Car catalogue questions 1 - displacement

Today we will talk about displacement. You will hear the word 'displacement' in car catalogues and when talking about cars. For example, in the specification introduction, "Mercedes-AMG A45S in-line four-cylinder2.0 litreTwin Turbo!" and 'Dutch Challenger V8'. 5.7 litresYou hear things like "NA!", right? I can tell you that the larger displacement is great, but then I'll try to explain which part of the engine I'm talking about specifically, together with the mechanism that makes the engine work.

The engine is driven by piston movement.

The engine contains a cylinder that looks like a syringe cylinder. Air and petrol are put into it, compressed, ignited and exploded to generate power.

In case you were wondering... Did you ever take apart a lighter when you were in primary or junior high school? The part of the lighter that is ignited by pressing a button is actually ignited when electricity runs for a moment and is then applied to the fuel. In a car, there is a 'plug', which is ignited by electricity running through it, causing it to explode.

Cylinder construction

The cylinder in the engine has a cylindrical structure like a syringe. It has a lid called a valve, which allows petrol, air and exhaust gases to enter and exit. The air in the cylinder expands and the piston is pushed to generate force.

The diameter of the cylinder is called the 'bore' and the height the 'stroke'. The term 'long stroke' or 'short stroke' indicates whether the piston has a long or short vertical movement.

Mechanism to exhaust

IMG_0510 – mbFAST Tuning — One cycle of intake, ignition and exhaust.

The intake valve opens and the piston drops down, allowing air and petrol to flow in.
The valve closes to create a sealed space. The piston compresses the gas in the cylinder.
The plug ignites and explodes, pushing the piston and creating force.
After the explosion the gas does not explode any further. The exhaust valve opens and the piston pushes out the exhaust gases. The exhaust volume is the amount of exhaust gas produced here multiplied by the number of cylinders.

Incidentally, the piston is actively moving in (1), (2) and (4), but is passively moved by the explosion in (3), so it is only in (3) that force is generated. (Differentiated by black and white arrows.)

These are the mechanisms by which the engine produces power.

How to find the displacement

$$ Displacement (cc)=(\frac{bore}{2})^2π x stroke x number of cylinders $$

スクリーンショット-2020-04-29-13.50.34 – mbFAST Tuning — W215 early model CL600

Specifically, the red letter values in the table above can be used to calculate the blue letter displacements. Bore and stroke should be converted to cm.

$$(\frac{8.40}{2})^2×π×8.70×12=5785.61$$

Yanase is not rounding up, lol.

Well, it doesn't matter, this is how you can find the displacement. It becomes obvious if you know a little about the construction of the engine.

There are things like what happens if the bore to stroke ratio is different, or what happens if there are fewer cylinders but the displacement is the same, but we'll talk about that another time.