1800cc's of displacement. In all the cylinders there is 1.8l's of space. Basically the bigger the engine, the more fuel and air you can fit in which equals a bigger boom and more power. There is alot of other physics to it, but that is the jist of it. Some smaller displacement engines make more power then a engine that is bigger, this is where the physics and design come in.
91 318is - M50NV (gone)
02 WRB Subaru WRX EJ207 forged, 320 AWHP stock turbo.
85 - 325
02 325i Sedan