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Torque Vs. Horsepower
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
I'm not sure exactly what you are saying here? But for example, I could take two electric motors, both of which produce say 100Kw of power. I could connect them to a common shaft, and run them in opposite directions. Neither one would do work, and of course the shaft would undergo serious strain, but I don't believe it means the motors make 0Kw of power. They simply aren't doing any work. But they have the ability to do work.
Tech Contributor
Joined: Jun 2004
Posts: 20,944
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Not to play Devils Advocate here, but then why do the F1 cars have top speeds of well over 200 MPH (256 being an unofficial speed record) when they have very little torque (but over 900HP) being produced from their 3.0 liter engines?
Areodynamics certainly come into play, but F1 cars are most certainly NOT designed for top-speed runs, the open-wheel design and extreme down-force aren't friendly to high-speeds...
Areodynamics certainly come into play, but F1 cars are most certainly NOT designed for top-speed runs, the open-wheel design and extreme down-force aren't friendly to high-speeds...
Le Mans Master
Joined: Jul 1999
Posts: 8,683
Likes: 6
From: Phoenix AZ
Very simple (but I'm going to give you a long winded answer). We both agree that high speeds mean high aerodynamic drag. To attain or maintain a high speed requires a lot of force to overcome the mass inertia or aerodynamic drag. We know that the drag force is against the bodywork. The propelling force that overcomes that drag has only one place to present itself. The tire contact patch. The tire (patch)transmits the force to propel the car. The force comes from the (torque) rotation of the axles, translated through a torque arm (the tire radius.) Assuming roughly a one foot tire radius, the torque applied to the axle is numerically identical to the force magnitude at the tire patch. Take this large torque value, divide it by the ring and pinion ratio, and the transmission gear ratio, and you will see that a small torque initiating from the engine will get multiplied by the overall gear ratio, resulting in a large torque value through the axle, which will then be translated into a large driving force at the tire patch. Small torque in, large torque out. Conversely, however, that requires large (engine) RPM in, small (tire) RPM out. Simple gearing/RPM tradeoff.
Yep, you certainly did take the long answer approach! I agree with you, it's all in the gearing. I just really enjoy these threads on "torque vs. horsepower", when in reality is not one versus the other, it's about having just the right amount of each for the application at hand.
Thread Starter
Racer
Joined: Jul 2007
Posts: 462
Likes: 21
From: Kansas City Missouri
Thanks for the overwhelming response. The reason I thought to post this thread in the first place was because some people were talking about the TPI set up being torquie and fun to drive in the city. With that in mind, I thought that I must have been confused because mine doesn't seem too impressive off the line in terms of acceleration.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Why would anyone ever want anything other than a C4?
So, due to the economics of it, they buy a small engine import that responds well to "juicing".
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Race Director
Joined: Dec 2002
Posts: 13,348
Likes: 233
From: SCMR Rat Pack'r Charter Member..Great Bend KS
(I said)Torque is how much work an engine can do.
(you said)Incorrect. Work is force times distance. Torque is a force at a distance. A difference.
(I say)What I said was correct. I said "can do (is capable of doing)", not "is doing".
(I said)Torque does not accelerate you, horsepower does....you can have massive torque to the rear wheels and not be moving.
(you said) Wrong. Horsepower does not exist prior to rotation. Torque causes the rotation, allowing you to calculate the horsepower.
(I say)It was correct. Torque does not necessarily cause rotation/movement, since you can have torque applied to a stationary object. Your "hp does not exist prior to rotation" statement illustrates this and is, interestingly enough, exactly what I stated.
Your turn....
Larry
code5coupe
________
not easily impressed....
(you said)Incorrect. Work is force times distance. Torque is a force at a distance. A difference.
(I say)What I said was correct. I said "can do (is capable of doing)", not "is doing".
(I said)Torque does not accelerate you, horsepower does....you can have massive torque to the rear wheels and not be moving.
(you said) Wrong. Horsepower does not exist prior to rotation. Torque causes the rotation, allowing you to calculate the horsepower.
(I say)It was correct. Torque does not necessarily cause rotation/movement, since you can have torque applied to a stationary object. Your "hp does not exist prior to rotation" statement illustrates this and is, interestingly enough, exactly what I stated.
Your turn....
Larry
code5coupe
________
not easily impressed....
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
If what you say is right, that torque = amount of work something can do, then I can do as much work as your LT1 (or whatever engine is in your car). Give me a 4' breaker bar and I can easily make 400+ lb-ft of torque. So if you are right, this indicates how much work I can do. I should be able to accelerate a Corvette with my breaker bar like nobody's business.
However, what you said is not right. Torque has no inherent relationship with work. And I would't be able to accelerate a car for ****.
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
most race car shops have a ''mover''...not much more than a 4ft breaker bar with an end plate to engage the wheel hub studs...standard prank is to fit the ''mover'' on and ask some 110 lb PYT to ''hold this up for a sec'' and watch panic set in as the car starts to roll...even if you're under 110 lb, ugly, and not a horse, i'd guess that (unseen) YOU could prolly generate enough torque to get enough speed to hit the shop wall and do 'some' damage.
gonna find a corner chair myself now, interesting how the vette crew is at least thinking about T and not just swallowing HP
gonna find a corner chair myself now, interesting how the vette crew is at least thinking about T and not just swallowing HP
Le Mans Master
Joined: Dec 2002
Posts: 6,715
Likes: 2
From: Santa Teresa New Mexico
most race car shops have a ''mover''...not much more than a 4ft breaker bar with an end plate to engage the wheel hub studs...standard prank is to fit the ''mover'' on and ask some 110 lb PYT to ''hold this up for a sec'' and watch panic set in as the car starts to roll...even if you're under 110 lb, ugly, and not a horse, i'd guess that (unseen) YOU could prolly generate enough torque to get enough speed to hit the shop wall and do 'some' damage.
gonna find a corner chair myself now, interesting how the vette crew is at least thinking about T and not just swallowing HP
gonna find a corner chair myself now, interesting how the vette crew is at least thinking about T and not just swallowing HP
"Horses" are stupid animals, 425 "horses" couldn't find thier way out of the barn if it was on fire. But 425 "horses" with 450 lbs of torque could pull that same barn down.
Make mine torque,,,to go.
Le Mans Master
Joined: Sep 2005
Posts: 6,551
Likes: 36
From: Jenks OK
Fun with math and physics!
Newton second law Force = mass x acceleration
Toss in a little algebra,
acceleration = Force / mass
torque is a turning force when measured at the wheels it is the force at which you turn said wheels.
so… your acceleration, is directly dependent on your force, and in fact assuming your wheels are sticking, your acceleration curve will be identical to your torque curve.
I remembered something from college, and they said all that alcohol kills brain cells.
Newton second law Force = mass x acceleration
Toss in a little algebra,
acceleration = Force / mass
torque is a turning force when measured at the wheels it is the force at which you turn said wheels.
so… your acceleration, is directly dependent on your force, and in fact assuming your wheels are sticking, your acceleration curve will be identical to your torque curve.
I remembered something from college, and they said all that alcohol kills brain cells.
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
Fun with math and physics!
Newton second law Force = mass x acceleration
Toss in a little algebra,
acceleration = Force / mass
torque is a turning force when measured at the wheels it is the force at which you turn said wheels.
so… your acceleration, is directly dependent on your force, and in fact assuming your wheels are sticking, your acceleration curve will be identical to your torque curve.
I remembered something from college, and they said all that alcohol kills brain cells.
Newton second law Force = mass x acceleration
Toss in a little algebra,
acceleration = Force / mass
torque is a turning force when measured at the wheels it is the force at which you turn said wheels.
so… your acceleration, is directly dependent on your force, and in fact assuming your wheels are sticking, your acceleration curve will be identical to your torque curve.
I remembered something from college, and they said all that alcohol kills brain cells.
You just said your acceleration is identical to your torque curve. So on a car with say 350 lb-ft @ 3200 rpm (216 hp) and say 300hp @ 6000 rpm (a measly 262 lb-ft), that from the time you pass 3200 rpm, acceleration drops off. It has to if what you said is true, because torque already peaked and is now declining.
That is incredibly easy to prove false just by going out and driving your car. See if that really happens, or if in fact it pulls a lot harder at the horsepower peak instead?
Last edited by Aurora40; Oct 4, 2007 at 08:07 PM.
Le Mans Master
Joined: Sep 2005
Posts: 6,551
Likes: 36
From: Jenks OK
Swing and a miss, your rate of acceleration will be lower at that point, you'll be going fast still but your acceleration will be lower.
The reality is your engine cannot rev indefinitely and continue to produce torque indefinitely, however to continue accelerating you want to produce as much torque as you can for as long as possible.
If your torque drops below the point you would be in the next gear, you need to shift, why? to maximize your torque!
Just thought I'd add this to your example, if your car is pulling hardest at your horsepower peak, why is it that we get wheel spin when you hit your torque peak...
The reality is your engine cannot rev indefinitely and continue to produce torque indefinitely, however to continue accelerating you want to produce as much torque as you can for as long as possible.
If your torque drops below the point you would be in the next gear, you need to shift, why? to maximize your torque!
Just thought I'd add this to your example, if your car is pulling hardest at your horsepower peak, why is it that we get wheel spin when you hit your torque peak...
Last edited by dclafleur; Oct 4, 2007 at 08:12 PM. Reason: addendum
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
So with an L98 for example., your fastest acceleration will come with like 3,500 rpm shifts, just after the torque peaks and acceleration drops (or drops according to you)?
Regardless of whether torque or horsepower causes wheelspin, don't you think it's a hell of a lot easier for the wheels to spin at say 5mph than at say 50mph?
Le Mans Master
Joined: Sep 2005
Posts: 6,551
Likes: 36
From: Jenks OK
Ok, if that's the argument you want to stick with... I doubt most people's reality will match it.
So with an L98 for example., your fastest acceleration will come with like 3,500 rpm shifts, just after the torque peaks and acceleration drops (or drops according to you)?
So with an L98 for example., your fastest acceleration will come with like 3,500 rpm shifts, just after the torque peaks and acceleration drops (or drops according to you)?
I'm going to give you the benefit of the doubt and assume you're confusing acceleration with speed.
Le Mans Master
Joined: Apr 2005
Posts: 6,413
Likes: 9
From: The Old Dominion
LOL! I'm pretty sure I already had it. But regardless, what kind of 1/4 mile times does your L98 run with 3,500 rpm shifts? 
Well, I was of course thinking of someone accelerating, so there would be no downshifting involved. So when you are in 1st gear and run your car up to the horsepower peak (because you aren't in a hurry, of course), then shift into 2nd. Lets assume a smooth shift so there is no shock to break the wheels loose. Then you are saying at that point as you pass through the torque peak again, you can peel the wheels which were not peeling in 1st at the power peak? Color me impressed.
Well, I was of course thinking of someone accelerating, so there would be no downshifting involved. So when you are in 1st gear and run your car up to the horsepower peak (because you aren't in a hurry, of course), then shift into 2nd. Lets assume a smooth shift so there is no shock to break the wheels loose. Then you are saying at that point as you pass through the torque peak again, you can peel the wheels which were not peeling in 1st at the power peak? Color me impressed.