See, I just summed my whole post up in a few sentences instead of a paragraph or two like I had before. I just like to explain myself so people can understand why I say what I say, thats all.
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BBW SEX

 

Ummmm, I do believe that is incorrect NB.

But worthy of discussion. Ya do remember I'm an engineer by education and not so much trade.

Horsepower is typically expressed in units of ft-lb/s and one horsepower from a mechanical point of view would be 550 ft-lb/s. Now the fun common sense part...which most of my engineering cohorts are not good at.

Put a big azze heavy tire on the klx and plop her on a dyno....measure horsepower..........now put a lil 12" rim on the klx with a light tire ...... measure horsepower.....Ya'll already know which dyno run will read a higher hp right.

It's all about the energy associated with changing the angular momentum of an object.....another common sense analogy....a heavy tire is harder to stop than a light one right.

So the real issue is ..... how much actual hp increase will one see at the tire by shaving 10oz off the flywheel....probably not much but THEORETICALLY it would increase and actually could be calculated provided we knew a few variables like the original weight of the flywheel and it's angular center of gravity for starters.

 

Oh....point of order.

If horsepower goes up a little ..... torque gotta come down a little. Just in case some were not clear on that.

 

From removing weight off the flywheel correct? Not in all applications? As in a power increaser, thinking V8 here.... supercharger... both go up.... You just meant for removing weight off the flywheel? Just to be clear.

What kinda engineer are you?

 

Yup, all other things being equal as in no power increase into the thermodynamic equation....like a supercharger. And that statement is not 100% correct, but for the purpose of this discussion it is applicable.

I'm an environmental engineer, but we all had to take Calc 1-3, dynamics, statics, thermodynamics 1&2, differential equations, blah, blah, blah.....lol, just don't get me started on organic chemistry, most of my core was in that. And I use thermodynamics everyday lately in the turbine power generation biz.

 

In point of fact, the flywheel doesn't reduce power, it merely smooths it out, stores the energy as a spinning mass, and returns it to the system a short while later. It is the kinetic equivalent of a spring if you want to think about it that way.

F = ma, a = F/m, and the rotational equivalents, so the heavier the mass, the less the acceleration given an equal force. And that is exactly the purpose of the flywheel - to smooth the hit. The force hasn't changed, just the mass. Work is Force applied over a distance, and Power is the rate of doing Work. Shave some mass off, you get a harder hit. But power has not increased, you are just spinning up a smaller mass with the same available power as before. How can power be increased if only the mass has been changed?

So lets take your tire example. Do you really think adding a heavy tire changes the HP of the bike? It sure doesn't. It feels like it does, but it doesn't.

To put it simply, your argument would be like saying that if you shave weight off your bike, it makes more power. It might feel like it makes more power because you have less mass to move around and that would certainly be true, but the power output is the same.

That why I said that this modification would change the "character" of the power delivery.

Don't mistake my response for anything that could be construed as against this mod in any way. In fact, I think it could make a pretty big difference to the feel of the bike. I think it should make it feel snappier, which is a big complaint from a lot of owners.

So is this where I start dropping my degrees?

 

Drop any degree you want.....actually what did you study in school? lol I don't even know....I figured you were electrical.

Mechanical engineering is not my field of expertise but you gotta provide provide sumthin to support your opine. So are you saying if I put a five pound weight on the rear tire of the klx it will not get a lower dyno hp reading than if said weight was not attached to the rim. No way.

Is that what you are saying and if so please explain your approach to that opine. Been a while since I have done angular momentum equations...but remember I am talking about HP put to the road not what the motor is putting out.

 

Fair enough. Here is my approach.

Forget about the dyno which is an indirect and imperfect measurement.

Go back to basics. Combustion applies a Force to the top of the piston which pushes it down and turns the crank, producing rotational energy. That force has not changed with this mod. In fact, the only thing that has changed is the mass of the flywheel which is attached to the crank.

So crank it out, excuse the pun. Work = Force * Distance. In this case, maybe think about one stroke of the piston. And Power = Work/time.

Has this mod done anything to affect any of those? And no frictional losses have been improved. And combustion has not been improved or increased (jetting) so the force of combustion is unchanged and the frictional losses are unchanged.

Therefore my answer to the question of whether power has been increased is no, this mod has not changed anything to increase power. And to be clear, I am speaking of power in the strictest sense, i.e., as defined in a physics text book.

As for the dyno, if you want to examine that, it doesn't measure the energy stored in the crank/flywheel. So when you lighten the flywheel, you surely see the effect at the rear wheel and on the dyno. But you have less mass spinning at the flywheel which means the energy stored there is less. So the engine outputs the same amount of power in both cases, but the dyno only measured one aspect of it, and did not measure the decreased energy stored in the flywheel in the case of the lightened flywheel.

So the increased output at the rear wheel also comes at a cost. The cost is that with a less massive flywheel, the crank has less energy stored, and is thus more prone to stalling in the slower technical trails.

If it actually increased the power output as you suggested, there would be no downside. So in effect, the flywheel mod simply robs from Peter to pay Paul.

 

Sheet I just Wikepedia'd HP....Actually HP measures force per distance, not acceleration per distance ... so the weight of the wheel would not affect HP since acceleration is constant and the energy associated with spinning it up does not affect hp .....damn I owe you a beer.

HP is a stupid measurement.

 

I don't drop degrees when debating. But since you asked, undergrad in physics (4 years, actually 5 - oops ) and grad in computer science (2 years). I'm grateful to have been able to go to school and respect that not everyone has the opportunity. There are tons of really smart people out there without degrees and I don't consider my opinion worth any more or less than theirs. You don't need a degree in something to have learned it, you just need to have wanted it. Some of the education I most value are what I learned on my own because I had a passion for it - electronics, for example. But I'm just a hack at that.