Hello all, When shifting to get the best ET should a bike be shifted when the rpm reaches peak HP or shift the bike when the next gear will land you at peak TQ?
OR is there another choice that I have overlooked?

Just tring to beat the braggers that say sportsters are slow.




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Both..or a combination of both.

your quickest acceleration is from peak to peak so you would want to shift just after the hp peak and drop to the tq peak. but since gear spreads aren't always perfect for this, you have to learn to favor one or the other a little and sometimes just favoring one based on which gear you are in.
Such as short shifting in the lower gears using torque to get you moving and winding out higher gears using hp for top speed.

The placement of the torque peak means absolutely nothing for maximum acceleration.

Don't believe me? Get two identical bikes going side by side, with both at the engine's torque peak. Whack one of them wide open. At the same time, downshift the other bike to put the motor at the power peak instead and whack it wide open.

It won't even be close. The bike at it's power peak will run away from the other bike.

Why? Because when you downshift, you multiply the torque. That means that even though the motor is making less torque, since you have more gear reduction in the lower gear, you end up with more torque at the rear wheel, and that's what accelerates the bike.

This is exactly what a horsepower curve is all about. It takes into account that the rpm the motor is turning is also a component of the performance. The more rpm you're turning, the more gear reduction you can apply at a given speed, and hence the more you can multiply the motor's torque. Horsepower is a complete description of performance, torque is not.

So anyway, to answer the question, you want the rpm range of the engine centered around the power peak, so that you maximize the area under the curve. So, for example, say you lose 800rpm on a gear shift (the exact number is purely a function of your gear ratios). In that case you'd want to rev 400rpm past your power peak, make your gearshift, and you'll land 400rpm below your power peak. That will give you the maximum amount of torque at the rear wheel as you accelerate through each gear, and the rear wheel is where it matters.

(now before some smart-ass talks about integrating the curve to precisely determine how to maximize the area, yeah yeah whatever, just centering it is plenty close).

At any given speed, maximum torque at the rear wheel occurs at the power peak.

If my dyno has a flat HP peak of 700 rpm, I should rev it 100 rpm past to land at the minimum rpm that peak HP occurs at. is this true?

given your stated 800 rpm gear shift scenario and a bike that had an 800 rpm flat peak HP you would shift at highest rpm that peak HP occured and fall after the shift to the start of the peak HP number. true?





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Mikel NY
One of the sport bike magazine, Sport Rider or Motorcyclist I believe had a excel formula in their magazine and on-line, that takes all the guess work out.
I'll see if I can dig it up for you. You will need a dyno sheet with torque and rpm numbers.
Running at the highest average peak torque in every gear is the short answer.

Mikel NY
One of the sport bike magazine, Sport Rider or Motorcyclist I believe had a excel formula in their magazine and on-line, that takes all the guess work out.
I'll see if I can dig it up for you. You will need a dyno sheet with torque and rpm numbers.
Running at the highest average peak torque in every gear is the short answer.

What I understand HP is Tq times RPM divided by a constant. So if the HP is higher then the TQ must be even though on a dyno sheet the TQ number is less the RPM makes up for it. (TQ x RPM / 5252 = HP). With that said the longer you can stay at a higher HP number the quicker your ET?



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sorta correct..

HP = (torque * revs) / 5252


and yes the longer you can stay at a higher HP number the quicker you'll be.. all other things being equal..


Think of HP as power in relation to time.... .. torque is the force but as Aaron just said a gearbox multiplies that force.. when you are doin anything in a real world timeframe you need power in relation to time and that is Horsepower .. the more of it ya got all other things being equal the faster you can go...



Just to add to what Aaron said and your comments... takin that 800 rpm number and splitting it is a good start but you may find your power curve drops off very quickly after it's peak, in which case you split the difference that gives the best area under the curve in that rpm drop range....


In the real world ya better off practicing ya starts than worrying about a few hundred rpm each way at the top...

Torque accelerates the bike. Putting the highest average amount of torque in each gear to the rear wheel, will yield the highest acceleration rate and horsepower numbers.

I agree with the Practice the starts... I have good clutch control but I don't have the brass to launch at 3000+ rpms !!

I was just setting the shift lights and wanted to figure what is the best starting setting for my bike.

On my dyno sheet the peak HP is long and flat. it is at peak from 5800-6500+ ( I never dynoed above 6500 ) that is 700 rpms. it may be more but I don't like turning the motor any faster ( ware & tare over time ).

This is exactly what a horsepower curve is all about. It takes into account that the rpm the motor is turning is also a component of the performance. The more rpm you're turning, the more gear reduction you can apply at a given speed, and hence the more you can multiply the motor's torque. Horsepower is a complete description of performance, torque is not.

If hp is a complete description of performance, then why show the torque curve? Why not just show the hp curve?

Your starts are something that will need practice. Talk to some of the guys here and at your local track about technique. It helps to see an example in person. You never want to drop the clutch, but slip it instead. With practice you'll easily be leaving the line at over 3000 rpm.
I'm still looking for that excel formula. I've applied the formula to many different applications: Jap bikes, Harleys, cars, trucks, etc., and had positive results with all. It eliminates the ifs, ands, buts, and erroneous opinions. :smoke

This is exactly what a horsepower curve is all about. It takes into account that the rpm the motor is turning is also a component of the performance. The more rpm you're turning, the more gear reduction you can apply at a given speed, and hence the more you can multiply the motor's torque. Horsepower is a complete description of performance, torque is not.


If hp is a complete description of performance, then why show the torque curve? Why not just show the hp curve?

Good Question, the top paragraph is the kind of answer or statement you will get from someone that might be a good wrench or dyno operator. But it won't be the same answer you'll get from good mechanical engineer, physicist, or even a well educated and intelligent racer.

Mikel NY
Running at the highest average peak torque in every gear is the short answer.

It might be a short answer, but it's a wrong answer.

Torque is twisting force, without any regard for speed. But speed is enormously important.

For example, if you have 80 ft-lbs at 3000 rpm, you can get twice as much done as if you had 80 ft-lbs at 1500 rpm. You're making the same torque, but you're making it twice as fast.

In fact, you could take that 80 ft-lbs at 3000 rpm, gear it down 2:1, and have 160ft-lbs at 1500 rpm. In other words, you have the option of making twice the torque, but doing it at the same speed as the weaker motor.

So you see, having more rpm is a huge advantage. You can make small torque into big torque if you have more rpm. That's what gear reduction is all about.

It's also exactly why a 600 race rep with 40 ft-lbs at 15,000 rpm will beat up on a Sportster making 80 ft-lbs at 5000 rpm. It may only have half the torque, but it's turning three times the rpm. So for any given rear wheel speed, it can have three times the gear reduction through the primary & tranny & final drive, which multiplies it's torque three additional times over that of the Sportster. Hence more torque reaches the rear wheel at any given rear wheel speed. Three times 40 is 120, and that's more than the 80 that the Sportster has.

That's exactly why you talk horsepower when you're talking about performance. Horsepower is literally torque times rpm. It combines the twisting force (torque) with the speed of twisting (rpm). Both are equally important when you're talking about performance. They're also totally interchangeable. Gear something down, you decrease rpm and increase torque. Gear something up, you increase rpm and decrease torque.

More in-depth explanation here:

http://www.nrhsperformance.com/tech_power.shtml

And in case you're wondering, yes, I am an engineer. But this is really basic physics, you don't need an engineering degree to grasp this.

It's also exactly why a 600 race rep with 40 ft-lbs at 15,000 rpm will beat up on a Sportster making 80 ft-lbs at 5000 rpm. It may only have half the torque, but it's turning three times the rpm. So for any given rear wheel speed, it can have three times the gear reduction through the primary & tranny & final drive, which multiplies it's torque three additional times over that of the Sportster. Hence more torque reaches the rear wheel at any given rear wheel speed. Three times 40 is 120, and that's more than the 80 that the Sportster has.

All you need to say right there.

To quote something I read somewhere else, that's what puts billy biker on the trailer and ricky ricer on the podium.


THIS NEEDS TO BE MADE A STICKY SOMEWHERE!!!

All you need to say right there.

To quote something I read somewhere else, that's what puts billy biker on the trailer and ricky ricer on the podium.


THIS NEEDS TO BE MADE A STICKY SOMEWHERE!!!

Apples to Oranges though.

Comparing an air-cooled OHV engine to a liquid cooled DOHC is like comparing Oscar de La Hoya to Mike Tyson. Sure they're both awesome in their own way... Different styles

If hp is a complete description of performance, then why show the torque curve? Why not just show the hp curve?

We are all very visual and like that...just saves the math really.
I once had a tq run over rpm and a hp run over mph....that was not fun to overlay....

edited for name calling -raysheen

At first I thought this was a slam, but no it's a joke, no it is a slam, if I understand your point. Is that really called for? GEESH ...

If hp is a complete description of performance, then why show the torque curve? Why not just show the hp curve?


Just showing the torque curve is really all that is necessary. Horsepower is nothing more than a mathematical calculation based on torque and time.

I don't have a clue what Sleeper's post 17 is tring to say!! I can't understand why you would post such a slam ( if it is a slam? )


So back to learning when to Shift.... By making the intake track longer one can move the TQ peak lower in the rpm range, so If I removed the spacer between my carb and intake tract, I would move the peak TQ up in rpms thus making more HP at higher RPMs. Is this true?

Just showing the torque curve is really all that is necessary. Horsepower is nothing more than a mathematical calculation based on torque and time.

At any given rear wheel speed, maximum rear wheel torque occurs at the engine's power peak, not at the engine's torque peak. That's a mathematical fact that's very easy to prove.

Let's just take a real world example.

http://www.nrhsperformance.com/images/drsamminnich.gif

Here's a motor we built for a guy several years ago.

The torque peak is 109.4 ft-lbs at 4600 rpm

The power peak is 117.6 hp at 6700 rpm

Pick a rear wheel speed. Let's just say 500rpm.

If we have the motor at 4600rpm, and we're in a gear that gives us 500rpm rear wheel speed, that means we have 9.2 of overall gear reduction, right? 4600 divided by 500 is 9.2.

Well, if the motor is making 109.4 ft-lbs, and you've got 9.2 of gear reduction between the crank and the rear wheel, you've got 109.4 times 9.2 equals 1006.48 ft-lbs of torque at the rear wheel. Agreed?

Okay, now let's see what happens at the power peak instead. If we have the bike at 6700rpm, and it's got 117.6 horsepower, that means it's making 92.2 ft-lbs of torque. torque = (hp times 5252) divided by rpm, if you work that out you'll get 92.2 ft-lbs, and you can see on the chart that's about right.

If we have the motor at 6700rpm, and we're in a gear that gives us 500rpm rear wheel speed, that means we have 13.4 of overall gear reduction, right? 6700 divided by 500 is 13.4.

Well, if the motor is making 92.2 ft-lbs, and you've got 13.4 of gear reduction between the crank an the rear wheel, you've got 92.2 times 13.4 equals 1235.48 ft-lbs of torque at the rear wheel. Agreed?

1235.48 is more than 1006.48. The power peak wins.

So as you can see, at the same rear wheel speed, you put more torque to the rear wheel when the motor is at the horsepower peak, not when the motor is at the torque peak.

This is exactly why horsepower is the meaningful number. It takes the engine's rpm into consideration. The engine's rpm is every bit as important as the engine's torque, because the more engine rpm we have, the more gear reduction we can apply for a given rear wheel speed. And the more gear reduction we can apply, the more we multiply the engine's torque. The important thing isn't how much torque the engine can make, or how much rpm it can turn, the important thing is how much of both it can do at once. That number is called "horsepower".

ps: there's a much more direct way to do that calculation, I did it the long way just to illustrate the concept. But the short way is just to calculate rear wheel torque directly, knowing rear wheel rpm and rear wheel horsepower. Remember, any time you know any two of the three components (torque, rpm, or power), you can can calculate the third.

Thank you Aaron, That answers my question quite nicely. I never Dynoed my motor higher than 6500 so I don't know when it starts to drop in power so I will set the shift lights 200 rpms less than the limiter and run it at peak HP ( I have a 700 rpm peak, flat at the top )


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This is exactly why horsepower is the meaningful number. It takes the engine's rpm into consideration. The engine's rpm is every bit as important as the engine's torque, because the more engine rpm we have, the more gear reduction we can apply for a given rear wheel speed. And the more gear reduction we can apply, the more we multiply the engine's torque. The important thing isn't how much torque the engine can make, or how much rpm it can turn, the important thing is how much of both it can do at once. That number is called "horsepower".

Aaron how would you comment on this that I found online. It says that in addition to rpm there is another key player, which is MEP. From what I understand you can either make power through high rpm or you can do it through MEP instead in which case you don't have to rely on high rpm. However, that will still show up as more hp on the dyno.

MEP vs. Rpm
There are just two major ingredients in horsepower. These are combustion's push (we have just looked at this in our consideration of thermal efficiency), and revolutions per minute (rpm). Combustion's push has a fancy name -- Mean Effective Pressure (MEP). MEP is simply the single pressure which, acting on the piston, could theoretically do the same work as all the sucking and blowing that goes on inside the cylinder. Engineers use MEP as an indicator of the stress on the engine from the inside-out -- i.e. the constant strain inside the pressurized container. The beauty of MEP is that it is platform-independent. It doesn't matter whether the engine is a four-stroke or a two-stroke, single cylinder or a V-12. It is concerned only with cylinder stress. However, cylinder pressure isn't alone. Before you can have power, you must also have time, and in an engine, time is measured in rpm. MEP and time go together. They are the twin giants holding up the horsepower universe -- the bookends bracketing all that is important about how an engine makes power. They are that significant. And, there is an interesting relationship between them -- they are essentially opposites. Find for example a high performance engine that makes its power through a lot of rpm, and you will discover (through calculation) that it produces a relatively low MEP. Conversely, the engine that produces power mostly through MEP will be one that doesn't need much rpm. Of course, many engines benefit from a careful combination of both, but even then, every engine works on an emphasis on one or the other, due to its internal design. This fact, the relationship between MEP and rpm, quickly evaporates all the barstool arguments. It also produces some fascinating conclusions. For example, to make a high-rpm engine make more power, do you perform modifications that make even more use of rpm, or do you go after MEP? Oddly, such an engine will usually respond best to modifications that increase MEP, not those which make use of rpm. Clearly then, contrary to popular wisdom, rpm is not always the major player in the game of increasing engine performance, even in high rpm engines.

Torque essentially comes from two things: cylinder pressure and the mechanical advantage it has on the crank.

Mechanical advantage on the crank comes from both the bore and the stroke. This is easy to visualize when you think of the stroke as a function of how far the crankpin is from the center of the crank. The stroke is essentially the size of the lever. More stroke means the rod has more leverage to turn the crank.

But bore size also gives more leverage. Pressure is described in pounds per square inch, right? Well, with a bigger bore, you've got more square inches to push on. So the bottom line is that both the bore and the stroke contribute to the torque.

The other ingredient of torque is of course the pressure you build. That pressure is a function of a whole bunch of things, including things like how well you filled the cylinder and how hard you compressed it on the compression stroke. The piston moving out of the way regulates the pressure. Ever wonder why a motor pings at high load? It's harder to move the piston out of the way at high load, hence the pressure gets too high.

Bottom line, MEP is just a platform independent way of talking about the cylinder pressure. And cylinder pressure of course has a close relationship to the torque. So in the above, they're really talking about the process that creates the torque. Horsepower is and always will be torque times rpm (divided by 5252, but conceptually, you can ignore that part, all it really does is scales the number to what Watt's horse could do).

If hp is a complete description of performance, then why show the torque curve? Why not just show the hp curve?

That's an excellent question, one that I wish more people would ask. Seems like every time I ever post a dyno sheet with horsepower only, people ask me about the torque. But they generally have no idea why, they just have it in their heads that it's important. It's generally not.

I'll tell you what a torque curve is really useful for: understanding how a motor is breathing. It shows you, at a glance and without having to extrapolate it from the horsepower, a map of the cylinder fill. On a given motor over the range of rpm, when the torque is high, you're filling the cylinder well; when it's low, you're not.

This is very important information for an engine builder. There are a lot of dynamic processes going on in a running engine. Our goal is to fill that cylinder over the rpm range that matters for the application. For some people, they want it down low. Race motors we want it up high (remember, horsepower is torque times rpm, so the more I can move that torque peak to the right side of the chart, the bigger my peak horsepower number will be). Most street motors we try to make a wide parabola out of it. Sizing the ports for the correct velocity, minimizing losses through the entire system, matching the intake close event timing to the intake port velocity, and effectively utilizing the overlap event in conjunction with the exhaust wave timing are the main ways we place and shape the torque curve.

in stock car racing, we have to gear the car to accelerate off the turn and wind it up down the straight...... every track is different..... we always try to keep the revs close to peak HP..... horsepower is everything when you're talking about going fast....... torque is not really a player, bulldozers make a shitload of torque......

roughly center each gear change on peak horsepower. .... all the racers know this.

Ww :smoke

I don't have a clue what Sleeper's post 17 is tring to say!! I can't understand why you would post such a slam ( if it is a slam? )


So back to learning when to Shift.... By making the intake track longer one can move the TQ peak lower in the rpm range, so If I removed the spacer between my carb and intake tract, I would move the peak TQ up in rpms thus making more HP at higher RPMs. Is this true?

The reason for the slam is any time I get on this subject. One of the boys from NRHS jumps in to correct me. I can live with that, and would be glad to learn more if they can prove their right. The problem is they have a good understanding of how torque and horsepower work, but not a full and accurate understanding of how they work. Being they are the experts at this forum and giving comments that aren't correct is something I don't like, and I would assume they don't want to do either.

Just showing the torque curve is really all that is necessary. Horsepower is nothing more than a mathematical calculation based on torque and time.

I'm glad, I'm not the only one that finds this easy to understand.
Thanks Dude

An inertial dynmometer actually comes closer to directly measuring HP than it does torque. Inertial dynos measure the time interval for each rotation of the drum and based upon the known physical characteristics of the drum directly calculate HP based upon the change in drum rotation time interval from one to the next.

To find engine torque, that HP is then divided by engine RPM and multiplied by 5252. So for an intertial dyno, it is HP that is the more rudimentary/directly measured performance parameter and torque is the result of more involved calculation.

On a brake dyno, torque is measured most directly and engine HP is then calculated based upon engine RPM. Note that if the torque is measured at the rear wheel on a chassis dyno with a brake, the torque actually being measured is the torque being applied to the drum, not the rear wheel and not the engine. So even then, some calculating is required to find engine torque. This involves knowing the engine speed.

I'd clarify as follows:

It is absolutely true that for any given rear wheel speed, maximum acceleration or maximum torque at the rear wheel, which incidentally equates to maximum thrust between tire and pavement, will be at peak HP. This is just recognizing that a lower gear provides a greater torque multiplication (drive ratio) between engine and rear wheel. We all agree that our motorcycles accelerate harder the lower the gear they are in, yes?

It is also true and perhaps as germaine to the discussion that for any given gear (drive ratio) the peak torque at the rear wheel will ocurr at the point of peak engine torque.

If the torque multiplication factor (drive ratio) remains constant (no downshifting) and rear wheel speed is allowed to vary, then torque at the rear wheel is just a multiple of that at the engine. The multiple being the overall drive ratio; well, to be perfectly accurate we'd need to subtract around 10% due to parasitic losses. But the point stands.

So for any given gear, our motorcycles actually accelerate harder with more thrust at their engine's torque peak.

Of course we all understand that downshifting to a lower gear has the effect of increasing drive ratio and thus increasing the torque multiplication between engine and rear wheel.

Air-cooled rules! :D

AC2W

Some questions to ponder...

Does it take more or the same or less HP to accelerate 20 mph in two seconds from 25 to 45 mph versus from 60 to 80 mph?

Does it take more or the same or less torque at the rear wheel to accelerate 20 mph in two seconds from 25 to 45 mph versus from 60 to 80 mph?

An inertial dynmometer actually comes closer to directly measuring HP than it does torque. Inertial dynos measure the time interval for each rotation of the drum and based upon the known physical characteristics of the drum directly calculate HP based upon the change in drum rotation time interval from one to the next.

To find engine torque, that HP is then divided by engine RPM and multiplied by 5252. So for an intertial dyno, it is HP that is the more rudimentary/directly measured performance parameter and torque is the result of more involved calculation.

On a brake dyno, torque is measured most directly and engine HP is then calculated based upon engine RPM. Note that if the torque is measured at the rear wheel on a chassis dyno with a brake, the torque actually being measured is the torque being applied to the drum, not the rear wheel and not the engine. So even then, some calculating is required to find engine torque. This involves knowing the engine speed.


This is absolutely correct. An inertia dyno, like a Dynojet, has a simple sensor that tells the computer every time the drum completes a rotation. Knowing the mass moment of inertia of the drum and seeing the speed and rate of acceleration, it can calculate the horsepower. If the operator has connected the tach pickup as well, and it knows engine rpm, it can calculate torque and plot it as well.

The important point you made here is that torque on the dyno sheet is at the crank, i.e. upstream from the gearing. It's calculated based on engine rpm, not rear wheel rpm. And the difference between engine torque and rear wheel torque is really the root cause of the confusion that some people have over this whole issue.


So for any given gear, our motorcycles actually accelerate harder with more thrust at their engine's torque peak.


This statement is absolutely true of course, but I've also seen people get awfully confused by it and read more into it than it means. The key words here are for any given gear. But in the real world, you're going a given speed, and you're interested in accelerating, and you're not constrained to staying in the current gear. If you downshift and put the motor at it's power peak instead (or any other rpm where the power is higher), even though the engine's torque is lower, more torque will reach the rear wheel due to the additional gear reduction, and you'll accelerate harder. That's what I was trying to show with my examples.


Of course we all understand that downshifting to a lower gear has the effect of increasing drive ratio and thus increasing the torque multiplication between engine and rear wheel.


Exactly, however, not everyone understands that.

I really think that some people latch on to this notion that "torque accelerates the bike" and argue emotionally around that. What they fail to understand is that torque at the rear wheel is what accelerates the bike, not torque at the engine. And the torque shown on a dyno sheet is torque at the engine, i.e. upstream from the gearing, as you did an excellent job of pointing out. But that gear reduction in the primary, transmission, and secondary changes everything. It can take less torque and make it more. The more rpm you have, the more gear reduction you can apply for a given rear wheel speed. So engine rpm ends up being every bit as important as engine torque when it comes to accelerating the bike. Hence when we talk performance, we don't talk in terms of torque, nor do we talk in terms of rpm, we talk in terms of their combination, torque times rpm, which is better known as "horsepower".

Oh, BTW, I haven't seen a chassis dyno that measures brake horsepower. Does a SuperFlow do this?

My Dynojet is equipped with a brake, but provides no facility for making a measurement when it's on. It's simply to control the rpm when mapping injection systems.

I have some experience with water brake dynos. They use a strain gauge to measure torque directly, and then calculate horsepower knowing the torque and rpm.

Does it take more or the same or less HP to accelerate 20 mph in two seconds from 25 to 45 mph versus from 60 to 80 mph?

Does it take more or the same or less torque at the rear wheel to accelerate 20 mph in two seconds from 25 to 45 mph versus from 60 to 80 mph?

Accelerating 20mph in a given amount of time takes the same amount of torque regardless of the speed you're going. This is essentially f=ma, or the rotational equivalent.

However, at the higher speed, the rear wheel rpm is higher. Since horsepower is torque times rpm (rear wheel rpm in this case), the power required is higher at the higher speed.

An inertial dynmometer actually comes closer to directly measuring HP than it does torque. Inertial dynos measure the time interval for each rotation of the drum and based upon the known physical characteristics of the drum directly calculate HP based upon the change in drum rotation time interval from one to the next.

To find engine torque, that HP is then divided by engine RPM and multiplied by 5252. So for an intertial dyno, it is HP that is the more rudimentary/directly measured performance parameter and torque is the result of more involved calculation.

On a brake dyno, torque is measured most directly and engine HP is then calculated based upon engine RPM. Note that if the torque is measured at the rear wheel on a chassis dyno with a brake, the torque actually being measured is the torque being applied to the drum, not the rear wheel and not the engine. So even then, some calculating is required to find engine torque. This involves knowing the engine speed.

I'd clarify as follows:

It is absolutely true that for any given rear wheel speed, maximum acceleration or maximum torque at the rear wheel, which incidentally equates to maximum thrust between tire and pavement, will be at peak HP. This is just recognizing that a lower gear provides a greater torque multiplication (drive ratio) between engine and rear wheel. We all agree that our motorcycles accelerate harder the lower the gear they are in, yes?

It is also true and perhaps as germaine to the discussion that for any given gear (drive ratio) the peak torque at the rear wheel will ocurr at the point of peak engine torque.

If the torque multiplication factor (drive ratio) remains constant (no downshifting) and rear wheel speed is allowed to vary, then torque at the rear wheel is just a multiple of that at the engine. The multiple being the overall drive ratio; well, to be perfectly accurate we'd need to subtract around 10% due to parasitic losses. But the point stands.

So for any given gear, our motorcycles actually accelerate harder with more thrust at their engine's torque peak.

Of course we all understand that downshifting to a lower gear has the effect of increasing drive ratio and thus increasing the torque multiplication between engine and rear wheel.

Air-cooled rules! :D

AC2W

Very well said.

This is absolutely correct. An inertia dyno, like a Dynojet, has a simple sensor that tells the computer every time the drum completes a rotation. Knowing the mass moment of inertia of the drum and seeing the speed and rate of acceleration, it can calculate the horsepower. If the operator has connected the tach pickup as well, and it knows engine rpm, it can calculate torque and plot it as well.

The important point you made here is that torque on the dyno sheet is at the crank, i.e. upstream from the gearing. It's calculated based on engine rpm, not rear wheel rpm. And the difference between engine torque and rear wheel torque is really the root cause of the confusion that some people have over this whole issue.



This statement is absolutely true of course, but I've also seen people get awfully confused by it and read more into it than it means. The key words here are for any given gear. But in the real world, you're going a given speed, and you're interested in accelerating, and you're not constrained to staying in the current gear. If you downshift and put the motor at it's power peak instead (or any other rpm where the power is higher), even though the engine's torque is lower, more torque will reach the rear wheel due to the additional gear reduction, and you'll accelerate harder. That's what I was trying to show with my examples.



Exactly, however, not everyone understands that.

I really think that some people latch on to this notion that "torque accelerates the bike" and argue emotionally around that. What they fail to understand is that torque at the rear wheel is what accelerates the bike, not torque at the engine. And the torque shown on a dyno sheet is torque at the engine, i.e. upstream from the gearing, as you did an excellent job of pointing out. But that gear reduction in the primary, transmission, and secondary changes everything. It can take less torque and make it more. The more rpm you have, the more gear reduction you can apply for a given rear wheel speed. So engine rpm ends up being every bit as important as engine torque when it comes to accelerating the bike. Hence when we talk performance, we don't talk in terms of torque, nor do we talk in terms of rpm, we talk in terms of their combination, torque times rpm, which is better known as "horsepower".

Torque accelerates the bike the period. Horsepower is a measurement of how quickly it accelerates the bike. I can't figure out how you can't understand this. My goal at least to start is get you to understand this.
Their are people who have responded here that know this is the facts.

As a little side note to everyone who has read any of my posts anywhere. The only time I edit my posts is for typing and spelling mistakes. I do not edit them to cover my own ass. If I make a mistake other wises I will admit it.

How about "other wises" and "know this is the facts"? Or is it just typing and spelling but not grammar?

EDIT - (sarcasm)

How about "other wises" and "know this is the facts"? Or is it just typing and spelling but not grammar?

EDIT - (sarcasm)

Thats definitely an area I need help in. :doh
I'll bet your a mechanical genius also. ;)

Here's an interesting article (http://vettenet.org/torquehp.html) that I found about torque and horsepower.

Mikel_NY

Wow, 88 torque kit, bet she's a monster! :)

I always thought the big engine dragsters basically stay at the same RPM, and just play with the clutch?

At any given rear wheel speed, maximum rear wheel torque occurs at the engine's power peak, not at the engine's torque peak. That's a mathematical fact that's very easy to prove.


I don't need an example. I understand exactly what you're saying.

A dynamometer measures torque. Horsepower is calculated later from torque and RPM.

There is really no need for a horsepower curve to be displayed. All one really needs is RPM and Torque and they can calculate it.

Torque accelerates the bike the period. Horsepower is a measurement of how quickly it accelerates the bike. I can't figure out how you can't understand this. My goal at least to start is get you to understand this.
Their are people who have responded here that know this is the facts.


I may be way out of line here since I only know at this point what I've read in this thread, but I think you and Aaron actually agree that torque is what accelerates the bike. It's just that he is saying the torque curve on a dyno sheet is not the rear wheel torque, it is instead the engine torque which equates to the rear wheel torque in a way that is entirely dependent on what gear the transmission is currently in, and is therefore not useful for finding out where you get peak acceleration (unless you calculated it based on the gear ratios, but this is more or less what the horsepower curve already is).

I am guessing that if you could measure both the rear wheel torque and rear wheel horsepower at the same time the graphs would be close to matching?



One more thing... Aaron, the rotational equivalent for f=ma is T=Ia... ( Torque=Moment of Inertia * Alpha ) where moment of inertia is calculated from the mass, size shape or whatever of the object being rotated and alpha is rotational acceleration.

Yay for engineering dynamics!

A dynamometer measures torque. Horsepower is calculated later from torque and RPM.



I think it's the other way around... The rear wheel horsepower is measured on a standard dyno and the engine torque is calculated. I think, anyway... :p

But the engine torque isn't really very useful unless you want to use your gear ratio number for each given gear to figure out your rear wheel torque.... If only we had the rear wheel torque on the graph, that would be more useful methinks.

A dynamometer measures torque. Horsepower is calculated later from torque and RPM.


Brake dyno's work that way. Inertia dyno's do not. Inertia dyno's actually measure horsepower and then, if the tach pickup was used, they calculate torque at the engine.


There is really no need for a horsepower curve to be displayed. All one really needs is RPM and Torque and they can calculate it.

You can also calculate the torque from the rpm and the horsepower, so it goes both ways.

The advantage to plotting horsepower instead of torque is that it shows you right where you need to be, rpm-wise, to get maximum performance. The horsepower curve plots the performance of the motor. The torque curve does not, although yes, if you do as you say, you can calculate it.

Now it's time for the crazy question. Speed is related to rpm. So
reaching higher rpm faster reaches higher speeds. Lighter flywheels
will make an engine spin up faster. So lighter flywheel's would
play a role in acceleration.

So would it be possible for let's say a 130 hp engine with heavier
flywheels to be beaten by a 115 hp engine with lighter flywheels? Or
is this a completely retarded question because the engine with the
lighter flywheels would be the engine that produced more hp?

I may be way out of line here since I only know at this point what I've read in this thread, but I think you and Aaron actually agree that torque is what accelerates the bike. It's just that he is saying the torque curve on a dyno sheet is not the rear wheel torque, it is instead the engine torque which equates to the rear wheel torque in a way that is entirely dependent on what gear the transmission is currently in, and is therefore not useful for finding out where you get peak acceleration (unless you calculated it based on the gear ratios, but this is more or less what the horsepower curve already is).

This is correct.


I am guessing that if you could measure both the rear wheel torque and rear wheel horsepower at the same time the graphs would be close to matching?


The problem with rear wheel torque is that it varies wildly depending on the gear you're in. In first gear, you're gonna have a mountain of it. In top gear, you'll have not so much. If you change sprockets on the primary or final drive you can affect it as well. So it's really only a useful number when you consider it in relation to the speed the rear wheel is turning. When you do that, it's called "horsepower".

What's more, even if it was a useful number, the dyno doesn't have enough information to calculate it. It can figure out how much force is applied to the drum, but torque is force at a one foot radius. So it'd also have to know the diameter of the wheel in order to be able to tell you actual rear wheel torque.

One more thing... Aaron, the rotational equivalent for f=ma is T=Ia... ( Torque=Moment of Inertia * Alpha ) where moment of inertia is calculated from the mass, size shape or whatever of the object being rotated and alpha is rotational acceleration.

Thank you, I knew it was something like that, mirroring f=ma, but I was too lazy to go look up the terms ;)

Now it's time for the crazy question. Speed is related to rpm. So
reaching higher rpm faster reaches higher speeds. Lighter flywheels
will make an engine spin up faster. So lighter flywheel's would
play a role in acceleration.

So would it be possible for let's say a 130 hp engine with heavier
flywheels to be beaten by a 115 hp engine with lighter flywheels? Or
is this a completely retarded question because the engine with the
lighter flywheels would be the engine that produced more hp?

That's not a crazy question at all, and in fact, it's an excellent observation.

A torque & hp measurement done on a brake dyno is done in a steady state. In other words, the motor is held wide open and enough load applied to hold the rpm to a desired number, and then using a strain gauge, the torque is determined. The torque and rpm are multiplied and you get the horsepower.

With this measurement method, the inertia of the flywheels has essentially no effect. Flywheels simply store energy. While the motor is sitting there spinning one rpm, the flywheels aren't sapping any power.

However, this is not true on an inertia dyno. Since the power measurement is made by spinning up a drum of a known mass moment of inertia, any additional flywheel mass will in fact slow the acceleration rate, as some of the power of the motor is diverted into storage in the flywheels.

For this reason, some people believe that a brake dyno is the superior instrument. On the other hand, you could argue that the inertia dyno is more real-world, since it's result is reflects the flywheels in the motor.

However, this is not true on an inertia dyno. Since the power measurement is made by spinning up a drum of a known mass moment of inertia, any additional flywheel mass will in fact slow the acceleration rate, as some of the power of the motor is diverted into storage in the flywheels.

For this reason, some people believe that a brake dyno is the superior instrument. On the other hand, you could argue that the inertia dyno is more real-world, since it's result is reflects the flywheels in the motor.

So the dyno charts people get on a dynojet should show more hp for a lighter flywheel?

The reason I asked is because my car seems to be faster than similar cars rated at 15 more peak hp that I have driven. That seems strange considering it is suppose to have 15 hp less. The only thing that I can notice is that my cars engine will spin up faster and easier than the other cars. I have always wondered if it was because of a lighter flywheel (it could also be gearing).

So the dyno charts people get on a dynojet should show more hp for a lighter flywheel?


Yes, but over the typical range of flywheel weights in an XL motor, it's not a huge difference. Unless you get one of those cute little pork chop jobs.

Here's an interesting tidbit for anyone still clinging to this notion that the torque curve is important for evaluating acceleration ... there's a very tried and true formula for calculating quarter mile times that can be expected:

ET = 5.92 x cube root of (weight / horsepower)

for example: 650lb bike with 140hp

ET = 5.92 x cube root of (650 / 140) = 9.88 seconds

Notice how there's no mention of torque in that formula (nor is there a mention of rpm, with which torque could be calculated). Horsepower and weight provide the entire answer. You won't find a formula like that relating torque to ET, because torque by itself is an incomplete description of performance.

AC2W: who are you? what's your name?

Thats definitely an area I need help in. :doh
I'll bet your a mechanical genius also. ;)

Nope. I just know the facts and how to use the English language in a slightly proper manner.

High & quick revving, high horsepower & good torque = fast bike. That's why guys like Aaron (and anyone else on here who's something of an "engineer") get paid to build and figure out the details, I learn a little bit, and get to watch everyone argue about which shade of blue the sky really is. ;)

Here's an interesting article (http://vettenet.org/torquehp.html) that I found about torque and horsepower.

Brucey, is using a car as his Torque example, and a water wheel as his horsepower example.
Seems like that in itself should raise some red flags, think about it.

Nope. I just know the facts and how to use the English language in a slightly proper manner.

High & quick revving, high horsepower & good torque = fast bike. That's why guys like Aaron (and anyone else on here who's something of an "engineer") get paid to build and figure out the details, I learn a little bit, and get to watch everyone argue about which shade of blue the sky really is. ;)

Good Grammar.
Great sucking-up. :p

This is correct.



The problem with rear wheel torque is that it varies wildly depending on the gear you're in. In first gear, you're gonna have a mountain of it. In top gear, you'll have not so much. If you change sprockets on the primary or final drive you can affect it as well. So it's really only a useful number when you consider it in relation to the speed the rear wheel is turning. When you do that, it's called "horsepower".

What's more, even if it was a useful number, the dyno doesn't have enough information to calculate it. It can figure out how much force is applied to the drum, but torque is force at a one foot radius. So it'd also have to know the diameter of the wheel in order to be able to tell you actual rear wheel torque.



Thank you, I knew it was something like that, mirroring f=ma, but I was too lazy to go look up the terms ;)

Zenbiker, your posts may have possibly put Arron and I on the same page.

Good Grammar.
Great sucking-up. :p

Fine.

http://i41.photobucket.com/albums/e262/sabbatical/thisround.jpg

Fine.

http://i41.photobucket.com/albums/e262/sabbatical/thisround.jpg

That's the nicest thing anyone has said to me all day. :smoke

Like I said in the beginning, if you have any doubts about whether it's the torque or the horsepower that matters, do a simple experiment.

Run two identical bikes side by side, at the same speed, at the torque peak. On one bike, whack the throttle wide open. At the same time, on the other bike downshift to put the motor near the power peak instead and whack the throttle wide open.

It won't even be close. You'll see very dramatically that it's horsepower that describes the bike's performance.

the wiki on HP is actually quite good if you have a couple minutes. http://en.wikipedia.org/wiki/Horsepower

Like I said in the beginning, if you have any doubts about whether it's the torque or the horsepower that matters, do a simple experiment.

Run two identical bikes side by side, at the same speed, at the torque peak. On one bike, whack the throttle wide open. At the same time, on the other bike downshift to put the motor near the power peak instead and whack the throttle wide open.

It won't even be close. You'll see very dramatically that it's horsepower that describes the bike's performance.

Yes the transmission is a torque multiplier, when you down shift you increase the torque (also know as driving force) to the rear wheel. Because the torque to the back wheel is increased the bike accelerate more quickly. The bike is now moving forward over a given distance in less time. Mathematically you are making more horsepower, your absolutely correct, but it's because you've increase the driving force (torque) to the rear wheel.

Umm, could it really be because shifting down puts you at higher RPM's where the motor makes more HP? No wonder it won't be close. HA HA HA, still beating the dead horse huh Sleeper?

the wiki on HP is actually quite good if you have a couple minutes. http://en.wikipedia.org/wiki/Horsepower

Thanks so much for finding this. :clap

There are different articles and opinions there. But the link below describes my reasoning, much better that I can.

http://craig.backfire.ca/pages/autos/horsepower

Umm, could it really be because shifting down puts you at higher RPM's where the motor makes more HP? No wonder it won't be close. HA HA HA, still beating the dead horse huh Sleeper?

Read post #56 again it went right over your head, unless your kidding of course. :doh
Next read the link in post #58. :)

Aaron,

I have one more question. Let's say your hp curve looks like this (I know I missed my calling I should have been an artist instead :laugh ). Basically, the hp is increasing to let's say 6000 rpm and then it goes flat all the way up to 6500 rpm.

http://i54.photobucket.com/albums/g115/sgozdzi/dontask.jpg

In that situation would you set the rev limit at 6000 rpm (hp peak) or set it at 6500 rpm (hp peak that has been flat for awhile). If you say that "you want the rpm range of the engine centered around the power peak so that you maximize the area under the curve" then wouldn't you set the rev limit at 6500 rpm?

It seems that if you set the rev limit at 6000 rpm you would be forced to shift at 6000 rpm where if the rpm dropped by 500 in the next gear it would put you below the hp peak in the next gear. If you set the rev limit at 6500 rpm then if the rpm dropped by 500 rpm, then that would put you at the hp peak again instead of below it.

The reason I ask is most people say to set the rev limit at the hp peak. However, if it remained flat for another 500 rpm instead of falling would that be an exception?

I'd set it at 7000. You want the limiter a little past the power peak.

You will need a dyno sheet with torque and rpm numbers.
Running at the highest average peak torque in every gear is the short answer.

I take it you now understand how wrong this statement was?

Select your gear shifts around "highest average peak torque" (whatever that is) and you're gonna lose the race. The guy who shifts around the horsepower peak instead will beat you every time.

Arron, when you use horsepower in any of the formulas you use. The torque and time to produce that horsepower has already been calculated.
When you get a horsepower reading on your inertia dyno, without a torque reading. It's because the engineers who designed the dyno know how much torque it takes to move the weighted drum. They have already done the math for you. Just because you don't see what torque and time values they use in their back ground programing, doesn't mean it's not there and not used.

I'll take that as a "yes" :)

Arron, when you use horsepower in any of the formulas you use. The torque and time to produce that horsepower has already been calculated.


This is incorrect.

The dyno measures the bike's horsepower. Without the tach pickup hooked up, it has no idea what mixture of torque and rpm the bike is making to get that horsepower.

Not only does it not know the motor's rpm or torque, it also doesn't even know the rear wheel's torque or rpm. It knows how much force is applied at the contact patch, but that doesn't tell you torque unless you also know the diameter of the tire. It knows the drum rpm, but again, since it doesn't know the diameter of the wheel, it doesn't know the rear wheel rpm. So it really has no idea what the rear wheel torque or rpm are.

So bottom line, without the tach pickup, the dyno measures the horsepower, but it doesn't know the combination of torque or rpm making up that horsepower, either at the bike's engine or at it's rear wheel. As far as the dyno knows, the bike could be making it's power with very high torque and very low rpm (like a Harley), or it could be making it's power with very low torque with very high rpm (like a 600 race rep). The dyno has no idea.

Only when you hook up the tach pickup does it get the additional information it needs to determine torque and rpm. And since the tach pickup is sensing engine rpm (which is upstream from the gearing), and the dyno knows the horsepower, the dyno can only calculate engine torque. It still can't determine rear wheel torque because it still doesn't know rear wheel rpm.



When you get a horsepower reading on your inertia dyno, without a torque reading. It's because the engineers who designed the dyno know how much torque it takes to move the weighted drum. They have already done the math for you. Just because you don't see what torque and time values they use in their back ground programing, doesn't mean it's not there and not used.

Your mistake here is that you're confusing drum torque with rear wheel torque. The dyno only knows the acceleration rate of the drum. It doesn't know whether the drum is being accelerated by a very small rear wheel turning a very high rpm, or by a very large rear wheel turning a very low rpm.

Imagine a 2" diameter roller accelerating the drum. It's going to have to turn much faster than say a 3' diameter roller turning the same drum, right? If both can accelerate the drum at the same rate from the same drum rpm, that means the small roller has relatively high rpm and low torque; conversely, the large roller is accelerating the drum with relatively low rpm and high torque. The dyno has no idea which it is. It only knows drum rpm and acceleration. It knows how much power is being applied to the drum to get that acceleration from that speed, but it has no idea what the mixture of rear wheel torque and rpm is making up that horsepower.

Arron
Your need to contact the dyno manufacture to get a lesson on how it work.
Not how to operate it, I have no doubt your an expert at operating it, but how it works.

Arron
Your need to contact the dyno manufacture to get a lesson on how it work.
Not how to operate it, I have no doubt your an expert at operating it, but how it works.

Do you know how it works? If so, come on with the info. This subject is very interesting to me. I like trying to figure out how things work. So far, I've googled just about every possible combination (I know, I know, don't believe everything you read on the internet) and what I've seen is that the Inertia Dyno uses the time it takes the drum to get to various speeds and calculates the HP. Then, if you know the RPM's, you can calculate torque from that.

Do you know how it works? If so, come on with the info. This subject is very interesting to me. I like trying to figure out how things work. So far, I've goggled just about every possible combination (I know, I know, don't believe everything you read on the internet) and what I've seen is that the Inertia Dyno uses the time it takes the drum to get to various speeds and calculates the HP. Then, if you know the RPM's, you can calculate torque from that.

Doc
I'll be the first one to tell you I'm not very articulate.
I do have a strong back ground, and high aptitude for electrical and mechanical thingamajiggers. So I will take a stab at it.

The resistance it take to turn the drum is a behind the scenes factor in calculating the horsepower. That drum resistance, primarily weight has a torque factor. That factor is know by the engineers and programed it to the system. It is not displayed or evident to the operator.
I don't know if the torque factor from the drum is used directly or if it's just a back calculation in the program. That type of dyno gets it calculations from drum resistance, speed, and time. I believe Arron said you have to hook up a timing sensor (can't think of the term) to read torque. That would indicate it's a back calculation in the program

The best people to talk to is the manufacture, but don't be surprised you don't get all the info, some stuff their going to conceder trade secrets.
You may get more pertinent info from the program designer than the mechanical designer.

I take it you now understand how wrong this statement was?

Select your gear shifts around "highest average peak torque" (whatever that is) and you're gonna lose the race. The guy who shifts around the horsepower peak instead will beat you every time.


I had mention in a earlier post a formula I saw a in Sport Rider magazine. The formula proves horsepower is not a necessary component in calculating shift points and acceleration.
Unfortunately I haven't found the article, and have not contacted the magazine yet to find out which issue it's in. They had a Internet link to the spreadsheet with the formula at one time (3 or 4 yrs ago).
The formula uses gear ratios, primary ratio (engine to trans.), secondary ratio (trans. to rear pulley), tire radius, and last but not least torque not horsepower.
The results of the calculation is termed "Driving Force".
The objective is to figure out when to shift up a gear because your driving force (torque and multiplication there of) will be greater in the next gear up.
The formula has no component of time or horsepower. Not in the numbers you enter, or in the back ground of the spreadsheet. This would make it very clear that horsepower is not a important factor at all, even if it a great tool for calculating results.
I used the term "highest average peak torque" if I had said "highest average torque" maybe it would have made more sense to you. I can see where that's weird terminology. What I was trying to get across was the torque level is not constant when accelerating. So you have to take the highest average level in each gear. Then find out where that level is in the next gear and shift at the over lap, if there is over lap.
If you think about it, if you increase the torque (driving force) , you don't need the time element or horsepower numbers, because good old fashion common sense will tell you, your going to go the same distance in less time.

Peace Out
for now.

so let me get this straight just so I understand your point of view.
In the following dynos, an 03 Hayabusa you would suggest centering your shifts around the 7k mark and not the 9.5k mark?


http://www.exoticsportbike.com/Charts/BozBros/HAYABUSA-03_DYNO-FULL.gif



...when would you shift for this machine below?

http://www.intense-racing.com/pics/wes_dyno_248_small.jpg

The resistance it take to turn the drum is a behind the scenes factor in calculating the horsepower.

Resistance doesn't turn a drum, it instead resists the turning of the drum. Force accelerates the drum. The force comes from the contact patch of the tire against the drum.

Resistance in this case would come primarily from the pillow block bearings that support the drum. And yes, the calculations would likely need to account for this to be accurate.

Of much more significance however is something called the "mass moment of inertia" of the drum.

That drum resistance, primarily weight has a torque factor. That factor is know by the engineers and programed it to the system.


It's not really weight, it's mass, as the effect of gravity is negligible in this case (except, of course, to the extent it affects bearing resistance). And it's not really mass, it's mass moment of inertia. That's an important distinction, because it takes into account the placement of the mass. If the mass of the drum was primarily centered around the axle, as opposed to the perimeter, the drum is much easier to accelerate. I'm sure you can visualize this. Mass moment of inertia actually increases as the square of the radius at which the mass is located. So two different drums of the same mass can have different mass moments of inertia, which of course affects the rate of acceleration when a given force is applied.

I don't know if the torque factor from the drum is used directly or if it's just a back calculation in the program.

Not sure what you mean by "torque factor" or "back calculation", but I can assure you that the mass moment of inertia of the drum is extremely critical information. The calculations are based on it.


That type of dyno gets it calculations from drum resistance, speed, and time.


No, it makes the calculation from the speed and acceleration rate of the drum, knowing it's mass moment of inertia.

I believe Arron said you have to hook up a timing sensor (can't think of the term) to read torque. That would indicate it's a back calculation in the program

The sensor you hook up detects the engine's firings. They provide you with a couple different kinds of sensors, one for the primary side of the coil and a different one for the secondary. You only use one or the other, depending on the accessibility of the respective wires and how clean of a signal you get. Then in the software you specify the number of crankshaft degrees represented by each firing. For a dual-fire arrangement, that's 360 degrees, for a single fire it's 720 degrees. It's from this information that the dyno can determine the engine rpm.

Since the dyno can measure only the horsepower, it needs this additional rpm information to determine torque, which it then calculates. If you fail to connect the ignitions sensor (which I generally refer to as the "tach pickup"), the software will not allow you to plot torque or rpm, it will only plot horsepower versus speed. That's because without the ignition pulse information, it doesn't know the rpm and therefore it can't calculate the torque.

Resistance doesn't turn a drum, it instead resists the turning of the drum. Force accelerates the drum. The force comes from the contact patch of the tire against the drum.

Resistance in this case would come primarily from the pillow block bearings that support the drum. And yes, the calculations would likely need to account for this to be accurate.

Of much more significance however is something called the "mass moment of inertia" of the drum.



It's not really weight, it's mass, as the effect of gravity is negligible in this case (except, of course, to the extent it affects bearing resistance). And it's not really mass, it's mass moment of inertia. That's an important distinction, because it takes into account the placement of the mass. If the mass of the drum was primarily centered around the axle, as opposed to the perimeter, the drum is much easier to accelerate. I'm sure you can visualize this. Mass moment of inertia actually increases as the square of the radius at which the mass is located. So two different drums of the same mass can have different mass moments of inertia, which of course affects the rate of acceleration when a given force is applied.



Not sure what you mean by "torque factor" or "back calculation", but I can assure you that the mass moment of inertia of the drum is extremely critical information. The calculations are based on it.



No, it makes the calculation from the speed and acceleration rate of the drum, knowing it's mass moment of inertia.



The sensor you hook up detects the engine's firings. They provide you with a couple different kinds of sensors, one for the primary side of the coil and a different one for the secondary. You only use one or the other, depending on the accessibility of the respective wires and how clean of a signal you get. Then in the software you specify the number of crankshaft degrees represented by each firing. For a dual-fire arrangement, that's 360 degrees, for a single fire it's 720 degrees. It's from this information that the dyno can determine the engine rpm.

Since the dyno can measure only the horsepower, it needs this additional rpm information to determine torque, which it then calculates. If you fail to connect the ignitions sensor (which I generally refer to as the "tach pickup"), the software will not allow you to plot torque or rpm, it will only plot horsepower versus speed. That's because without the ignition pulse information, it doesn't know the rpm and therefore it can't calculate the torque.

Your right about the resistance thing, but I'm sure you knew what I was saying. You just prefer to trash me on it.

So lets say it's "mass moment of inertia" I have no problem with whatever you call it, it has a torque factor. Lets re-phase it load factor. The truth is it takes torque to move it, and that factor is in the program calculations.

so let me get this straight just so I understand your point of view.
In the following dynos, an 03 Hayabusa you would suggest centering your shifts around the 7k mark and not the 9.5k mark?


http://www.exoticsportbike.com/Charts/BozBros/HAYABUSA-03_DYNO-FULL.gif



...when would you shift for this machine below?

http://www.intense-racing.com/pics/wes_dyno_248_small.jpg

Bare with with me. I will get back to you with an accurate answer.
Good to see their is someone who might believe me, thanks.

This thread was very informative

This Thread is Living Proof of this thread:

HOWMANY (http://xlforum.net/vbportal/forums/showthread.php?t=66390)

This Thread is Living Proof of this thread:

HOWMANY (http://xlforum.net/vbportal/forums/showthread.php?t=66390)

Ya know if my beer buss wasn't almost as good as your beer buss, I might take offense to that comment.

Bare with with me. I will get back to you with an accurate answer.
Good to see their is someone who might believe me, thanks.
hey now don't get too carried away...I didn't say I believed you, I just wanted to understand what you were saying :laugh :D

It shouldn't take time to get back with an accurate answer...heck there aren't any calculations involved...I'm just wondering where (roughly) you would shift these two bikes...shifting around the torque curve vs shifting around the hp curve will be different for sure if I'm understanding your take on the matter. :)

This thread was very informative

We're glad your processing all this information and arriving at your own conclusions.
I don't want to speak for the others that have contributed to this tread.
Whether you agree with me or the other contributors, it's been fun, but it's not over yet. :)

hey now don't get too carried away...I didn't say I believed you, I just wanted to understand what you were saying :laugh :D

It shouldn't take time to get back with an accurate answer...heck there aren't any calculations involved...I'm just wondering where (roughly) you would shift these two bikes...shifting around the torque curve vs shifting around the hp curve will be different for sure if I'm understanding your take on the matter. :)

Don't believe me, no problem dude.
No calculations involved, now that's funny. :D
Man I'm no master of the universe, I'm just a toothless redneck from Florida that relies on cold hard facts.






NRHS is a heavy hitter here.
Got you scared don't I. Can I continue here with freedom of speech or not.

Accelerating 20mph in a given amount of time takes the same amount of torque regardless of the speed you're going. This is essentially f=ma, or the rotational equivalent.

However, at the higher speed, the rear wheel rpm is higher. Since horsepower is torque times rpm (rear wheel rpm in this case), the power required is higher at the higher speed.

You nailed it. Should have exempted you from answering. :) With torque remaining constant, HP increases linearly with speed or RPM, so the HP required would be approximately double since the average speed of 70 mph is double that of 35 mph.

A hard assed professor might score your answer a 99. A 100 would require the clarifying statement "neglecting aerodynamic drag and other frictional effects." :)

Sleeper,

Aaron understands perfectly.

I don't like to downshift, so I like big low end torque/HP. :) Aaron is a land speed racer, so he's all about optimizing top end torque/HP.

As to the dyno plots and where to shift to maintain maximum acceleration, you'd want to up-shift the busa at around ten grand and the Harley at around 6800 rpm.

Don't believe me, no problem dude.
No calculations involved, now that's funny. :D
Man I'm no master of the universe, I'm just a toothless redneck from Florida that relies on cold hard facts.

NRHS is a heavy hitter here.
Got you scared don't I. Can I continue here with freedom of speech or not.

please continue! ...I just want a simple answer as to where you think the best place to shift that busa would be so that I understand your point of view correctly (since I don't completely understand what you are saying). Please reference the cold hard facts that you speak of...I'm merely trying to understand what you are saying and would like a reference for your point of view that you consider to be fact that's all.

Obviously Aaron and I have very conflicting opinions on the hp and tq issue. I do have a hard time getting my views across.
I posted a link earlier that comes closer to the way I see things. But I don't agree with everything that guy says. Damn I'm stubborn :laugh , I reallies that. There was a quote from Carroll Shelby "Horsepower sells cars, Torque wins races". I'd love to have a few beers with Mr. Shelby and get his view on this subject, maybe he could straighten me out.
Aaron is a Mechanical Engineer, Business Owner, World Class Engine/Bike Builder, and holds World Records.
There is something missing in the way I look at Aarons views though.
It finally dawned on me what it is, and how to solve the problem.
I'm will humbly ask Aaron to share his technique in calculating shift points.
More specifically what equation or formula do you use, and what numbers do you take from hp dyno sheet that apply to the equation.
Obviously all dyno sheets are different. But as a science, not an art or conjecture, there are specific hard numbers (ex. peak hp) to be enter into the equation.
Could you Please share this information with the forum. It will help everyone who is interested calculate when to shift, whether it's there Sportster, big twin, foreign bike, car, truck, whatever. It also may help bring to light your views to me.
Thank You. :)

The horsepower curve plots the performance of the motor. The torque curve does not, although yes, if you do as you say, you can calculate it.

I don't know if that's really a fair statement to make. The torque curve plots performance of the motor (volumetric efficiency).

Horsepower curve may plot the performance of the whole bike in general (speed) but torque is what tells you how efficiently the engine is operating.

I'm very far from an expert, but I would simply calculate a shift point for a given gear like this:
SP = P_HP + .5 * RPM_D

Where:
P_HP = Peak horse power
RPM_D = the drop in rpm from the next shift
SP = Shift point in rpm

Obviously Aaron and I have very conflicting opinions on the hp and tq issue.

That's impossible, since I don't have an opinion on the subject. I understand what the terms mean, I understand the concepts, I can do the math, I can describe how it works and give examples, but none of that has anything to do with anyone's opinion.

I do have a hard time getting my views across.

The laws of physics have nothing to do with anyone's views, at least not on a subject as basic as this. Maybe some of the out-there theories, like how time slows down as gravity increases and time stands still in a black hole or neutron star, you may get into someone's views, but even then, they have evidence and calculations and computer models to back up the theory or it doesn't survive scientific scrutiny.

But this is physics 101, very basic stuff, very well understood by anyone with an even beginner knowledge of physics. There are no vectors involved, no differential equations, just good old basic arithmetic, and there's no controversy over the facts at all. If I make a statement, or you make a statement, or anyone else makes a statement, it's either true or it isn't and it's not a matter of views or opinions.

There was a quote from Carroll Shelby "Horsepower sells cars, Torque wins races".


I can make a million ft-lbs of torque with a hand-held battery powered drill motor if I gear it deep enough. You'd have to time it with a calendar, but it'd make a mountain of torque. If you put that in a motorcycle, how many races do you think you'd win?

I'm will humbly ask Aaron to share his technique in calculating shift points.

See Raysheen's post above. That's plenty close. Now, what Stevo said is absolutely true, it's possible that the power falls off faster on one side or the other of the horsepower peak, and therefore you don't necessarily want to center the rpm drop from each gearshift around the power peak. But he also correctly noted that it's kind of in the noise, there's much more time in things like launch technique than there is in getting your shift point resolution down to the gnat's ass.

To truely accurately calculate it you'd basically have to integrate the horsepower for the range of rpm as defined by the drop when you shift, and figure out where on the chart you have the largest area under the curve. But you're going for a resolution that's far smaller than that you can actually hit in a real world shift anyway. Bottom line, Raysheen's formula above is real world. You can certainly fine tune empirically from there.

It also may help bring to light your views to me.


Again, my views have nothing to do with any of this. This is pure physics.

I now have another question. On a Dynojet I have seen that changing a rear tire ( same size, brand, etc. ) will show a loss in power up to 5 HP.

A Dynojet is an inertia dyno SO the question....

When I install a lighter rear rim and shave a rear tire to min. legal limits so the end diameter is the same as the one removed, WHY will the dyno read a higher HP number when no motor work was done? ( lighter rotation weight ) will the "new power be felt in the real world street riding?

That's impossible, since I don't have an opinion on the subject. I understand what the terms mean, I understand the concepts, I can do the math, I can describe how it works and give examples, but none of that has anything to do with anyone's opinion.



The laws of physics have nothing to do with anyone's views, at least not on a subject as basic as this. Maybe some of the out-there theories, like how time slows down as gravity increases and time stands still in a black hole or neutron star, you may get into someone's views, but even then, they have evidence and calculations and computer models to back up the theory or it doesn't survive scientific scrutiny.

But this is physics 101, very basic stuff, very well understood by anyone with an even beginner knowledge of physics. There are no vectors involved, no differential equations, just good old basic arithmetic, and there's no controversy over the facts at all. If I make a statement, or you make a statement, or anyone else makes a statement, it's either true or it isn't and it's not a matter of views or opinions.



I can make a million ft-lbs of torque with a hand-held battery powered drill motor if I gear it deep enough. You'd have to time it with a calendar, but it'd make a mountain of torque. If you put that in a motorcycle, how many races do you think you'd win?



See Raysheen's post above. That's plenty close. Now, what Stevo said is absolutely true, it's possible that the power falls off faster on one side or the other of the horsepower peak, and therefore you don't necessarily want to center the rpm drop from each gearshift around the power peak. But he also correctly noted that it's kind of in the noise, there's much more time in things like launch technique than there is in getting your shift point resolution down to the gnat's ass.

To truely accurately calculate it you'd basically have to integrate the horsepower for the range of rpm as defined by the drop when you shift, and figure out where on the chart you have the largest area under the curve. But you're going for a resolution that's far smaller than that you can actually hit in a real world shift anyway. Bottom line, Raysheen's formula above is real world. You can certainly fine tune empirically from there.



Again, my views have nothing to do with any of this. This is pure physics.


Actually I thought Raysheen's answer was pretty good myself.

If you say use Raysheen's equation, no problem.

As far as the my view, your view thing don't take it so personally.

No ones going to be able to shift at an exact point, I agree.

I just thought a guy with a extensive knowledge of physics and mechanical engineering would be very detail oriented.
I'm sure you take great care when engineering and assembling your engines and bikes for yourself and your customers.

But aren't "exact results", the "standard" for Physics, Mathematics, Engineering, and other sciences? Whether you reach those standards are not, it should always be the ultimate quest.

Even though I'm just an old Florida cracker, I like to start a project with as much accurate information as possible. Then tweak things as needed from there.

I don't know if that's really a fair statement to make. The torque curve plots performance of the motor (volumetric efficiency).

Horsepower curve may plot the performance of the whole bike in general (speed) but torque is what tells you how efficiently the engine is operating.

Dang twodownzero, your comments make perfect sense to me. :)

I don't know if that's really a fair statement to make. The torque curve plots performance of the motor (volumetric efficiency).

Horsepower curve may plot the performance of the whole bike in general (speed) but torque is what tells you how efficiently the engine is operating.

If you define "performance" as the point where the engine is at peak efficiency, then you're right, the power peak is probably not that spot.

However, I've never been to a drag race where they declared the winner based on who was most efficient. It's always who gets to the finish line first (without breaking out or red lighting of course). And if that's your definition of "performance", you're interested in your horsepower.

I now have another question. On a Dynojet I have seen that changing a rear tire ( same size, brand, etc. ) will show a loss in power up to 5 HP.


Mike, I've never seen what you describe. I'd be real hesitant to conclude that it was the tire that caused it even if I saw it. There's a repeatability to the measurement you have to take into consideration. Conditions affect the result, simply because the correction process isn't perfect (particularly on older models without the automatic weather station), but things like the temp of the motor play an enormous role as well. It's one of the most important things about dyno tuning, establishing repeatability. If you don't do that, you can easily get fooled and end up out in the weeds. I've seen that happen many many times. Bottom line, if I saw a 5hp change from swapping on an identical tire, I'd be looking for something else. I'd think I was getting fooled by something.

If you define "performance" as the point where the engine is at peak efficiency, then you're right, the power peak is probably not that spot.

However, I've never been to a drag race where they declared the winner based on who was most efficient. It's always who gets to the finish line first (without breaking out or red lighting of course). And if that's your definition of "performance", you're interested in your horsepower.

The term "efficiency" to me means when the engine is turning the least amount of fuel into the most amount of torque.

Without question, the most "efficient" point any engine operates at is its torque peak. At that point, the cylinders are getting the max fill that they will get at any point in the power band, and at that point they are most efficiently turning fuel into power.

I didn't say anything about winning races. Even with with a downward sloping volumetric efficiency curve and increased friction and heat at higher RPMs, engines typically produce more horsepower at higher RPMs until VE drops off so sharply that the increase in RPMs can no longer make up the difference.

I agree with most arguments that horsepower is a better measure of engine output as far as speed is concerned than torque alone, but I definitely disagree with any statement that connects efficiency to horsepower. They are related, but definitely not directly proportional.

The term "efficiency" to me means when the engine is turning the least amount of fuel into the most amount of torque.


I don't think that's correct. Technically efficiency is power out divided by power in. In the real world I think it's expressed as where you're getting the most power per unit of a given fuel (pound, gallon, whatever). It's certainly not where you're making the most torque per unit of fuel. Torque doesn't do any work; you can theoretically have torque without power. Only when it's in motion is something getting done. Torque and motion over time is known as power.

Without question, the most "efficient" point any engine operates at is its torque peak.


Again, I don't think this is right. I've built motors with a torque peak at over 6000 rpm. The engine isn't very fuel efficient up there; it's losing way too much to frictional losses and losing too much heat.


At that point, the cylinders are getting the max fill that they will get at any point in the power band,

That's true.


and at that point they are most efficiently turning fuel into power.


Not necessarily, not if the frictional losses are lower at a lower rpm.



I didn't say anything about winning races.

No, but you equated performance and efficiency. That's where the disconnect was. I was talking performance in terms of acceleration, you talked about performance in terms of efficiency.

Even with with a downward sloping volumetric efficiency curve and increased friction and heat at higher RPMs, engines typically produce more horsepower at higher RPMs until VE drops off so sharply that the increase in RPMs can no longer make up the difference.


100% correct. But really what's going on is that as the motor turns faster and faster, there's less and less time to fill the cylinder, hence cylinder fill suffers, hence torque drops.


I agree with most arguments that horsepower is a better measure of engine output as far as speed is concerned than torque alone,

No, the measure of speed is rpm, not power. Power is the combination of torque and rpm. You can have power with very low speed (but not zero) if the torque is high enough. Power is not a measure of speed, at least not speed by itself.

but I definitely disagree with any statement that connects efficiency to horsepower. They are related, but definitely not directly proportional.

Again, I'm reasonably sure that efficiency is best expressed as power per unit of a given fuel burned. But without studying it, I won't say for sure. It's certainly not torque per unit of fuel burned. Torque by itself doesn't mean squat.

Damn this threads still going.. :(


I was discussing this subject with some mates yesterday and in trying to explain I remembered my high school physics teacher tryin to pummel into us the difference between force and work..

You can apply any amount of force you like but unless the object moves you didin't do any work...

Torque is a measurement of force.... it is force in a radial direction which is why it's measured in foot pounds... pounds is the linear force applied a certain distance from the centre which then gives the radial force foot/pounds.... which is torque, the radial meausrement of force.

We can apply a huge amount of this force to a bolt in tryin to undo it but if it doesn't move then we havn't done any work... ya boss will ask if ya got it undone not how long ya carressed it for ;)


Horsepower is work done... it is what happens when the force applied moves... if you wish to get something to work in the real world it takes horsepower.. this goes back to Watt and the prony brake dyno.. the dyno measured the force but Watt needed something to relate it to real world WORK .. so he calculated how much force a typical horse could apply in a set amount of time pulling around a load cell like the prony brake dyno... this is why we ended up with the formula HP = (torque *rpm) 5252 .. that 5252 comes calculating from pi and the radius..to give a circular force..



So as myself and others have said Horspower is a measurement of how much WORK the motor can do in a set amount of TIME..... it is a measure of the force applied when it's actually USED...


Torque is theory.. HP is practical ... HP wins races because HP is the REAL world... because everything in our world relates to time...


If you don't care how long it's gonna take to get there then stick to torquein about it.. ;)

Well put, Stevo. Torque without time and distance doesn't mean squat. Back to my hand held drill motor example. Gear it down enough and you can make a million ft-lbs with it. But it'll turning too slow to be useful. What matters is not the torque you can make, or the rpm you can make, what matters is the total combination of torque and rpm you can make. That's called "horsepower" for short. Horsepower is torque times rpm.

You're right, too, about the origin of the 5252. Basically Watt found that his horse could lift 1lb 33,000 feet in 1 minute. Well, one ft-lb of torque is defined as 1 lb of force at a 1 foot radius. If you work out the distance travelled at a 1 foot radius turning 5252 rpm in one minute, it comes out to 33,000 feet. So dividing by 5252 is to scale the number to what Watt's horse could do.

BTW, AC2W here in this thread is our banned friend Blake ;)

Some people just can't help 'emselves ;)


I'm gonna have to get into all this theory shortly when I try and get this old dyno I bought working.... I want to put some more modern gauges on it but I'll need to fully understand how it all works so I can get some sensors that will read in the ranges I want...

It'll be fairly easy with the one of the bikes I'm going to be using it for as we have a full data logger on the bike :D .. so I can use it as a rolling road..

Unfortunately I wont be so fortunate with the sporty but I'll get readings off a few other dynos so I can set mine up to give similar readings........ I'll probably be measuring in PSI upline from the restrictor valve and extrapolating those numbers to useable figures.... using the numbers from other dynos to reverse engineer... so long as I can get repeatable numbers I'm not too concerned what they are, it's only a means of quantifying what I've done without going to the strip allowing me to tune in the shop..


'sides there's only one dyno I believe in and that's the big black 1/4 mile one .... everything else is smoke and mirrors.. :cheers

'sides there's only one dyno I believe in and that's the big black 1/4 mile one .... everything else is smoke and mirrors.. :cheers

Uhh, I think you mean the great WHITE dyno ;)

I'm trying to get ready, our first race starts September 2. One bike is done and loaded in the trailer, the other needs my attention, nothing major though.

Timbo can't make it this year so I'm gonna swing a leg over the orange bike myself again. Bumping up the motor a tad so I can run it in the 2000cc class rather than run against Timbo's 213 record at 1650cc. The 2000cc class has no AMA record. Timbo's a ton faster than me and besides, might as well go after additional records.

My wife is gonna ride her little black Buell S1. It runs 1350cc unfaired. The bike holds a couple BNI records in the 167mph range, she'll be running it against a 146 AMA record.

Damn this threads still going.. :(


I was discussing this subject with some mates yesterday and in trying to explain I remembered my high school physics teacher tryin to pummel into us the difference between force and work..

You can apply any amount of force you like but unless the object moves you didin't do any work...

Torque is a measurement of force.... it is force in a radial direction which is why it's measured in foot pounds... pounds is the linear force applied a certain distance from the centre which then gives the radial force foot/pounds.... which is torque, the radial meausrement of force.

We can apply a huge amount of this force to a bolt in tryin to undo it but if it doesn't move then we havn't done any work... ya boss will ask if ya got it undone not how long ya carressed it for ;)


Horsepower is work done... it is what happens when the force applied moves... if you wish to get something to work in the real world it takes horsepower.. this goes back to Watt and the prony brake dyno.. the dyno measured the force but Watt needed something to relate it to real world WORK .. so he calculated how much force a typical horse could apply in a set amount of time pulling around a load cell like the prony brake dyno... this is why we ended up with the formula HP = (torque *rpm) 5252 .. that 5252 comes calculating from pi and the radius..to give a circular force..



So as myself and others have said Horspower is a measurement of how much WORK the motor can do in a set amount of TIME..... it is a measure of the force applied when it's actually USED...


Torque is theory.. HP is practical ... HP wins races because HP is the REAL world... because everything in our world relates to time...


If you don't care how long it's gonna take to get there then stick to torquein about it.. ;)

Darn Stevo you were right on track with yours teacher explanation, and they got derail. If you try to turn that bolt and it doesn't move. You have applied torque which is measurable, but you haven't accomplished work (horsepower), which is unmeasurable in this case. That's torque without horsepower. What a crazy concept, huh.

You're right, too, about the origin of the 5252. Basically Watt found that his horse could lift 1lb 33,000 feet in 1 minute. Well, one ft-lb of torque is defined as 1 lb of force at a 1 foot radius. If you work out the distance travelled at a 1 foot radius turning 5252 rpm in one minute, it comes out to 33,000 feet. So dividing by 5252 is to scale the number to what Watt's horse could do.


Actually he used a pony and multiplied the output by 1.5 since he didn't have a horse. So horsepower really is "pony power x 1.5" not really horsepower. Not that it's all that significant anyway, but if you're going to go through the word history, might as well do it right.

I am in general agreement with the majority here on horsepower being a much better indicator of actual work accomplished.

I will also add that the reason VE drops off at high RPM is not entirely a function of time, but a function of cam/port design. Some engines are capable of 100% VE @ 6,000 RPM and a similar engine of the same displacement and everything with smaller head ports and a smaller camshaft may hardly be capable of a peak VE of 85% @ 3000 RPM. Time is certainly not the only factor affecting cylinder fill.

This is especially true in cars where dual plane intake manifolds are common. Dual plane intake manifolds certainly cut peak volumetric efficiency significantly compared to a single plane design, but typically the benefits in low end torque outweigh the costs in peak horsepower/torque on the big end.

I don't really see how any of this discussion has much significance to what we're actually talking about (other than in theory) but it's a fun discussion anyway.

Actually he used a pony and multiplied the output by 1.5 since he didn't have a horse. So horsepower really is "pony power x 1.5" not really horsepower. Not that it's all that significant anyway, but if you're going to go through the word history, might as well do it right.

I am in general agreement with the majority here on horsepower being a much better indicator of actual work accomplished.

I will also add that the reason VE drops off at high RPM is not entirely a function of time, but a function of cam/port design. Some engines are capable of 100% VE @ 6,000 RPM and a similar engine of the same displacement and everything with smaller head ports and a smaller camshaft may hardly be capable of a peak VE of 85% @ 3000 RPM. Time is certainly not the only factor affecting cylinder fill.

This is especially true in cars where dual plane intake manifolds are common. Dual plane intake manifolds certainly cut peak volumetric efficiency significantly compared to a single plane design, but typically the benefits in low end torque outweigh the costs in peak horsepower/torque on the big end.

I don't really see how any of this discussion has much significance to what we're actually talking about (other than in theory) but it's a fun discussion anyway.

twodownzero is right again. :)

Darn Stevo you were right on track with yours teacher explanation, and they got derail. If you try to turn that bolt and it doesn't move. You have applied torque which is measurable, but you haven't accomplished work (horsepower), which is unmeasurable in this case. That's torque without horsepower. What a crazy concept, huh.

No I didn't get derailed...

That's exactly what I said....

Toque is measureable, I never said it wasn't BUT until it moves you've done no work and therefore have accomplished nothing...

the torque curve tells me how I'm filling the cylinders and how the harmonics are working... the Horsepower curve is just how I'm going to use that torque in the real world....




To put it another way I'd say all your torqueing is achieving nothing.... arguing for the sake of arguing doesn't give you any power it just makes you appear to be a horses ass :banana

Uhh, I think you mean the great WHITE dyno ;)

I'm trying to get ready, our first race starts September 2. One bike is done and loaded in the trailer, the other needs my attention, nothing major though.

Timbo can't make it this year so I'm gonna swing a leg over the orange bike myself again. Bumping up the motor a tad so I can run it in the 2000cc class rather than run against Timbo's 213 record at 1650cc. The 2000cc class has no AMA record. Timbo's a ton faster than me and besides, might as well go after additional records.

My wife is gonna ride her little black Buell S1. It runs 1350cc unfaired. The bike holds a couple BNI records in the 167mph range, she'll be running it against a 146 AMA record.



Unfortunately the big white daddy is too far from me... I'm further away than ya mate that ran a few years ago is...


I'm also gonna put the clipons and fairing back on the gixxer so I can go play back down the strip, we have our annual All Bike Drags on next month... the streetfighter setup is great for stunting but not much good for getting over the front on the strip ..

The cadence is quite different between the sporty and the gixxer but as the sporty will heading into the 10's this time it wont be as big a difference and it'll get me some track time to tune me ready for the development process of getting the sporty quicker than it's been before...

Unfortunately the big white daddy is too far from me... I'm further away than ya mate that ran a few years ago is...


I saw the world's fastest Indian. You can't say you are too far away. :laugh

I saw the world's fastest Indian. You can't say you are too far away. :laugh


yeah but he did nothing else BUT that..... and damn fine job he did of it too... there's no substitute for empirical data if you have the time..



I've got a shed full of bikes and I like playing up the mountains, stunting, going to rallies and just general bikin...... and I have a lady I like spendin time with :tour

Just a note on the origional question..


my gixxer is quicker if I short shift it at 10500 .. yet according to the dyno chart I have it doesn't flatten out till 11500 .. and yet if I change at 11500-12000 it's slower than the 10500 changes..

go figure....

so do I belive the dyno chart of the time cards????

time cards ... every time .. thats the REAL world.. there's nothing to say this dyno chart is correct ;)

I will also add that the reason VE drops off at high RPM is not entirely a function of time, but a function of cam/port design. Some engines are capable of 100% VE @ 6,000 RPM and a similar engine of the same displacement and everything with smaller head ports and a smaller camshaft may hardly be capable of a peak VE of 85% @ 3000 RPM. Time is certainly not the only factor affecting cylinder fill.


Less time available at high rpm is the fundamental reason that port velocity goes too high (necessitating bigger ports and valves), and less time available is the reason the cam timing is wrong (less time to evacuate the cylinder requires an earlier exhaust open event and less time per degree of crank rotation requires a later intake close event for maximum fill). So really what you're talking about is some of the ways we try to compensate for less time available.

You missed a big one though: exhaust augmentation of intake flow. It's probably bigger than adjustments to port size and cam timing.

Even doing all those things, though, it's fundamentally harder to fill the cylinder when you have less time to do it.

Here's what it looks like when you get it right:

http://www.nrhsperformance.com/images/drdannorlin82.gif

We've got the cam timing, the exhaust system, and the port sizes all working together to fill the cylinder at high rpm. Moving that torque hump to the right is how you make big power. This motor is a measly 1350cc (82ci).

There are more things that can be done, too, but this bike races under a set of rules that require stock port heights.

few people realise how much effect the exhaust design has over over the cylinder fill on a 4 stroke... yet most can grasp it's importance on a 2 stroke..
Especially at the higher revs with a cam that has the overlap to allow it to affect the intake.... granted a full understanding of everything involved is a bit more than ya gonna learn as a mechanic ;) as it IS rocket science when ya get into the maths involved.


that's where ya look at the shape of the torque curve... to work out where everything is working together or against each other..



I've also got half a dozen sets of pipes/exhausts up my sleeve to start on the development on the sporty.... plus plenty of bends to make my own as I think that will be the key to the big numbers... (even tho I have about 8 sets of heads to play with too)

Horsepower is an intangible, a measurement only. Yes it's a very usefully tool.
Torque is a tangible, it accelerates the bike and is of course measurable.

Just a note on the origional question..


my gixxer is quicker if I short shift it at 10500 .. yet according to the dyno chart I have it doesn't flatten out till 11500 .. and yet if I change at 11500-12000 it's slower than the 10500 changes..

go figure....

so do I belive the dyno chart of the time cards????

time cards ... every time .. thats the REAL world.. there's nothing to say this dyno chart is correct ;)

Excellent observation about your gixxer Stevo. At least you seem more open minded to the chance those horsepower numbers may not be all that important in real world riding and racing. Especially when knowing when to up shift for maximum acceleration.

Just a point on that rpm of the gixxer..

I wasn't there when that was done, I had a customer take the bike down as I was working....

I looked at my chart and the chart for CLive's gixxer thou.. his made 4 HP more than mine... but looking ta the rpm axis on the graph it didn't make sense between the two charts... he then said they didn't attach anything to the bike, so the rpm was taken off the drum and calculated back thru a theoretical gearing... boht our bikes had different gearing..

So basicly the HP curve on the graph is a waste of time... ;)


The torque curve shows the cylinder fill but agin not at the correct rpms...

So back to the real world and I'll change where it's gonna give me the quickest times.... and don't believe the dyno chart unless ya know the operator knows what he's doin..

Just a point on that rpm of the gixxer..

I wasn't there when that was done, I had a customer take the bike down as I was working....

I looked at my chart and the chart for CLive's gixxer thou.. his made 4 HP more than mine... but looking ta the rpm axis on the graph it didn't make sense between the two charts... he then said they didn't attach anything to the bike, so the rpm was taken off the drum and calculated back thru a theoretical gearing... boht our bikes had different gearing..

So basicly the HP curve on the graph is a waste of time... ;)


The torque curve shows the cylinder fill but agin not at the correct rpms...

So back to the real world and I'll change where it's gonna give me the quickest times.... and don't believe the dyno chart unless ya know the operator knows what he's doin..

It's a pleasure for me to finally have a conversation with a intelligent man with an open mind and your diverse technical experience.

I came across an article about 4 yrs. ago, that changed my outlook on the HP/TQ controversy.

I have contacted the publishing company about ordering a back issue of that article. They don't keep there old issues that long.

But I had a bit of luck anyways. I was able to find a website with a condensed version of that article. There was also a link that was mentioned in the original article. That link had the equation on a spreadsheet that proved when shifting to a higher gear, that peak HP was not a calculation or factor in the equation. The equation was for "driving force". The only power factor in the equation was torque. All other factors were the ratios that increased torque to the rear wheel. The other factors are gear ratio, primary ratio, secondary ratio, and tire ratio. Horsepower is not a factor.
Unfortunately the link to the spreadsheet is no longer working.
I believe I can still get my hands on a copy of that spreadsheet. But at this time I can't produce it. I am working on it and expect to get it.
You mentioned earlier you had better results short shifting your gixxer, the
equation will prove to you why.
I have applied the equation to Harleys, Jap bikes, cars, and trucks. I have had positive results with all, no exception.
For now here is the link to the on-line article. I will get you the spreadsheet.

http://www.sportrider.com/tech/146_0402_art/

I just want to chime in and tell ya all that I am reading every post, I just haven't had the real world expertize.