All About the Internal Combustion Engine

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Podcast Transcript

One of the technologies which helped make the modern world is the internal combustion engine. Without it, the world would be a very different place today. 

Yet it wasn’t a technology that appeared fully formed. It was developed incrementally over a century. To get it to a point where it was viable for use in vehicles took numerous innovations. 

Learn more about the internal combustion engine, how it was developed and all the problems that had to be solved, on this episode of Everything Everywhere Daily.


This episode is sponsored by Audible.com.

My audiobook recommendation today is Are We There Yet? The American Automobile Past, Present, and Driverless by Dan Albert

Crusades against the automobile are nothing new. Its arrival sparked battles over street space, pitting the masses against the millionaires who terrorized pedestrians. When the masses got cars of their own, they learned to love driving, too. 

During World War II, Washington nationalized Detroit and postwar Americans embraced car and country as if they were one. Then came 1960s environmentalism and the energy crises of the 1970s. 

Many predicted, even welcomed, the death of the automobile. But many more rose to its defense. They embraced trucker culture and took to Citizen Band radios, demanding enough gas to keep their big boats afloat. Since the 1980s, the car culture has triumphed and we now drive more miles than ever before.

You can get a free one-month trial to Audible and 2 free audiobooks by going to audibletrial.com/EverythingEverywhere or clicking on the link in the show notes.


I think a good place to start this discussion is to define what an engine is. An engine is something that converts combustion into work. It is distinct from a motor that converts electricity into work. Even though the terms are often used interchangeably, motors and engines are very different things. 

The first engines were steam engines. A steam engine was based on creating heat, either through wood, coal, or some other combustible substance, and boiling water. The steam would then turn a turbine which would turn a crank that could do work. 

The key to a steam engine was simply the creation of heat so water could be boiled. What was burned to create the heat was dependent on what was available and cheapest. 

An internal combustion engine works differently. An internal combustion engine relies on the combustion of fuel and the subsequent expansion of the hot gas which is created. The combustion has to be enclosed in a space to capture the pressure of the expanding gas, or in other words, it has to be internal. 

An internal combustion engine is far more difficult to engineer than a steam engine for this reason. The basics of a steam engine were first built in ancient Greece. The internal combustion engine, however, wasn’t developed until the second half of the 19th century. 

The first internal combustion engine was developed by the Belgian engineer Jean Joseph Étienne Lenoir in 1859.  His engine was rather crude insofar it was a steam engine which was converted to burn coal gas. 

The person who is considered the originator of the modern internal combustion engine was the German engineer Nicolaus Otto who defined the Otto Cycle in 1877 and built the first multistroke engine.


What is the Otto Cycle? The Otto Cycle described the four-stage process by which fuel is burned in an engine.

I’ll explain it briefly here because it is the basis of everything going forward. This is how a typical four-stroke engine works in most cars in the world. There are variations on this process and smaller engines, like lawnmowers, use a two-stroke process. But for the purpose of this episode, I’m going to talk about the four-stroke process. 

This all takes place in a cylinder with a movable piston at the bottom of the cylinder, with fuel and air intakes and an exhaust port at the top which can be turned on and off. 

The first stroke is called the intake stroke. Here the piston will pull down creating a suction that will pull in a fuel-air mixture through an open intake valve. 

The second stroke is the compression stroke. Now that the cylinder is filled with a fuel-air mixture, the intake valve is closed and the piston moves up compressing the fuel-air mixture.  All of the valves are closed in this phase.

The third stroke is the combustion stroke. A spark will combust the compressed fuel-air mixture in the cylinder creating a small explosion, and the force of the explosion will push the cylinder back down. 

The fourth stroke is the exhaust stroke. In this stroke the piston goes back up the cylinder, pushing the exhaust out of the exhaust valve. 

The piston which is being pushed up and down are connected to other pistons via a crankshaft, which ensures that when one piston is down, another piston is up. This is why engines will always have an even number of pistons and cylinders. Most cars today will have 6 or 8 cylinder engines, but there are some small cars with 4 cylinders, and some powerful high-end cars that might even have 10 or 12 cylinders. 

The crankshaft which connects the pistons also is what drives whatever work needs to be done by the engine. In the case of a car, it would be the transmission. 

Everything I’ve just described isn’t necessarily that hard to understand at least in theory. However, it creates a ton of problems to make it work in practice. 

If you remember back to my episode on electric cars, steam and electric automobiles were actually as popular as internal combustion engine automobiles up until about 1910. What eventually made internal combustion engine automobiles dominate was solving many of the problems that went along with them. 

So, based on what I just described with the four-stroke cycle, let’s look at all the engineering problems that need to be solved. 

The first is the fuel-air mixture which goes into the cylinder. You can’t just fill a cylinder with a bunch of liquid gasoline. Liquids don’t compress very well. It needs to be put into a mist and mixed with air. This used to be done by a device known as a carburetor. The act of mixing air and fuel together is called carburation. Today, most cars will do the same thing which a device called a fuel injector. 

Air has to come from outside the engine. Moreover, the air needs to be clean, so it requires an air filter to remove any particulate matter. This is also why an automobile will stall if it is underwater. Some specialty vehicles will have a snorkel that puts the air intake over the roof so they can cross rivers.

Once the fuel-air mixture is in the cylinder it has to be ignited. This is done with a spark plug which allows electricity to create a spark between a gap at the top of the spark plug. The spark has to be timed with the maximum compression of the fuel-air mixture. 

The piston and the cylinder are both made out of metal, and metals don’t like to rub against each other. That means you need some sort of lubricant between the piston and the cylinder, which is where motor oil comes in. Without motor oil, the friction between the piston and cylinder would cause them to get stuck and for the entire engine to seize up.

In the exhaust stroke, the waste from the combustion has to be eliminated and that has to go somewhere. That all as to be directed out the exhaust pipe. Some cars will have a catalytic converter that will convert certain toxic gases.

The combustion stroke is a small explosion, and explosions are noisy. Automobiles can be pretty noisy, but they would create far more noise without a device to reduce the sound, called a muffler. If you have ever driven a car without a muffler, you know just how loud a car can really be. A muffler is fundamentally an acoustic device.

The cycle is a process that goes over and over. The question is, how does the cycle get started? In really old automobiles, there was a crank that you had to physically turn to get the cycle started. Eventually, this was moved to an electric motor, called a starter. 

The electrical starter, as well as the spark plug, necessitates an electrical system to make the engine work. That requires a battery to store the electricity, but also a generator to create electricity. The mechanical energy from the engine is used to generate electricity. In modern cars, this is called an alternator because it creates an alternating current.

So this explains the fuel and air coming in, the exhaust going out, and the lubrication of the piston and cylinders. However, there is another huge problem. 

Internal combustion engines are actually very inefficient. Efficiency is defined as how much of the energy in the fuel is transferred to motion.  The most efficient internal combustion engines have an efficiency of only 40%, and most automobiles might have an efficiency of around 20%. 

If only 20% of the energy in the fuel is converted to work, where does the rest go? It is converted into heat. 

Heat is a huge problem. Heat makes metal expand, which is really not great if there are moving parts, and it can cause the metal to crack and deform. If you have ever put your hand on or near an engine after you’ve stopped a car, you have an idea as to just how hot it can get. 

You can literally cook food on an engine. There are many videos online of people cooking food wrapped in foil on a car engine. If you are ever in a situation like a blackout and have no means of cooking food, this is an inefficient, if effective way to cook. 

This means that a cooling system has to be integrated into the engine. 

In most engines, there will be a fluid that runs through chambers in the engine block which to carry away heat. The fluid is then run through a device called a radiator, which has a high surface area, and air is blown over the radiator to cool the fluid.


The entire engine cooling system requires fluid, a pump to move the fluid, tubes, and hoses to channel the fluid, and finally belts to operate the fan. 

Everything I’ve just gone over is required for the engine to function. If the lubrication, air intake, cooling, fuel injection, or electrical system were to fail, then the entire thing will just stop. If you’ve owned an automobile long enough, there is a good chance one or more of these things has gone wrong with your car.

The more you think about the whole system, it really does seem like a Rube Goldberg device….and I haven’t even gotten into the other vital systems on a car such as the transmission, brakes, and suspension.

Nonetheless, over the decades engineers have gotten very good at making everything work. It was getting all these parts of an engine to function properly and in union, which made the internal combustion engine automobile possible. 


The associate producers of Everything Everywhere Daily are Thor Thomsen and Peter Bennett. 

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