Diesel engines are similar to gasoline engines, but they have no spark plugs.
A diesel engine uses diesel as fuel. Compared to gasoline, diesel is less volatile and does not mix with air easily. Therefore, the cylinder takes in only air, not an air-fuel mixture. The air is compressed and heated up to a high temperature. When fuel is injected into the cylinder, it ignites spontaneously.
There are two types of brakes: drum brakes and disc brakes. Both braking systems use hydraulics.
When the brake pedal is pressed, it moves the piston in the master cylinder, and raises the pressure of the brake fluid in the pipes that lead to the wheels. This pressure pushes pistons in the wheel cylinders, and forces the brake shoes out against the brake drums.
Disc brakes use the same hydraulic system as that of drum brakes. A disc brake has a disc and a caliper. The disc is fixed to the wheel, and the caliper contains two brake pads and two hydraulic cylinders. The hydraulic pressure pushes pistons in the cylinders and, as a result, pushes the pads against both sides of a spinning disk.
The suspension of a car enables it to drive smoothly on the road. This system absorbs bumps and jolts caused from driving on rough road surfaces and maintains driving stability. A suspension system mainly consists of a coil spring, a shock absorber, and control arms.
Coil spring: This supports the car body and keeps the tire in firm contact with the road surface.
Shock absorber: This reduces the bouncing movement of the spring and provides a comfortable ride.
Control arms: These connect the car body to the wheel and keep the wheel upright.
A gasoline engine is an internal combustion engine.
A gasoline engine burns a mixture of air and gasoline in cylinders. Each cylinder contains a piston. When the mixture explodes, the pressure generated forces down the piston. The piston then turns a crankshaft that is linked to the wheels.
Most gasoline engines are four-stroke engines. A stroke is an upward or downward movement of a piston.
＜The cycle of a four-stroke gasoline engine＞
1. Induction stroke: The inlet valve opens. The mixture of gasoline and air enters the cylinder. The piston moves downwards.
2. Compression stroke: The inlet valve closes. The piston moves upwards and compresses the mixture.
3. Power stroke/Ignition stroke: The spark plug produces a spark, which ignites the mixture. The increased pressure forces down the piston.
4. Exhaust stroke: The outlet valve opens. The piston moves upwards and forces the exhaust gases out of the cylinder. The outlet valve closes.