Race cars - Torque vs Hp - The Undiscovered Country (for many)

[zanick]

As far as being wrong, you haven't pointed one single point out to that effect. I would certainly like to hear that. What we have been arguing about is the chicken and egg aspects of force and power. I still think its a valid debate. I don't need to win it, as long as we can discuss the way we can apply power and torque curves to race car performance.

The biggest problem that I see with your argument as I see it, is that you keep on bringing the comparisons to the same gear for two equal power sources. Two problems happen here. This gives the power source with a higher rpm, lower torque characteristics a situation where much less than its full HP, or comparitive HP can be realized and we are comparing output speeds that are grossly different. Since, power is the RATE of doing work, and Work is Force x distance. If you have just a force, applied at ANY vehicle speed, it can be created by a high rpm, low torque power source, or a low rpm high torque source. Power dictates a force at any vehicle speed. No net force is applied, until there is movement. if there is movement, there is work, and the faster the rate of doing work the greater the power.


Your analogy if you don't have the torque and you just apply the torque at a faster rate, you still don't move the load is flawed. You are looking strictly at the power source and not what is available at the drive wheels. as you apply the same torque at a higher drive wheel speed, the power requirements to move the load go way up! You have to keep the vehicle speed the same in any comparison , or the comparison or test is flawed. Gearing is used to keep a vehicle as close to its max HP range as possible. in the end, the most amount of hp-seconds used , wins the acceleration race over any speed range.

You still never answered the truck vs the F1 engine powered truck. You made a bold statement that the F1 powered engine, at the same HP counldnt move the load up the hill. IN fact, it can. This is very easy to prove by using the F1 engine at its max HP at higher rpm and with deeper gearing.

Power is a force's capacity to do work. my 6 year old can generate 600ft-lbs of torque. Its not going to do much work, or accelerate anything very fast, because his rate of doing work is very small. However, a 600ft-lb torque engine with 6000rpm available, will be able to accelerate a 3000lb car to 100mph in near 10 seconds!

If you are comparing two same HP engines, or motors, and you don't keep the relative vehicle speeds the same, you are not allowing one of the engines to be at or near its useable HP range.

I do care about being correct. I have asked many times to discuss the venacular of the proper use of watt-seconds, HP-seconds, in looking at the time spent at the higher rpm of the HP curve and the total rear wheel forces created in those engine speed ranges.
certainly, when ploting to vehicle speed, you could use gear ratios, engine torque curves and find optimal shift and thus acceleration values. This will exactly parallel engine HP curves.(as measured at the rear wheels off a dyno, as well as engine torque values as calculated back to the engine). "Parallel" meaning the effects, not the rear wheel torque curves .

If I have this wrong, please show me one example where proportiona gearing is available, where this is not true with two equal HP cars with one having much more engine torque than the other. Here is a couple of engine HP curves of the exact, real life example. which powerplant would you want if you were going racing on a road course?


Again, not trying to get into a wrestling match here. Just in search of truth. Trust me, I know what I am saying works out on paper, works at the track and follows alll the basic equations. But, I've come here for the correct terminology and ways of explanation.

If I am wrong, I CERTAINLY want to know it.

Again, here are two different engines, both at 290rwhp, but grossly different torque values. I contend that the lower torque engine of the two is going to be better on the race track at any speed or point on the race track. use what ever gears you want that suits one over the other, as long as the shift points are at the same MPH in vehicle speed.
See if you agree or not.
mk

Look if you care in the slightest about being correct about the physics of this.

Buy/borrow/steal and read the following books.

John Heywood - Internal Combustion Engine Fundamentals
Richard Stone - ICE
A.G Bell - Four-Stroke Performance Tuning
Paul Van Valkenburgh- Race Car Engineering & Mechanics

1. is probably least relevant but is pretty much the engine bible.
2. stone is good for practical workings.
3. Good non technical book reguarding practical tuning
4. a very good all round car setup book. especially the section on gearing and performance.

I have read all of these at some point over the last 3 years. They are all thorough and will show you where you've gone wrong.

Read Bell first. then any of the others. I am in no way inclined to type out whole sections from the book.

 

[zanick]

I think I might understand out disconnect from what you wrote below. You seem to be saying, if we can play with gearing the point is moot. same HP, will create the same acceleration at any vehicle speed. And you say, if you don't have the abilty to change gears to optimal values to equal two vehicle's speeds for comparison, you need to know power AND torque. however, i contend if you know the power it is enough. You are talking about a power rating that you may or not be able to use due to lack of gear selections. If this is the case, then of course, without the lack of gear selections, you won't be able to utilize the POWER potentially available. Again, if you can realize the power, you will be able to move the load with a predicted force and will know the rate at which it can be accelerated at any velocity. It is the power rating that will determine the rate of acceleration at any speed. If you are not able to utilize the power rating at that speed, then you are operating at a lower power setting. all this proves is that you didnt gear the car properly for the test.

mk

likewise if you had a force that ws not large enough DID NOT HAVE THE POTENITAL due to incorrect gearing. you could have all the power available in the gear but you wouldn't shift he block.



THIS IS THE POINT YOU NEED TO KNOW BOTH! POWER AND TORQUE TO KNOW IF IT'LL MOVE. YOU CAN KNOW POWER and RPM or torque abd RPM. or anything else, but in the end you'll always be boiling down the equations for a torque and power.

 

[xxChrisxx]

I am going to make one final statement (its not this one its coming next) addressing your last post and then that's it.

I have no inclination to try to help you to understand the flaws in your thinking if you just keep repeating what you have said before. I have reccomended some books that, IF you read them, you will see where you went wrong.

 

[xxChrisxx]

I invite you to respond to the below, if you wish to dispute anything said you must give evidence to back up your claim. The evidence must be listed so that it can be found by all. By evidence I mean something remotely scientific, not an observation you made and are asserting as true.

As far as being wrong, you haven't pointed one single point out to that effect. I would certainly like to hear that. What we have been arguing about is the chicken and egg aspects of force and power. I still think its a valid debate. I don't need to win it, as long as we can discuss the way we can apply power and torque curves to race car performance.

WHERE YOU ARE INCORRECT:

YOU STATE: chicken and the egg debate about force and power.
REALITY: It is NOT a chicken and egg thing. The physical process is you apply a force and something moves a given distance. You cannot apply power at a speed and create a force.

The physical process is Newtons first law of motion.

"A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force." Newton 1st Law

The above do NOT work in reverse, something simply cannot start moving spontaneously and a force is created as a result. Because of this:

P = F * V is true, a force acting at a speed will give a power.
P/V = F Cannot occur in nature, as it breaks Newtons 1st law. What you are doing with the equation in this form is finding the NECESSERY force to create a power at a gien speed. It does not mean, if you apply a power at that speed you will get that force.

Energy, and by extention power cannot be directly measured. It is always calculated from more fonamental things.

There is no absolute measure of energy, because energy is defined as the work that one system does (or can do) on another. Thus, only of the transition of a system from one state into another can be defined and thus measured.

"Methods

The methods for the measurement of energy often deploy methods for the measurement of still more fundamental concepts of science, namely mass, distance, radiation, temperature, time, electric charge and electric current." wikipedia. but you can get this from pretty much any physics book.Conclusion to this: Power cannot be directly measured, it requires more fundamental principles to quantify and give context. Applying a power at a speed cannot occur as it violates Newtons 1st law of motion. The fundamental factor in this must therefore be force distance and time. Of which the only one that has potential to do work is force.

Force therefore is first, and power is a method by which we quatify what that force has done.

The biggest problem that I see with your argument as I see it, is that you keep on bringing the comparisons to the same gear for two equal power sources. Two problems happen here. This gives the power source with a higher rpm, lower torque characteristics a situation where much less than its full HP, or comparitive HP can be realized and we are comparing output speeds that are grossly different. Since, power is the RATE of doing work, and Work is Force x distance. If you have just a force, applied at ANY vehicle speed, it can be created by a high rpm, low torque power source, or a low rpm high torque source. Power dictates a force at any vehicle speed. No net force is applied, until there is movement. if there is movement, there is work, and the faster the rate of doing work the greater the power.

This (the power speed force bit) is incorrect for as it violates Newtions first law as stated above.

By the same reason that force and speed can bve used to find power:

P = T * angular velocity torque and angualr velocity can be used to find power
P/angualt velocity = T you can't do it this way. The find the necessary torque. not the actual.You say that the faster the rate of doing work by the engine the greater its power output. This is indeed correct. Now for where you are going wrong with it.

"The engines power output is set. It is defined by:

P=(thermal efficieny * volumetric efficieny * displaced volume * number of revolutions * fuel heating value * density of the air * (fuel air ratio)/2" Equation from Heywood

This defines the amount of work a given engine can do. The POWER OUTPUT IS SET IT DOES NOT CHANGE DEPENDING ON THE GEARING. So if you geared it 1:1 you'd have the same power at the rear wheel as if you used a 100:1 gearning. It would be going this work more slowly, but it would be doing more work.

You are NOT doing more work at the rear wheels by using a higher gear ratio.

"W = F * d" wiki or books.

You are using a higher force but moving

 

[rcgldr]

I think we all understand that torque corresponds to force, and power is the same for both angular and linear environments.

If you only know the torque, gearing, and radius of tire, then you know the force, but you won't know the speed at which the force can be applied.

If you only know the peak power, then you don't know the torque versus rpm curve and wouldn't know how to set the gearing.

If you know torque or power versus rpm, then you can calculate power or torque versus rpm from that information, and you would know how to optimize the gearing for a specific load range, and the rate of acceleration versus speed for a given load.

 

[xxChrisxx]

Yup that's bang on the money Jeff.


OP doesn't understand that its torque not power deermining the magnitude of the force. as he's stated that power determines the acutal force at the rear wheels when it doesnt.

 

[zanick]

Exactly, but with one comment. you would need to know the HP vs RPM (not just peak HP) as you say in you last sentence, which has been the point of the discussion. by knowing the HP curve, you can optimize max acceleration for any range of speeds by using gearing, without knowing the engine torque values. you could also calculate the applied forces as well at any vehicle speed.

mk

I think we all understand that torque corresponds to force, and power is the same for both angular and linear environments.

If you only know the torque, gearing, and radius of tire, then you know the force, but you won't know the speed at which the force can be applied.

If you only know the peak power, then you don't know the torque versus rpm curve and wouldn't know how to set the gearing.

If you know torque or power versus rpm, then you can calculate power or torque versus rpm from that information, and you would know how to optimize the gearing for a specific load range, and the rate of acceleration versus speed for a given load.

 

[zanick]

I fully understand that torque does the work (or force does the work) . But, HP ratings (rate of doing the work) can determine rear wheel torque, or forces at any vehicle speed. in otherwords, go back to the electric motor and the power source. If the ratings are such that we can create x-KW-hours, with that unit measure of work, we can determine how fast we can do that work and for how long. just as if we had a power sourse being a spinning flywheel that has stored KE. That can be applied quickly or slowly. The force will be a result of how that energy is released. In the end, the change of KE is the work done. the rate of change is the Power.
For any given power, or rate of change of KE, we can determine the force acting on a moving body at any velocity.
This discussion has clearly changed my way of thinking of power as more of a rating, but none the less, if you know the rating, and it is being used, you can determine the force at any speed.

Ill take a look at a couple of the books you have listed, but I think if anything, it will change my way of explaining what we see in reality. Did you have a chance to look at the HP curves I supplied. tell me which one would be better on a race track at any speed. Only given is say the cars have 4 gears, all with 25% rpm drops per shift. Keep MPH shift points the same, to level the playing field and let me know what you think. In the end , the lower torque engine, will have more rear wheel torque. why, because it has more average HP and more HP-seconds available to create the forces at the rear tires.

mk

Yup that's bang on the money Jeff.


OP doesn't understand that its torque not power deermining the magnitude of the force. as he's stated that power determines the acutal force at the rear wheels when it doesnt.

 

[zanick]

Chris, I am going to do my best to answer your challenge. Again, I am not questioning that the force is what creates movement. I am saying that power can create the force. doesn't the explosion create the force. (force doesn't create the explosion) Energy can't be created nor destroyed, right? Energy is converted to mechanical energy (watt-seconds), J, etc. or do I have that backwards?

See my inserts to you comments and see If I am on the right track. with the:
>>>>>>>>>>>>>>>>>>>>>>>>

I invite you to respond to the below, if you wish to dispute anything said you must give evidence to back up your claim. The evidence must be listed so that it can be found by all. By evidence I mean something remotely scientific, not an observation you made and are asserting as true.




WHERE YOU ARE INCORRECT:

YOU STATE: chicken and the egg debate about force and power.
REALITY: It is NOT a chicken and egg thing. The physical process is you apply a force and something moves a given distance. You cannot apply power at a speed and create a force.

The physical process is Newtons first law of motion.

"A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force." Newton 1st Law
>>>>>>>>>Agreed, but if I have a spinning flywheel with a known KE, if I release that through a clutch, isn't a force created. I stopped the flywheel and use the rate of change of KE to produce a rate of doing work, (i.e. Power) Didnt I create the force by converting he KE to another form. Force did the work but didn the KE produce the force?


The above do NOT work in reverse, something simply cannot start moving spontaneously and a force is created as a result. Because of this:

P = F * V is true, a force acting at a speed will give a power.
P/V = F Cannot occur in nature, as it breaks Newtons 1st law. What you are doing with the equation in this form is finding the NECESSERY force to create a power at a gien speed. It does not mean, if you apply a power at that speed you will get that force.

Energy, and by extention power cannot be directly measured. It is always calculated from more fonamental things.

>>>>>>>>>I agree. Even in its best case, HP would be calculated form a rate of change of KE. you need to know speed change vs time and mass.

There is no absolute measure of energy, because energy is defined as the work that one system does (or can do) on another. Thus, only of the transition of a system from one state into another can be defined and thus measured.

"Methods

The methods for the measurement of energy often deploy methods for the measurement of still more fundamental concepts of science, namely mass, distance, radiation, temperature, time, electric charge and electric current." wikipedia. but you can get this from pretty much any physics book.


Conclusion to this: Power cannot be directly measured, it requires more fundamental principles to quantify and give context. Applying a power at a speed cannot occur as it violates Newtons 1st law of motion. The fundamental factor in this must therefore be force distance and time. Of which the only one that has potential to do work is force.

Force therefore is first, and power is a method by which we quatify what that force has done.
>>>>>>>>>>>>>>Doesnt KW-hours, watt-seconds, HP-seconds quantify how much work can be done? If I have a battery or a gas tank filled with electrons or fuel, I have potental energy here. is the capacity for how much work can be done. I can do it fast or slow, in the end its work (fs). How fast I do that work, or rate of doing work is power. If push a button and release electrons in motor at a known rate, and it is converted, i know, at any given speed, what the force will be. The force does the work, but the power is the indicator of what the force will be at any particular speed.




This (the power speed force bit) is incorrect for as it violates Newtions first law as stated above.

By the same reason that force and speed can bve used to find power:

P = T * angular velocity torque and angualr velocity can be used to find power
P/angualt velocity = T you can't do it this way. The find the necessary torque. not the actual.


You say that the faster the rate of doing work by the engine the greater its power output. This is indeed correct. Now for where you are going wrong with it.

"The engines power output is set. It is defined by:

P=(thermal efficieny * volumetric efficieny * displaced volume * number of revolutions * fuel heating value * density of the air * (fuel air ratio)/2" Equation from Heywood

This defines the amount of work a given engine can do. The POWER OUTPUT IS SET IT DOES NOT CHANGE DEPENDING ON THE GEARING. So if you geared it 1:1 you'd have the same power at the rear wheel as if you used a 100:1 gearning. It would be going this work more slowly, but it would be doing more work.

>>>>>>>>>>>>>>>>>>>You just made my point right there. sure, if I was at max power and we had 1:1 gearing, the force would be a heck of a lot different greater, at the driven wheels at 100:1 gearing. I think you made a critical mistake next. The rate of doing work would be IDENTICAL the amount of work per unit of time would be identical. Since we are talking the same " car " here. if power is the same in both cases, acceleration and thus rear wheel forces will be proportional to power and inversly proportioal to speed. IN this case, fundamemtally, you changed the conditions by comparing power at two different speeds. (100:1 vs 1:1). power is constant, rate of work is the same, acceleration and force are different based on the car's speed.
To answer your comment directly, if power didnt change with gearing, then the HP curve would be flat, and torque would be very high at start and very low at the higher speeds . If this was the case, rate of work still would be equal and forces would go down with speed proportional to speed.


You are NOT doing more work at the rear wheels by using a higher gear ratio.

"W = F * d" wiki or books.

You are using a higher force but moving

>>>>>>>>>as said above, you are doing the same amount of work, if you are using ANY ratio, if the power is the same. high rpm, low torque vs low rpm, high torque. If they trade off, the amount of work stays the same. Getting back to lifting a mass, 550lbs lifted in 1 second, one foot, is 1hp. 1000lbs lifted 1 foot in 2 seconds is 1 hp. 275lbs lifted 1 foot in .5 seconds is still 1 Hp. (746watt-seconds, 746J, 1hp-second, etc).

I can only think about this in a much broader analogy. what meteor objects to fall to earth, the Earth's mass (power) or gravity (force)? The fact that the Earth has such a large mass creates force that cause objects to be attracted and fall to earth. the more objects that fall to earth, the more the mass the Earth gets and the the greater the force of gravity . Its "power" goes up and creates a greater force. This is where I am either very confused, or think think the discussion is a kind of "chicken and egg" one. :)

 

[xxChrisxx]

Please buy some books and read them.

No you didnt create a force from the energy. It was the momentum stored that caued the force, due to conservation. Energy stores are not good examples of what you are trying to say as they require forces in.

You can express the energy that its storing, but that energy doesn't create the force.

Read any statics book. Or the flywheel section in Shigley - Mechanical engineering design.YOU DONT USE KE OR RATE OF CHANGE OF IT TO CALCULATE FORCES! YOU USE MOMENTUMS! USING KE IS NOT REPRAT NOT WHAT HAPPENS IN REAL LIFE!
Tell me how do we measure power or energy directly. That means not using any more fundamental principle? I want to see proof of this.I'll respond to your odd thinking about gravity at a later time.

 

[russ_watters]

Long thread for a relatively simple concept, but Chris is right here: Power is typically calculated from torque and rpm in real life, so it generally makes more sense to discuss the concept from that angle than to say [paraphrase] 'if you know the power and rpm, you can calculate the torque and acceleration'. In other words - if you know the power and rpm, you probably already measured the torque directly. Sure, you can read the power off a performance curve, but where did that curve come from? It came from measuring the rpm and torque!

The wiki for a dyno says it pretty clearly:

A dynamometer or "dyno" for short, is a machine used to measure torque and rotational speed (rpm) from which power produced by an engine, motor or other rotating prime mover can be calculated.

http://en.wikipedia.org/wiki/Dynamometer

Yes, you can make life more complicated if you want and it'll usually work to approach the problem from the opposite direction, but it isn't really all that useful to do it that way. However, the way the issue was stated in the OP, though a little unclear, is clumsily worded and implies something that is not correct. And the conclusion statement in the last paragraph, with the graph that goes with it, is most certainly not correct: Even if, you gear the cars differently to account for the slop difference in the engine performance curve, the car that runs at a higher torque and lower rpm will accelerate faster because the drive losses are less in such a car.

The really therefore is that by overcomplicating the issue and looking at it backwards, you've confused yourself enough about the particulars to get the conclusions wrong.

 

[zanick]

It might be simple but it is one of the most confusing for most in the racing world. (except the very top engineers). You have to understand, that sometimes we only have dyno graphs to go off of, so that addresses you last point, because the resultant torque and HP measured, is at the rear wheels, incorporating the effeciency losses. So, if two engines with their drivetrains have the same rear wheel HP at any vehicle speed, they will have the same rear wheel forces. the advantage of one vs the other will follow the HP curve. (providing the same spacing of the gears) Now, of course, as I have said many times, using the gear output torque curves will tell you what you want to know, but you need to know the engine torque curves, the gear rations, tire diameters and vehicle speeds. With knowing HP curves and vehicle speeds ranges, all you need to know is gear spacing in %.

The conculsion I have come with , is that if two cars have equal HP curves, (as measured at the rear wheels) they will both have the same rear wheel torque at any vehicle speed. This is still true, even if i am coming at it from the wrong direction. The interesting thing about using HP is that it already incorporates engine speed, so in comparisons, it is easy to use to determine which engine is better, where the shift points should be and where its advantages and disavantages would be on a race track.

The entire point of the topic was to get the terminology correct to bring it back to the racing world. a you know, we want to optimize our time spent at the max hp range of the engine. (not max engine torque range of the engine). There is also a factor of the time spent at the higher rpm ranges. Just getting average power or even average torque found at the rear wheels, doesn't show the entire picture. I can even more accurately integrate the HP curve useable range and get a value that might not indicate which engine is going to create more HP-seconds, or Ft-Lb-seconds at the rear wheels. I think the only way to know this is to get a Ft-lb-seconds value based on known time over an operational speed range.

I only got on the chicken and egg discussion because the criticism was in the areas of actually using Hp curves to determine optimal rear wheel forces. Again, I understand that the force is what does the work, but was taking it a bit futher associating power with energy, as a potential that creates the force. Unit measures of work are also in HP-seconds, KW-hours, Watt-seconds and thought it could address the basic question brought up in the beginning. Yes, there was some terminology confusion in the beginning, but that was in areas of engine torque, rear wheel torque as measured at the drive wheels but calculated back to the engine, rear wheel HP and rear wheel torque and forces at generated at the drive wheels.

by the way, there are dynos that are called chassis dynos that do nothing but measure the rate of acceleration of the drums that the car drives. since it needs to know speed, rate of change of speed, and the mass, you might say it is measuring hp as well, right? It can't tell you engine torque, unless it has a engine speed signal. all it can tell you in that case is the tangental force at the driven tires, it can't even tell you final drive torque of the vehicle! However it can accurately provide a MPH vs HP curve.

Now, I've been doing this a long time and have a lot of experience optimizing race cars for the track to be more competitive.
What I do know is that what I am talking about works, even if I am coming at it from the wrong or "odd" direction. Thats why I came here, to get the terminology straightened out.

Mk

Long thread for a relatively simple concept, but Chris is right here: Power is typically calculated from torque and rpm in real life, so it generally makes more sense to discuss the concept from that angle than to say [paraphrase] 'if you know the power and rpm, you can calculate the torque and acceleration'. In other words - if you know the power and rpm, you probably already measured the torque directly. Sure, you can read the power off a performance curve, but where did that curve come from? It came from measuring the rpm and torque!

The wiki for a dyno says it pretty clearly: http://en.wikipedia.org/wiki/Dynamometer

Yes, you can make life more complicated if you want and it'll usually work to approach the problem from the opposite direction, but it isn't really all that useful to do it that way. However, the way the issue was stated in the OP, though a little unclear, is clumsily worded and implies something that is not correct. And the conclusion statement in the last paragraph, with the graph that goes with it, is most certainly not correct: Even if, you gear the cars differently to account for the slop difference in the engine performance curve, the car that runs at a higher torque and lower rpm will accelerate faster because the drive losses are less in such a car.

The really therefore is that by overcomplicating the issue and looking at it backwards, you've confused yourself enough about the particulars to get the conclusions wrong.

 

[zanick]

You said this:
This defines the amount of work a given engine can do. The POWER OUTPUT IS SET IT DOES NOT CHANGE DEPENDING ON THE GEARING. So if you geared it 1:1 you'd have the same power at the rear wheel as if you used a 100:1 gearning. It would be going this work more slowly, but it would be doing more work.

This is not correct, but you still stand by it?

The bottom line, is I might not be using the right analogies. I only used the gravity, meteor for an analogy that there could be something that is responsible for the force, in terms of energy or the change in energy.

In my mind power is just torque with a rpm attached to it. Just a short cut to find out what i need in comparative environments.

mk

Please buy some books and read them.

No you didnt create a force from the energy. It was the momentum stored that caued the force, due to conservation. Energy stores are not good examples of what you are trying to say as they require forces in.

You can express the energy that its storing, but that energy doesn't create the force.

Read any statics book. Or the flywheel section in Shigley - Mechanical engineering design.


YOU DONT USE KE OR RATE OF CHANGE OF IT TO CALCULATE FORCES! YOU USE MOMENTUMS! USING KE IS NOT REPRAT NOT WHAT HAPPENS IN REAL LIFE!



Tell me how do we measure power or energy directly. That means not using any more fundamental principle? I want to see proof of this.


I'll respond to your odd thinking about gravity at a later time.

 

[zanick]

Chris,
You did say this below, you know. I think we started out agreeing and then ended up in disagreement. thoughts?

mk

Yeah, i'll admit I don't know a super amount about racing boxes. Its been a while since I've done anything with transmissions.

Getting slightly back on topic. I'm glad this thread has swung around to what really matters for acceleration. The gear ratios! Yes peak torque and peak horsepower figures are great for willy waving in the paddock, but careful selection of gear ratios and usefulness of the powerband is king.

 

[xxChrisxx]

The thoughts are, you are wrong about the technical side. And I don't think you are going to be able to break that 'old skool dyno room habit' of using incorrect terminology. I'm now kind of resigned to that fact.(was a bit stresses out about other things yesterday) The subtle difference between things like kinetic energy and momentium is case in point. You talk in terms of KE when its really correct to say momentum. I've given you some books to read if you wwant to get the technical stuff correct.However, from a practical stand point, even though want you are saying is not what is acutally happening, mathematical equtions have been developed to allow you to calculate it. What you do says if something will work, but not WHY it works. And i suppose if all you are after is a 'will it work' then your calculations are fine. Just use HP and calcualte the area, talk in terms of kWh or Hpseconds or sometihng else. Thats perfectly valid for explaining what you want, but it does skew your thinking.

you are correct, I view HP and simply an rpm corrected torque curve. But I know that both variabels are important. For what you want just use HP as that's valid.Just for the hell of it, you keep saying you have more power in a lower gear. And that I am wrong in sayin that you have the sme power whether you have 1:1 or 100:1 ratio.

Prove me wrong, do some calculations and post them. Please TRY to show I am wrong. Dont just state it.

 

[zanick]

I never said that you would have more power in a lower gear, I said if you had the same power at 1:1 or 100:1, the speed of the vehicle would be totally different. but, if the speed of the vehicle was the same, Yes, you would have much less hp with 1:1 gearing. How can you compare the two? You also said that If you did gear it, one would be doing work more slowly but "doing more work". (see your quote below). I said, at the same HP, both would be doing the same amount of work over a given time. I think you might have just made a small unintentional error below. did you ? what I was saying is that for any same speed of the vehicle, the 100:1 gear ratio could allow for operaton at near max hp, while at that same speed, using 1:1, you would have much less hp at that same vehicle speed. See the difference? I am keeping my comparisons at the same vehicle speed, you are not. I don't think the discussion makes much sense unless we keep the speed and mass the same.


You said this:
"This defines the amount of work a given engine can do. The POWER OUTPUT IS SET IT DOES NOT CHANGE DEPENDING ON THE GEARING. So if you geared it 1:1 you'd have the same power at the rear wheel as if you used a 100:1 gearning. It would be going this work more slowly, but it would be doing more work."

So, what you are wrong about, is that if a car had 1:1 or 100:1 gearing and the same HP with each, the rate of doing work would be the same. one would be doing the work more slowly, but the work (Fs) would be the same over the same time period even though one would use a higher force less frequently vs a lower force more frequently

Just for the hell of it, you keep saying you have more power in a lower gear. And that I am wrong in sayin that you have the sme power whether you have 1:1 or 100:1 ratio.

Prove me wrong, do some calculations and post them. Please TRY to show I am wrong. Dont just state it.

 

[xxChrisxx]

you are correct i didnt mean more work, i meant more load. just going round this iritating debate is now staring to annoy me and I am beginning to make stupid errors in my haste to correct you.

so more load at lower speed,
less load at higher speed.
all the same work.
you don't have to keep the speeds the same to compare power.You are correct in saying that 100:1 would allow you to have more power at the same speed. THE ONLY REASION YOU HAVE MORE POWER IS MORE TORQUE.

I cannot state it any simpler than this. you can find this out from the HP curve, but once you are dividing by the speed you are really looking at torque at the reat wheel. just like if you were using torque nd then applied an angualr velocity you are taling about power.

call it what ever the hell you like. do it howeverthe hell you like. You wanted to be correct in the physics and several poeple have attempted to correct you. You clearly don't give a flying arse about being correct in the physics, you just wanted someone to affirm what you are saying.so purely to lay this thread to rest.

What you are doing with the horsepower curve will work, maximise Hpseconds for maximum go. Use that terminology.

good day

 

[russ_watters]

It might be simple but it is one of the most confusing for most in the racing world. (except the very top engineers). You have to understand, that sometimes we only have dyno graphs to go off of, so that addresses you last point, because the resultant torque and HP measured, is at the rear wheels, incorporating the effeciency losses. [emphasis added]

That's not the scenario you gave in the OP:

I posted a set of engine HP/torque curves... [emphasis added]

In the first quote, you're talking about performance measured at the wheels, and in the second you are talking about performance at the crankshaft. Now the wording in the paragraph from the OP (the rest of it) is clumsy enough that I can see you might have meant the measurements were taken at the wheels, but that isn't what you said. As chris has said, most of this thread has been an attempt to get you to correct your clumsy thought process and presentation of the issues. I think we've beaten this issue to death. Thread locked.

[edit] Actually, just to clarify that one last little confusion between you and chris - if the output of an engine in HP (and therefore rpm and torque) is fixed, the gearing (assuming equal drive losses) produces equal HP at the wheels. A 100:1 gear ratio produces 100x as much torque and 1/100th as much rpm at the wheel as a 1:1 ratio. But the speeds and accelerations are different, which is the point being made: You can't ever view HP as independent of other factors. You must combine it with rpm and when you do that, you're just rearranging that equation that relates the three.