How to Calculate Engine Displacement?
Date 2006/1/18 9:28:17 | Topic: General Automotive
| How to Calculate Engine Displacement?You see 1.5L, 1.8L, 2.0L, and 5.0L all the time in car ads. Do you wonder what it means? Well this is a SIMPLE, quick, and dirty way of calculating your engine displacement. To understand how the number of liters your car has directly affect the amount of engine power, you need a basic understanding of how your car engine works.
This is a quick low-down on how the four stroke engine cycle under your hood work. The four-stroke combustion cycle is made up of these strokes: intake stroke, compression stroke, combustion stroke, and finally, the exhaust stroke.
1. Intake stroke:
The piston first starts at the top of the cylinder. The intake valve opens to let the air into the cylinder. The piston moves down, creating a vacuum that lets the cylinder get filled with the mixture of air and fuel.
2. Compression stroke:
The piston then moves up again. This compresses the mixture of air and fuel. This compression is necessary to make the next stroke, the combustion stroke, more potent.
3. Combustion stroke:
While the piston is at the top of the cylinder, the spark plug gives off a spark. This spark ignites the air and fuel mixture and creates an explosion. This explosion is what drives the piston back down.
4. Exhaust stroke:
When the piston gets to the bottom of the cylinder, the exhaust valve opens. This sucks the exhaust out of the cylinder to exit out of the exhaust piping.
This cycle is also called the Otto Cycle and is repeated over and over again. It seems simple, but this cycle occurs hundreds of times per minute and is the heart of what an engine is.Defining Engine DisplacementEngine displacement is the amount of the air and fuel mixture that all of your cylinders can take in during a complete engine cycle: intake stroke, compression stroke, combustion stroke, and exhaust stroke. The more displacement your engine has, the more fuel it can burn.
Now for a little more vocabulary. Bore is the width of your cylinder. Stroke is the height your piston travels within your cylinder. This is called 'bore x stoke' or bore times stoke.Calculating your Engine's DisplacementCalculating your engine displacement is the SAME as finding the volume of a cylinder. Yes, the same thing you learned in elementary science and math class!
1. You find the area of the circle inside of your cylinder.
2. You multiply that area by the height of the cylinder.
Keep in mind that the area of a circle is pi times the radius squared. (Pi is the same as 3.14).
volume = pi x radius x height
A circle's radius is half its diameter, so the formula becomes:
volume = pi 4 x diameter x height
Let's say we have a car with these engine specifications:
The diameter (bore) of one (1) cylinder is 4.0 inches. Its piston travels (stroke or height) 3.62 inches during one cycle. It has 8 cylinders.
Now, let's calculate this car's engine displacement!
displacement = pi 4 x bore x stroke x cylinders
1. To keep things simple, go ahead and divide pi (3.14) by 4.
2. Break down the squaring of the bore.
If you do this, you will get this formula:
displacement = 0.785 x bore x bore x stroke x cylinders
Now just plug in what you know.
displacement = 0.785 x 4.0 inches x 4.0 inches x 3.62 inches x 8
You'll get 363.7376, which is rounded up to 364 cubic inches. You can then convert this to liters by multiplying by 0.016 to get 5.824 then round up to get 6.0 liters or 6.0L.
To break it down even further, a 6.0L engine pulls in 6.0 liters of the air and fuel mixture while its 8 cylinders are making one full cycle though the engine.
So now you know how to calculate the displacement of an engine. You can usually find the bore, stroke, number of cylinders, and other engine specifications in your manual or under the hood.
You can get larger cylinders to increase your engine displacement. This is a major modification and you should really take time to decide if it would make more sense to do an engine swap instead.
2003-2006 Import Rival
|
|