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  • Writer's pictureJeff Guymon

Engine Displacement

Finding your vehicle’s engine displacement gives you insight into your engine’s power output and fuel efficiency. Engine displacement is a measurement used heavily in advertising a vehicle's engine speed and power capacity. You may be wondering the following frequently asked questions:

  • What is engine displacement?

  • How can I calculate my Engine displacement?

  • Where can I find my engine’s displacement?

  • Why does engine displacement matter?

To ease your mind and save you time, this article will delve into the answers to each question above.

What is engine displacement?

Engine displacement is the measurement of the air/fuel mixture intake from a single stroke an engine can draw in during one complete engine cycle. In regards to a piston engine (an engine that uses pistons to generate power), displacement means finding the cylinder volume of air that a single-piston displaces. As the crankshaft rotates, the piston moves up and down with the cylinder. As the pistons go through the combustion chamber, the volume in each cylinder changes. Further, finding displacement for a piston engine means finding the swept volume of air that is swept as the piston travels from the top center to the bottom center.

How can I calculate my Engine displacement?

Displacement is usually expressed using cubic centimeters (cm3), in cubic inches (CI), or in liters (L). For a standard reciprocating piston engine, engine displacement is found by multiplying three different variables. Multiply the stroke length (distance traveled by the piston) by the cylinder bore (circular area of the cylinder) by the number of total cylinders in the whole engine. The formula for finding engine displacement in its entirety is laid out below:

This formula is intended for standard piston engines only. Using it to calculate the displacement on Wankel designs or oval piston engines such as those seen in Honda NR motorcycles can lead to inaccurate data. On engines other than piston types, manufacturers and regulators develop a unique formula to calculate engine displacement.

The following link is for a digital engine displacement calculator. All you need to do is input:

  • Bore diameter in inches

  • Crankshaft stroke length in inches

  • Number of cylinders

You have the option to use imperial measurements or metric measurements and this calculator will determine your engine displacement in cubic inches.

What is an example of calculating engine displacement?

Use the following variables:

  • Bore of 5 inches

  • Stroke length of 3.21 inches

  • V8 engine

Where can I find engine displacement?

Engine displacement is shown below a vehicle’s engine description. Let's take the description:

The 2020 RAM 1500 Tradesman 3.6L

The engine displacement is the 3.6L. This represents how powerful this RAM’s engine is. A higher displacement means more power.

You can think of engine displacement in a simpler way using only information found in a vehicle’s advertising. You need the following information of a vehicle’s engine:

  • How many liters your engine is (Engine displacement)

  • Total number of pistons

Divide the number of liters your engine in by the total number of pistons in order to find how many liters of air one piston displaces.

For example:

The 2020 RAM 1500 Tradesman 3.6L is a V6 cylinder engine

3.6/6=0.6 liters of air per stroke intake of one piston

To put this calculator into perspective, each piston’s air intake is .6, so when you multiply .6 by 6 you get 3.6. This answer translates to the engine sucking in a total of 3.6 liters of air. This is what the 3.6L represents in a vehicle’s engine description.

Why does engine displacement matter?

Engine displacement is frequently used to compare the maximum power a car engine is capable of producing. It is also a representation of the engine size and maximum fuel consumption. It tells consumers how much horsepower and torque the engine produces. The higher an engine’s displacement is, the more fuel it can consume, while a lower engine displacement shows that the engine can’t take in as much fuel. Engines with a higher fuel intake have the potential to generate more power than engines with lower fuel intake. Essentially, the larger engines have more power and the smaller engines are more efficient as they have better fuel economies.

Some countries use engine displacement measurements as a factor when taxing vehicles. Even though the United States does not tax based on displacement, a vehicle with a higher engine displacement is more costly.

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