For most people, an automobile is something they fill with fuel that moves them from place to place. But have you ever stopped and thought, How does it do that? What makes it move? How does an engine work, exactly?
Specifically, an internal-combustion engine is a heat engine in that it converts power from the heat of burning gas into mechanical work, or torque. That torque is carried out to the wheels to make the car move. And unless you’re using a historical two-stroke Saab (which feels like a vintage chain saw and belches oily smoke out its exhaust), your engine works on the equal simple principles whether or not you are wheeling a Maruti or a Ferrari.
Engines have pistons that pass up and down in inner metal tubes known as cylinders. When using a bicycle your legs circulate up and down to move the pedals. Pistons are connected through rods (they are like your shins) to a crankshaft, and that they move up and down to spin the engine’s crankshaft, the same manner your legs spin the bike’s pedals which in turn powers the bike’s drive wheel or car’s pressure wheels. Depending on the vehicle, there are could be 2 to 12 cylinders in its engine, with a piston moving up and down in each.
1. Where the engine power comes from
- What powers the one’s pistons up and down are lots of tiny managed explosions occurring each minute, created by mixing fuel with oxygen and igniting the mixture.
- Each time the fuel ignites it is referred to as the combustion, or power, stroke.
- The heat and expanding gases from this mini-explosion push the piston down in the cylinder.
- Almost all of the cutting-edge internal-combustion engines are of the four-stroke variety.
- Beyond the combustion stroke, which pushes the piston down from the top of the cylinder, there are 3 different strokes: consumption, compression, and exhaust.
- Engines need air (particularly oxygen) to burn fuel.
- During the consumption stroke, valves open to allow the piston to behave like a syringe because it acts downward, drawing in ambient air through the engine’s consumption system.
- When the piston reaches the lowest of its stroke, the intake valves close, effectively sealing the cylinder for the compression stroke, that’s inside the opposite path as the consumption stroke.
- The upward motion of the piston compresses the consumption charge.
2. The four strokes of a four-stroke engine
- In most modern-day contemporary engines, gas is injected at once into the cylinders to the top of the compression stroke. (Other engines premix the air and fuel at some point of the intake stroke.)
- In either case, just before the piston reaches the top of its travel, referred to as top dead center, spark plugs ignite the air and fuel mixture.
- The resulting expansion of hot, burning gases pushes the piston within the opposite course (down) for the duration of the combustion stroke.
- This is the stroke that receives the wheels on your vehicle rolling, just like while you push down on the pedals of a bike.
- When the combustion stroke reaches the bottom end center, exhaust valves open to permit the combustion gases to get pumped out of the engine (like a syringe expelling air) because the piston comes up again.
- When the exhaust is expelled it continues through the car’s exhaust device before exiting from the back of the vehicle.
- The exhaust valves close at the top dead center, and the whole process starts over again.
- In a multicylinder vehicle engine, the individual cylinders’ cycles are offset from each other and sufficiently spaced so that the combustion strokes do no longer occur simultaneously.
- This is done so that the engine is as balanced and smooth as possible.
- But no longer all engines are created equal.
- They come in many shapes and sizes.
- Most vehicle engines arrange their cylinders in a straight line, which includes an inline-four or combine two banks of inline cylinders in a V, as in a V-6 or a V-8.
- Engines are also classified considering their size, or displacement, which is the combined volume of an engine’s cylinders.
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