Can someone explain how the engine gets bigger with just new pistons?

 

By increasing the piston bore (and the stroke length of the crankshaft) the displacement on the engine is increased.

Now, please put on your Nomex suit for the rest of your fan club.

 

you should learn the complexities of a keyboard and the english language before trying to tackle the designs of a motor

 

First lets start off by describing how displacement is calculated.

Area of bore formula = PI * (Diameter/2)^2
Area of 4G63t bore = 3.142 * (8.5cm/2)^2 = 56.75 cm^2
Stroke of 4G63t = 88mm= 8.8cm
Displacement formula = (area of bore)*(stroke)*(number of cylinders)
4G63t displacement = 56.75cm^2 * 8.8cm * 4= 1997cm^3


So what happens if you increase the stroke to 100mm?
Displacement = 56.75cm^2 * 10cm * 4 = 2270 cm^3

Thats 2.27L or commonly known as 2.3L

Increasing the bore 5mm only yields a 1% increase in displacement 2.02L