And then there are examples like this: A Cummins in a brand new Dodge pickup is putting out nearly 400hp now and about 800ft-lbs torque. Many big rigs run 13-15 liter diesels that are putting out 400-500 hp. Now, some uninformed new Dodge diesel customer might mistakenly think he literally has big rig power in his pickup... not so fast their Mr. Fatwallet, that same 400hp Cat C-13 that's making darn near the same HP as your 6.2 Cummins is making in the ballpark of 1500ft-lbs torque, nearly double the torque of your just about 400hp Cummins.
Why is this?? It's always been my thought that the much heavier rotating components in the bigger 13+ liter big rig mill, IE: Crank, flywheel, even pistons, all play a part in making so much more torque while keeping HP lower relatively speaking. I'm sure this is not the sole explanation, but rather a significant part of it.
Taking this back to saws, while I'm sure the weight of the major internals of your typical saw engine doesn't play nearly as large a role in production of torque. I only made the above comparison to illustrate that HP and torque are not necessarily directly related, even when comparing engines of like design. Some great points have been made here, but I think wcorey nailed it. With these little wing-dingers, everything we do is a trade-off to some degree. In larger versions found on snowmobiles, ATV's and dirt bikes I have found that porting layout is MUCH more complex than any saw cylinder I have laid eyes on. Over the years the manufacturers and builders in those industries have come up with quite a few innovations and inventions to help broaden the power curve of the 2-stroke engine and still maintain good peak RPM and HP. Things like R.A.V.E (Rotax Adjustable Variable Exhaust) and other "powervalve" designs that basically give you a variable exhaust port height depending on RPM and engine load, boost ports, pistons with a port on the intake skirt, rotary intake valves, expansion chamber pipes tuned for a specific power curve, and on and on, I'm sure I'm missing a few... Comparatively speaking, a saw really is a one-trick pony when compared to larger powersports oriented 2-stroke mills. Obviously, things like rotary intake valves and variable exhaust valves add alot of bulk to something as small as a saw engine, which is not desirable.
In my rookie opinion, when we build our saws to gain in the area of max RPM, we do in fact pick up some HP and torque, but as wcorey eluded to, the meat of the peak power curve is raised in the RPM range a bit... How much depends on how fast you want it to run at peak. If taken to the extreme, you end up with what's commonly referred to as a "lightswitch" power curve, something frequently said about bike/sled/ATV cylinders that are ported for all out drag racing and hill shooting. Nothing down low and then BAM, you're hangin on for dear life... Obviously in this application, these guys are doing high RPM clutch drops at the launch and the idea is to never even be below where the power comes on when the machine leaves the gate. Pin it, never lift, shift. I would not want a saw that runs like that, not for what I do... But I'm sure there are saw racers out there running basically drag porting, that is where technique and practice come in to keep that thing in the power.
Cool topic!
