Bore & Stroke

[Maelfyn]

Bore = diameter of the piston?
Stroke = Difference between TDC and BDC?

In terms of performance behavior, what are the consequences of being oversquare, undersquare, and square?

[vvtlikick]

Bore is the diameter of the cylinder, the piston will be <i>slightly</i> smaller inorder to fit inside.

Stroke is just what you said.

Oversquare: For high-revving engines, you want a short stroke, so the piston doesn't need to move much for each rev.

Undersquare: For low-rpm performance, you want a relatively long stroke. It's better for volumetric efficiency at low rpm.

It's important to note that both the 1ZZ &amp; 2ZZ are undersquare (long strokes), with the 2ZZ being less so.