake might be clogged, so there is fuel but not enough air.
• The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.
• There might be an impurity in the fuel (like water in your gas tank) that makes the fuel not burn.

Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:

• Your piston rings are worn (allowing air/fuel to leak past the piston during compression).
• The intake or exhaust valves are not sealing properly, again allowing a leak during compression.
• There is a hole in the cylinder.

The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.

Engine Valve Train and Ignition Systems

Most engine subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines, beginning with the valve train.

The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down

Most modern engines have what are called overhead cams. This means that the camshaft is located above the valves, as you see in Figure 5. The cams on the shaft activate the valves directly or through a very short linkage. Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag between the cam's activation of the valve and the valve's subsequent motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync with the pistons. The camshaft is geared to turn at one-half the rate of the crankshaft. Many high-performance engines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams." See How Camshafts Work for details.

The ignition system (Figure 6) produces a high-voltage electrical charge and transmits it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylinders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a spark from the distributor at a time. This approach provides maximum smoothness.

Engine Cooling, Air-intake and Starting Systems

he cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance

So now you know how and why your engine stays cool. But why is air circulation so important? Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor.

ncreasing your engine's performance is great, but what exactly happens when you turn the key to start it? The starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:

All of the internal friction caused by the piston rings

The compression pressure of any cylinder(s) that happens to be in the compression stroke

The energy needed to open and close valves with the camshaft

All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc.

Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor.

Black Smoke

Black smoke is caused by too much fuel being processed inside your car's engine and then released from the tailpipe of your car. Malfunctions in fuel delivery or internal system leaks will cause black smoke to come from the tailpipe. Before fuel injection became available in automobiles in the mid 1980's, the carburetor was the main fuel and air mixer in most vehicles. A carburetor was a simple device that supplied the engine with proper fuel to air mixtures. Carburetors performed two operations 1. meter air flow 2. deliver the correct amount of fuel to air mixture. This mix could be kept even during the wide range of extra factors associated with an engine such as high temperature, cold starting, hot starting, idling and acceleration.

The primary difference between a carburetor and a fuel injection system is that the fuel injection system atomizes fuel by pushing it through a small nozzle under pressure, while a carburetor utilizes vacuum created by air flow into the intake manifold. Airflow in an injection engine is controlled by the throttle body; fuel is distributed directly in each cylinder. This creates better fuel control, lower emissions and faster acceleration. The process of measuring the amount of fuel a fuel injector is dispersing is determined by the ECM (engine control module). The fuel injection system has several parts: the mass airflow sensor or map sensor, throttle body, throttle position sensor, idle control valve, fuel pump, fuel pressure regulator, fuel lines, and oxygen sensors.

Cause of Black Smoke

Black smoke is caused when the mix of fuel and air becomes un-balanced. Normal mixture is 14.5 parts air to1 part fuel. When the fuel to air mixtures change because of a malfunction the mixture can go as high as 14.5 to 2 or 3, two to three times the proper amount. The black smoke is the excess fuel generated from the rich mixture and can be cause by one of the following:

Plugged Air Filter

Shorted or stuck fuel injector

Failed fuel pressure regulator

Vacuum leak

Shorted ECM Sensor

How a Serpentine Belt Tensioner Works?

A multi rib belt tensioner is designed to automatically hold a predetermined amount of tension on a drive belt while the engine is in operation. If the drive belt is loose the tensioner has failed or the wrong size belt has been installed. The tensioner should be about half way through its travel to hold proper tension, most have a gauge stamped on them to determine belt stretch for replacement On rare occasions an engine can buck or jerk at start up and can suddenly cause a belt to jump out of place. Other problems can occur if the belt itself snaps this can be due to fatigue of the belt. The most common reason for the belt to snap is age coupled with the natural wear and tear of the belt. Before belt tensioners there was a simple adjustment bolt that was used to set the tension on the belt. The disadvantage to this set up is once the belt stretches slightly it would have to be re-adjusted. If re-adjustment is not performed the belt can create a loud screeching noise. A belt tensioner consists of a main body, swing arm, tension spring, pulley and pulley bearing.

What is a Backfire?

There are typically two kinds of engine backfires, one is generated from the intake manifold of the engine, and the second is expelled from the exhaust pipe at the rear of the car. A backfire is an explosion of sorts in the intake manifold or the exhaust system. A backfire occurs when there is an imbalance in the air to fuel ratio required for your vehicle to operate properly. If the fuel mixture is too lean (not enough fuel) you may have a backfire in the intake, or too rich (too much fuel) you may get a backfire out of the exhaust system. Most backfires are easily repaired by correcting the imbalance and providing a greater or lesser percentage of fuel to the mixture.

Common Problems and Solutions

Most causes of backfires in the exhaust system can be addressed by troubleshooting the reason for the air to fuel ratio imbalance. The solution usually involves checking for vacuum leaks, changing the airflow sensor, oxygen sensor, or fuel filter to ensure the fuel system is functioning properly.

A common backfire situation occurs when there is a small leak in the air injection system that feeds the exhaust system. This can cause unburned fuel to explode suddenly. One of the most common causes is a stuck or faulty air intake or gulp valve near the exhaust manifold.

Backfiring can also occur with a sudden drop in fuel pressure. This may be due to a faulty fuel pump or a plugged fuel filter. Correcting problems in the fuel system usually resolves these issues.

Incorrect ignition timing to the spark plugs is another cause of backfire. Adjusting the ignition distributor, if the engine is so equipped, may resolve this problem. Adjusting engine timing is not difficult and can be done with a timing light by following the timing adjustment procedure for your car. If you do not know your car's ignition timing procedure please visit our car repair manual page. A vehicle that is not timed properly will not idle, run or operate correctly and will often backfire rapidly. On newer cars you will need to scan the pcm to check for CKS (crankshaft angle sensor) and CMS (camshaft position sensor) related trouble codes.

Maintenance

To prevent backfires there are several things you can do:

Change the fuel filter as needed, the fuel filter is a vital part of your fuel system and can cause a backfire(s) if the filter is clogged and not changed regularly. A bad fuel filter can cause low fuel pressure creating a perfect situation for a backfire to occur. Changing the filter is simple and can save gas with improved performance of your vehicle's engine reducing the occurrence of backfires.

Tune up and service your fuel injection system in accordance with the maintenance schedule for your particular car. This ensures correct fuel consumption with the correct amount of emissions. Fuel that is not burned completely will leave ample opportunity for a backfire to occur. These maintenance requirements are associated with other systems on your vehicle. Avoiding maintenance on your car can increase the risk of backfiring and other system malfunctions.

Acceleration

Acceleration is the process of changing the rate of velocity or movement. This is the result of available power from the engine. Usually, the bigger the engine, the power it makes. However, a turbo charged or supercharged (forced induction) engine provides an exception to the rule. When air is forced into an engine using a turbo/supercharger it can produce more power and improved acceleration with a smaller engine.

Whenever you hear someone mention horsepower the first thing that usually comes to mind are cars; fast cars with extreme torque, muscle cars with lots of power, and vehicles capable of extreme speed. But why is horsepower so important? James Watt, a famous 19th century engineer, created the term "horsepower" in 1782 as he improved the power of the steam engine. While watching horses haul coal out of a coal mine he came up with the idea of defining the power exerted by these animals, thus the term "horsepower" was born.

He calculated that a normal horse attached to a mill that ground corn or cut wood walked in a circle that was 24 feet in diameter. He then calculated that the horse pulled with a force of 180 pounds. Watt noticed the horse could make 144 trips around this circle in an hour. That is 2.4 trips per minute. Using these numbers he calculated that the horse traveled about 180.96 foot per minute then rounded up and came up with 181 foot per minute. He then multiplied the 181 foot per minute by 180 pounds of force the horse exerted and came up with the number 32,580 foot pounds per minute then rounded up again to the number 33,000 foot pounds per minute. This number is equal to one horsepower.

Mr. Watt used his new term to rate the power of the steam engine. Since most people were unfamiliar with the steam engine he had to come up with a comparison measurement that the farmer of the day would understand. As with any measurement there are different variations and different methods of measuring horsepower or hp. The normal measurement of horsepower is called mechanical horsepower.

Alternator and Charging System

A battery is needed to power the operating system of your car. Once the vehicle is running an alternator that is driven by the engine charges the battery. While in operation the alternator creates electricity, about 13.6 to 14.3 volts, and recharges the battery to its original state of charge. The alternator is one of the hardest working electrical components in your vehicle. When your vehicle is running the alternator is busy creating electricity to provide the engine and the car accessories with needed power. When the car is not running and your battery is severely discharged some electrical components such as alarms or other memory retaining items may still operate or operate poorly. Typically, these components are designed to operate properly at 12 volts; if the system voltage is low it can cause erratic symptoms.

Common Problems and Solutions

When jump-started a severely discharged battery can cause the alternator to overload and internally fail. If this occurs replace or charge the battery before replacing the alternator. This will help prevent a second alternator failure. Most vehicles use a multi-ribbed belt connected to the engine to rotate the armature inside the alternator. If the belt fails it should be replaced immediately. Belt tension should be taught. If it isn't, check the belt tensioner, it may need to be replaced or the incorrect size belt may have been installed. Either of these conditions can cause the vehicle to stall and not restart.

Additionally, problems can occur if the alternator is overcharging the system. Some symptoms of overcharging include a swollen or seeping battery, both headlight bulbs failing at the same time, and other electrical component problems. To perform an alternator system check for this condition use a voltmeter on both positive and negative terminals while the engine is idling. If the voltmeter reading is over 15 volts this is an indication of an overcharging alternator. The alternator should be replaced with an OE (original equipment) unit. While an inferior rebuilt alternator is often much cheaper, it can fail prematurely causing another costly replacement.

The most common alternator problem is "undercharging." This condition is often accompanied by symptoms such as a low state of charge on the battery, poor or erratic performance from electrical components and dim headlights and other lighting systems. The first symptom of an undercharging alternator is a slow cranking engine. The next symptom is a "machine gun" sound when the engine is cranked as the system voltage drops below normal operating levels. In order to correct this problem a replacement alternator must be installed after the battery has been replaced or charged.

Maintenance

To ensure that your alternator lasts as long as possible there are several things you can do. Be sure all battery connections are tight and both terminals are clean. This should be inspected periodically regardless of when the battery was changed as even new batteries can have problems and be defective. While the engine is off, visually inspect the alternator belt and replace the belt if cracks or tears are observed.

Serpentine Multi Rib Belt

The drive belt or multi ribbed belt is an essential component of your vehicle. The primary belt function is to supply power to the steering system, water pump, air pump (if equipped) air conditioner and alternator. The belt is connected to the drive pulley of the engine to supply power. If the belt fails it will almost always render your vehicle inoperable until the drive belt is replaced. Typically most people are able to replace a serpentine belt themselves with basic automotive repair knowledge. When replacing the belt draw a diagram of the belt routing before you start to avoid confusion. If you have removed the drive belt and need the belt routing you can look it up on a belt routing diagram.

There are two different types of belts primarily; the first is a serpentine belt which tends to cross the motor several times to operate additional components. There are several names that are used to describe a serpentine belt, including Poly-V, Multi-Rib, and even a Micro-V Belt. However, all of these terms mean the exact same thing and do not change the way the belt is routed, or the type of material the belt is constructed from. A serpentine belt tends to have several V's in the belt that act as better grip for the drive pulley and components of the drive belt system.

How a Car Engine Works

A gasoline engine operates on the principle of combustion. A fuel/air mixture is pulled into a cylinder, the cylinder is then closed off and the piston is thrust upward to create compression. A spark is introduced to ignite the mixture to create combustion to thrust the piston downward in the engine block.

There are a number of pistons inside an engine depending on the design, 4 to 12 cylinders usually. The pistons are connected to a crankshaft through a connecting rod. Pistons fire consecutively to rotate the crankshaft inside the engine block. The oil pump pushes oil through the oil filter and then supplies oil to vital engine parts including the crank and camshaft, cylinder walls and piston rings, valve train, cam lifters and the timing gears or chain. Motor oil is used to lubricate and cool internal engine parts. Oil is pumped up through the engine, then returns to the bottom of the engine and is gathered in the oil pan.

Over Head Camshaft Engine - 4 Cylinder (courtesy of beaudaniels.com)

The cylinder head is connected to the top of the engine block and allows air/fuel mixture and exhaust into and out of the cylinder block. The cylinder head has the duty of holding the air/fuel mixture charge inside the cylinder as it combusts, forcing the piston downward. The cylinder head is connected to the engine block using head bolts, using a head gasket to seal both parts.

How a Fuel Pump Works?

A fuel pump is used to supply fuel to the fuel injection system. A fuel injection system is more efficient than its predecessor the carburetor and can better operate at extreme temperatures while becoming more dependable at start up. A fuel injection system reacts better to situations such as high altitudes, extreme temperatures and variable fuel quality. Fuel is forced under pressure into the fuel injection system and then into an internal combustion engine. The fuel injection system is an integral part of a modern vehicle's engine fuel management system.

Simply put, the purpose of a fuel pump is to draw fuel from the fuel tank then to deliver it to a fuel injector. All vehicle engines operate by way of a mechanical pump or via a fuel injected pump. Chances are if your engine requires a mechanical pump it is quite old and has carbureted fuel pumping at a low pressure from a fuel tank to the carburetor. Nonetheless, most likely your engine uses a fuel injected pump as do most modern engines and transfers fuel at a high pressure into the fuel injection system from an electrical pump mounted outside the fuel tank.

Typical Fuel Injection System

Mechanical Pumps

Before the modern prevalent usage of electronic fuel injection pumps most carbureted vehicle engines used mechanical fuel pumps to move fuel from the fuel tank into the fuel sections of the carburetor. However, more recently, as vehicle engines shifted from carburetors to fuel injection, mechanical fuel pumps are increasingly being replaced with electric fuel pumps. This is because electronic fuel injection systems generally run more effectively at higher fuel pressures than mechanical pumps.

Fuel Injected Pumps

Fuel injection pumps are basically a fuel delivery apparatus that supplies fuel pressure into the fuel injection system. Fuel injection pumps are part of an electronic system which means that they are controlled by a computer system that oversees key factors including the air to fuel ratio, the contents of the exhaust gases and the actual position of the throttle. Fuel injection pumps, which are usually electric, are located within the fuel tank or near the gas tank in order to maintain a steady amount of fuel and to utilize the fuel in the tank to cool the pump.

When Fuel Pumps Fail

There are a couple of reasons why your fuel pump will fail, be it mechanical or electrical. Fuel pumps can experience wear and tear on the armature, brushes or bearings. In addition, roller gears and pump vanes can also wear down. This will cause a gradual loss of pressure and poor engine performance. Some causes of fuel pump failure can include rust or dirt because they can get past the inlet filter sock which is set up to block these sediments. When this occurs the fuel pump will break down because of contaminants that have infiltrated the pump and cause it to jam. This will result in having the motor overheat and burn out. Sometimes a fuel pump will not work properly if it is not given the proper amount of fuel needed to run adequately. Your vehicle’s fuel pump relies on fuel running through it to cool and lubricate it. Starving your fuel pump for fuel can cause your vehicle's fuel pump to fail prematurely.

How Car Filters Work

All filters incorporate a filtering device constructed from various materials. These materials can vary from cloth fibers, paper fiber and wire mesh screens or any combination of the three. Most fuel and oil filters are housed within a metal container connected to the engine or fuel system. Most vehicles have one or more filters that require regular maintenance (replacement). These filters range from an air filter, fuel filter, air cabin filter and oil filter. A properly maintained filter system will enhance the performance and extend the life of vehicle. Air filters remove debris from the air before it is allowed into the engine. If dirt where allowed to enter the engine it would cause premature failure.

nspecting the air filter is very simple and typically only involves opening the hood and finding the air filter box that is usually above the battery in the vehicle. Removing the clips that hold the lid of the box will allow you to easy access the air filter. You can quickly inspect the filter to determine if it needs to be changed. Some slight discoloration is acceptable; however an air filter that is dusty or dark should be changed to restore proper airflow to your vehicles engine. Checking the air filter of your engine is a simple process that only takes about five minutes. A fuel filter located in the fuel system ensures that debris in the gas tank is not passed through to the fuel injection system. A clogged fuel filter can cause low power and fuel sediments are the #1 cause of system failure.

Fuel Injection System

A fuel injection system is used to inject fuel, under pressure into an internal combustion engine. The fuel injection system is an integral part of a modern vehicle's engine management system. A fuel injector is constructed from two main sections: main valve and spray nozzle. The pressurized fuel for the system is supplied by a fuel pump.

A Fuel injection system is more efficient than its predecessor the carburetor and can better operate at extreme temperatures while becoming more dependable at start up. A fuel injection system reacts better to situations such as high altitudes, extreme temperatures and variable fuel quality.

Fuel metering is determined by a combination of the engine air charge, vacuum and speed. Some vehicles utilize a mass airflow sensor to determine engine air intake, other systems use a MAP sensor (manifold absolute pressure)

Engine Harmonic Balancer

A harmonic balancer is connected to the front of the engine crankshaft and is designed to help reduce vibration. The harmonic balancer is comprised of two separate pieces, the first is the mass which connects to the crankshaft and the second is the energy dissipating element. These elements are separated by a rubber insulator. The mass is designed to absorb vibration created from the crankshaft while in operation.

Failed Harmonic Balancer

Almost all vehicles are equipped with a harmonic balancer. Due to the stress and strain that is placed upon the harmonic balancer the unit can sometimes crack or separate. If upon inspection the harmonic balancer shows signs of weakness such as cracks, missing pieces or misplaced insulator you will need to replace the balancer. To replace the harmonic balancer a special tool is required. A balancer that is damaged can cause excessive strain on the engine crankshaft. In extreme cases it can require the crankshaft to be replaced as well as the harmonic balancer. If the harmonic balancer is exposed to oil it can cause the balancer to fail. Check for oil leaks to prevent failure of the harmonic balancer. Proper engine performance can keep the harmonic balancer operational. The balancer can be overworked by a poorly running engine.

How Horsepower Works

Whenever someone mentions horsepower the first thing that comes to mind is cars. Fast cars with extreme torque, vehicles with large power and extreme speed. But what makes horsepower measuring so meaningful? And why is it called horsepower? The word horsepower was created in 1782 by James Watt, a famous 19th century engineer while he was developing a way to improve the power of a steam engine. While watching horses haul coal out of a coal mine he came up with the idea of defining the power exerted by these animals. He calculated that a normal horse attached to a mill that ground corn or cut wood walked in a circle that was 24 feet in diameter. He then calculated that the horse pulled with a force of 180 pounds. Watt noticed the horse could make 144 trips around this circle in an hour. That is 2.4 trips per minute. Using these numbers he calculated that the horse traveled about 180.96 foot per minute then rounded up and came up with 181 foot per minute. He then multiplied the 181 foot per minute by 180 pounds of force the horse exerted and came up with the number 32,580 foot pounds per minute then rounded up again to the number 33,000 foot pounds per minute. This number equals one horsepower.

r. Watt used his new found term to rate the power of the steam engine. Since most people were unfamiliar with the steam engine he had to come up with a comparison measurement that the normal farmer of the day would understand. As with any measurement there are different variations and different methods of measuring horsepower or hp. The normal measurement of horsepower is called mechanical horsepower.

Metric Horsepower

In Europe horsepower is measured a slightly different way. Horsepower is known by the various countries literal translation of the word horsepower. Some acronyms include PS, CV, pk and so on. Depending on the origin of the engine in question its horsepower is measured by that country's standards. Metric horsepower is defined as .73549875 kW. This is roughly 98.6% of mechanical horsepower.

Horsepower in Europe

Other countries have their own ways to measure horsepower. PS stands for Pferdestarke or horse strength. This is the German equivalent of horsepower. It is no longer used in Germany but it is in some other counties. It has since been replaced by the kilowatt but the EEC where horsepower was still used in advertisements as most people do not know the use of the kilowatt as a power measurement for combustion engines. Mathematically a PS = .73549875 kW = 0.9863201652997627 hp. The Dutch have the paardenkracht (pk). The Swedish have the hastkraft (hk). The Finnish have the hevosvoima (hv). All of these are equal to the German (ps). RAC horsepower, or taxable horsepower, is a British standard measurement of an automobile's power. It was adopted by the Royal Automobile Club. Taxable horsepower does not reflect true horsepower but it is a calculation based on the engine's bore size, the number of cylinders and a presumption of engine efficiency. The figure is no longer used as a standard in the UK but it is still put to use for the calculation of a vehicle's tax. The equation is RACh.p.= D squared * n/2.5 where D is the diameter of the bore of the cylinder in inches and n is the number of cylinders.

How a Car Ignition System Works

The ignition system in your car ignites the fuel inside the engine's combustion chamber at the optimal time in the piston stroke to produce the most power while emitting the least amount of emissions as possible. There are many configurations of ignition systems but all operate on the same principle, create a low energy field and collapse it onto a high energy coil and that transfers the electrical energy into the secondary ignition system, i.e. coil wire, distributor cap and rotor (if equipped) plug wires and finally the spark plug.

This system is triggered by the primary ignition system, this system varies depending on manufacturer but all operate on the same principle, use some kind of low voltage trigger system i.e. crankshaft position sensor (CKP), camshaft position sensor (CAS). This low voltage system (1.5 to 3.0 volts) is amplified to 12 volts by using an ignition module (amplifier) and then transferred to the primary side of the ignition coil. The ECM (engine control module) controls the engine ignition timing by advancing and retarding the primary trigger signal. In old cars a points, condenser and a vacuum advance unit performed this job.

gnition Coil Cut-away

This ignition coil is a pulse-type it consists, in part, of two coils of wire. These wires are wrapped around two iron cores. Because this is a step-up transformer, the secondary coil has far more turns of wire than the primary coil. The secondary coil has several thousand turns of thin wire, while the primary coil has just a few hundred raps. This allows 40,000 volts or more of voltage to be generated by a car battery.

How Does an Idle Air Control Valve Work? (IAC)

IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The car computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. An IAC motor can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the IAC control motor to react slowly, either failure will cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak IAC motor. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed.

Common Problems

An IAC motor is highly susceptible to carbon and coking build up; if an IAC goes too long without cleaning it can cause stalling and poor idle quality. Some cars are designed with a large vacuum transfer hose that connects the intake manifold to the IAC (idle air control) motor. If a broken or dilapidated these vacuum lines can cause the engine to lose vacuum which will allow the engine to run roug and die. Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. Any car that is designed with a magnetic non-motor operated IAC like Lexus is subject to carbon and should be cleaned about every 40,000 miles to avoid stalling.

Basic Maintenance

To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out. If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed

Distributor Cap and Rotor

The distributor cap and rotor are two essential pieces that distribute electrical current to the spark plugs. The distributor cap connects to the spark plugs directly using a spark plug wire. The number of plug wires connected depends on the amount of spark plugs that are in the engine. For example, an eight cylinder engine will have eight plug wires.

The rotor is designed to spin inside of the distributor cap, just missing the terminals inside the cap. A worn or damaged rotor can cause your vehicle to run rough, or even stall completely. The rotor is rotating at the same speed as the camshaft which also happens to be 1/2 the speed of the crankshaft.

A problem occurs when the contacts inside the distributor cap can become dirty and worn. It is best to replace the distributor cap and rotor every tune up to ensure the contacts are clean to transmit power to each spark plug. The distributor cap and rotor generally have few problems other than worn connections that results in the cap needing to be replaced. There are numerous brands of distributor caps and rotors that are available. It is your decision to select the appropriate brand based on your individual wishes. However, when selecting the distributor cap and rotor it is best to select an OE (original equipment) replacement for proper performance and durability. If a misfiring problem has occurred and you cannot determine the cause of it, it is advisable to inspect the distributor cap and rotor for corrosion. Worn ignition components can cause the vehicle to misfire which leads to wasted fuel, rough running and stalling. Some early distributor ignition systems featured a point set and condenser. A solid state system was later adopted.

Mass Air Flow Sensor

The mass air flow sensor works in conjunction with the oxygen sensor and the engine control system. While the oxygen sensor determines the oxygen levels in the exhaust system, the mass air flow sensor is used to monitor the amount of air passing through the engine while running. A vehicles mass air flow sensor delivers a signal to the ECM (engine control module). It is usually difficult to detect when a mass air flow sensor fails. The "check engine light" or engine symbol will probably not be illuminated. Your car, truck or SUV may have a poor idle quality, stall, low power or all three. Your PCM may have no trouble codes because the ECM cannot detect a problem

What has occurred is the sensing element or "hot wire" that is used to give electronic feedback to the ECM for processing has become contaminated by air partials. The mass air flow sensor is reporting to the ECM that less air is running through the engine than actually is. The ECM will then lean the fuel mixture down to the point of run ability problems. There is not enough variance in the system to trigger a MIL (malfunction indicator light) - "Check Engine" light so this particular repair problem can be difficult to detect through normal trouble shooting methods.

A mass air flow sensor is most common in newer vehicles, this sensor is used to help maximize efficiency and reduce emissions. One of the benefits of the mass air flow sensor is that it can vary responding to changes in air intake flow. There are no moving parts in a mass air flow sensor. Most vehicles mass air flow sensor locations are in the air intake for the engine, this allows easy replacement. It is recommended that the sensor be replaced approximately every 60,000 miles..

Oxygen Sensor

The oxygen sensor in your vehicle is an electronic component that is designed to measure levels of oxygen in the engine exhaust. Typically, the oxygen sensor is mounted to the exhaust system tube, with the sensor part inside the tube. This measures the oxygen mixture by generating a small amount of electricity do to the difference in atmosphere, oxygen and carbon dioxide. The ECM monitors this voltage and adjusts the fuel system and engine timing accordingly.

The engine control unit adjusts fuel intake necessary for correct combustion. The oxygen sensor is in continuous communication with the electronic engine control unit. When the engine is cold the oxygen sensor is not as active. To correct this condition the oxygen sensor has been constructed with a 12 volt heater element. This heater allows the sensor to read at maximum efficiency quicker. When the throttle is wide open and under max load the oxygen sensor will go full voltage until normal operating conditions return. Typically changing an oxygen sensor when necessary is a simple process. Most solutions to oxygen sensor problems result in changing the oxygen sensor. Due to the severe usage the sensor endures, it is common for most sensors to last approximately 60,000 miles, however it is not uncommon for an oxygen sensor to last only 30,000 miles depending on your driving habits and vehicle conditions

How Does a Starter and Solenoid Work?

Introduction:

An engine starter is designed to utilize a 12 volt, high amperage electrical system made to turn an engine over for starting purposes via a flywheel. Basically a starter is an electric motor with a small pinion gear and bendix assembly. This starter bendix drive is designed to extend and mesh with the flywheel teeth when the ignition key is turned to the "crank" position and then retract when the ignition key is released after the engine has started. A starter motor is constructed with a main outer housing that contains the armature magnets, the armature contains the starter windings, a brush set that is used to contact the armature to transfer the electrical energy. The starter bendix is directly connected to the starter pinion gear. A starter solenoid acts as the main power switch to begin the starter operation. Because the starter motor draws such high amperage a conventional switch would short circuit very quickly. Most starter solenoids are located on the starter motor itself. Some Ford models have located the starter solenoid on the inner fender panel near the battery. The electrical system that controls the starter motor is comprised of an ignition switch, neutral safety switch (automatic transmissions only) a clutch engagement switch (manual transmissions only) a battery, battery cables, anti theft system and the starter itself.

Typical Starter Motor

Most starter motors are mounted underneath the car near the flywheel on either the left or right side. The flywheel is located between the engine and transmission. Some models have located the starter under the intake manifold, which makes replacement difficult. When the ignition key is turned to the "engine crank" position a 12 volt low amperage electrical signal is sent to the anti-theft system which in turn can monitor the gear selection or clutch safety switch position. Only then will the signal continue to the starter solenoid that activates the high amperage side of the electrical system to engage the starter motor.

Once the starter motor has been engaged the starter bendix senses the armature momentum and is forced to extend into the flywheel. Once the engine has started and the ignition key released the bendix loses momentum and the bendix is forced to return to idle position. If the flywheel is worn it can cause a grinding noise when the starter bendix/pinion gear is engaged. The objective of the starter motor is to rotate the engine between 85 and 150 rpm's necessary for engine ignition process. A starter will typical last between 60,000 and 100,000 miles and is a normal replacement item.

Replacement Guide

Tools needed:

Set of sockets and socket wrench with extensions

Phillips and standard screw drivers

Pliers

Wrench set

Replacement Procedure:

Start with engine cold

Remove the negative battery cable at the battery

Remove all electrical wires that lead to the wiring harness and main battery cable connections. (note: sometimes this step is easier after the starter motor has been removed)

Remove all accessories (if any) to access starter motor mounting bolts, next remove starter motor mounting bolts, remove the starter.

Clean starter mounting surfaces thoroughly

Install new starter and tighten evenly

Reconnect wiring and cable

Reconnect the negative battery cable (note: if major spark are present when the battery is re-connected the starter battery connection needs to be inspected)

Recheck starter operation (note: if the starter motor operation is exce

ssively noisy the starter motor may need to be repositioned using shims)

How an Engine Thermostat Works

Inside your car's engine, thousands of controlled explosions called combustion events caused by igniting fuel/air mixture inside the engine generate heat. If this heat is not controlled the engine will over heat and internal damage will occur. These high temperatures are controlled with the help of the cooling system. A cooling system consists of a water pump, thermostat, radiator hose, hose clamps, radiator, radiator cap and coolant. The thermostat is designed stop the flow of coolant through the cooling system while the engine is warming up to operating temperature. An engine needs to operate at a particular heat range to be efficient. Once the engine is warm the thermostat will open to allow coolant flow and cool the engine. Most thermostats are designed to open at about 195° F but other temperatures are available for a variety of applications. A thermostat consists of a main housing, a plunger style of valve and a temperature sensitive wax filled plunger that acts as the sensing and activating device with a return spring. A thermostat maintains engine temperature as is opens and closes

Engine Thermostat

When a thermostat malfunctions it can stick close not allowing the coolant to circulate causing the engine to overheat. Or the thermostat could stick open causing the engine to run too cold. In this case the service or check engine soon light could illuminate, followed by a trouble code. To test a thermostat remove unit. Prepare a pan of water deep enough to cover the thermostat completely. Next install a temperature gauge into the water along with the thermostat. A cooking thermometer works well for this. Next, start heating the water while watching gauge, the thermostat should remain closed until the water reaches 190° at this point the thermostat should start opening and be completely open at about 195°. If the thermostat stays closed through the boiling point the thermostat has failed and needs replacing. If the thermostat is stuck open or broken it has failed and needs replacing. Never run an engine without a thermostat because the thermostat works as a system flow regulator as well. What this means is the thermostat has a specific opening that regulates the flow through the cooling system. If the coolant is allowed to flow to quickly through the radiator the coolant will not have time to transfer the heat it has absorbed. This will cause the engine to overheat.

Engine coolant is used to transfer heat from the engine to the radiator by the cooling system. The radiator removes heat from the coolant by forcing air through the radiator fins. Without coolant your engine will over heat and if left unattended sever engine damage will occur. Coolant colors can vary from green, orange, blue and yellow each having their own protective properties. (Note: coolant and antifreeze refer to the same product, in below freezing, coolant lowers the freeze point hence the name anti-freeze and in warm weather coolant helps raise the boiling point, "coolant")

How a Timing Belt Works

Introduction:

A timing belt is used to drive the engine's camshaft. The engine crankshaft utilizes a drive sprocket to connect with a larger camshaft sprocket via a timing belt. A typical timing belt is constructed of a fiber enforced rubber belt with horizontal ribs molded to the inside of the belt. Tension is held on the belt by a belt tensioner which is spring loaded, oil pressure activated or set manually. Timing belts can be used to drive accessories such as a water pump or power steering pump. Some engines utilize a timing belt to drive balance shafts inside the engine that help neutralize engine vibration. When a timing belt fails it will allow the horizontal ribs to shred allowing the driven shaft to stop or become misaligned resulting in engine operation failure. Each engine has a unique set of timing crankshaft, camshaft and accessory marks that can be located: timing belt marks or in a car repair manual.

To check the condition of the timing belt (engine off) remove the top dust/safety cover from the upper section of the engine front by removing a few bolts you can access the timing belt. Next, using a flash light inspect the condition of the belt, check for cracks, especially at the base of drive teeth. If the timing belt shows signs of wear or if you are replacing it for maintenance purposes complete exposure of the belt and related components are necessary. For step by step instructions for your particular car engine you must consult a car repair manual.

Basic Replacement Procedure:

Remove all obstructions from engine front, if an engine mount is in the way, support the engine from the top or bottom whichever is more convenient

Remove upper and lower timing belt covers to gain access

Remove or loosen timing belt tensioner to release the timing belt

Remove timing belt and clean all debris from area

Use a timing belt diagram to time the crankshaft to the camshaft - Timing belt diagrams

Replace timing belt with tensioner (if needed)

Re-install timing belt and reassemble as needed

Note: If the timing belt drives the water pump it is a good idea to replace it at this time to avoid failure. Occasionally when bearing tension is released and then reloaded it can have an adverse effect on internal bearings.

How a Turbo Charger Works

A turbo charger is designed to help improve the power output of an engine beyond its normal operating capacity. A normally aspirated engine uses a mixture of air and fuel that is pulled into it from vacuum created by the cylinders. A turbo charger helps increase the amount of air injected into the engine, which also allows more fuel to be injected. This increase provides a higher power output.

A turbo charger increases the compression of the engine so to combat engine ping, low compression pistons are installed. A turbo charger utilizes a turbine which is driven by hot engine exhaust, when these gases expand it will spin the turbine at high speeds, which forces air into the engine. Engine oil is used to cool the turbine shaft in the turbo housing.

To help regulate the air intake pressure a device called a waste-gate is designed to release boost at a measured pressure point. This is done to limit the amount of boost the engine receives; if the engine is boosted too much it can cause internal engine failure. Turbo chargers help reduce the amount of fuel that is required to achieve the same level of power.

A turbo charged engine requires oil changes be more frequent than a non turbo charged engine. The turbo charger will break oil down sooner because of the added stress on the engine. When a turbo charger has failed it can cause the engine to have less power and burn oil excessively. A regular maintenance routine for a turbo charged vehicle will ensure proper operation and have less risk of breaking down, as well as damaging components.

How Variable Cam Timing Works (VCT)

Car manufacturers have developed a variable cam timing system that adjusts the cam to crankshaft timing depending on change in the engine speed and load. The engine computer plays a vital role in the engine's performance as it adjusts the camshaft timing depending on the vehicle's engine speed and load. In any range of engine speeds only one camshaft position (in relationship to the crankshaft) is optimum for power and economy. Pressurized engine oil is control by the engine computer through an oil control valve which allows engine oil to flow to the cam timing actuator (or phaser), as the oil is forced into the actuator the camshaft timing advances, when the pressure is released a return spring supplies force to return the actuator to standard position.

There are many types of camshaft arrangements; some common types are single overhead cam or SOHC, double overhead cam or DOHC and pushrod, rocker arm style of systems. In a single overhead cam type, the engine is equipped with only one cam per cylinder head. Therefore, there is one cam in a four cylinder engine, also with straight six cylinder engine. In v6 or v8 engine configurations there will be one camshaft for each cylinder head, two camshafts and double the camshafts for DOHC engines. The valve spring maintains pressure against the valve forcing the valve to contact the valve seat, sealing the intake or exhaust port. If the valve spring is weak or is broken the valve will lose pressure and will cause the engine to run poorly.

he specialty of a double overhead cam engine is that it has two cams per head. This means that the inline engines are equipped with two cams, four cams in V style engines. The use of double overhead cams is more common in engines which have more than two valves per cylinder. This is because a single camshaft doesn't have the ability to include sufficient cam lobes that can accommodate all the valves present in a three or four valve per cylinder engine. Double overhead cams give the advantage of adding more exhaust and intake valves. More valves allow the exhaust and intake gases to flow freely because of the increase in the number of openings, this in turn improves engine power and economy.

This system is not as efficient because of the increase in weight of the system. In turn, increases the valve springs load, slowing the engine down. Overhead camshaft engines are more efficient and can produce more power.

A Camshaft is commonly used to operate poppet valves in a piston engine. A cylindrical rod is situated in the cylinder block or cylinder head which has oblong lobes or cams which push a tappet or lifter to raise and lower the intake and exhaust valves. This force is applied on the valve directly or through an intermediate mechanism such as a rocker arm, lifter (cam follower) and push rods are used to press against the valve for movement. Each valve utilizes a spring which will return them to their original position (closed) after the force is removed.

ams are designed according to the RPM and horsepower range desired. When the intake valve is pushed open, the piston travels down pulling an air/fuel charge into the cylinder. This intake charge is a mixture of air and fuel and is ready for combustion. The faster the engine is running the faster the air and fuel mixture moves into the engine which also means that the intake and exhaust valves open and close quicker. This parameter is known as the valve duration and is controlled by the cam lobe width profile.

Basic Maintenance

A camshaft is driven by the crankshaft of the engine by a timing chain or timing belt. The timing belt or chain needs to be replaced per manufacturer's specifications because they wear out and fail without warning and stall the engine. Because a timing chain configuration is more durable when compared to the timing belt style a timing belt will need to be replaced more often, comparatively. Timing belts are more common in overhead cam engines and are more easily serviced.