For most people, a car is a thing they fill with gasoline that moves them from point A to point B. But have you ever stopped and thought, how does it actually do it? What moves it If you haven’t already adopted an electric car as your daily driver, the magic of how the internal combustion engine matters comes is the noise under the hood. But how does an engine work exactly?
In particular, an internal combustion engine is a heat engine in that it converts energy from the heat of the burning gasoline into mechanical work or torque. This torque is applied to the wheels to set the car in motion. And unless you’re driving an old two-stroke Saab (which sounds like an old chainsaw and has an oily exhaust pipe), your engine operates on the same basic principles whether you’re driving a Ford or a Ferrari.
Engines have pistons that move up and down in metal tubes called cylinders. Imagine riding a bicycle: your legs move up and down to turn the pedals. The pistons are connected to a crankshaft by rods (they are like your shins) and move up and down to turn the engine’s crankshaft, just as your legs turn the bike, which in turn is the drive wheel of the bike or the drive wheels of the car drives. Depending on the vehicle, there are usually two to twelve cylinders in the engine, with one piston moving up and down at a time.
Where Engine Power Comes From
What drives these pistons up and down are thousands of tiny controlled explosions that occur every minute, created by mixing fuel with oxygen and igniting the mixture. Every time the fuel ignites it is known as the combustion, or power, stroke. The heat and expanding gases of this mini-explosion push the piston down in the cylinder.
The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke.
Almost all internal combustion engines today (to keep it simple, let’s focus on gasoline power plants here) are four-stroke engines. In addition to the combustion stroke, which pushes the piston down from the top of the cylinder, there are three other strokes: intake, compression, and exhaust.
Engines need air (namely oxygen) to burn fuel. During the intake stroke, the valves open to making the plunger act like a syringe as it moves down and draws in ambient air through the engine’s intake system. When the piston reaches the bottom of its stroke, the intake valves close, effectively sealing the cylinder for the compression stroke, which is in the opposite direction as the intake stroke. The upward movement of the piston compresses the induction charge.
The Four Strokes of a Four-Stroke Engine
In today’s most modern engines, gasoline is injected directly into the cylinders near the top of the compression stroke. (Other engines premix air and fuel during the intake stroke.) In either case, spark plugs ignite the air-fuel mixture just before the piston reaches the top of its stroke, known as top dead center.
The resulting expansion of hot, burning gases pushes the piston in the opposite direction (downward) during the combustion stroke. This is the hub that makes your car’s wheels roll, just like when you step on the pedals of a bicycle.
When the combustion stroke reaches bottom dead center, the exhaust valves open to allow the combustion gases to be pumped out of the engine (like a syringe expelling air) when the piston comes back up. When the exhaust is expelled, it passes through the vehicle’s exhaust system before exiting the rear of the vehicle. The exhaust valves close at top dead center and the whole process starts over.
In a multi-cylinder car engine, the cycles of the individual cylinders are offset from one another and evenly distributed so that the combustion strokes do not occur at the same time and the engine is as balanced and quiet as possible.
But not all engines are created equal. They come in many shapes and sizes. Most automobile engines arrange their cylinders in a straight line, such as an in-line quad, or combine two rows of in-line cylinders in a V, as in a V-6 or a V-8. Engines are also classified according to their size or displacement, which is the total volume of an engine’s cylinders.
The Different Types of Engines
There are, of course, exceptions and tiny differences between the internal combustion engines on the market. Atkinson engines, for example, change valve timing to make a more efficient but less powerful engine.
Charging and supercharging turbochargers, grouped under the forced aspiration options, pumps extra air into the engine, increasing the available oxygen, and therefore the amount of fuel that can be burned, resulting in more power when you are wish so, and to be more efficient when you don’t need the strength.
Diesel engines do all of this without spark plugs. Regardless of the engine, the fundamentals of functionality remain unchanged as long as it is an internal combustion engine. And now you know her.
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