How do exhaust systems work?

Exhaust System

The purpose of the exhaust/emission system is to deaden the sound made by the internal combustion engine, reduce the temperature of the exhaust, and control the emissions that come out of your vehicle.
Vehicles create harmful gases during the combustion of fuel. The catalytic converter in the exhaust system turns these gases into mostly harmless ones that do much less damage to the environment.
Some of the harmful gases that the exhaust system controls are:

• Hydrocarbons (unburned)
• Carbon Dioxide
• Sulfur Dioxide
• Carbon Monoxide
• Nitrogen Oxides
• Phosphorus
• Lead and Other Metals

Exhaust Manifold

The exhaust manifold conducts gases from the combustion chambers of the engine to the exhaust pipe. It is usually constructed of cast iron and smooth curves to improve the flow of exhaust.

Catalytic Converter

The catalytic converter reduces harmful emissions from engine exhaust. It uses a combination of heat and metals that act as catalysts. A catalyst is a metal (or chemical) that causes other chemicals to go through a reaction without being affected itself. The inside of the catalytic converter consists of metals like aluminum oxide, platinum palladium. These metals cause the carbon monoxide and hydrocarbons to react and produce water vapor and carbon dioxide which are much less harmful to the atmosphere.

Resonator

The muffler alone cannot always quiet all of the engine noise. Many exhaust systems also include a resonator which is like a mini muffler. They are usually straight pipes filled with sound muffling materials. The resonator can be either before of after the muffler in the exhaust system.

Exhaust Pipe

Exhaust pipe connects all the other parts of the exhaust system.

Muffler

The muffler quiets the noise of the engine. There are two kinds of mufflers. Onc uses baffled chambers to reduce noise. As sound waves move through this type of muffler, they bounce off the baffles and expend their energy inside the muffler, losing force and volume. The other type forces the exhaust straight through a perforated pipe that contains metal, fiberglass, or some other kind of sound-absorbing material. This muffler is designed to reduce back pressure (exhaust going back up the pipes) and consequently makes a little more noise.

Tail Pipe

The tail pipe comes out of the muffler, past the rear bumper of the vehicle, directing exhaust gases away from the vehicle. On many newer cars it also serves as a decorative function and is tipped in chrome.

Steering Mechanisms

The steering system on an automobile starts with exerting force on the steering wheel. This turning force is passed on to the pinion gear and is transferred to the rack. The tie rod on the end of the rack pushes or pulls the spindle to make the wheels turn.

Power Assist Piston

The power assist piston is a hydraulic unit that helps transmit force from the rack to the tie rod making it possible to steer the car while exerting less force on the steering wheel.

Pinion Gear

The pinion gear is attached to the steering wheel by the steering shaft. When the steering wheel is turned, the pinion gear turns. The teeth in the pinion gear mesh with the teeth on the rack, transferring the rotating motion to a side-to-side motion.

Rack

The rack is moved side to side by the motion of the pinion gear. The rack pushes or pulls on the tie rods which transmit the motion to the wheels. In a manual steering vehicle, all of the motion is controlled by the pinion gear moving the rack. In a power steering vehicle, there is a piston attached to the rack to help transmit the movement to the tie rods.

Tie Rod

The tie rod connects the key parts of the steering mechanism. They pass on the movement from the rack and pinion unit to the spindle connected to the wheel.

Spindle

The spindle is attached to the wheel and causes the wheel to turn when it is pushed or pulled by the tie rod, thereby turning the vehicle.

Rack and Pinion Unit

The rack and pinion unit houses the rack and pinion gear assemblies as well as the power assist piston.

Tire

The tire provides traction for steering and stopping the vehicle.

Suspension Systems

The purpose of the suspension system is to provide a smooth ride in the car and to help maintain control of the vehicle over rough terrain or in case of sudden stops. There are two basic types of suspension used in most cars today. Strut suspension and Conventional suspension. Suspension systems control the movement of the car and keep the tires in contact with the road, providing a better and safer ride.

Shock Absorber

Shock absorber's are attached to the car's frame near each wheel on most cars with conventional suspension systems. Shock absorbers are either housed inside coil springs, or mounted beside them.
When your car hits a bump, the spring contracts. The shock absorber works with a piston and thick fluid inside it to keep the spring from rebounding too quickly, making your car ride smoother, improving control and reducing tire wear.

Coil Spring

Coil Springs are a component in both Strut and Conventional Suspension systems. When your car goes over a bump or has to stop quickly, the coil spring contracts then rebounds. It is the job of the Strut or Shock Absorber to keep the coil spring from rebounding too quickly.

Strut Assembly (Strut and Cartridge)

Most front wheel drive cars have some kind of Strut Suspension. The strut is a special type of shock absorber that helps to minimize the motion of the suspension. The coil spring surrounds the strut assembly. Struts and shock absorbers work in very similar ways. However, struts function as a structural part of the Suspension System, and therefore also affect things like wheel alignment, vehicle control and suspension wear.

Strut Suspension System

Most front wheel drive cars have some sort of Strut Suspension System. In the Strut Suspension System, a coil spring with a bearing plate at each end supports the car. The spring assembly rests on a seat. The Strut Suspension System helps to cushion the movement of the coil spring when a car hits a bump or a pothole and works to hold the tires to the road and provide better vehicle control.

Conventional (Shock Absorber) Suspension System

In conventional (Shock Absorber) Suspension Systems, two control arms are attached to the frame of the car and a coil spring and shock absorber are attached to the frame and one of the control arms. The spring and shock absorber work together to smooth the ride of the car over the roughness of the road. This suspension system works to hold the tires to the road and provide better vehicle control.

Disk Brake System

Disk brake systems work by using hydraulic pressure to press a pad against the rotor to slow the vehicle. When the brake pedal is pressed, it acts upon the piston in the master cylinder which sends pressure via the brake lines to the caliper. The pad-to-rotor friction stops the wheel from turning.

Rotor

The rotor is a circular plate that is gripped by the brake pads in order to slow the vehicle.

Brake Pad

The brake pad is friction material that is pressed against the rotor to stop the wheel from turning.

Caliper

The caliper holds the brake pads. It straddles the rotor and uses hydraulic pressure from the brake lines, along with internal pistons, to force the brake pads against the rotor.

Brake Pedal

The brake pedal works as a lever to apply pressure against the master cylinder.

Master Cylinder

The master cylinder moves brake fluid under pressure to the rest of the braking system.

Drum Brake System

Drum brake systems work by using hydraulic pressure to press a pad against the brake drum to slow the vehicle. When the brake pedal is pressed, it acts upon the piston in the master cylinder which sends pressure via the brake lines to the wheel cylinders inside the brake drum. The shoe-to-drum friction stops the wheel from turning.  

Brake Drum

The brake drum is a heavy flat-topped cylinder, which is usually located between the wheel rim and the drive wheel. When the brakes are applied, the friction material of the brake shoes is forced into contact with the brake drum to slow the rotation of the wheels.

Wheel Cylinder

The wheel cylinder is a cylinder that contains pistons which use hydraulic force from the master cylinder to push the brake pads against the brake drum.

Brake Shoe

The brake shoe holds the brake lining and is used to force the lining against the drum when the brake is depressed.

Master Cylinder

The master cylinder moves brake fluid under pressure to rest of the braking system.

Brake Pedal

The brake pedal works as a lever to apply pressure against the master cylinder.

Engine Cooling System

An internal combustion engine creates a large amount of heat. Much of the heat goes out of the car through the exhaust system, but a great deal is still absorbed by the engine. Your engine runs best when it is warm, but if things get too hot, the pistons can weld themselves to the cylinders and that's the end of the engine. The cooling system is responsible for allowing the car to warm up to the correct working temperature and for maintaining that temperature.

Radiator Cap
The radiator cap has two functions. First, it is a "lid" for your radiator. Second (and more important), it is designed to hold the coolant inside the cooling system at a pre-determined amount of pressure. Liquids under pressure take a longer time to reach their boiling points. If the radiator cap did not keep the liquid coolant under pressure, all of the coolant would boil away, leaving your cooling system dry and your engine un-protected from the heat.

Radiator

The radiator is designed to dissipate the heat that the coolant has absorbed from the engine. Radiators are filled with tubes that the coolant passes through. Airflow from outside of the car and the fan carries heat off of the radiator. The coolant enters the receiving tank at the top of the radiator, passes through the tubes inside, losing the heat it has collected, then collects in the dispensing tank at the bottom for the water pump to circulate it back through the cooling system.

Fan

The coolant goes into the radiator to dissipate the heat that it collected in the engine. The heat is drawn off by air passing through the radiator. If the car is not moving fast enough to push air through the radiator, the fan will come on and pull the air through. The fan is usually mounted on the water pump shaft and is powered by the same belt that runs the water pump. Running the fan takes power from the engine, so it's only turned on when it is needed. The fan is controlled by a thermostat switch that tells it when the temperature has risen to a point where the fan is needed.

Water Pump

The water pump forces coolant to circulate through the engine block.

 Upper Hose

Coolant flows from the engine block back to the radiator through the upper radiator hose. This hose is blocked by the thermostat valve unless the temperature is high enough to allow the valve to move and let coolant through. Hoses are made from flexible rubber with either spiral wire embedded in them or fabric reinforcement. Hoses vary in size according to engine specifications. There are three types of hoses used in most vehicles: Straight, pre-bent, and accordion.

Thermostat

The job of the cooling system is to allow the engine to warm up to its optimum working temperature (between 180 and 200 degrees F) and then maintain that temperature. The thermostat regulates the temperature of the engine. It sits between the engine and the radiator and has a temperature sensitive valve that prevents coolant from entering the radiator when the temperature is too low. The valve recycles warm coolant through the engine block until it reaches the right temperature. At that point, the valve opens and the coolant enters the radiator to begin dissipating un-needed heat.

Coolant

The coolant in a car must be able to hold the heat from the engine then release it in the tubes of the radiator. Water is excellent for holding heat, but it freezes to readily to be an effective winter coolant in most places. The addition of antifreeze to the water significantly lowers the freezing temperature of the coolant. It also raises the boiling point, reducing the risk of boiling the coolant out of the system. The main ingredient in most standard antifreezes is ethylene (EG), most also add ingredients to prevent rust and corrosion in the cooling system.

Heater Core

The heater core is a mini-radiator that keeps your car warm when it's cold outside. The heater core is mounted under the dash of the car. It works on the same principle as the radiator (coolant flows through tubes inside it and releases heat into the air being forced by the tubes) but the heater fan blows the heat into the car instead of out of it. The heater core draws heat off the engine, so if your car is running a little hot, turning the heat on can help reduce heat in the engine until you can get to a mechanic.

Heater Fan

The heater fan blows air through the heater core into the cabin of your vehicle. It is activated by the controls on the dash board.

Engine Block

The engine block and cylinder head are manufactured in one piece with precast "Water Jackets", or passages for coolant. The water pump sends the coolant into the water jackets where the coolant absorbs the heat from the engine before returning to the radiator.

Lower Hose

The lower hose carries the coolant from the dispensing tank to the water pump. Hoses are made from flexible rubber with either spiral wire embedded in them or a fabric reinforcement. Hoses vary in size according to engine specifications. There are three types of hoses used in most vehicles: Straight, pre-bent, and accordion.

The Air Conditioner

There are many different types of vehicle AC systems, but they all work in basically the same manner. Warm air passes over a refrigerant, transfers its heat to the refrigerant and becomes cool air entering your vehicle.

Vent

Air passes through the vent into the interior of the vehicle.

Expansion Valve

The Expansion Valve determines the correct amount of refrigerant going into the evaporator, and it lowers the pressure of the refrigerant. When the compression starts, the expansion valve opens and the liquid refrigerant flows into it. Once in the expansion valve, the refrigerant is correctly pressurized. As the evaporator calls for more refrigerant, the expansion valve allows the required amount of refrigerant into the coils.

Evaporator

The evaporator is a long tube that goes back and forth through a set of cooling fins. The refrigerant enters the evaporator and a fan blows warm air over the evaporator. The cold refrigerant absorbs the heat from the warm air. Once it has absorbed the heat from the warm air, the warm air isn't warm anymore. The same blower that blows the warm air (that is now "cool" air) over the evaporator, keeps on blowing it into the interior of your car, and you have -- air conditioning!

Compressor

The compressor in your car works in a similar way to the one in your refrigerator. The job of the compressor is to move liquid refrigerant around in a pipe. The compressor pumps the liquid from the evaporator into the condenser and expansion valve, and then back to the evaporator.

Condenser

The condenser is a long tube that goes back and forth through a set of cooling fins. The condenser is mounted in front of the radiator to catch the forced air provided by the fan and the motion of the car. As the refrigerant flows into the condenser, it gives off heat. The refrigerant is warmer than the air passing over it so the condenser hands its heat off to the air and turns the refrigerant back into cool liquid in the expansion valve, where it heads back to the evaporator.

The Catalytic Converter

When your engine burns fuel, it produces gases that are bad for the environment. To prevent these gases from polluting the environment, a catalytic converter is included in the emission system. The catalytic converter is installed in the exhaust line, between the exhaust manifold and the muffler. The chemicals it contains cause a reaction in the pollutants in the exhaust. The pollutants are changed from harmful gases to harmless ones before they are let into the air through the tail pipe.

Inlet From Air Pump

The air pump sends compressed air into the catalytic converter. The oxygen in the pressurized air helps to burn any unburned fuel and so converts the poisonous carbon monoxide into harmless carbon dioxide.

3 Way Catalysts

The materials inside a catalytic converter vary between cars. Newer catalytic converters have a two part design. The front half is a "3 way" catalyst, which burns pollutants, and reduces hydrocarbons, carbon monoxide, and oxides of nitrogen into water, carbon dioxide and nitrogen.

Mixing Chamber

Newer catalytic converters have a two part design. The font half is a "3 way" catalyst. The rear section is the normal oxidation catalyst. Air from the air pump is injected into the center of these converters. Here the air is allowed to mix with the exhaust before it passes into the oxidation catalyst, where it burns off its toxic chemicals and reduces emissions.

Oxidation Catalyst

The materials within a catalytic converter vary between cars. Some catalytic converters use what is called an "oxidation" catalyst; this usually consists of ceramic beads coated with platinum to reduce hydrocarbons and carbon monoxide. Through the catalytic action, the hydrocarbons and carbon monoxide are "burned" to create water vapor and carbon dioxide.

Catalytic Pellets

Catalytic converters are designed to do different things, depending on their design. Some catalytic converters use what is called an "oxidation" catalyst; this usually consists of ceramic beads coated with platinum to reduce hydrocarbons and carbon monoxide. Through the catalytic action, the hydrocarbons and carbon monoxide are "burned" to create water vapor and carbon dioxide.