Stroke is the distance the piston travels during once revolution = 2 x the crank radius.
Bore is the bore diameter of the cylinder, which is approximately equal to the piston diameter.
If Stroke=bore, the engine has a bore/ stroke ratio of 1 (square).
If Stroke<bore, the stroke/bore ratio <1 . AS best I know, F1 engines run very short strokes which limits the peak piston velocity ( and hence forces on the conrod and piston)and hence allows them to rev higher. The downisde is a very small crank radius and hence less torque for the same piston pressures.
If Stroke>bore, the stroke/bore ratio>1 . Diesel engines often have this configuratio as it give the necessary high compression ratio. The benefit is a large crank radius and hence more torque. The downside is that for a given crank rpm, the piston speeds and accelerations get very high, which imposes a limitation on the maximum crankshaft rotational speed.
And an even more important factor in a engines reliability and powerband is its rod/stroke ratio. Use the same logic as above to figure out what that means.
Here is a good site for you to read the more technical details of BORE/STROKE and quite a few other things related to racing engines.
I have heard that the reason they are running such short stroke engines is cause the G forces on the con rod. They are running the maximum distance in stroke that the con rod material will allow without separating from the acceleration at high RPM.
Also last month in one of the race mags they showed a Ferrari Con rod and piston. The piston skirt is trimmed off to just a few mills below the rings.
