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Whats the new harley that is supposed to spank all jap litter bikes- is it a super bike or a sport cruzer?
 

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Interesting - that is the bike with the Rotax designed V-twin. Specs call for 147 hp and 82 lb-ft of torque - the horsepower is about on par for a 750 cc class machine. But, the dry weight is 375 lbs, which is also on par with a 750 cc class machine. It won't be class competitive with other 1000 cc supersports, but it's probably a fun ride nonetheless.
 

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I think you would be talking about the new Buell. I don't think it's being taunted as a I-4 killer, but I think it will be a great bike and a big step for Buell.

I wouldn't be surprised that in 20 years or less that you will start to see dealerships that say "BUELL MOTORCYCLES and Harley Davidson motorcycles "
 

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Mister Tee said:
Interesting - that is the bike with the Rotax designed V-twin. Specs call for 147 hp and 82 lb-ft of torque - the horsepower is about on par for a 750 cc class machine. But, the dry weight is 375 lbs, which is also on par with a 750 cc class machine. It won't be class competitive with other 1000 cc supersports, but it's probably a fun ride nonetheless.
Just to point a few things, 375 is not the dry weight, 375 is its running weight , and its officially 146Hp and 84 lb-ft.
Buell designs thier bikes for the road and the twisty rides.


p.s. what 750CC class machine puts out 84lbs of tourque?
 

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JeffNights said:
Just to point a few things, 375 is not the dry weight, 375 is its running weight , and its officially 146Hp and 84 lb-ft.
Buell designs thier bikes for the road and the twisty rides.


p.s. what 750CC class machine puts out 84lbs of tourque?
i think he was comparing the weight and general horsepower....not many sportbikes have that kind of tourque.
 

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Meat_Shield said:
i think he was comparing the weight and general horsepower....not many sportbikes have that kind of tourque.
Correct - torque specs are fairly meaningless since you can compensate with gearing if you want - it's the torque to the wheel that counts, not at the crankshaft.

That said, I'm sure that big V-twin has a nice, flat torque curve, so I'm not discounting it at all. It looks like an impressive bike. I'd like to ride it.
 

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Mister Tee said:
Correct - torque specs are fairly meaningless since you can compensate with gearing if you want - it's the torque to the wheel that counts, not at the crankshaft.

That said, I'm sure that big V-twin has a nice, flat torque curve, so I'm not discounting it at all. It looks like an impressive bike. I'd like to ride it.
On a technical standpoint, i beg to differ, Tourque is actually the only measureable stat, Horsepower is actually just a formula equation.
 

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Originally posted by Mister Tee
Correct - torque specs are fairly meaningless since you can compensate with gearing if you want - it's the torque to the wheel that counts, not at the crankshaft.

That said, I'm sure that big V-twin has a nice, flat torque curve, so I'm not discounting it at all. It looks like an impressive bike. I'd like to ride it.
Originally posted by JeffNights
On a technical standpoint, i beg to differ, Tourque is actually the only measureable stat, Horsepower is actually just a formula equation.
Note that he didn't mention horsepower.

While it's true that torque is the measured quantity, it is torque at the wheel that produces acceleration. 40 ft-lbs. of torque at 10000 rpm engine speed is twice as much torque than 100 ft-lbs of torque at 2000 rpm engine speed when geared down to the same wheel speed.
 

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mkeeney said:
Note that he didn't mention horsepower.

While it's true that torque is the measured quantity, it is torque at the wheel that produces acceleration. 40 ft-lbs. of torque at 10000 rpm engine speed is twice as much torque than 100 ft-lbs of torque at 2000 rpm engine speed when geared down to the same wheel speed.
Ok, we will have to agree to disagree on your math.
 

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JeffNights said:
Ok, we will have to agree to disagree on your math.
Maybe I didn't explain the example well enough. The math is right though. There's nothing to disagree on.

If both bikes are turning their wheels at 60 mph while one engine is at 2000 rpm/100 ft-lbs and the other is at 10000 rpm/40 ft-lbs, the one at 10000 rpm will produce twice as much torque at the wheel. It's simple gear reduction/torque multiplication.
 

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maybe I can clear this up a touch.. or not.

While its true that F=MA the engine does not produce constant force, so the torqe spec is the maximum force it produces ( about halfway down from tdc). Each piston produces force less than a quater of the time.

In other words, its kind of like lifting weights. Benching 150 could be something to brag about if you do it in sets of 20. However if you do it just once, its a different story isnt it?

The easiest way to get lots of torque out of an engine is to make it long stroke. Longer stroke=longer connecting rod=bigger leverage on the crank. The basic example is a tractor engine. On the opposite end, you have engines that produce very little force, but spin very fast and produce tons of power. Like a jet turbine. A 2000 HP turbine weights less than a motorcycle engine.

Back to the math. power is the rate at which work is done (work/time) since time is 1/rpm you can say that power=work*rpm. Work is measured in foot pounds, so we can substitute torque there and say that power=torque*rpm.

A dyno measures torque, and it also measures the engine rpm
(also some measure wheel rpm), which are the two components of power. So it calculates the power from that. You could build one that works the opposite way. You could hook the wheel up to a generator, measure the ammount of electricity produced, devide by the rpm to get torque.
 

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The point that I was trying to make is that acceleration and top speed are both limited by horsepower, not by torque. Any combination of RPM and torque that will result in equal horsepower, will give equal performance, geared appropriately.

The thing that makes big V-twin motors different than inline 4's in terms isn't that they can generally produce a higher numerical crankshaft torque, but it's because the torque (and horsepower) curve is more LINEAR, so there is more horsepower and torque available over a greater RPM range.

So, given equal horsepowers, big V-twins = less shifting, possibly of which could translate to faster acceleration under practical riding conditions, but not higher speeds.
 

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Mister Tee said:
The point that I was trying to make is that acceleration and top speed are both limited by horsepower, not by torque. Any combination of RPM and torque that will result in equal horsepower, will give equal performance, geared appropriately.

The thing that makes big V-twin motors different than inline 4's in terms isn't that they can generally produce a higher numerical crankshaft torque, but it's because the torque (and horsepower) curve is more LINEAR, so there is more horsepower and torque available over a greater RPM range.

So, given equal horsepowers, big V-twins = less shifting, possibly of which could translate to faster acceleration under practical riding conditions, but not higher speeds.
+1

A twin has fewer cylinders, requiring larger ones. Larger cylinder are heavier, limiting the maximum speed at which engine can rotate. Thus getting high peak horsepower is harder with a twin, and they are instead tuned to deliever less power over a great range. With a higher red line, it makes sence to extract more peak hp out of a inline engine, but the narrower band necessitates more shifting from the rider. Thus the twin are typically easier to operate, which will make them faster in the hands of less expirienced riders. However, a rider that can keep the narrow band inline in its powerband will have a definite horsepower (and speed, and acceleration) advantage over his twin powered rival.
 

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Class dismissed.




LOL that was an excellent lesson! i think it should answer everyones questions.
 
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