Foot lbs or Pound ft = torque?
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,935
Likes: 8,036
From: poway
OK gentlemen, I do agree on 5252. However, I do know that I have 119 lb/ ft of torque and 104 hp at the rear wheel. It was explained to me from a very reputable builder on this form that that is not possible. Would one of you please explain why and how that is possible, so the unnamed individual can understand that it is possible. Thanks guys for everything, I never thought this post would go this far, but Im glad it has. Just because someone says something and you dont agree because you dont understand, doesnt necessarily Make the statement false.
What? That you can achieve 119 fp tq and not achieve 104 HP? Or neither occurs at 5252? I've had build that have hit close to those numbers.
Club Member
Joined: Jul 2014
Posts: 11,469
Likes: 3,572
From: Idaho
Actually, I do. I believe that our disagreement is based on the fact that you are looking at this in the real world, and I am looking at it mathematically. Obviously, in the real world, the real world wins.
In the real world, with all dyno charts and all dyno software, the scales are always the same. ALWAYS. They have to be, otherwise, the graph would be meaningless, because if every chart had different scales then every graph would be different and the dyno tech and engine builder would not be able to get any useful information from it. I agree 100%.
If the scales are the same, then the tech can clearly see the relationships between torque, horsepower, and rpm. The tech can clearly see the bumps and dips, the smooth curves and the flat spots, the peaks, and where those all occur. The tech can clearly see the before-and-after when a tune is done, or clearly see the differences between two different bikes. 100% agree.
If, for the purpose of this discussion, the two scales were made extremely different, then one line could be almost vertical and the other almost flat. The graph would be meaningless, and impossible to interpret. 100% agree.
But, and this is the point I'm trying to make, if you have to tape another two feet of paper to one side of the graph so you can extend the almost-vertical curve far enough, the lines would intersect at 5252. They must. There is no other possible alternative. The dyno software has the equations in it, and algebra is not subject to personal interpretation.
On the other hand, scales notwithstanding, there is a way that the curves would never intersect, and that would be if you cut the throttle before you get to 5,252 rpm.
Club Member
Joined: Jul 2014
Posts: 11,469
Likes: 3,572
From: Idaho
OK gentlemen, I do agree on 5252. However, I do know that I have 119 lb/ ft of torque and 104 hp at the rear wheel. It was explained to me from a very reputable builder on this form that that is not possible. Would one of you please explain why and how that is possible, so the unnamed individual can understand that it is possible. Thanks guys for everything, I never thought this post would go this far, but I’m glad it has. Just because someone says something only be one way and you don’t agree because they don’t understand, doesn’t necessarily make the statement false.
Almost all Harley-Davidsons have more torque than horsepower, and 104/119 are very reasonable numbers for a motor that has had some work done to it. My '15 RGS with just a solid Stage 2 made 98/108 at the rear wheel.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,935
Likes: 8,036
From: poway
Actually, I do. I believe that our disagreement is based on the fact that you are looking at this in the real world, and I am looking at it mathematically. Obviously, in the real world, the real world wins.
In the real world, with all dyno charts and all dyno software, the scales are always the same. ALWAYS. They have to be, otherwise, the graph would be meaningless, because if every chart had different scales then every graph would be different and the dyno tech and engine builder would not be able to get any useful information from it. I agree 100%.
If the scales are the same, then the tech can clearly see the relationships between torque, horsepower, and rpm. The tech can clearly see the bumps and dips, the smooth curves and the flat spots, the peaks, and where those all occur. The tech can clearly see the before-and-after when a tune is done, or clearly see the differences between two different bikes. 100% agree.
If, for the purpose of this discussion, the two scales were made extremely different, then one line could be almost vertical and the other almost flat. The graph would be meaningless, and impossible to interpret. 100% agree.
But, and this is the point I'm trying to make, if you have to tape another two feet of paper to one side of the graph so you can extend the almost-vertical curve far enough, the lines would intersect at 5252. They must. There is no other possible alternative. The dyno software has the equations in it, and algebra is not subject to personal interpretation.
On the other hand, scales notwithstanding, there is a way that the curves would never intersect, and that would be if you cut the throttle before you get to 5,252 rpm.
In the real world, with all dyno charts and all dyno software, the scales are always the same. ALWAYS. They have to be, otherwise, the graph would be meaningless, because if every chart had different scales then every graph would be different and the dyno tech and engine builder would not be able to get any useful information from it. I agree 100%.
If the scales are the same, then the tech can clearly see the relationships between torque, horsepower, and rpm. The tech can clearly see the bumps and dips, the smooth curves and the flat spots, the peaks, and where those all occur. The tech can clearly see the before-and-after when a tune is done, or clearly see the differences between two different bikes. 100% agree.
If, for the purpose of this discussion, the two scales were made extremely different, then one line could be almost vertical and the other almost flat. The graph would be meaningless, and impossible to interpret. 100% agree.
But, and this is the point I'm trying to make, if you have to tape another two feet of paper to one side of the graph so you can extend the almost-vertical curve far enough, the lines would intersect at 5252. They must. There is no other possible alternative. The dyno software has the equations in it, and algebra is not subject to personal interpretation.
On the other hand, scales notwithstanding, there is a way that the curves would never intersect, and that would be if you cut the throttle before you get to 5,252 rpm.
No they are not, it really depends on how the pliting SW is setup. For 1 look at the graph, HP scale is one one side and a TQ on the other.. If scales are the same, the lines will cross at 5252.
Club Member
Joined: Jul 2014
Posts: 11,469
Likes: 3,572
From: Idaho
Sigh. The lines always cross at 5252. They do that because of arithmetic. If the scales are different, the lines still cross at 5252, it will just be at a different spot on the chart.
EDIT: Ok, I actually know, personally, two PhDs in Mechanical Engineering, who spent the last several years at Navistar, doing research using mathematics that makes MY ears bleed. I'll bounce this question off them and see what I hear.
Stay tuned.
EDIT: Ok, I actually know, personally, two PhDs in Mechanical Engineering, who spent the last several years at Navistar, doing research using mathematics that makes MY ears bleed. I'll bounce this question off them and see what I hear.
Stay tuned.
Last edited by IdahoHacker; Apr 23, 2022 at 01:23 PM.
Thread Starter
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Stellar HDF Member
Joined: Jun 2018
Posts: 2,296
Likes: 494
From: WI
of course it's possible. I don't understand why your engine guy says it's not. Unless, he's saying that those numbers are not possible from the work that was done.
Almost all harley-davidsons have more torque than horsepower, and 104/119 are very reasonable numbers for a motor that has had some work done to it. My '15 rgs with just a solid stage 2 made 98/108 at the rear wheel.
Almost all harley-davidsons have more torque than horsepower, and 104/119 are very reasonable numbers for a motor that has had some work done to it. My '15 rgs with just a solid stage 2 made 98/108 at the rear wheel.
thankyou........................
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,935
Likes: 8,036
From: poway
Sigh. The lines always cross at 5252. They do that because of arithmetic. If the scales are different, the lines still cross at 5252, it will just be at a different spot on the chart.
EDIT: Ok, I actually know, personally, two PhDs in Mechanical Engineering, who spent the last several years at Navistar, doing research using mathematics that makes MY ears bleed. I'll bounce this question off them and see what I hear.
Stay tuned.
EDIT: Ok, I actually know, personally, two PhDs in Mechanical Engineering, who spent the last several years at Navistar, doing research using mathematics that makes MY ears bleed. I'll bounce this question off them and see what I hear.
Stay tuned.
Sorry they don't cross at 5252 because the scales are different. Still the values of both lines as read from the graph are the same at 5252.
I don't believe this is correct, and I did a lot of graphing of mathematical equations back in the day.
You are absolutely correct that HP=(RPMxT)/5252, and then solving for T: T=(HPx5252)/RPM. The constant 5252 appears in BOTH. That is the commonality between the two equations, because while torque, horsepower and rpm all vary, 5252 never changes.
Because the constant 5252 never changes and appears in both equations, the lines will ALWAYS cross at 5252. They cannot cross anywhere else, because that is the only constant that appears in both equations.
If the scales for hp and t are not the same, then the lines will be either flatter or more curved, steeper or less steep, but they will always cross at 5252.
You are absolutely correct that HP=(RPMxT)/5252, and then solving for T: T=(HPx5252)/RPM. The constant 5252 appears in BOTH. That is the commonality between the two equations, because while torque, horsepower and rpm all vary, 5252 never changes.
Because the constant 5252 never changes and appears in both equations, the lines will ALWAYS cross at 5252. They cannot cross anywhere else, because that is the only constant that appears in both equations.
If the scales for hp and t are not the same, then the lines will be either flatter or more curved, steeper or less steep, but they will always cross at 5252.
The bottom line is that if you have HP scaled to 100 and TQ scaled to 150, the lines wont visually intersect on a graph because you are graphing two scales on top of each other. If you look at the HP value at 5252 and the TQ value at 5252 they will be equal. Thats a cold hard fact.
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SIGH...Ummm without being able to click on 5252, looking at that graph HP at 5252 looks about 112 and torque at 5252 is the same. This is exactly what every single post I made states will happen. Horsepower and torque cross at 5252 ALWAYS. Visually when scaled differently they do not because you are graphing two different scales on one piece of paper.
Click on 5252 and you will the light.