Power to Weight ratio questions.

[Holeshot]

Given the same P:W ratio, will a light bike leave the line faster?

Take a 700 pound bike/rider with 100 hp (7:1) vs a 450 pound bike/rider with 65 hp (7:1) ... which one leaves the line first?

Given for the sake of argument that "power" is just that ... total power. Let's pretend the torque:weight ratios are proportionate.

Sooo ... ???

Holeshot ..

 

[bobzdar]

Cant say, depends on too many things. Could be the lighter bike will wheelie too easily or the heavy bike wont have as much traction and will spin more easily. Given everything the same, they will leave the line together.

 

[Holeshot]

Hmm ... I'm not convinced it's that obvious.

All things being equal and optimum, for some reason it just doesn't "fit" in my head as easily as all that.

I suppose I should frame it differently. Given the choice, which is generally more preferable for the task?

 

[MtnMax/Magniac]

I would go with the lighter bike, because if you wheelie it and it comes back over on you, it won't hurt as much! Jus' sayin' . . . ;^))

 

[Holeshot]

I would go with the lighter bike, because if you wheelie it and it comes back over on you, it won't hurt as much! Jus' sayin' . . . ;^))

:bike1:

Haa!...

 

[Redbone]

I think there are so many variables it is going to hard to say one is going to faster than another. In real life, on the street or the strip, two identical bikes are most likely are going to have differences due to rider.
Now, you throw the two bike up there with your parameters, one being a lightweight sport bike and the other being the heavier Vmax I say the Vmax leaves first because it is setup better to utilize the p/w ratio than the sport bike in a drag race. The shorter wheelbase sport bike will wheelie much easier whereas the Vmax will be able to utilize full power on the launch. :confused2:
I'm not sure what your looking for, but in real life I go up against my brother on his FZ1; he weighs 100 lbs less than me, his bike weighs 150 lbs less than mine yet I can beat him out of the hole until we are near the end of my second gear where he goes by me. Running a 1 mile long course he can hit 165 mph and I'm topped out at ~140.

 

[satariel666]

Given the same P:W ratio, will a light bike leave the line faster?

Take a 700 pound bike/rider with 100 hp (7:1) vs a 450 pound bike/rider with 65 hp (7:1) ... which one leaves the line first?

Given for the sake of argument that "power" is just that ... total power. Let's pretend the torque:weight ratios are proportionate.

Sooo ... ???

Holeshot ..

You've missed few very important factors like torque curve, tyres, suspension etc...

 

[Blurr]

If ,as you said previously all thing are equal (torque curves, rider skill, bike dynamics) with the only effective variable being weight and corresponding power to weight ratios, I'd go with lighter. While the acceleration would be the same, control of the bike wouldn't. The lighter bike would slow down faster, change directions with less effort, respond to inputs with lighter touch. Anyone who as spend much time down at the drag strip as seen odd pairings that ran the same time despite differences in weight; one just used all the run out while the other used half.

Fun theoretical exercise... now go put it into practice =)

 

[Rusty McNeil]

if Torque/lb and HP/LB is the same I don't know what the answer is; I suspect mathematically the result would be about the same...??:ummm: From start to finish, as long as both of 'em are geared so that they are both staying in whatever optimum RPM is for each of them???

Now if were talking total power, some mathematical combination of TQ and HP that results in total power, even tho' one has more TQ and the other has more HP?????

I dunno??:ummm::ummm: Is there such an equation to equivocate the two resulting in "Total Power"

 

[Rusty McNeil]

I suppose I should frame it differently. Given the choice, which is generally more preferable for the task?

I'd say which ever one is more controllable.........

You'd have to give 'em both the same geometry and length but different weights and HP and TQ to honeslty test this theory.....???

 

[one2dmax]

They would be identical with all else equal. That's a mathematical certainty. BUT, things are never that equal.

In the real world drag race world the hayabusa's and ZX14's are dominating the dragstrip due to their weight and stability. The 1000's have better power to weight but have a very difficult time launching.

Sean

 

[EvilD]

In the real world I would think the 100 hp bike would leave harder due to the fact that it will have more overall torque. even thou the w/lb ft would be the same.

 

[bobzdar]

In the real world I would think the 100 hp bike would leave harder due to the fact that it will have more overall torque. even thou the w/lb ft would be the same.

Force = Mass x acceleration, so Acceleration = Force/Mass. If the (Force/Mass) is the same for both bikes, acceleration will be the same. Simple math. In the real world, it will be determined by something other than the Force/Mass portion (so chassis setup, traction, driver skill etc).

 

[acammer]

Force = Mass x acceleration, so Acceleration = Force/Mass. If the (Force/Mass) is the same for both bikes, acceleration will be the same. Simple math. In the real world, it will be determined by something other than the Force/Mass portion (so chassis setup, traction, driver skill etc).

... in a vacuum. If the bikes accelerated uniformly off the line, as drag increased the more powerful but heavier bike would start to show an advantage. This advantage would continue to grow as speeds increased, as drag builds up exponentially.

Consider this example:

2005 Lotus Elise. 2000lbs, 190hp, 0-60 in 5.1 seconds, 1/4 mile of 13.5 @ 103mph.
2011 Chevy Camaro SS 3860lbs, 426hp, 0-60 in 5.1 seconds, 1/4 mile of 13.1 @ 110mph.

There are two cars, one light, one heavy, that run an identical 0-60 time, but by the time they are into the triple digits one is pull away. And if this was a measured mile, you'd really see the difference grow quite a bit more. Of course, should you turn them both loose on a tight road-course, the Elise would hand the F-body it's chucky rear end, but that wasn't the discussion.

 

[satariel666]

... in a vacuum. If the bikes accelerated uniformly off the line, as drag increased the more powerful but heavier bike would start to show an advantage. This advantage would continue to grow as speeds increased, as drag builds up exponentially.

Consider this example:

2005 Lotus Elise. 2000lbs, 190hp, 0-60 in 5.1 seconds, 1/4 mile of 13.5 @ 103mph.
2011 Chevy Camaro SS 3860lbs, 426hp, 0-60 in 5.1 seconds, 1/4 mile of 13.1 @ 110mph.

There are two cars, one light, one heavy, that run an identical 0-60 time, but by the time they are into the triple digits one is pull away. And if this was a measured mile, you'd really see the difference grow quite a bit more. Of course, should you turn them both loose on a tight road-course, the Elise would hand the F-body it's chucky rear end, but that wasn't the discussion.

I was not going to interupt this thread as it obvious to me but I must agree with you and post an adequate link:

http://www.youtube.com/watch?v=RXqSedWSu2k

 

[EvilD]

Force = Mass x acceleration, so Acceleration = Force/Mass. If the (Force/Mass) is the same for both bikes, acceleration will be the same. Simple math. In the real world, it will be determined by something other than the Force/Mass portion (so chassis setup, traction, driver skill etc).

Like I stated, in the real world...

 

[bobzdar]

... in a vacuum. If the bikes accelerated uniformly off the line, as drag increased the more powerful but heavier bike would start to show an advantage. This advantage would continue to grow as speeds increased, as drag builds up exponentially.

Consider this example:

2005 Lotus Elise. 2000lbs, 190hp, 0-60 in 5.1 seconds, 1/4 mile of 13.5 @ 103mph.
2011 Chevy Camaro SS 3860lbs, 426hp, 0-60 in 5.1 seconds, 1/4 mile of 13.1 @ 110mph.

There are two cars, one light, one heavy, that run an identical 0-60 time, but by the time they are into the triple digits one is pull away. And if this was a measured mile, you'd really see the difference grow quite a bit more. Of course, should you turn them both loose on a tight road-course, the Elise would hand the F-body it's chucky rear end, but that wasn't the discussion.

I believe the questions was off the line, not top end charge. However, the Elise in the above example has a lower power/weight ratio so should be slower. It probably has better traction off the line, so jumps the more powerful Camaro right off the start but eventually gets reeled in and passed.

If both have the same frontal area and CoD, then the more powerful car/bike will start to pull away at higher speeds even though it has more weight.

 

[bobzdar]

Like I stated, in the real world...

In the real world, it would depend on something other than the power/weight if they're equal.

 

[one2dmax]

I am a very big american muscle fan (no surprise there) but would love to get some seat time in either one of those incredibly awesome cars. Considering the years of development and discoveries found after the F1 was made it still held it's own in my opinion!

Sean

 

[acammer]

I believe the questions was off the line, not top end charge. However, the Elise in the above example has a lower power/weight ratio so should be slower. It probably has better traction off the line, so jumps the more powerful Camaro right off the start but eventually gets reeled in and passed.

If both have the same frontal area and CoD, then the more powerful car/bike will start to pull away at higher speeds even though it has more weight.

The original question was would a lighter bike with an equal power to weight ratio have an advantage off the line. The elise camaro example shows this not to be the case, we have two cars with a very similar power to weight ratio that are essentially even off the line, and further demonstrates the heavier more powerful cars advantage as the race goes on. The Mclearen Bugatti demonstrates the same thing.