Engines 101: The Basics of How Engines Work | Toyota

0:00 Just about everyone knows that a typical automobile gets its power from an engine under the hood. But how many people can say they actually know how that engine works? While a modern internal combustion engine is obviously an extremely complex piece of machinery, the basic principle behind it is pretty simple. Let's take a closer look. At a high level, a gasoline engine can be thought of somewhat like an air pump, except that the exhaust coming out is more of a side effect. This pump's real purpose is to rotate an internal shaft, which in turn rotates the vehicle's wheels. It does this by connecting that shaft, called a crankshaft, to pistons that move due to a mixture of air and gasoline combusting inside their cylinders, which creates a sort of chain reaction

0:46 that keeps the engine turning. Before getting deeper into this process, let's first touch on the two main parts of an engine. On the bottom, A lower block is home to the pistons, cylinders, and crankshaft, the latter of which sends the engine's power out to the transmission and wheels. And above, the head contains the top of the cylinders and manages their airflow and combustion through valvetrain, fuel injection, and ignition systems. So let's explain that part a little more. You may have heard the term four-stroke to describe a vehicle engine. This refers to its four stages of operation. First, the piston moves down, creating a vacuum in the cylinder chamber that pulls air

1:31 in through precisely controlled intake valves. Next, the valves close and the piston raises back up, compressing all that air, along with some gasoline that was mixed in from the fuel injection system. Now the fun part. The ignition system creates a spark at the end of the spark plug, creating a controlled explosion of compressed air and fuel that sends the piston back down. Then finally, the piston moves back up, pushing that spent air-fuel mixture through the exhaust valves and out to the, you guessed it, exhaust pipes. And since we're dealing with multiple cylinders with pistons all working from the same crankshaft, each one essentially creates the four-stroke process for the next one. Pretty ingenious, right? Now, speaking of multiple cylinders,

2:19 let's talk about the various engine configurations. Four-cylinder engines are probably the most common design these days, but who doesn't love a V6 or even a V8? These terms simply refer to the number of cylinders in the engine and their layout. Nearly all four-cylinder engines have their cylinders arranged in a row, called inline or straight. But it's also pretty typical to see engines group their cylinders into two banks connected at an angle, a V. Doing it this way effectively cuts the engine length in half, enabling it to fit more easily under the hood. So a V6, three cylinders on either side, creating a V-shape. And what if that V-shape was opened up all the way, a 180-degree angle? Well, then you'd have what's called a boxer or flat

3:08 engine design. All right, so what about those other numbers you always see, 2.0, 3.5? Well, that refers to the engine's displacement. often simply thought of as its size. That number is literally the volume in liters that the pistons displace with every engine cycle. So essentially, if you were to fill up the cylinders of a two-liter engine with liquid, it would take, well, two liters. And if it's a four-cylinder engine, each one displaces half a liter. So what's the end result of all this? Power. The measurable output of an engine is called its torque. basically the strength with which it turns its crankshaft. Torque is measured in pound-feet, which, as the name implies,

3:55 is the force created by one pound of weight at a distance of one foot. Imagine a one-pound weight sitting at the end of a one-foot wrench. That nut is being turned with one pound-foot of torque. So now, going back to the displacement concept, bigger cylinders pull in more air and fuel, typically resulting in more muscle. They turn the crankshaft with more force, which is perfect for large vehicles, towing, or even just spirited driving. So now you're probably thinking, isn't that horsepower? Well, yes and no. In fact, horsepower doesn't technically exist. Okay, yes, that requires a bit of explanation. Horsepower is obviously a real thing, but it's actually a calculation, not a physical measurement like torque is. It's basically torque over time.

4:45 So this means the faster that engine turns, its revolutions per minute or RPM, the more work it can do and the more horsepower it has. Put in extremely simplified terms, torque times RPM equals horsepower. But that doesn't mean making big horsepower is as simple as spinning the engine faster since that takes more and more energy as the engine speed increases. And as that torque decreases, the horsepower calculation eventually can't keep up either. This is also why transmissions are so critical in keeping everything in the appropriate sweet spot, but that's a topic for another video. So that's the general idea behind internal combustion engines. But this was just a high-level look at the basics, engines 101, if you will. There's obviously a whole lot more to

5:33 say about engine tech, so be sure to check out the other videos in this series to learn more.