wookie@alice.UUCP (06/15/83)
Of major concern in the Torque area is the bore and stroke of the engine. Given engines with equal displacement, an engine with a longer stroke and smaller bore will give higher torque than an equal engine with a short stroke and large bore. This is because of the longer arm on the crankshaft throw that the piston has to push on and since we are concerned with lbs pressure exerted over a distance for lb ft torque this becomes obvious. Now comes the trade-off. The longer stroke engine has much higher reciprocating forces and cannot go to as high an RPM level as the shorter stroke version. Since Horsepower is directly related to RPM this limits the maximum power output of the engine. Thus one must determine whether the engine is to be used for heavy hauling requiring lots of torque or whether high speed cruising is the goal requiring horsepower. In racing you will see that the engines are all very large bore with very small stroke (something in the neighborhood of say a 3.5 inch bore and a 1.5 inch stroke but don't quote me!!!) This allows the engine to safely run out to 10,000 or 11,000 RPM or even higher!!! But the engine has lousy torque.....did you ever wonder why the pit crews at Indy are often seen helping the cars to get going? The more cylinders the engine has the smoother it runs and of course the parts can be made smaller for the same displacement thus again allowing better horsepower and lower torque. This is a rather complicated subject and there are no simple rules of thumb to be followed but maybe this will help a bit for those who are wondering! Keith Bauer White Tiger Racing