View Poll Results: Who won the debate: MK (HP) or VR (Torque)
Mk won with a simple to understand concept that HP determines torque at the wheels at any speed.
25
17.48%
MK won: When comparing equal HP cars, the one with less torque COULD be better on the road course.
6
4.20%
VR won: When comparing equal HP cars, the one with more torque is better on a road course.
44
30.77%
Neither, as physics dont apply to race cars
18
12.59%
I don't want to open this can of worms again!
50
34.97%
Voters: 143. You may not vote on this poll
Poll: Who won the HP vs Torque debate?
03-22-2009, 01:55 PM
#376
Rennlist Member
Thread Starter
Good observation. I was REALLY tuned into this in every close battle with the two cars. even the panos vs the porsche or ferrari showed no real difference. most of which are going to be car or driver input. The reason is that these are real race cars and the designers use gear boxes that optimize the HP curve of the vehicle.
The main point here, is that when you compare a car like the Audi vs the Acura and understand that the Acura is half the torque, yet near the same HP (or at least same hp/weight), AND understand that the audi has a very broad HP curve, (Not flat torque curve, thats not the point as the engine is used in the downward sloped side of the torque curve anyway), it is clear to see that the Audi CAN use only a 5 speed gear box to keep power near optimum, while the Acura needs to keep the close ratio gear box to keep things near EQUAL.
You guys are really missing the point here though . Its has nothing to do with engine torque as a unit of comparitive measure. ITS HP, and HP available at any time. remember the basic equasion?
acceleration = power/(mass x velocity)
This is absolutely true and fact at any vehicle speed. off a turn, up a hill, down a straight, etc.
If we are talking of rear wheel torque, then you can talk all day long and be correct. when you start talking about engine torque as a value of comparison, you make absolutely no sense. thats the same if i was to say, "my car is faster down the straights, because I have a max rpm of 10,000rpm" !!!!!
The main point here, is that when you compare a car like the Audi vs the Acura and understand that the Acura is half the torque, yet near the same HP (or at least same hp/weight), AND understand that the audi has a very broad HP curve, (Not flat torque curve, thats not the point as the engine is used in the downward sloped side of the torque curve anyway), it is clear to see that the Audi CAN use only a 5 speed gear box to keep power near optimum, while the Acura needs to keep the close ratio gear box to keep things near EQUAL.
You guys are really missing the point here though . Its has nothing to do with engine torque as a unit of comparitive measure. ITS HP, and HP available at any time. remember the basic equasion?
acceleration = power/(mass x velocity)
This is absolutely true and fact at any vehicle speed. off a turn, up a hill, down a straight, etc.
If we are talking of rear wheel torque, then you can talk all day long and be correct. when you start talking about engine torque as a value of comparison, you make absolutely no sense. thats the same if i was to say, "my car is faster down the straights, because I have a max rpm of 10,000rpm" !!!!!
A major blow to the Torque side of this arguement IMO is the ACURA LMP1 car that just entered ALMS. It's on the pole with short developement times. Has only 370 ft lbs compared to the Audis and Peugeots turbo diesels with tons of torque (like 800 ft-lbs).
If torque was so much better the Acura wouldn't have a chance with such a huge deficit. The Acura seems to get off the corners just fine despite a lack of torque.
Seems like I said that if you were to even the hp/weight restrictions between LMP1 and LMP2 that the Porsches and Acuras would REALLY own the Audis, seems like that is coming true. And this is on a high speed track where the torque will have the best chance. Too bad Audi isn't running the whole season.
I don't see how anyone can say definitively one way or the other, because it will vary. But there is no way that torque is the deciding factor when these cars have nearly identical hp. Trying to say the Acura handles that much better to overcome over 400 ft lbs of torque deficit is reaching for straws.
If torque was so much better the Acura wouldn't have a chance with such a huge deficit. The Acura seems to get off the corners just fine despite a lack of torque.
Seems like I said that if you were to even the hp/weight restrictions between LMP1 and LMP2 that the Porsches and Acuras would REALLY own the Audis, seems like that is coming true. And this is on a high speed track where the torque will have the best chance. Too bad Audi isn't running the whole season.
I don't see how anyone can say definitively one way or the other, because it will vary. But there is no way that torque is the deciding factor when these cars have nearly identical hp. Trying to say the Acura handles that much better to overcome over 400 ft lbs of torque deficit is reaching for straws.
03-22-2009, 02:14 PM
#377
Rennlist Member
Thread Starter
Now, you cant catagorize torque and HP this way. It just is not true.
momentimm is just mass x velocity. It has nothing to do with acceleration.
neither does kinetic energy have anything do to with power and acceleration
Its the RATE OF CHANGE OF KINETIC energy. (i.e. acceleration of a mass at a known speed.)
HP is the rate of change of kinetic energy. Torque is just a factor of HP, just like RPM. Now, if you want to know what the acceleration will be at any vehicle speed. (off a corner, down a straight) its the power available, OR the rear wheel torque. since we will not know the rear wheel torque unless you calculate the gear reductions and engine torque, its easieer to look at engine power, and IMPOSSIBLE to look at just engine torque to get any valuable information of acceleration potential of any car.
Even in 1st gear, its power that determines acceleation, however, you are right , acceleration will only be able to follow the engine's torque curve. All things being equal, gear ratios can be selected to optimze power on launch and acceleration. If two comparitive cars have a 40mph redline, and the same shaped HP curve,dumping the clutch will have the same acceleration regardless of the torque values of the engine. (e.g. 10,000rpm vs 5,000rpm redline and one engine half the peak torque as the other).
Remember, we are talking about engine torque ONLY as a limiting or comparitive factor. everything else has to be the same. This means the two cars in question in any example might have a gear ratio set up, both 5 speeds, both have redline vehicle speeds of 50, 80, 120, 150, 180mph for example.
Again, if we are talking about "Torque", and comaring two different cars, it has to be that of what is found at the rear wheels, through the gear box at any speed. This is absolutely, positively determined by Power!!!
mk
momentimm is just mass x velocity. It has nothing to do with acceleration.
neither does kinetic energy have anything do to with power and acceleration
Its the RATE OF CHANGE OF KINETIC energy. (i.e. acceleration of a mass at a known speed.)
HP is the rate of change of kinetic energy. Torque is just a factor of HP, just like RPM. Now, if you want to know what the acceleration will be at any vehicle speed. (off a corner, down a straight) its the power available, OR the rear wheel torque. since we will not know the rear wheel torque unless you calculate the gear reductions and engine torque, its easieer to look at engine power, and IMPOSSIBLE to look at just engine torque to get any valuable information of acceleration potential of any car.
Even in 1st gear, its power that determines acceleation, however, you are right , acceleration will only be able to follow the engine's torque curve. All things being equal, gear ratios can be selected to optimze power on launch and acceleration. If two comparitive cars have a 40mph redline, and the same shaped HP curve,dumping the clutch will have the same acceleration regardless of the torque values of the engine. (e.g. 10,000rpm vs 5,000rpm redline and one engine half the peak torque as the other).
Remember, we are talking about engine torque ONLY as a limiting or comparitive factor. everything else has to be the same. This means the two cars in question in any example might have a gear ratio set up, both 5 speeds, both have redline vehicle speeds of 50, 80, 120, 150, 180mph for example.
Again, if we are talking about "Torque", and comaring two different cars, it has to be that of what is found at the rear wheels, through the gear box at any speed. This is absolutely, positively determined by Power!!!
mk
I've been trying to stay out of this debate as it's so heated... But power and Torque are both limiting factors. It's a two-part equation; torque is required for momentum, power for kinetic energy- depending on the engine, gear and conditions, either could be the car's limiting factor at any given time. Engines/transmission systems are designed so that both these factors are addressed simultaneously, though, otherwise you might end up with hp you can't use or massive torque that tops out at 5mph. Assuming good transmission gear ratios:
1st gear is generally torque limited, especially from a stop. You simply can't make use of all that high-end horsepower when your engine is only running at low RPM, and it's not practical for a lower end 1st gear. At higher rpms, rote hp is generally more important as torque can be geared for, hp can't.
.
1st gear is generally torque limited, especially from a stop. You simply can't make use of all that high-end horsepower when your engine is only running at low RPM, and it's not practical for a lower end 1st gear. At higher rpms, rote hp is generally more important as torque can be geared for, hp can't.
.
03-22-2009, 02:44 PM
#378
Drifting
Now, you cant catagorize torque and HP this way. It just is not true.
momentimm is just mass x velocity. It has nothing to do with acceleration.
neither does kinetic energy have anything do to with power and acceleration
Its the RATE OF CHANGE OF KINETIC energy. (i.e. acceleration of a mass at a known speed.)
mk
momentimm is just mass x velocity. It has nothing to do with acceleration.
neither does kinetic energy have anything do to with power and acceleration
Its the RATE OF CHANGE OF KINETIC energy. (i.e. acceleration of a mass at a known speed.)
mk
F=ma. For an engine, F=TORQUE. It doesn't matter what the peak HP is of the car, it's not going to accelerate any faster than the torque to the wheels allows.
E=1/2mv2. No matter what the engine torque is, there has to be sufficient power to impart enough kinetic energy to change the velocity.
A lot of the torque vs horsepower arguments in this thread are rather silly because torque and horsepower are so closely related, and people completely ignore RPM in their arguments. RPM is what links the two, and it matters. Gear ratio, as well.
Imagine you have two cars. They both have one gear, geared for top speed. One is powered by a waterwheel type engine and has an almost infinite amount of torque, but it spins so slowly that it has very little horsepower. The other car is powered by a screaming little engine with practically no torque, but is spinning at 100,000rpm and at 100k, can produce 1000hp.
00s: Drop the flag!
01s: TORQUE shoots off the line like he's hit by a locomotive, almost instantly going 0-30mph! HP is just a few inches off the starting line, the motor nearly stalled, and turning very slowly.
20s: TORQUE is still at 30mph; he lacks the power to overcome the wind resistance. HP is now up to a blistering 10mph.
60s: Both cars are now up to 30mph, but TORQUE has the lead
120s: HP is up to 60mph, and has left TORQUE in the dust!
600s: HP's acceleration is slowing as he approaches 250mph, but he's so far ahead, it doesn't matter.
Point being, Torque and HP BOTH matter. We select gears so we don't see this happening, but it is happening, every time a cars moves.
Edit: I just reread your post again and think we're just describing the exact same thing in a different way.
Last edited by sjfehr; 03-22-2009 at 03:31 PM.
03-22-2009, 03:03 PM
#379
I kindly disagree. 
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
03-22-2009, 03:13 PM
#380
Drifting
I kindly disagree.
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
When you're talking instantaneous numbers (velocity is simply the integrations of all that instantaneous acceleration), F=ma and you can't violate it no matter how much horsepower you have.
Edit: I see you're talking about "average", which is not correct. You have to look at this as the integration of instantaneous numbers and the calculus of it. Imagine your car rolling from a stop in 1st gear. You gun the engine, but only get 3000rpm. How much hp did it take to accelerate from 0-5rpm? How much torque?
I wonder how different this thread would look if every instance of "HP" was replaced by "Torque x rpm"?
03-22-2009, 04:08 PM
#381
I don't agree here.
The velocity is a integration of instant acceleration, but it's integrated over time.
Acceleration over time can't be justified with F = ma. <- not a function of time, but a moment.
It has to be F(t) = ma(t)
F(t) is a result of RPM and F.
With:
F=ma,
F is only a result of plain simple F.
------------------------------------------------
But as I interpret your example above, you've included a huge loss of energy in the HP vehicle and not the Torque one. Which I find a bit unfair here. If the applications are going to be compared, they have to have the same losses (or lack of).
The "horsepower" engine in your example dogs, rpm dies and then the HP goes down. If the high-rpm can get a "perfect/no-loss slip" on the rear wheels/clutch, it will accelerate faster.
If the HP-machine dogs,
The "Torque" engine will actually produce more horsepower in the beginning than the "horsepower" engine.
If we gear them correctly for no spin on either. Both will accelerate according to their HP
The velocity is a integration of instant acceleration, but it's integrated over time.
Acceleration over time can't be justified with F = ma. <- not a function of time, but a moment.
It has to be F(t) = ma(t)
F(t) is a result of RPM and F.
With:
F=ma,
F is only a result of plain simple F.
------------------------------------------------
But as I interpret your example above, you've included a huge loss of energy in the HP vehicle and not the Torque one. Which I find a bit unfair here. If the applications are going to be compared, they have to have the same losses (or lack of).
The "horsepower" engine in your example dogs, rpm dies and then the HP goes down. If the high-rpm can get a "perfect/no-loss slip" on the rear wheels/clutch, it will accelerate faster.
If the HP-machine dogs,
The "Torque" engine will actually produce more horsepower in the beginning than the "horsepower" engine.
If we gear them correctly for no spin on either. Both will accelerate according to their HP
03-22-2009, 04:24 PM
#382
Rennlist Member
I think we all know your preference, but Ive already proved...Ive shown factual evidence showing with his guidlines, actually, the lower torque engine might work better on all road courses.
(because of a broader HP curve)...
VR, this picture shows one possiblity of Dez's requirment of two equal HP engines. which one would you pick?
This graphically shows why any of the 37 that selected that higher torque is always better, should review the curves and change their vote. Clearly, this shows that a lower torque engine can be better off turns and down straights.
also shown here with two other real case, equal HP cars.
(because of a broader HP curve)...
VR, this picture shows one possiblity of Dez's requirment of two equal HP engines. which one would you pick?
This graphically shows why any of the 37 that selected that higher torque is always better, should review the curves and change their vote. Clearly, this shows that a lower torque engine can be better off turns and down straights.
also shown here with two other real case, equal HP cars.
I am sorry, my gladiator-loving friend, but neither you nor your zillions of charts and graphs have proved anything of the kind. And your "factual evidence" is actually nothing more than your opinion. And that's fine--your opinion is just as valid as mine. But the harder you try to "prove" you're "right...and the more 500 word essays you post one after the other, the weaker and more desperate-appearing your case gets, Mark. I do not say that in a disparaging way. You'll note that (unlike you) I have never disparaged your occupation or your driving skills. But Mark, as another person helpfully pointed out earlier in this thread, you are being openly mocked here.
Just let it go.
On a related note, we're at 26 pages come 30!!!!!!!!
Professional Racing and Driving Coach
03-22-2009, 04:30 PM
#383
Drifting
I think we're just quibbling over semantics here, because horsepower is torque x rpm. So, to put it another way:
Originally Posted by sjfehr
That's kinda what I was getting at, though- it's impossible to gear correctly for all possible speeds, therefore we DO have to consider the engine at less-than-peak torque x rpm. Specifically, starting from a stop, as we typically have 5 or 6 gears. (Unless the car has a hp/rpm converter or CVT, in which case... heh) If we have two engines that both make the same torque x rpm, but one makes it at high-rpm with very little hp/rpm and the other at low-rpm and high-hp/rpm, the latter is going to be faster off the line because the engine produces more hp/rpm at low rpm. In both cases, you're not going to be using anywhere near the peak torque x rpm the engine is capable of until getting up to higher speeds.
03-22-2009, 06:16 PM
#384
That's kinda what I was getting at, though- it's impossible to gear correctly for all possible speeds, therefore we DO have to consider the engine at less-than-peak horsepower. Specifically, starting from a stop, as we typically have 5 or 6 gears. (Unless the car has a torque converter or CVT, in which case... heh) If we have two engines that both make the same horsepower, but one makes it at high-rpm with very little torque and the other at low-rpm and high-torque, the latter is going to be faster off the line because the engine produces more torque at low rpm. In both cases, you're not going to be using anywhere near the peak horsepower the engine is capable of until getting up to higher speeds.
I think we're just quibbling over semantics here, because horsepower is torque x rpm. So, to put it another way:
I think we're just quibbling over semantics here, because horsepower is torque x rpm. So, to put it another way:
Glad that our world of physics align! Then we can leave the theory part.
We have the gearing (gearbox, clutch, tire size etc etc..) left and you're right it's not possible to gear correctly for all speeds. It's a compromise trying to utilize as much horsepower as possible. At standstill start we'll be getting really low HP and once we've got some speed, the gearing will make the engine surpass peak HP and then drop when we shift to below HP. I presume you agree with this.
This compromise is to me both ways. If I gear to high, I'll be far from reaching the effective power band. But I can also gear low and reach the HP power band quick enough that it will not be affective.
In general, if I gear the 100k RPM engine down to the wheels to the same top speed as the windmill. The 100k RPM application will accelerate faster than Windmill. Since it will develop more torque at the same RPM @ wheels. Gearing in this application being a result of gearbox, wheel slip, clutch slip, etc...
As you said, HP = Torque x RPM x k(konstant)
If we add a gearing. Engine HP = Wheel Torque x RPM x k x gearing
Now, this can of course be discussed in a real word application how much is possible to do and what other differences/problems will it cause. But if we have engines with equivalent power bands, peaking HP at 3k or at 6k. That's a simple 1:2 ratio. Both cars will then get the same acceleration and same top speed. The one with the high-rev RPM having 1:2 ratio on all gears compared to the low-rev one. It's one of the reason if I run a stock Cup, stock gearbox, I shouldn't change the rolling radius of the wheels if I don't want to change the performance.
*caugh*
Come one VR, both you and Mark have poked at each other. No one has been a saint here.. (me included)
P.S Slow down on the avatar changes, I can hardly keep up with the pace you change them!!
Last edited by Rassel; 03-22-2009 at 06:34 PM.
03-22-2009, 08:05 PM
#385
Rennlist Member
Thread Starter
youre right. But, you might be explaining it in a way that is glazing over the fundamental problem here.
He is still missing the point that engine torque doesnt determine rear wheel torue. (force at the rear wheels ) when discussing a=F/m
Hp does this! HP determines rear wheel torque, at any speed, even at an instant.
We dont need to get into calculus here. The concepts are simple
mk
He is still missing the point that engine torque doesnt determine rear wheel torue. (force at the rear wheels ) when discussing a=F/m
Hp does this! HP determines rear wheel torque, at any speed, even at an instant.
We dont need to get into calculus here. The concepts are simple
mk
I kindly disagree.
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
F=ma can't be used like that.
It physically impossible to determine a cars continuous acceleration that way.
a = instant acceleration. (Acceleration in an instant moment)
As soon time passes, which is does directly.
You need average acceleration over time.
This is determined by average force over time. F will be a result of how much force the combustion gives and how often it was applied over time.
F is then not determined by torque itself, but also RPM. These combined will be HP.
Last edited by mark kibort; 03-22-2009 at 08:48 PM.
03-22-2009, 08:16 PM
#386
Perhaps I do, I just wanted to make sure it wasn't the F= ma, which is a common culprit since it describes instant acceleration and is not the same as average acceleration over time.
03-22-2009, 08:34 PM
#387
Rennlist Member
Thread Starter
Let me see if I can cut through the weeds here. Lets keep in real simple so we dont get too side tracked on the point. Point is, what determines acceleration at the rear wheels. Yes, Torque and logitudinal force determine acceleration, and follow acceleration=Force/mass. Remember this is at the rear tires!
HP determines this, OR engine torque, x rpm x gear ratio. This is why Acceleration = power/(mass x velocity) is so usefull. you can tell a relative acceleration only by the HP available without knowing engine torque or rpm. (as long as we are talking about same car, only changing the drivetrain as this subject is all about)
let me insert my comments below because you logic below is a little unclear.
>>>>>>>>>>>>>>>>>>>>
HP determines this, OR engine torque, x rpm x gear ratio. This is why Acceleration = power/(mass x velocity) is so usefull. you can tell a relative acceleration only by the HP available without knowing engine torque or rpm. (as long as we are talking about same car, only changing the drivetrain as this subject is all about)
let me insert my comments below because you logic below is a little unclear.
>>>>>>>>>>>>>>>>>>>>
F=ma. Acceleration is directly related to torque.
>>>>>>> yes, a=F/m. No argument there except for it has to be measured at the rear tires to the road.
I'm not going to get into the calculus, but the difference between any two velocities is going to be a function of both kinetic energy and accelleration. BOTH matter.
>>>>>>>>>>I can store a bunch of kinetic energy with very little power, torque and force. It has nothing to do with acceleration, other than the rate of change of kinetic energy which is , by definition, power!
Energy and momentum are both conserved, so the engine needs to impart both to the car. You can't just dump energy into an equation and come up with speed, you have to solve for momentum as well.
>>>>>>>> not true, momentum is what we are keeping constant at any speed,right. thats the " mass x velocity" part. Accleration = Power/mass x velocity so that its the power that changes rates of acceleration, not anthing to do with conservation of energy or momentum per se.
It's why the space shuttle engines are described by pounds of thrust and not horsepower.
>>>>>>>>>>>>>>>>rockets, jets and other near constant force devices use thrust, as there is no need to look at power, as it is a varable, due to Power=fs. However, there is a rating for thrust based propulsion. Often mis-understood as well. Power = 375/thrust. remember this is NET thrust, and NET power. Lets not go down that rat hole. a jet with 20,000lbs of thrust might start out at 0hp and end up at 50,000hp at 120mph, while the hp-seconds. (a unit measure of work) might the exactly the same for a 500hp.
F=ma. For an engine, F=TORQUE. It doesn't matter what the peak HP is of the car, it's not going to accelerate any faster than the torque to the wheels allows.
>>>>>>>>>Wrong, dead flat wrong. 250ftlbs and 500ftlbs can produce the exact same acceleration if the RPMs allowed are in proportions. (i.e. 500ft-lbs at 4000rpm vs 250ftlbs at 8,000rpm). This is so easy to prove. Try and find one actual instance where this is not true.
E=1/2mv2. No matter what the engine torque is, there has to be sufficient power to impart enough kinetic energy to change the velocity.
>>>>>>>>>>>>>>ah, kind of. I think you are saying the same thing ,when it takes power to change the kinetic energy and that energy required will go up faster than the speed exponentially.
A lot of the torque vs horsepower arguments in this thread are rather silly because torque and horsepower are so closely related, and people completely ignore RPM in their arguments. RPM is what links the two, and it matters. Gear ratio, as well.
>>>>>>>Thats why HP is so valuable, as it takes the rpm and torque values in to account so you dont need to mess with gear box ratios at any speed. all you need to know is that you have the same hp at any vehicle speed, and you will have the same acceleration, regardless of engine torque and engine rpms.
Imagine you have two cars. They both have one gear, geared for top speed. One is powered by a waterwheel type engine and has an almost infinite amount of torque, but it spins so slowly that it has very little horsepower.
>>>>>>>>>>>>we are talking about same HP, so this comparison is not very usefull.
The other car is powered by a screaming little engine with practically no torque, but is spinning at 100,000rpm and at 100k, can produce 1000hp.
00s: Drop the flag!
01s: TORQUE shoots off the line like he's hit by a locomotive, almost instantly going 0-30mph! HP is just a few inches off the starting line, the motor nearly stalled, and turning very slowly.
>>>>>>> by not using gear ratios, you are limited to the one gear and the Hp curves of both of the contraptions. anyway, the reason the waterwheel vehicle jumps a head, is that it has MUCH more hp than the 100,000rpm motor.
Remember, HP determines acceleration. Yes, or rear wheel torque. in this case, the rear wheel torque is much higher with the water wheel and has much higher HP as well. remember rate of change in kinetic energy!
20s: TORQUE is still at 30mph; he lacks the power to overcome the wind resistance. HP is now up to a blistering 10mph.
60s: Both cars are now up to 30mph, but TORQUE has the lead
120s: HP is up to 60mph, and has left TORQUE in the dust!
600s: HP's acceleration is slowing as he approaches 250mph, but he's so far ahead, it doesn't matter.
>>>>>>>what you have shown is that you need gears to effectively apply the engines hp to the rear wheels! you are not showing anything here , than an unbalanced comparison. If you cant apply the 100,000hp to the ground, its not much use. the higher torqe engine with lower gearing has an unfair advantage. all you are showing is that the two comparisons, one has no power and the other has HI hp, but gearing shows opposite performance due to gearing limitations.
Point being, Torque and HP BOTH matter. We select gears so we don't see this happening, but it is happening, every time a cars moves.
Edit: I just reread your post again and think we're just describing the exact same thing in a different way.
>>>>>>>>Yes, i see you point, but it makes a case for equal power. if you have equal applied power, and that is what we are discussing, you have equal acceleration regardless of engine torque values. Agreed?
>>>>>>> yes, a=F/m. No argument there except for it has to be measured at the rear tires to the road.
I'm not going to get into the calculus, but the difference between any two velocities is going to be a function of both kinetic energy and accelleration. BOTH matter.
>>>>>>>>>>I can store a bunch of kinetic energy with very little power, torque and force. It has nothing to do with acceleration, other than the rate of change of kinetic energy which is , by definition, power!
Energy and momentum are both conserved, so the engine needs to impart both to the car. You can't just dump energy into an equation and come up with speed, you have to solve for momentum as well.
>>>>>>>> not true, momentum is what we are keeping constant at any speed,right. thats the " mass x velocity" part. Accleration = Power/mass x velocity so that its the power that changes rates of acceleration, not anthing to do with conservation of energy or momentum per se.
It's why the space shuttle engines are described by pounds of thrust and not horsepower.
>>>>>>>>>>>>>>>>rockets, jets and other near constant force devices use thrust, as there is no need to look at power, as it is a varable, due to Power=fs. However, there is a rating for thrust based propulsion. Often mis-understood as well. Power = 375/thrust. remember this is NET thrust, and NET power. Lets not go down that rat hole. a jet with 20,000lbs of thrust might start out at 0hp and end up at 50,000hp at 120mph, while the hp-seconds. (a unit measure of work) might the exactly the same for a 500hp.
F=ma. For an engine, F=TORQUE. It doesn't matter what the peak HP is of the car, it's not going to accelerate any faster than the torque to the wheels allows.
>>>>>>>>>Wrong, dead flat wrong. 250ftlbs and 500ftlbs can produce the exact same acceleration if the RPMs allowed are in proportions. (i.e. 500ft-lbs at 4000rpm vs 250ftlbs at 8,000rpm). This is so easy to prove. Try and find one actual instance where this is not true.
E=1/2mv2. No matter what the engine torque is, there has to be sufficient power to impart enough kinetic energy to change the velocity.
>>>>>>>>>>>>>>ah, kind of. I think you are saying the same thing ,when it takes power to change the kinetic energy and that energy required will go up faster than the speed exponentially.
A lot of the torque vs horsepower arguments in this thread are rather silly because torque and horsepower are so closely related, and people completely ignore RPM in their arguments. RPM is what links the two, and it matters. Gear ratio, as well.
>>>>>>>Thats why HP is so valuable, as it takes the rpm and torque values in to account so you dont need to mess with gear box ratios at any speed. all you need to know is that you have the same hp at any vehicle speed, and you will have the same acceleration, regardless of engine torque and engine rpms.
Imagine you have two cars. They both have one gear, geared for top speed. One is powered by a waterwheel type engine and has an almost infinite amount of torque, but it spins so slowly that it has very little horsepower.
>>>>>>>>>>>>we are talking about same HP, so this comparison is not very usefull.
The other car is powered by a screaming little engine with practically no torque, but is spinning at 100,000rpm and at 100k, can produce 1000hp.
00s: Drop the flag!
01s: TORQUE shoots off the line like he's hit by a locomotive, almost instantly going 0-30mph! HP is just a few inches off the starting line, the motor nearly stalled, and turning very slowly.
>>>>>>> by not using gear ratios, you are limited to the one gear and the Hp curves of both of the contraptions. anyway, the reason the waterwheel vehicle jumps a head, is that it has MUCH more hp than the 100,000rpm motor.
Remember, HP determines acceleration. Yes, or rear wheel torque. in this case, the rear wheel torque is much higher with the water wheel and has much higher HP as well. remember rate of change in kinetic energy!
20s: TORQUE is still at 30mph; he lacks the power to overcome the wind resistance. HP is now up to a blistering 10mph.
60s: Both cars are now up to 30mph, but TORQUE has the lead
120s: HP is up to 60mph, and has left TORQUE in the dust!
600s: HP's acceleration is slowing as he approaches 250mph, but he's so far ahead, it doesn't matter.
>>>>>>>what you have shown is that you need gears to effectively apply the engines hp to the rear wheels! you are not showing anything here , than an unbalanced comparison. If you cant apply the 100,000hp to the ground, its not much use. the higher torqe engine with lower gearing has an unfair advantage. all you are showing is that the two comparisons, one has no power and the other has HI hp, but gearing shows opposite performance due to gearing limitations.
Point being, Torque and HP BOTH matter. We select gears so we don't see this happening, but it is happening, every time a cars moves.
Edit: I just reread your post again and think we're just describing the exact same thing in a different way.
>>>>>>>>Yes, i see you point, but it makes a case for equal power. if you have equal applied power, and that is what we are discussing, you have equal acceleration regardless of engine torque values. Agreed?
03-22-2009, 08:37 PM
#388
Rennlist Member
Thread Starter
I know.
Also, thats why i like HP-seconds, as it is a total amount of power used to accelerate. as opposed to average HP , where that doesnt take into account the different time that you spends over an acceleration speed range, at the different rpm. This can be looked at as ft-lb-seconds as well, but they have to remember, its at the rear tires. Thats the problem that most have when discussing this topic. they all know F=ma, etc but its the F at the rear wheels, and that is the curve ball most miss.
mk
Also, thats why i like HP-seconds, as it is a total amount of power used to accelerate. as opposed to average HP , where that doesnt take into account the different time that you spends over an acceleration speed range, at the different rpm. This can be looked at as ft-lb-seconds as well, but they have to remember, its at the rear tires.
Thats the problem that most have when discussing this topic. they all know F=ma, etc but its the F at the rear wheels, and that is the curve ball most miss.mk
03-22-2009, 08:42 PM
#389
Rennlist Member
03-22-2009, 08:47 PM
#390
Rennlist Member
Thread Starter
I gave you a graph, started by the guy that started with the question! Des.
now, look at that graph i provided and see if it fits. Would you recomend a client to buy the same car with the powerplant with the higher torque peak?
Based on facts I provided, certainly not. Unless there is some other reason you are thinking of, that last graph i plotted, fully meeting Dez's guidlines, the lower torque engine would provide more usable torque at the rear wheels at any vehicle speed.
How about the actual dyno runs of two 290rwhp engines? same thing. the lower torque engine would make more rear wheel torque at any same vehicle speed. SURE, this is the minority for what you will usually see, but its the argument and discussion. Im sorry you dont think the facts are facts here.
VR, com'mon, you have been as disparaging as anyone here. And, i recently took the high road back to the facts.
Now, since the beginning, no one has put up one shred of evidence supporting that a high torque engine of the same HP can produce any more torque at the wheels, such as in getting out of a corner. know why?? because its always a possiblity that the curves can look as I posted and that generality would be wrong. Hence, the entire meat of the argument/discussion here.
Mk
now, look at that graph i provided and see if it fits. Would you recomend a client to buy the same car with the powerplant with the higher torque peak?
Based on facts I provided, certainly not. Unless there is some other reason you are thinking of, that last graph i plotted, fully meeting Dez's guidlines, the lower torque engine would provide more usable torque at the rear wheels at any vehicle speed.
How about the actual dyno runs of two 290rwhp engines? same thing. the lower torque engine would make more rear wheel torque at any same vehicle speed. SURE, this is the minority for what you will usually see, but its the argument and discussion. Im sorry you dont think the facts are facts here.
VR, com'mon, you have been as disparaging as anyone here. And, i recently took the high road back to the facts.
Now, since the beginning, no one has put up one shred of evidence supporting that a high torque engine of the same HP can produce any more torque at the wheels, such as in getting out of a corner. know why?? because its always a possiblity that the curves can look as I posted and that generality would be wrong. Hence, the entire meat of the argument/discussion here.
Mk
I am sorry, my gladiator-loving friend, but neither you nor your zillions of charts and graphs have proved anything of the kind. And your "factual evidence" is actually nothing more than your opinion. And that's fine--your opinion is just as valid as mine. But the harder you try to "prove" you're "right...and the more 500 word essays you post one after the other, the weaker and more desperate-appearing your case gets, Mark. I do not say that in a disparaging way. You'll note that (unlike you) I have never disparaged your occupation or your driving skills. But Mark, as another person helpfully pointed out earlier in this thread, you are being openly mocked here.
Just let it go.
On a related note, we're at 26 pages come 30!!!!!!!!
Professional Racing and Driving Coach
Just let it go.
On a related note, we're at 26 pages come 30!!!!!!!!
Professional Racing and Driving Coach