How do gasoline engines work

For most people, a car is a thing they fill with gas that moves them from point A to point B. But have you ever stopped and thought, How does it actually do that? What makes it move? Unless you have already adopted an electric car as your daily driver, the magic of how comes down to the internal-combustion engine —that thing making noise under the hood. But how does an engine work, exactly? Specifically, an internal-combustion engine is a heat engine in that it converts energy from the heat of burning gasoline into mechanical work, or torque.

That torque is applied to the wheels to make the car move. And unless you are driving an ancient two-stroke Saab which sounds like an old chain saw and belches oily smoke out its exhaust , your engine works on the same basic principles whether you're wheeling a Ford or a Ferrari.

Engines have pistons that move up and down inside metal tubes called cylinders. Imagine riding a bicycle: Your legs move up and down to turn the pedals. Pistons are connected via rods they're like your shins to a crankshaft, and they move up and down to spin the engine's crankshaft, the same way your legs spin the bike's—which in turn powers the bike's drive wheel or car's drive wheels. Depending on the vehicle, there are typically between two and 12 cylinders in its engine, with a piston moving up and down in each.

What powers those pistons up and down are thousands of tiny controlled explosions occurring each minute, created by mixing fuel with oxygen and igniting the mixture. Each time the fuel ignites is called the combustion, or power, stroke.

The heat and expanding gases from this miniexplosion push the piston down in the cylinder. Almost all of today's internal-combustion engines to keep it simple, we'll focus on gasoline powerplants here are of the four-stroke variety.

Beyond 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. Diesel engines are one type and gas turbine engines are another. Each has its own advantages and disadvantages. There is also the external combustion engine. The steam engine in old-fashioned trains and steam boats is the best example of an external combustion engine. The fuel coal, wood, oil in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine.

Internal combustion is a lot more efficient than external combustion, plus an internal combustion engine is a lot smaller. Internal Combustion The principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy-density fuel like gasoline in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas.

Intake stroke Compression stroke Combustion stroke Exhaust stroke. The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work. Compression makes the explosion more powerful. Part 2 of the animation When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline.

The gasoline charge in the cylinder explodes , driving the piston down. Part 3 of the animation Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. Part 4 of the animation. Basic Engine Parts " ". Figure 2. Inline: The cylinders are arranged in a line in a single bank. Figure 3. V: The cylinders are arranged in two banks set at an angle to one another.

Figure 4. Flat: The cylinders are arranged in two banks on opposite sides of the engine. They keep oil in the sump from leaking into the combustion area, where it would be burned and lost. Engine Problems " ". Car engines can have all sorts of problems, whether fuel related or battery related. You are out of gas , so the engine is getting air but no fuel.

The air intake might be clogged, so there is fuel but not enough air. The fuel system might be supplying too much or too little fuel to the mix, meaning that combustion does not occur properly.

There might be an impurity in the fuel like water in your gas tank that prevents the fuel from burning. The intake or exhaust valves are not sealing properly, again allowing a leak during compression.

There is a hole in the cylinder. If your sparkplug or the wire leading to it is worn out, the spark will be weak. If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark. If the spark occurs either too early or too late in the cycle i. If the battery is dead, you cannot turn over the engine to start it.

If the bearings that allow the crankshaft to turn freely are worn out, the crankshaft cannot turn so the engine cannot run. If the valves do not open and close at the right time or at all, air cannot get in and exhaust cannot get out, so the engine cannot run. If you run out of oil, the piston cannot move up and down freely in the cylinder, and the engine will seize.

Engine Valve Train and Ignition Systems " ". Engine Cooling, Air-intake and Starting Systems " ". This diagram shows details of how a cooling system and the plumbing is connected.

All of the internal friction caused by the piston rings The compression pressure of any cylinder s that happens to be in the compression stroke The energy needed to open and close valves with the camshaft All of the other things directly attached to the engine, like the water pump, oil pump, alternator, etc.

The exhaust system of your car includes the exhaust pipe and the muffler. Producing More Engine Power " ". Adding a turbocharger to a car's engine can help increase it's overall power and performance. Engine Questions and Answers Here is a set of engine-related questions from readers and their answers: What is the difference between a gasoline engine and a diesel engine?

In a diesel engine, there is no spark plug. Instead, diesel fuel is injected into the cylinder, and the heat and pressure of the compression stroke cause the fuel to ignite. Diesel fuel has a higher energy density than gasoline, so a diesel engine gets better mileage. See How Diesel Engines Work for more information. What is the difference between a two-stroke and a four-stroke engine? Most chain saws and boat motors use two-stroke engines. A two-stroke engine has no moving valves, and the spark plug fires each time the piston hits the top of its cycle.

A hole in the lower part of the cylinder wall lets in gas and air. As the piston moves up it is compressed, the spark plug ignites combustion, and exhaust exits through another hole in the cylinder.

You have to mix oil into the gas in a two-stroke engine because the holes in the cylinder wall prevent the use of rings to seal the combustion chamber. Generally, a two-stroke engine produces a lot of power for its size because there are twice as many combustion cycles occurring per rotation.

However, a two-stroke engine uses more gasoline and burns lots of oil, so it is far more polluting. See How Two-stroke Engines Work for more information. You mentioned steam engines in this article — are there any advantages to steam engines and other external combustion engines? The main advantage of a steam engine is that you can use anything that burns as the fuel. For example, a steam engine can use coal, newspaper or wood for the fuel, while an internal combustion engine needs pure, high-quality liquid or gaseous fuel.

See How Steam Engines Work for more information. Why have eight cylinders in an engine? Why not have one big cylinder of the same displacement of the eight cylinders instead? There are a couple of reasons why a big 4. The main reason is smoothness. A V-8 engine is much smoother because it has eight evenly spaced explosions instead of one big explosion.

Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders 1 liter through their compression strokes, but with one big cylinder you would have to compress 4 liters instead. How Are 4-cylinder and V6 Engines Different? The Fusion V6 Sport comes standard with a 2. A car engine is an internal combustion engine. What is the function of a car engine? What are the parts of a car engine? Other key parts include the spark plug, valves, piston, piston rings, connecting rod, crankshaft and sump.

How does a car engine work, step by step? They are intake stroke, compression stroke, combustion stroke and exhaust stroke. Why won't my engine start? Animated Engines Erbman's Engine Emporium. Sources Associated Press. Cite This!

Try Our Sudoku Puzzles! More Awesome Stuff. A camshaft's job is to regulate when fuel is let into the engine, and when exhaust is let out.

The purpose of a fuel injector is to atomize the fuel. This means to turn the liquid fuel into a mist, which drastically increases its surface area.

This allows the fuel to combust more quickly, giving greater impulse to the piston. The crankshaft is the glue that connects the parts of the engine. Its purpose is to turn the linear up and down motion of the pistons into rotational motion. One end of the crankshaft is attached to the camshaft, via a timing belt.

The other end is connected to the flywheel, which regulates the power coming out of the engine, sort of like a surge protector for your computer. The flywheel is a power management device for the engine. It is connected to the clutch, which is connected to the transmission. To learn more about how an engine delivers its power to the wheels, click here.