How Does Your Engine Work?

November 29, 2011

Everyone knows what an engine is, right? It’s what makes your car go! But how does it work? Let’s take a closer look; it’s not as complicated as it seems.

In cars, the engine type used is internal combustion—all that means is the fire is on the inside, not the outside. An example of an external combustion engine would be a steam engine. Fuel is burned to boil water in a reservoir to produce steam. The steam runs the engine while the combustion takes place “outside” the engine itself.

An internal combustion engine produces power by burning fuel in an “internal” combustion chamber. In our cars, there is a combustion chamber at the top of each cylinder.

While there are different types of internal combustion engines, the type found in the majority of cars and trucks is a four-stroke piston engine. In the most basic terms, these engines are simply an air pump. The amount of power produced is based on the amount of air pumped through the engine. These engines can run on many different types of fuel—most commonly gas and diesel. How the fuel is delivered to the cylinders and ignited to begin the combustion process is what differentiates one from the other.

So what goes on inside? Let’s look at how this air pump works. The pistons move up and down inside each of the cylinders. As the piston is pulled down by the rotating crankshaft, air is drawn into the cylinder. The rotating crankshaft then pushes the piston back up, compressing the air. Fuel and air burn rapidly, the force of which pushes the piston down. The crankshaft then pushes the piston back up, forcing the combustion gases out of the cylinder.

For each power-producing (combustion) event, the piston must move down, up, down, up. The four “strokes” of the piston give this engine type its name. Each stroke has a name: Intake, Compression, Combustion, and Exhaust. These are playfully referred to as: Suck, Squeeze, Bang, and Blow.

Piston pulled down by crankshaft > Intake > Suck > Down

Crankshaft pushes piston back up > Compression > Squeeze > Up

Fuel and air burn; piston goes down > Combustion > Bang > Down

Crankshaft pushes piston back up > Exhaust > Blow > Up

As the RPM (revolutions per minute) of the crankshaft increase, the engine pumps more air, generating more power. Many high performance engines are capable of rotating at very high RPMs (up to 8,000 crankshaft revolutions per minute) some racing engines have reached 21,000 RPM. 

Specialized air intake, exhaust, and valve timing systems also help the engine to “breathe” better, allowing the engine to pump more air. Turbochargers and superchargers compress the air before it enters the cylinders, which allows the engine to pump more air. Therefore, the engine produces more power by simply pumping more air.

So there you have it! Of course there are many complicated systems necessary to allow the engine to run properly and efficiently, but now you know the basics of what goes on inside. To learn more about other engine and automotive systems, please stay tuned.

Question: Can you name the world’s largest producer of internal combustion engines?

Hint: Gas powered garden equipment and motorcycles count!

About the Author

Jim Taddei has been in the automotive field since 1975 and has over 25 years of experience with General Motors products, achieving the designation of GM Master Technician. He is also currently certified as an ASE Master Technician, and holds an Advanced California Smog Check License. He has been the lead technician and team leader at a multi-line dealership. After leaving the dealership he spent a couple of years working in an independent shop and now uses his experience and expertise to help verify the quality of RepairPal Certified shops.

2 User Comments

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By < of , December 13, 2011
Is it Honda?
By , December 14, 2011
Congratulations to SB Automotive! Honda is the worlds largest manufacturer of internal combustion engines, producing approximately 14 million each year. Honda engines power everything from weed eaters to airplanes. They produce engines for automobiles, light trucks, motorcycles, garden equipment, power generators plus marine & aerospace applications.