That's one thing I have never understood. If an XB9 engine "revs faster" than a XB12, then the XB9 should accelerate faster than a XB12 as long as they have the same gearing. But I have not experienced a stock XB9 that accelerates faster than a stock XB12. The XB9 has a lower primary ratio so it might just sound faster? Hmmm?
The 9 will seem to go through it's RPM range faster because it is geared lower. Though at a given engine speed, the 12 will produce more horsepower (actual work done), because of it's higher ratio primary drive, the complete amount of force exerted to the rear wheel is very similar, with the edge to the 12, and always at a lower engine RPM relative to rear wheel speed. What I think is cool is that each engine has it's own character, and because of that, the same machine can seem a lot different, depending whether it's a 9 or 12. I really like the 9 in a Firebolt, but I would absolutely love to have a Super TT, and the 12 engine would be one of the cool things about it. Having the engine making so much more low end power would be sweet, and I'd probably end up going to the 9 primary; I still have a thing for Big Block powered cars with short gears, and I think that a short geared TT would be freakin' sweet.
Eric, that isn't the case, because at a given RPM, the 12 is making more HP than the 9.
HP is what matters, and when people talk about "torque" what they really mean is usually "The HP versus RPM curve". So they say Buells have great torque, but what the mean is that Buells produce good horsepower at even low RPMS.
Reep - HP is calculated using torque and RPM HP = (TQ * RPM)/5252
So, HP really doesn't matter. Torque and RPM are what really matter. That's why a current literbike can make so much more HP with so little torque, it has more revs.
You are correct, and it would be relevant, if all motors had the same redline, and none had transmissions.
Transmissions multiply torque. So an engine that makes 1/2 the torque but can go 10x the RPMs is simply a faster bike. It will always be a quicker bike also, provided you get the gearing right and the operator can use a clutch aggressively.
Torque, taking into account the RPM that it can be maintained at, is Horsepower. Thats why these discussions should be about horsepower.
If torque was the main point, I could go infinitely fast just by continuing to change the gearing on my motorcycle.
Why not use an infinitely variable drive? It might be an interesting intellectual challenge to make it work, but if you could do it.... well, maybe not. Lack of gear changes might suck on a bike.
