HP Torque, Weight etc

[pdedse]

I'm curious about what more HP / Torque at different RPM really means when one takes into consideration the weight of the bike.

Powerdubs showed with dyno tests that his modified CB1100 showed more HP / Torque compared with a number of other bikes. But how much power is negated by the heft of a bike? The '17ex weighs 562 lbs. I checked the other bikes PD refers to and found the following...not sure all these are "wet" weights, but still gives one the idea:

Z900RS SE 472lbs
2023 Suzuki GSX-R600 412lbs
2023 Kawasaki Ninja ZX-6R 430lbs
2016 Triumph Thruxton R 450lbs
BMW NineRT 490lbs
Indian Scout 551lbs
Triumph speed twin 1200 476lbs
Street Triple RS 414lbs
Ducati Monster 1200 465lbs

With the exception of the Scout, all the bikes are around 100-150 lbs lighter. So in the world of riding, does PD's modified, but heftier CB1100, still "win" vs any of these bikes? Does it take off faster from a stop? Does it have more "passing power" at 70mph? A higher top speed (if it had no limiter)? Or by "win" are we just saying "it makes more power"?

Is there a formula that says, for example, "all other factors being roughly equal: for every 25 lbs (or whatever number), a heavier bike needs 5HP more (again, whatever number) to be equal in acceleration to a lighter bike?"

I'm curious.

 

[pdedse]

^is a fair point. for sure. I know this, i can run dead with an 18 z900 up to about 120, and its lighter and has more hp. but.. where? its not all about power to weight... a lot of it is, but not all of it. length of torque curve & area under the curves is what really matters in real world riding performance. thats what translates to real world conditions.

"length of torque curve"...I've never really paid too much attention to the charts / readings, but I gather that means that while 2 bikes might both gain a certain "torque max", perhaps one can sustain it longer while accelerrating, or something like that...is that what they call the "power band"?

 

[Tev62]

Power = (2*Pi*N*T)/60.

Where N= RPM /60 to get revs per second.
T=Torque

This formulae stands for a given rev value of course but it does highlight the simple relationship (in formulae form) of Torque and Power.

A common strategy of motorcycle manufacturers is to lighten up engine components, pistons, con rods, valve train, etc. and just increase the maximum red line with little real torque increase. Then they shout from the rooftops about how much extra power they have over their competitors. But given most riders do not sit at 11,000RPM most will never see that extra power. Now if a manufacturer can increase his torque lower down the rev range we can all feel that and possibly use it, especially on heavier motorcycles.

 

[pdedse]

Cool, thanks for the replies. Most of the times I rides because it's fun, the bikes look cool. But every little bit of the hows and whys makes me more appreciative of the outings.

 

[misterprofessionality]

I've learned over the years that I always fall in love with mid-range power bands and flat-but-hefty torque curves. I guess it's just the style that appeals to me. Scientifically speaking though I think it's just more accessible and "easier" to have fun without overthinking everything.

 

[misterprofessionality]

Well high rpm lightweight bikes that want to lift up in a corner are more about keeping the rpms high all the way through a corner and slowing down as little as possible and apexing as much as possible and yadda yadda....that whole thing is about pushing as far to the edge as possible so that you can smoothly transition through those peaks. That's also how you avoid lifting the front end. That whole style carries so little room for error and requires so much focus. I think that's where the fun dies off for me.

Considering where torque and HP and weight fall in order of importance, I'd always say weight and torque are first and HP should be just enough to keep the acceleration smooth.

 

[PowerDubs_imp]

I'm curious about what more HP / Torque at different RPM really means when one takes into consideration the weight of the bike.

Powerdubs showed with dyno tests that his modified CB1100 showed more HP / Torque compared with a number of other bikes. But how much power is negated by the heft of a bike? The '17ex weighs 562 lbs. I checked the other bikes PD refers to and found the following...not sure all these are "wet" weights, but still gives one the idea:

Z900RS SE 472lbs
2023 Suzuki GSX-R600 412lbs
2023 Kawasaki Ninja ZX-6R 430lbs
2016 Triumph Thruxton R 450lbs
BMW NineRT 490lbs
Indian Scout 551lbs
Triumph speed twin 1200 476lbs
Street Triple RS 414lbs
Ducati Monster 1200 465lbs

With the exception of the Scout, all the bikes are around 100-150 lbs lighter. So in the world of riding, does PD's modified, but heftier CB1100, still "win" vs any of these bikes? Does it take off faster from a stop? Does it have more "passing power" at 70mph? A higher top speed (if it had no limiter)? Or by "win" are we just saying "it makes more power"?

Is there a formula that says, for example, "all other factors being roughly equal: for every 25 lbs (or whatever number), a heavier bike needs 5HP more (again, whatever number) to be equal in acceleration to a lighter bike?"

I'm curious.

It's in the name... lb/ft

You can do the math for the lb.

But then compare that to the area of the curve- where is that lb/ft made...for how long?

How long until you get there?

How long until you need to shift?

How much mechanical advantage of the gear you are in VS the next gear are you losing by shifting?

Gearing is simply tq multiplication- so the moment you need to go to next gear you are at a great disadvantage as to someone who can hold a lower gear longer.

Not just in time allowed in a lower hear to accelerate... but if holding a gear longer allows you to be in a higher tq/hp area once you drop revs when you shift... that is the reason true race bikes have close gearing and need to sift often. High peaked but narrow power range- so very little drop when shifting.

A better build / tune is a wider range of good power- with gearing to match.

NOT- a magazine tune / what sells bikes..

There are an awful lot of people riding/driving 'fast' paper cars/bikes that get awakened at the drag strip (and street) with reality.

 

[The Gecko_imp]

Power = (2*Pi*N*T)/60.

Where N= RPM /60 to get revs per second.
T=Torque

This formulae stands for a given rev value of course but it does highlight the simple relationship (in formulae form) of Torque and Power.

A common strategy of motorcycle manufacturers is to lighten up engine components, pistons, con rods, valve train, etc. and just increase the maximum red line with little real torque increase. Then they shout from the rooftops about how much extra power they have over their competitors. But given most riders do not sit at 11,000RPM most will never see that extra power. Now if a manufacturer can increase his torque lower down the rev range we can all feel that and possibly use it, especially on heavier motorcycles.

Hi Tev, is that so ? then if you look at a power and torque curve of some engine in a narrow rpm band, where the power curve is flat without peaks or much change, and the torque curve has a big kink or two ... or the opposite? Both cases are frequently seen in such charts. Since all the other multipliers in the equation are just constants ... how would you explain this ?

 

[Cormanus]

Don’t know whether this is helpful, Gecko. How to Calculate Horsepower - Power Test, LLC

 

[Tev62]

Power = (2*Pi*N*T)/60.

Where N= RPM /60 to get revs per second.
T=Torque

This formulae stands for a given rev value of course but it does highlight the simple relationship (in formulae form) of Torque and Power.

A common strategy of motorcycle manufacturers is to lighten up engine components, pistons, con rods, valve train, etc. and just increase the maximum red line with little real torque increase. Then they shout from the rooftops about how much extra power they have over their competitors. But given most riders do not sit at 11,000RPM most will never see that extra power. Now if a manufacturer can increase his torque lower down the rev range we can all feel that and possibly use it, especially on heavier motorcycles.

Hi Tev, is that so ? then if you look at a power and torque curve of some engine in a narrow rpm band, where the power curve is flat without peaks or much change, and the torque curve has a big kink or two ... or the opposite? Both cases are frequently seen in such charts. Since all the other multipliers in the equation are just constants ... how would you explain this ?

Hi Tev, is that so ? then if you look at a power and torque curve of some engine in a narrow rpm band, where the power curve is flat without peaks or much change, and the torque curve has a big kink or two ... or the opposite? Both cases are frequently seen in such charts. Since all the other multipliers in the equation are just constants ... how would you explain this ?
It is normally the torque curve that is fairly flat and the power curve climbing with speed. Don't forget that this calculation is only in a certain RPM. A torque curve can have a dip but the power curve still climbing because the revs are still increasing too on the given chart.