Engine Basics – The Core of Your Car

Engines

The best way to convert gasoline into motion in a car is to burn it in a chamber, so that it can be converted into mechanical energy. The “chamber” in which this is done is called an internal combustion energy. An internal combustion engine (ICE) is one in which combustion takes place inside the engine. In contrast to this, an external combustion engine burns energy outside the engine, like in a steam engine where the coal is burnt separately.

Advantages of an ICE over an ECE include more fuel efficiency and a better size to power ratio. A disadvantage is that in an ECE, any fuel can be used to produce motion, whereas a specific ICE is usually configured to run on a specific type of fuel.

Since all cars run on internal combustion engines, we’ll look at how they work in this article.

The Internal Combustion Engine (ICE)

The principle behind an ICE is that when even a small drop of fuel is ignited in a small enclosed space, it has the capability to push down the piston with enormous force. This force is used to rotate the crankshaft and then run the car by transmitting the power to different parts of the engine.

The different parts of an engine are the cylinder, piston and valves. The piston is a component which fits in the cylinder and moves up and down. This piston is connected to a shaft, called the crank shaft, which transmits power to different parts of the car. The cylinder is a chamber in which fuel is burnt. The movement of the piston produces the power to run your car. Valves are positioned in the fuel intake and the exhaust outlet, so as to let in fuel and give out the exhaust gases at different strokes.

Different kinds of strokes

The cycle used in an internal combustion engine is called a four stroke cycle. This cycle is called an Otto cycle, named after Nikolaus Otto. The four strokes involved in this process are

1. Intake stroke

In this stroke, one valve opens and lets the fuel into the cylinder. The piston moves down in the cylinder to accomodate the mixture of air and fuel. The fuel is taken in in the form of small drops so that efficiency is as high as possible.

2. Compression stroke

The compression stroke is next. Here, the piston pushes up, compressing the air and fuel mixture. Compression is done so that when power is produced due to exhaust gases, they have increased tendency to expand. This increased tendency is because of two factors.

               1. High pressure : Compressing the fuel air mixture causes the exhaust gases to be compressed as well. Since they are compressed, they already possess a tendency to escape.

               2. High Temperature : Combustion results in hot gases. Hot gases occupy extra volume due to expansion, and this further increases the tendency to expand.

More the tendency to expand, more the power produced due to expansion, when it takes place.

3. Combustion stroke

The combustion stroke is the most important stroke in an engine. In this stroke, the compressed air and gas mixture is ignited by a spark plug placed at the top of the cylinder, next to the valves. The spark plug acts as an ignition, producing a spark to initiate combustion. This produces an enormous amount of power, pushing the piston down, and rotating the shaft in the process.

4. Exhaust stroke

Now that the exhaust gases have done their job pushing the piston down and producing work, they have to be pushed out. This is the job of the exhaust valve. As soon as the piston reaches the bottom of the stroke, the exhaust valve opens and the gases are let out when the piston moves up again.

This cycle is repeated again and again and the rotation of the crank shaft is transmitted to the wheels of the car, which produces rotational motion on the surface of the road, thus moving your car forward.

The parts that make it work

Now, let’s look at the parts involved in doing this in more detail.

The Cylinder

As we saw earlier, the main part of an engine is the cylinder. A typical engine has more than one cylinder, arranged in a particular formation. Usually, a car has 4, 6 or 8 cylinders in one of three common configurations.

In an inline configuration, the cylinders are arranged in a straight line and the pistons are connected to the crank shaft in an alternating or synchronized pattern.

In a V configuration, the cylinders are at an angle (usually 90º) to each other. The final configuration is a flat configuration, where the cylinders are arranged so that the pistons reciprocate in opposite directions to each other.

The Spark Plug

The spark plug is an important component in the engine, as it induces the combustion in the engine. It is simply a device which produces a high amount of voltage, high enough to ionize the air next to it and create s spark. This helps in igniting the mixture of fuel and gas.

Valves

Valves are of two types – intake and exhaust. These valves open at the right time to let in the fuel and let out the exhaust. One thing to note here is that during compression and combustion, both valves remain closed so the cylinder is completely sealed.

Piston and Piston rings

The piston is a component that moves up and down in the cylinder depending on the stroke. It is one of the main sources of wastage of energy, due to friction between the walls of the cylinder and the piston.

Piston rings are rings that are fitted on top of the pistons. They seal the gap between the cylinder and the piston. The main purpose of piston rings is to prevent oil provided for lubrication of the crank shaft from going into the cylinder and burning up. It also prevents fuel and air from leaking out of the cylinder.

The Connecting rods and the Crank Shaft

Connecting rods connect the piston to the crank shaft. It rotates at both sides of the crankshaft, so as the piston moves up and down, it keeps on rotating the crank shaft in the same direction.

The crankshaft converts the up and down motion of the piston into rotational motion.

The Oil Sump

The sump contains oil, which is used to lubricate the connecting rod and the crank shaft. Oil collects at the bottom of the sump, called oil pan.

All these parts of the engine have to work perfectly and intricately for us to make our daily commute to work in peace. Newer types of engines have been influencing the market ever since, but the compactness and the wide usage of the ICE has kept it under the hood of your car for so long. And it will remain there for longer, until a better technology arrives and radically changes our perception of a car.