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« Last post by MerleLowe on Today at 09:54:09 AM »
This is a gross generalization, but more cylinders of smaller capacity allow the engine designer to use a shorter stroke for the same displacement. Power (in general again) is made by increasing the number of combustion events within a given time. The shorter stroke allows higher RPM due to lower piston speeds and inertial forces. The use of smaller cylinders makes for smaller valves, also lowering inertial forces permitting higher speed operation. Now that the reciprocating assembly and valvetrain can withstand higher speed operation, you can optimize the tuning to move more air/fuel mix at those high RPMs. More bangs = more power all else being equal.
Torque comes from cylinder pressure and displacement. You'll notice that most modern engine designs make similar torque numbers for like CCs with very different peak HP numbers. WHERE that torque peak occurs is a different matter. Notice that most 1000cc engines come in a bit above 70 lb/ft but at very different engine speeds.
In practice, inline 4s for motorcycles are generally (there it is again) quite oversquare with relatively large valve area. This makes for a relatively high flow cylinder head with lots of valve area. In that case you can still use somewhat mild cam timing and still get good cylinder fill at high speeds without killing cylinder pressure at lower RPM. The end result is a very wide torque curve but with a peak relatively high up the RPM scale.
Also in practice, twins end up with longer strokes, higher piston speeds and lower redlines. The tuning is then (generally again) optimized for lower-speed operation. This means often the rider is running the engine closer to the torque peak and gets fast strong response to throttle inputs. This is interpreted as "torquey" since it is so immediately available.
That's when aesthetics comes into play. You might prefer the running characteristics of a lower-hp engine that gives the feel, sound and throttle response that you prefer. Just know that the choice can greatly affect performance. The extreme end of this would be the current HD and Indian air-cooled v-twins. Peak torque is at very low speeds.
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