What torque and horsepower mean for cars

[Spuds]

Unfortunately I don't have the time tonight to answer this fully. However the best way for all of this torque and power stuff to make sense is to:

1. Learn basic calculus in addition to the basic physics you already understand
2. Examine 2 or more Dyno charts
3. Transform those charts into instantaneous acceleration charts for the respective cars (gear ratios, what are those? Lolol). You are going to want both cars to have the same gearing and wheels to make this easier.
4. Transform those into speed/time charts (integration)
5. Transform those into distance/time charts (integration)
6. Figure out which car is faster


Note, actual calculus won't really be useful in this example but the concepts will help you understand why what you are doing makes sense.

[bfrank1972]

In your prior example, you were comparing car A and B. They both produce the same torque number, table flat torque curve. A revs to 7000 rpm. B revs to 8000 rpm. B will have a higher peak horsepower due to the higher max rpm.

Now, here's why gearing is important. Say both cars have same gearing. Same weight. Same aero. Same everything. Car A can hit 40 mph in 3 seconds in first gear. How fast can car B hit 40mph? 3 seconds.

But car B has more HP, so how can they be the same? If car A hits redline at 7000 rpm at 40 mph. Car B will carry on to nearly 47 mph at redline before having to shift (and will pull ahead). Conversely, if you want them both to redline at 40mph, you shorten the *gearing* of car B. With shorter gearing they both will stop at 40mph in 1st gear. But car B will get there faster - same torque, higher horsepower, higher rpm allows for greater mechanical advantage but still gets it to 40mph in 1st gear.

That's why gearing, with all other things being equal, is an important aspect to understand when understanding the relationships between torque and horsepower. Hope this helps.

Originally Posted by Johnny Horsepower

Yeah, people say that, but then I see things like this: https://www.roadandtrack.com/car-cul...wer-vs-torque/



Sure, those other things are going to make a huge difference. But without some simplifying assumptions, no question could ever be answered. This is confusing enough already for a seemingly simple question.

I think it's reasonable to assume that cars A and B have the same weight, aerodynamics, and gearing, even if that's not quite realistic. (Like more torque might mean a bigger engine, which changes other things.) If that's too much to assume, then OK, let's say this is for entertainment purposes only, to provide a simple illustration of the concepts of power and torque.

[Captain Snooze]

Originally Posted by Johnny Horsepower

They're definitely related, but I wouldn't say 2 sides of the same coin. Say you have car A and car B. Car A has more peak torque, but car B has more peak horsepower (due to a higher redline). Other things being equal, isn't car B going to accelerate faster and have a higher top speed?

I knew what I meant I shall elaborate.
You are give a dyno graph: torque vs rpm. At any given rpm there is a torque value and only one corresponding power value. That is, at any give rpm the torque and power are directly related.
I.e, 2 sides of the same coin.

[bfrank1972]

Originally Posted by Captain Snooze

I knew what I meant I shall elaborate.
You are give a dyno graph: torque vs rpm. At any given rpm there is a torque value and only one corresponding power value. That is, at any give rpm the torque and power are directly related.
I.e, 2 sides of the same coin.

Yup, directly related. Torque is force applied. HP is work rate.

I think back to when I was a kid and my dad had an old school ice cream maker. You know, the one you crank by hand. My arm could apply X amount of torque on that crank. When the ice cream got thick/stiff, I can tell you it was a lot easier to turn it slow than to turn it fast. Applying same force, but turning it fast requires a lot more work (HP).

[Johnny Horsepower]

@Spuds, @bfrank1972, thanks, I'll have to take a closer look at what you said later.

Originally Posted by Tcoat

If you want the real basics then you received the answer in the first reply to this thread. If you chose to ignore that then you will never get a true grasp of it.

The video in the link you gave explains it all perfectly. If you can't get it from that then I give up.

I don't think the first reply was a very good answer, and it's certainly different from what the video says. I hadn't watched the video until just now, but it's actually pretty good.

It basically says it's power that moves the car, not torque per se, which is what I had concluded as well. So then why all the myths, such as torque is how far you move the wall (which is clearly absurd)?

Originally Posted by Captain Snooze

I knew what I meant I shall elaborate.
You are give a dyno graph: torque vs rpm. At any given rpm there is a torque value and only one corresponding power value. That is, at any give rpm the torque and power are directly related.
I.e, 2 sides of the same coin.

OK, for a given car at a given rpm, you know both the torque and the power.

But how about this: according to an FR-S dyno graph I'm looking at now, if the torque is 140, the hp could be either 70 (at 2700 rpms) or 170 (at 6400 rpms). Clearly the performance is going to be very different at 70 hp vs 170 hp. So torque is part of the story, but power is the whole story.

[Tcoat]

Originally Posted by Johnny Horsepower

@Spuds, @bfrank1972, thanks, I'll have to take a closer look at what you said later.



I don't think the first reply was a very good answer, and it's certainly different from what the video says. I hadn't watched the video until just now, but it's actually pretty good.

It basically says it's power that moves the car, not torque per se, which is what I had concluded as well. So then why all the myths, such as torque is how far you move the wall (which is clearly absurd)?



OK, for a given car at a given rpm, you know both the torque and the power.

But how about this: according to an FR-S dyno graph I'm looking at now, if the torque is 140, the hp could be either 70 (at 2700 rpms) or 170 (at 6400 rpms). Clearly the performance is going to be very different at 70 hp vs 170 hp. So torque is part of the story, but power is the whole story.

Torque is part of the power equation. There can be no acceleration or HP without it.







Read this. If you still don't understand or believe then we are wasting our time here.
https://www.carthrottle.com/post/werzmjy/

[jonboy99]

Originally Posted by Johnny Horsepower

...but also having high rpm at a given torque means you feel the push more. So high power means you feel the push more, right?

No, you wouldn't feel the push more, for any given gear, with any given gearing. If you're in a car which makes a flat torque curve from 2000-8000rpm, then flat out in second gear at 2000rpm will give you just the same acceleration as flat out in second at 8000rpm. It may seem faster, because of the noise.

[IceFyre13th]

[Tcoat]

Originally Posted by IceFyre13th

Ahhh so you have read his other thread!

[humfrz]

Originally Posted by bfrank1972

Yup, directly related. Torque is force applied. HP is work rate.

I think back to when I was a kid and my dad had an old school ice cream maker. You know, the one you crank by hand. My arm could apply X amount of torque on that crank. When the ice cream got thick/stiff, I can tell you it was a lot easier to turn it slow than to turn it fast. Applying same force, but turning it fast requires a lot more work (HP).

Ya, but licking the paddles was worth it -


humfrz

[Irace86.2.0]

There is a channel for this stuff - Engineering Explained.

[why?]

Originally Posted by Irace86.2.0

There is a channel for this stuff - Engineering Explained.

not sure op could figure that stuff out. It might be too complex for him.

[Johnny Horsepower]

Originally Posted by Tcoat

Torque is part of the power equation. There can be no acceleration or HP without it.

Yes, I agree. I never said otherwise. I gave that same equation in the original post. Can you read?

Speed is distance / time. Distance is part of the speed equation. There can be no speed without it. But if you want to know how fast a car is going, do you look at speed or distance? Speed, duh!

Originally Posted by Tcoat

Read this. If you still don't understand or believe then we are wasting our time here.
https://www.carthrottle.com/post/werzmjy/

You said the earlier video explained it perfectly. Is this link better than perfect? These sources saying conflicting things can't all be right.

This article mentions that a = F/m. But wouldn't F be the car's net force vector in the forward direction rather than the twisting force at the engine or wheels? Those are different things; they don't even use the same units.

[Tcoat]

Originally Posted by Johnny Horsepower

Yes, I agree. I never said otherwise. I gave that same equation in the original post. Can you read?

Speed is distance / time. Distance is part of the speed equation. There can be no speed without it. But if you want to know how fast a car is going, do you look at speed or distance? Speed, duh!



You said the earlier video explained it perfectly. Is this link better than perfect? These sources saying conflicting things can't all be right.

This article mentions that a = F/m. But wouldn't F be the car's net force vector in the forward direction rather than the twisting force at the engine or wheels? Those are different things; they don't even use the same units.

Are you really this obtuse?


You have said several times that torque does not mean anything
i.e. "It basically says it's power that moves the car, not torque per se, which is what I had concluded as well"


Giving the equation and understanding the equation are not the same thing. You are still attempting to think of "power" as something separate from torque. It is not separate, it is the result of torque and RPMs.


I have no clue what you are babbling about speed for. The statement I made is there can be no acceleration without torque. Speed had no part in it.


The video obviously was above your comprehension so I thought print would be better. They do not say conflicting things at all they just say the same differently. Maybe we can break out some crayons and draw some pictures that you can understand.


You asked a question and we are trying to answer it but all you do is spew drivel that supports your original thoughts on the subject. This is as basic as it gets and an 8th grader should be able to understand it so if you don't want to listen to the answers don't ask the bloody questions.