MNG: Home of the Customer Retention System: References: Systems

MechanicNet Group, Inc.
7150 Koll Center Parkway, Suite 200
Pleasanton, CA 94566
1-877-MECH-NET
info@mechanicnet.com

What Makes A Car Go?

What happens when you turn the key? How is it that when you push on the gas pedal, your car zooms off? We want to help you figure out what makes your car go and understand the basic automotive systems of your car.

It may sound a little frightening that there are actual little explosions happening under your hood, but that’s exactly what makes your engine go. But it all starts with a turn of the key:

1. You insert the key into your car’s ignition and turn it to Start. This causes a switch to close, allowing the electrical current to pass from your car’s battery to the starter via the starter solenoid switch. The starter causes the engine to rotate (or turnover) and then begin to run.

2. Once the engine begins to run, gasoline hustles through fuel lines from the fuel tank at the rear of the car to the fuel pump. The fuel pump then pumps the gas through a fuel filter and into the carburetor or fuel-injectors.

3. The fuel begins to mix with air to form a vapor mixture that passes into the cylinders in your engine. Once inside the cylinders (or combustion chamber), the fuel vapor is compressed into a very small space by the upward motion of the pistons.

4. Then a spark from the spark plugs ignites and explodes this mixture, powerfully forcing the piston downward.

5. As the pistons are forced up and down, connecting rods that are attached to the bottom of the pistons begin to turn the crankshaft in circles, which eventually causes the car’s wheels to turn. It’s like when you ride a bike: your knees go up and down while your foot pedals around and around.

6. At the other end of the crankshaft is a box of gears called the transmission. When you shift the gear into Drive, or First if you have a “stick shift”, the gears cause the crankshaft to turn. At the point where the crankshaft leaves the transmission, it’s called the driveshaft and runs to the rear wheels where it meets up with another set of gears called the differential. The differential essentially changes the direction of the power coming from the driveshaft so that the wheels will turn. The differential also allows the wheels to rotate at different speeds when you are turning.

7. The drive wheels then begin to turn and push the car forward or backward and away you go!

Once your car is started and running, many other systems work together to help it run smoothly.

Ignition

Cooling

Lubrication

Exhaust

Brake

The Ignition System

Just as electricity was needed to start your car, it’s also necessary to keep it running. This is another role of the ignition system. As your car is running, the spark plugs continue to provide the sparks which keep the air and fuel mixture burning. How does this work? Well, the electrical current passes from the alternator to the coil. The coil converts the low voltage current from your battery to a very high voltage current used to ignite the fuel. From the coil, the current goes to the distributor which smartly directs it through the spark plug wires to the proper spark plug at the appropriate time. As the current jumps the spark plug gap, the fuel in a cylinder is ignited to cause the explosion that in turn drives the pistons.

The Cooling System

All this burning fuel and friction going on in your engine can really heat things up. This is where the cooling system comes in to quickly reduce the engine’s temperature. If your engine water cooled (most are), it is done by continuously circulating water and coolant via a water pump from your radiator through pipes in your engine called water jackets. The water picks up heat as it goes through the water jackets in the engine, then gets cooled down when it goes through the radiator. Ever notice that a fan may come on in your engine when you come to a stop? Well, air is also valuable in keeping your engine cooled down. As you’re driving, air passes through naturally, but when you stop, your engine may need the fan to come on and keep the air circulating. In some cars, the fan is triggered by an electric switch so it only comes on when needed. In other cars, the fan is driven by a belt in which case it is always turning when the engine is on.

The Lubrication System

Oil circulates through your engine to keep its moving parts lubricated to move freely. It reduces the friction that causes your engine to heat up and suffer wear and tear. These moving parts include the pistons, valves, connecting rods and crankshaft. The oil is usually poured through an opening at the top of the engine. It is held a the bottom of the engine to be pumped and splashed throughout. An oil pump keeps the oil circulating and an oil filter keeps it clean. Without oil, driving your car will cause permanent damage to your engine. You can check the amount of oil remaining in your engine by pulling out the oil dipstick and comparing the oil level with the specified marks.

The Exhaust System

The exhaust system serves as the waste disposal system for your car. Exhaust gases are created from the burnt fuel and air mixture that was ignited in the cylinders and passes through exhaust pipes to the tailpipe. Before the burnt gasses leave the car, it passes through usually two devices. Newer cars are equipped with a catalytic converter which re-burns some of the unburned gas in the tailpipe to reduce pollution. Because these gases contain carbon monoxide which is poisonous to breathe, the catalytic converter plays a crucial role in keeping our air clean. In most states, you are required to take your car in for regular smog checks to ensure that your emission control systems are working properly. Another device, called the muffler, controls the noise of the escaping gases. If it’s not working properly, you could definitely hear it!

The Brake System

We all know that to stop a car, you step on the brake pedal. When you press the brake pedal, it presses against a piston in what’s called a master cylinder that is filled with brake fluid. When the piston is pushed by the brake pedal, it forces the brake fluid out of the master cylinder into tubes called brake lines, which run to each wheel of your car. The brake fluid then forces little pistons into the flat steel discs at each wheel (i.e., disc brakes). Brake pads located between the disc and the pistons grab the disc with their rough surfaces and force the disc to stop turning, which in turn forces the wheels to stop turning. Some cars use drum brakes. In this case, the pads are located inside a hollow rotating drum. The brake fluid forces little pistons that push pads outwards to stop the rotating drum which in turn stop the wheels.