Bore/Stroke Ratio

[Lextreme II]

1UZFE: 1.058
2UZFE: 1.118
3UZFE: 1.102

I wonder what is the significant of the B/S ratio. What does it means and how would it affect hp and torque? Here are some data i posted http://www.lextreme.com/stroke.html

 

[sc300tt]

I'm not sure what you are looking to discuss here, but oversquare (Bore greater than stroke) engines tend to make more tq than than a similar engine with similar displacement, but they have a longer stroke, therefore cannot rev as high due to physical limits of increased rod/piston speed. Undersquare engines are just the opposite. The selection of which route to take has a lot to do with intended use, head design/limitations, etc.

But all the xUZs are undersquare and appear to be able to be stroked with no adverse effects.

 

[Cobolt]

Square bore/Stroke = bore equals stroke

Undersquare = more efficient engine, better mileage, max torque earlyer in the powerband.

Oversquare = more responsive engine, max torque higher up in powerband, more horsepower.

The stroke/rod ratio also say alot about how much revs and abuse an engine can take as more rod minimizes the angle in wich the rod works.

Ultimate the pistonspeed is what creates g forces when the direction changes and limits the rev capability. More stroke = more pistontravel, aka pistonspeed on a specific rev.