No, torque isn't what moves a car.

"DeWayneV8" (squirmish) 05/12/2015 at 08:37 • Filed to: None

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Every time I hear someone spout the old axiom “torque is what moves a car” I want to vomit out my internal organs. Torque is a static figure, I can grab a breaker bar and apply 200 lb-ft of torque to the input shaft of a transmission but it doesn’t mean that I can move the car at any significant rate.

I think that the misconception comes from the fact that large torquey engines tend to produce more average horsepower over their operating range than a small peaky engine. While torque isn’t inconsequential, it’s the combination of torque and engine speed that really moves the car.

Also, while we are at it, it’s lb-ft for torque. A ft-lb is a measure of work, not torque.

EDIT: I want to point out that when I say “move”, I mean move an object from point A to point B. I think many people are mistaking that for instantaneous acceleration rate.

What I’m trying to say is that horsepower is a better indication of vehicle performance than torque.

Laird Andrew Neby Bradleigh > DeWayneV8 05/12/2015 at 08:46

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So.. which is better.. a 1 hp 100 lb-ft engine or a 1 lb-ft 100 hp engine? ;)

DeWayneV8 > Laird Andrew Neby Bradleigh 05/12/2015 at 08:48

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The 100 hp engine will definitely make whatever vehicle it’s in faster if geared correctly.

Hermann > DeWayneV8 05/12/2015 at 08:51

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It’s a complicated concept that’s hard to grasp for most regular folks. Being pedantic about it is often not worth explaining what’s work, power, resulting force, etc. Most people get more confused by all that the more you try to make it clearer.

Here in Brazil they use KgFM to measure torque, and most people don’t understand it really. When you show them the same value in Nm instead of KgFm they seem to understand the concept easier. Not sure why.

BiTurbo228 - Dr Frankenstein of Spitfires > Laird Andrew Neby Bradleigh 05/12/2015 at 08:51

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Better for what? Powering a generator: 100 lb-ft. Powering a rotary cutter: 100hp.

For a car, probably the 100hp engine. You can stick a gearbox behind it with shitloads of very short gears. The only way you’d be able to get a 100hp/1lb-ft engine is a tiny displacement engine that revs to the moon, so lots of gears will get it moving :)

Laird Andrew Neby Bradleigh > DeWayneV8 05/12/2015 at 08:54

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I know, it was a crude joke.. sorry :)

It will be faster IF geared correctly, that was kinda what I was getting at. I small engine that can do 10k rpm would be bloody fast on most applications right? But a large engine that can only do 1500 rpm could be quite fast as well right?

What I’m trying to say is that I understand what you’re saying, but that it’s not as simple as torque and engine speed, you need to think about gearing as well :)

DeWayneV8 > Hermann 05/12/2015 at 08:55

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While I agree that physics just confuses the layman, most car people have put at least 100 lb-ft of torque on a breaker bar at some point. You’d think this concept of static torque would carry to realizing that they can’t make a vehicle move fast with that breaker bar.

It’s really sad how little even educated people know about physics.

Snuze: Needs another Swede > DeWayneV8 05/12/2015 at 08:56

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Amen! This always annoys me too. I think the reason is that torquey engine’s “feel” faster than high horsepower engines, especially in day to day driving situations. You can feel that “torque hit” just off idle leaving a stoplight when you mash it hard, but how many opportunities do you have to wind you some peaky high horsepower engine?

Laird Andrew Neby Bradleigh > BiTurbo228 - Dr Frankenstein of Spitfires 05/12/2015 at 08:56

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Yeah. as I explained in my post to OP I wasn’t trying to be stupid, I just wanted to make it clear that we need to think about gearing and such as well :)

davesaddiction @ opposite-lock.com > DeWayneV8 05/12/2015 at 08:56

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more torque = more power at lower revs

Simple as that.

http://www.1728.org/mtrtrq.htm

RamblinRover Luxury-Yacht > DeWayneV8 05/12/2015 at 08:57

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This seems a trifle nitpicky. A high torque number relative to max horsepower is *usually* an indicator of good development of torque down low, hang the top end. In order to “get a car moving” with any quickness, having plenty of torque low in the power band is easier to work with in terms of getting off the line unless you have a lot of gearing to turn a peaky motor into anything useful at the wheels. You’re stringing out the axiom in a reductio ad absurdem - of course the axiom is meant to mean *ability for getting a car moving initially* rather than “move a car” in general, which is usually well reflected by the torque numbers.

And ultimately, yes, torque is what moves a car from a certain point of view, it just doesn’t dictate how fast the car gets moved. It matters how sustainable your 200lb-ft via breaker bar is to higher speed than about 30 RPM, but you will definitely get the car moving, where you might not with a ratchet handle. There are certain inherent limits your little experiment would highlight quite well.

BiTurbo228 - Dr Frankenstein of Spitfires > DeWayneV8 05/12/2015 at 08:58

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I’ve always wondered whether there’s a third statistic that would give us further insight into how an engine performs in addition to peak horsepower and peak torque: average torque.

It would be expressed in lb-ft/rpm and would be an average of an engine’s torque output at every given rev rate.

So, modern turbocharged cars with their broad torque curves between 1500 and 4000rpm would have a high average torque, whereas the near-race peaky old NA engines would have a lower average horsepower.

DeWayneV8 > davesaddiction @ opposite-lock.com 05/12/2015 at 09:00

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If the vehicle is geared correctly, it won’t matter what revs you are at. Now....do you want to be driving on the highway at 6k rpm? Probably not, but that’s a separate issue. Fact is, if the engine is geared so that it can reach it’s powerband then horsepower is all that matters.

DeWayneV8 > BiTurbo228 - Dr Frankenstein of Spitfires 05/12/2015 at 09:02

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Well I think average horsepower over the range the engine sees between shifts is what matters. This is why it’s important to have an engine that can rev higher than its peak horsepower RPM, with a bell shaped curve you want to be on both sides of the power peak over the shift range.

Party-vi > DeWayneV8 05/12/2015 at 09:04

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Do you think this is

A mother-fucking game?

DeWayneV8 > RamblinRover Luxury-Yacht 05/12/2015 at 09:05

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Again....horsepower is what moves the car even in the breaker bar example. It moves slow....because the RPM is slow and thus the horsepower is low. You need to do work to move an object, and torque is NOT work.

DeWayneV8 > Party-vi 05/12/2015 at 09:06

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Can’t....breathe....

You can tell a Finn but you can't tell him much > DeWayneV8 05/12/2015 at 09:12

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Since we’re being pedantic today, ft-lb = lb-ft since multiplication is commutative.

BiTurbo228 - Dr Frankenstein of Spitfires > DeWayneV8 05/12/2015 at 09:13

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That would be useful. It’d even be useful as a performance statistic to have the average horsepower from shift-point to redline. It’s all stuff you could get from a detailed dyno printout, but I’ve never seen an OEM manufacturer release one...

Mattbob > DeWayneV8 05/12/2015 at 09:13

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1) force moves a car.... F=MA —> F/M=A Torque is force at distance, so if we want to be pedantic neither torque or HP move a car.

2) lb ft is the same thing as ft lb.... It is multiplication.... The order doesn’t matter.

davesaddiction @ opposite-lock.com > DeWayneV8 05/12/2015 at 09:13

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My cars revs to 8600, but yeah, I don’t usually set the cruise at 6000 RPM. Ha!

DeWayneV8 > Snuze: Needs another Swede 05/12/2015 at 09:14

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Yea, if you have a 3.0 engine making 300 hp naturally aspirated and a 5.0 engine making the same number, the 5.0 engine will feel faster at 2000 RPM. You have to rev the smaller engine higher to get the same performance.

This is because the 5.0 engine is making more hp at 2000 RPM.

Mattbob > BiTurbo228 - Dr Frankenstein of Spitfires 05/12/2015 at 09:16

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taking the integral of the torque curve would probably do it.

BiTurbo228 - Dr Frankenstein of Spitfires > Mattbob 05/12/2015 at 09:17

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That would be good wouldn’t it? It’d be bloody hard to figure out from a picture of a dyno printout, but if you had the data and a computer it would be easy as :)

vwbeamer > DeWayneV8 05/12/2015 at 09:18

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I disagree, Torque moves the car, HP is a measure of the ability to do work. If you put your breaker bar on the transmission, the car is going to move. I agree it will be at a slow pace, but torque is what is moving the car. I also agree a higher HP car will be faster than a High torque car if geared properly. BTW, you would have zero HP without torque.

RamblinRover Luxury-Yacht > DeWayneV8 05/12/2015 at 09:20

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Amended: horsepower is what moves the car *within a given time*. Your insistence that force times distance over time is a better representation of force times distance than force alone is arguable, but not 100% representative either. You need to do work to move an object, yes, understood, *BUT*: in the case of linear motion would you say that the force was not what moved the object? Would you nitpick that it was, in fact, the force times the distance? You’re still in giga-nitpick mode - the torque is absolutely analogous to force in this case, and as far as you’re representing *something*, *anything* as being the agent of motion - a “thing” doing a “thing”, then the torque (at the wheels) is absolutely that abstracted “thing”. A horsepower is not an abstracted agent of change in that respect, not usually.

May I further point out that your criticism is that the statement is incomplete, and thus inaccurate, but your proposed expansion (an attempt to answer “what moves a car/gets a car moving *quickly* *and keeps it moving*”) is expanding the statement to greater completion in a subtly different direction than what those who use it would intend. You’re effectively putting words in their mouth.

I’m not even disagreeing with you that horsepower is a better reflection of “get moving, keep moving”, because that’s absolutely true... *if properly geared/transmitted*. However, you’re making a mountain out of a molehill and making a poor argument to serve that.

DeWayneV8 > Mattbob 05/12/2015 at 09:21

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Well, with F=MA the torque provides an angular acceleration rate, but acceleration rate doesn’t mean the car will move anywhere because it’s an instantaneous number. You still need work to have displacement because you have to put out some energy.

It’s a little known fact that lb-ft and ft-lb aren’t the same.

http://en.wikipedia.org/wiki/Foot-poun…

http://en.wikipedia.org/wiki/Pound-foo…

heeltoehero > DeWayneV8 05/12/2015 at 09:24

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Horsepower is just math.

(Torque x RPM)/5252.

Dynos measure torque and then calculate the horsepower for you.

DeWayneV8 > vwbeamer 05/12/2015 at 09:25

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Torque only provides an acceleration rate instantaneously. It doesn’t mean you’ll move anywhere because it’s a static figure, it means nothing in the context of time. If you want to move an object from point A to point B in a given time horsepower is what matters. In the breaker bar example, if you were to move the car 3 feet it’s because you put out some energy.

I agree, you need a force to do work. What I’m getting at is that just because you have a lot of torque doesn’t mean you are doing any work.

Mattbob > DeWayneV8 05/12/2015 at 09:26

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neat, but technically Neither moves the car. A combinations of them produces acceleration. Also the foot-pound thing is just arguing symantics. Enough people use ft-lb for torque to where it isn’t confusing.

DeWayneV8 > RamblinRover Luxury-Yacht 05/12/2015 at 09:33

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I see what you are saying, and I suppose that even my title of “No, torque isn’t what moves a car” is probably phrased wrong.

The problem is that people honestly believe that torque has something to do with getting a vehicle from point A to B. From a mathematical standpoint it does, but if someone tells me how much torque their engine outputs, I can draw no conclusions about vehicle performance from that.

I was merely trying to highlight difference between power and torque, which you clearly understand. I wasn’t intending to make a “mountain out of a molehill”. As an automotive engineer these things are frustrating.

Axial > Hermann 05/12/2015 at 09:35

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Kilogram Fucking Meters...

I like it.

DeWayneV8 > Mattbob 05/12/2015 at 09:36

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I mean if we really want to get technical, the latent energy in the gasoline moves the car. My intention is to point out that torque by itself gives no indication of actual vehicle performance.

DeWayneV8 > You can tell a Finn but you can't tell him much 05/12/2015 at 09:39

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While from a math standpoint I agree, actually historically they are different.

http://en.wikipedia.org/wiki/Pound-foo…

http://en.wikipedia.org/wiki/Foot-poun…

one is torque and one is energy.

Hermann > Axial 05/12/2015 at 09:41

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Ahahahah. I’m going to use this one!

Mattbob > DeWayneV8 05/12/2015 at 09:41

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sure it does! The torque curve gives you a picture of where the car will accelerate in it’s rev range, and how it will drive. You could get this information from a HP curve, but that is jsut derived from the torque curve anyway. It’s not about peak numbers anyway man, it’s about the characteristic of the curve unless you are in a HP pissing contest.

The point I was getting at, is that you are being pedantic, this argument could go back and forth on technicalities, and no one really gives a shit. Did you just take physics? why are you so worked up over this?

RamblinRover Luxury-Yacht > DeWayneV8 05/12/2015 at 09:42

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As a rule of thumb, though - when offered a choice between higher peak torque and higher peak horsepower, the former is *generally* an indication the power on tap is easier to work with, and that’s all the phrase is meant to highlight, say, among hot rodders. I’m not sure giving the “right” breakdown to the hot rodders’ friends and family who might otherwise pick up the phrase is possible, though. Simplistic explanations are usually wrong, but this is one of those cases where the simplistic explanation is accurate-ish a lot of the time and easy to digest. “Hey, XXX, which of these two cars is likely to feel faster and jump from a stoplight better?” “Well, YYY, go with the bigger torque number - ‘torque moves the car’”. Not correct as such, but sensible to a degree.

Sir_Stig: and toxic masculinity ruins the party again. > DeWayneV8 05/12/2015 at 09:42

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Counterpoint: Without torque your car won’t move anywhere.

Also, given infinite gears a 1hp, 100lb-ft engine can do the same work as a 100hp, 1lb-ft engine can.

DeWayneV8 > RamblinRover Luxury-Yacht 05/12/2015 at 09:46

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Yes I agree because even a “high torque” engine will still turn a reasonable RPM rate.

I understand where the generalization comes from, but I think in general I wish people had a better grasp on physics.

Sir_Stig: and toxic masculinity ruins the party again. > DeWayneV8 05/12/2015 at 09:48

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And because the hp at an rpm is based on torque, you could say that the 5.0L engine can move the car faster/easier because of it’s higher torque values.

DeWayneV8 > Sir_Stig: and toxic masculinity ruins the party again. 05/12/2015 at 09:49

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No....no it can’t. You could gear the 100 hp, 1 lb-ft engine incorrectly to make them do the same work because it never got into the powerband, but they will not do the same work if they are both allowed to reach max horsepower.

While I understand your counterpoint, and it’s why I edited my original post, just because you have torque doesn’t mean the car will move anywhere. That is my main point: torque gives no indication of vehicle performance by itself.

DeWayneV8 > Sir_Stig: and toxic masculinity ruins the party again. 05/12/2015 at 09:50

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Again...it can move it faster AT THAT RPM. If both are allowed to reach their powerbands, they will move the vehicle at the same rate.

Axial > DeWayneV8 05/12/2015 at 09:53

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Well, no, torque is exactly what moves the car, at least on the specific impulse where it starts moving. It moves it because at a given static engine torque figure (multiplied through the gearbox), the stress is enough to overwhelm the forces holding the axles static and start them rolling. With the above argument, what you are essentially saying is that 5,000,000 psf on the back-end of a rocket isn’t what causes it to start lifting up. That would be wrong, because that is exactly what starts it moving up. The continued application of that amount of force over time is what causes it to keep lifting up and at some given rate of acceleration.

Basically, you are ignoring the necessity of the impulse function with your post, and the impulse function is what your average street guy is talking about even if he doesn’t know it.

BloodlessWeevil > DeWayneV8 05/12/2015 at 09:56

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Negative, a moment is the static figure. Torque is the motion associated counterpart. Instantaneous torque is what moves a car. The difference between your breaker bar and the engine is that the engine can apply that torque at thousands of RPM (the is instantaneous power by the way.) You and your breaker bar can certainly accelerate the car just as quickly as an engine supplying 200 lb-ft, but you will stop doing so when you are incapable of turning the wrench faster (generating more power.)

Based on your second paragraph, I think you have a good understanding of the physics involved. You are just being pedantic.

V8Demon - Prefers Autos for drag racing. Fite me! > DeWayneV8 05/12/2015 at 09:56

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Horsepower is the mathematical derivative of torque, so it does in fact matter.

Reasonably easy to understand article here: http://www.houseofthud.com/cartech/torque…

DeWayneV8 > Axial 05/12/2015 at 09:57

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I edited my original post to reflect what I meant, and I disagree. The average street guy wants to beat his buddy in a stoplight drag race, and to move a vehicle from point A to point B you need power.

You are correct, torque matters for instantaneous acceleration, but I do feel that people want to cover grand at a high rate when they talk about vehicle performance.

DeWayneV8 > V8Demon - Prefers Autos for drag racing. Fite me! 05/12/2015 at 10:00

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I edited my original post to clarify, but yes I agree. It’s just that if someone tells me “my engine makes 500 ft-lb of torque” this gives me absolutely no indication of vehicle performance. If they tell me “my engine makes 500 horsepower”, I can draw some conclusions about vehicle performance from that.

DrJohannVegas > davesaddiction @ opposite-lock.com 05/12/2015 at 10:07

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More torque at low revs = more power at low revs.

More torque at high revs = more power at high revs.

Please don’t use torque as a synonym for a powerband with a peak at low/mid engine speed.

DeWayneV8 > Mattbob 05/12/2015 at 10:10

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The torque curve only gives you an indication of vehicle performance because you can see the RPM on the graph.

I used the example before, but if someone tells me their engine makes 500 lb-ft of torque I can draw absolutely no conclusions about vehicle performance from that. If they tell me it makes 500 horsepower, I can draw some conclusions.

Now, from experience I know that no modern engine is going to have a max RPM of 1000, so if someone tells me it makes 500 lb-ft I know it won’t be slow because of experience. Technically though, torque gives no indication of vehicle performance.

To be clear, I edited my original post to say that I consider vehicle performance to be moving from point A to point B, not instantaneous acceleration rate.

Sir_Stig: and toxic masculinity ruins the party again. > DeWayneV8 05/12/2015 at 10:10

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But it’s all about wheel hp, not engine hp. If you were running the high torque engine through a cvt that multiplied the engine rpm you should be able to get the same wheel hp, no?

DeWayneV8 > BloodlessWeevil 05/12/2015 at 10:14

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I’ve used this example in a couple comments, but if someone tells me the engine makes 500 lb-ft, I can’t draw any conclusions about vehicle performance. If they tell me it makes 500 horsepower, I can see the car will not be slow.

Rusty Vandura - www.tinyurl.com/keepoppo > DeWayneV8 05/12/2015 at 10:15

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Well, this thread certainly went down a rabbit hole.

Isn’t it most simply put that torque is a measure of force and not of work ?

And if you want to get some work done, you’d better apply some force .

And if your engine can apply a crap-ton of of force , then there is ideally a significant potential to get down the road in a relative hurry...

davesaddiction @ opposite-lock.com > DrJohannVegas 05/12/2015 at 10:16

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Yeah, what I put was simple, but really too simplistic.

DeWayneV8 > Sir_Stig: and toxic masculinity ruins the party again. 05/12/2015 at 10:20

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No, no you can’t.

To make 1 hp with 100 lb-ft of torque, you’d have to make 100 lb-ft at ~53 RPM. To make 100 hp with 1 lb-ft of torque, you’d have to make 1 lb-ft at 525,200 rpm. This means you could gear the low torque engine at 100:1 gear ratio and still make 100 wheel lb-ft at 5252 rpm. That’s still 100 hp. No matter how you gear something the horsepower never changes.

Axial > DeWayneV8 05/12/2015 at 10:22

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The instantaneous torque is what is going to determine how anything starts moving so, even if you are already moving, the instantaneous torque is what’s going to start moving it faster than it already is. So if the instantaneous torque keeps increasing, your rate of acceleration increases.

So it’s still the impulse function being talked about. No torque curve is ever actually flat, they all have a peak with some sort of lead-up, which means that Bubba jack-jawing about the peak of his car implies there’s also a related build-up, which extends to implying more accelerated acceleration (hehehe) if that peak is higher than the other guy’s. Could also mean he just spins his tires in gears 1 through 3.

So yes, you need power, and it is ultimately power that we’re talking about holistically, but power is a time-function of force and you can convert any time function into an instantaneous equivalent that just keeps iterating on itself over and over.

In related talks, I fuckin’ love calculus and differential equations.

DeWayneV8 > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 10:22

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I think you want your engine to output a crap ton of work.

If someone tells you an engine makes 500 lb-ft, you don’t know if it would make something fast because it might make that number with a max RPM of 100. If someone tells you an engine makes 500 horsepower, you know it could moves something quickly.

Horsepower is a MUCH better indication of vehicle performance.

Mattbob > DeWayneV8 05/12/2015 at 10:23

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that is why it is a graph, not just a number. Did you not get what I meant when I said it isn’t about the peak number, but about the shape of the curve? Also, performance isn’t jsut moving from point a to point b, but how you get there. How easy is it to keep the car in the power band during speed changes, how fast you can get into the power band. These are dictated by the shape of the curve, not the peak numbers. We are talking about cars driven by people, not machines that are kept perfectly at those peak numbers for the whole trip. You are neglecting the fact that driving is dynamic, not static, just at peak numbers. Your lack of driving experience is showing.

For example. Take your 500HP figure. If say that car had a turbo with a lot of lag, and it only hits the 500HP way up in the rev range, but really has nothing down low, it is still a crap car to drive despite it’s large power output. If it is say a naturally aspirated car with the same 500HP, the torque curve is going to be way different, and it will greatly effect PERFORMANCE. Essentially, get your head away from thinking these peak numbers tell you performance. They don’t.

DeWayneV8 > Axial 05/12/2015 at 10:25

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I think what it really comes down to is that horsepower is the real indicator of vehicle performance. Someone could say their engine makes 600 lb-ft, but it might redline at 3000 rpm and thus not be very “quick” (point A to B). This is why diesels are slow.

Axial > DeWayneV8 05/12/2015 at 10:32

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Which is true. It’s also why racing tends to emphasize RPM, though I also think they do so because gobs of low-end torque is bad for hooking up. Over time, you’ve accelerated too fast with a lot of low-end torque. Instantaneously, you’ve started moving too forcefully. Less torque on the low-end means you can more readily mash your foot in, hook up, and rocket off.

Axial > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 10:36

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The key word there is potential . If you don’t let the engine spin up sufficiently, then all that potential is wasted and suddenly you have a 1,000 lb. ft. beast taking 5 minutes to reach 30 miles an hour.

Rusty Vandura - www.tinyurl.com/keepoppo > DeWayneV8 05/12/2015 at 10:37

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I’m going to ask an engineer friend about this, not because I have anything to prove, but because I’ve got some things to learn.

And as for slow diesels...

DeWayneV8 > Mattbob 05/12/2015 at 10:37

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Again...the graph, you can see torque AND RPM. In non specific terms, horsepower. That’s why the torque graph is useful.

I do agree about laggy turbo engines and things such as that, average horsepower over the RPM range between shift points is the real indication of vehicle performance. Still, it’s about the horsepower.

Sir_Stig: and toxic masculinity ruins the party again. > DeWayneV8 05/12/2015 at 10:37

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So you are saying is that if I used a 1:100 gear ratio on my 100lb-ft, 53 rpm engine I wouldn’t get 100 hp and 1 torque at 5252 rpm?

Axial > BiTurbo228 - Dr Frankenstein of Spitfires 05/12/2015 at 10:38

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Nah, it wouldn’t be hard to do with a dyno chart, especially if you have its outputs in digital form. Just look at the resultant torque figures for each section, perform a regression on it, and then integrate that regression through whatever means you like (I’d do it by hand for funsies).

Presto, area under the curve!

DeWayneV8 > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 10:39

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I am an automotive engineer! I design engines for a living.

DeWayneV8 > Sir_Stig: and toxic masculinity ruins the party again. 05/12/2015 at 10:41

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If you use 1:100 gear ratio on the 100 lb-ft engine you’d get 1 lb-ft of torque at 5252 RPM.

hp = (torque x rpm)/5252

So you’d still have 1 hp.

DeWayneV8 > Axial 05/12/2015 at 10:43

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I think somewhat that’s true (see: Hellcat), but if you gear the vehicle for the correct wheel speed in the low and high torque engines the one with more power will be faster. HP never changes with gearing, the torque value does. If an engine has too much low end torque, run less gear!

Axial > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 10:50

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He’s an automotive engineer, and I’m a systems engineer. We are both credible sources of information, though him more so than myself if you want automotive specificity.

Sir_Stig: and toxic masculinity ruins the party again. > DeWayneV8 05/12/2015 at 10:50

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Ah, so I’m just silly. in my defence, it’s early. I still would say on average most people feel momentary acceleration more than the overall speed in any given car.

Axial > DeWayneV8 05/12/2015 at 10:53

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True, but then you are running into stress (and comfort) problems with the materials having such a shock when you stuff your foot in and they are suddenly exposed to a massive amount of force. That, combined tons of with low-RPM torque usually being a road car thing, is why we still see low gears with such engines.

DeWayneV8 > Sir_Stig: and toxic masculinity ruins the party again. 05/12/2015 at 10:53

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That may actually be true, and partly why laggy turbo engines feel exciting when they finally “hit”.

For me though, I want to beat someone from point A to point B. The proverbial stoplight drag race if you will.

DeWayneV8 > Axial 05/12/2015 at 10:58

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Yea, you’re right, particularly with differentials. It’s so tough to design a differential with a high torque capacity and good NVH.

Rusty Vandura - www.tinyurl.com/keepoppo > DeWayneV8 05/12/2015 at 11:06

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No affront intended; sorry if one was perceived.

I teach 7th grade math. Wanna swap jobs for a term?

It seems to me that there ought to be zero room for debate in any of this, but a framework of clearly defined, well understood principles.

To me, the torque spec idea has always made sense: apply torque, accelerate the car.

Rusty Vandura - www.tinyurl.com/keepoppo > Axial 05/12/2015 at 11:12

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No affront intended; I did not mean to imply that either of you were not credible.

It seems to me that from an academic standpoint, there should be no debate and that the physics ought to be exhaustively defined and framed and you and DeWayne ought to be telling the rest of us how it works, and that’s that.

As I understood things, the work is accomplished by applying force. (Horsepower generated by applying torque?) The rest, perceived acceleration, is all affected by gear ratios, tire friction, air resistance, inertia (vector function of mass?), momentum (scalar?), and whatever else.

DeWayneV8 > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 11:14

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None taken!

You’re right, apply torque and you get an acceleration. Thing is....it takes time for acceleration to equal velocity. It takes time for velocity to equal displacement.

You can apply torque, but you need displacement to do any work. That rate at which you output that work is power. F = MA is an instantaneous value, it doesn’t give an indication of what is happening over a period of time.

Rusty Vandura - www.tinyurl.com/keepoppo > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 11:14

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Which is not to suggest that your comments ought to be somehow limited. I am a teacher and a parser and I get caught up in definitions. If I were less jalop, I might have made a successful attorney. But then I would have to repent constantly...

DeWayneV8 > heeltoehero 05/12/2015 at 11:15

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Absolutely true, but that math equation gives you a picture of how quickly something will be displaced to another point. The torque value alone does not do that.

Axial > DeWayneV8 05/12/2015 at 11:15

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NVH: Pick two. :p

Personally, I’m totally okay with gear noise. And chain noise. They sound cool to me. Unfortunately, I don’t drive sales. Ha!

DeWayneV8 > Axial 05/12/2015 at 11:18

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I like hearing the mechanical pieces too. Unfortunately, the average person makes a connection between silence and quality. “Perceived quality” is a nice way of saying “what the great unwashed think quality means”.

Mattbob > DeWayneV8 05/12/2015 at 11:19

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so you don’t get it. Okay. thats fine.

Axial > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 11:24

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It is and it isn’t true, which is why there remains confusion. It all depends on how you are observing the system. At any given instant during its operation, you can say that the torque is accelerating the car. But the world doesn’t run on discrete instants; that would be merely three dimensional. It has a fourth dimension: time. Everything we experience, we experience over time and time is not discrete. Over time, the application of force (torque in this case) is called power, and so it’s power that ultimately accelerates the car.

So if you want to take an instantaneous slice of time for the operation of the vehicle (a slice is called an impulse and is some amount of time that is greater than zero by an infinitesimally small amount), it’s torque providing acceleration while power at that impulse is how fast you were already going. If you are observing the system in its real application, then it’s always power doing the work, because power and work are literally the same thing and the movement of the car is just the movement of the engine crank-shaft being translated through the drive train and the wheels.

DeWayneV8 > Mattbob 05/12/2015 at 11:25

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I do get it, but whenever you say “torque curve” it’s really the horsepower curve that matters. Now I know mathematically that hp is derived from torque, but it’s also derived from angular velocity as well. That matters.

I’ve driven many, many vehicles. I design engines/powertrain systems for a living. I deal with things like transient response, time to max BMEP, etc.

I agree with you, the average over a given RPM range (probably the rpm between shifts) is the real indicator of vehicle performance. I maintain that it’s the average power over that range that matters though. Torque is static, driving is dynamic like you said.

McLarry > DeWayneV8 05/12/2015 at 11:27

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Torque is force. Horsepower is power (force*distance/time). I’d say it’s more accurate to say the torque moves the car, but horsepower allows application of that torque over a distance in a given amount of time (ie speed). You can’t really decouple them because one effectively represents the application of the other.

Axial > Rusty Vandura - www.tinyurl.com/keepoppo 05/12/2015 at 11:30

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Lawyers are engineers with no conscience. :p

Also, if you are a good teacher (and I’m going to assume you are), we need way more of you than we do lawyers. I loved math in 7th through 12th grades (6th grade had a teacher who struck me as a pedophile), and it was good teachers that made me do so. Without good teachers in maths and sciences, kids won’t want to take to them and that’s sad because the things you can do with numbers are astonishing.

So thank you for being a teacher and not a lawyer, despite a paycheck that is lower by an order of magnitude. :)

DeWayneV8 > McLarry 05/12/2015 at 11:36

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Well, it just shows you need a moment and angular velocity from an engine to beat your buddy in a stoplight drag race. Horsepower.

I think people hold the misconception that torque will make you cover ground quickly by itself.

Mattbob > DeWayneV8 05/12/2015 at 11:36

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are you saying that torque has nothing to do with angular velocity? How can you say that when torque is what drives angular acceleration? to pull from wikipedia: For two-dimensional rotational motion (constant ), Newton’s second law can be adapted to describe the relation between torque and angular acceleration:

,

where

is the total torque exerted on the body, and

is the mass moment of inertia of the body.

alpha being angular acceleration.

TJDMAX > DeWayneV8 05/12/2015 at 11:40

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You’re not really 100% correct here. Torque is indeed what accelerates a car. Torque like you said is a rotational force so its the measurement of the amount of force that your crankshaft sends to the transmission and thus your wheels. Its all rotational movements and thus torque is a very valid measurement for how a car can “move”. Yes you can apply 200-lb-ft to a breaker bar but the difference is you can do it once and its an impulse force. Where as your motor in your car is constantly making torque (assuming a constant RPM).

Horsepower isn’t the end all measurement for a car’s performance. There is the old saying that torque is acceleration and horsepower is top speed. Of course gearing is a huge factor as are many other things like aerodynamics and tires and weight but on a simplistic level torque is a very good estimation of a vehicles acceleration potential.

Horsepower and torque are going to describe two different performance characteristics of a vehicle. Go drive any diesel vehicle and you will understand what i’m talking about. Diesels for the most part always have a low horsepower rating to their respective torque rating. If you just looked at the horsepower number you wouldn’t think a diesel would be a quick car and in a top speed race they typically aren’t, but their torque makes them much quick accelerating than their horsepower number alone would have you believe.

Axial > DeWayneV8 05/12/2015 at 11:42

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Yup. That’s why I cringe whenever somebody goes off on how the “build quality” of a particular car is so great when only considering materials used on the interior or panel gaps on the exterior. Just because it looks nice, doesn’t mean it is nice. Looking at the reliability track records for the cars people typically rave about “great build quality” for, I shake my head. That Toyota Camry may be an ugly, plastic shitbox, but it’s a shitbox that will go for 200,000 miles without breaking and with minimal maintenance and with more than acceptable levels of comfort. That’s build quality. That BMW? Yeah, it looks nice and seats marginally better than the Camry, but it’s worn out at 80,000 and had frequent repairs leading up to that point.

Sorry for the mini-rant. It’s one of those gear-grinding things with me.

DeWayneV8 > Mattbob 05/12/2015 at 11:42

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Again....acceleration and velocity aren’t the same thing. You have to apply the acceleration for a period of time before it becomes velocity. Torque is an instantaneous measurement, covering ground includes time.

Standing on the ground force is being applied to my body by both the ground and gravity, but I’m not moving anywhere, no work is being done. Torque is meaningless BY ITSELF.

DeWayneV8 > TJDMAX 05/12/2015 at 11:46

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This is why I edited the original post to clarify, torque only provides an instantaneous acceleration. Covering ground is based on horsepower. Racing is determined by covering ground.

Maybe a person might “feel” torque, but they won’t beat their friend in the other lane without more horsepower.

DeWayneV8 > TJDMAX 05/12/2015 at 11:48

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Instantaneous acceleration is meaningless, you need to be able to apply acceleration with corresponding velocity. Torque means nothing without wheel speed, horsepower.

Rusty Vandura - www.tinyurl.com/keepoppo > Axial 05/12/2015 at 11:50

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It’s kind of you to say those things; thank you. I especially like to encourage my female students in their math studies. We could have a separate conversation sometime about what’s wrong with public education in the United States. You said maths ; are you British?

My thing is, as an educator, I like to package things neatly. As I try to consume what’s been written in this thread, for the sake of the avid amateurs like myself, there ought to be a moderator, a synopsizer. But I’m hanging in there.

I intended to study engineering initially, but the other students were very competitive and I did not enjoy that aspect. So I studied math instead, failed at several jobs, and became a teacher. Isn’t that how it’s supposed to go?

But there is a deep irony in my career choice: in high school, I never passed Algebra. I like to say, now, that I never had me as a teacher, either.

TJDMAX > DeWayneV8 05/12/2015 at 11:52

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Sure the general public may be lacking some grasp on physics but i think you are as well right now. Horsepower doesn’t accelerate the vehicle. That in fact is torque. A rotational force (what torque is) is what spins the wheels. So If someone told me how much torque their engine had I would definitely know right away what kind of acceleration it would have. You can’t look at just torque or horsepower to get a complete picture of a vehicles performance but in terms of getting a vehicle moving initially torque is what does the trick.

Mattbob > DeWayneV8 05/12/2015 at 11:52

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no. You apply force for a period of time which in turn becomes acceleration, which is a change in velocity. Lets lay this out. Torque creates angular acceleration. Angular acceleration is a change in angular velocity. wheels turn angular velocity into linear velocity. Torque creates changes in linear velocity. There are no major logical leaps here. Changes in linear velocity matter in the performance of a car.

TJDMAX > DeWayneV8 05/12/2015 at 11:56

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You also wouldn’t be able to beat your friend if you could never make it off the line because you had no torque. Assuming a scenario where you weren’t traction limited, the higher torque car is going to accelerate faster, and thus initially cover more ground. Yes horsepower is important but for stop and go traffic, or cruising around town, or any acceleration your torque figure is what you are feeling. I agree that you can’t have one or the other, but you’re not understanding what torque does. When you drive your car around at legal speeds you “use” the torque and thus “feel” the torque more than your horsepower figure.

DeWayneV8 > Mattbob 05/12/2015 at 11:59

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No....force for a period of time becomes velocity. Acceleration rate is instantaneous. Acceleration is just force with mass taken into account.

Yes, torque creates changes in velocity....given time.

You are confusing acceleration rate with work. You need velocity and acceleration to move something, acceleration by itself is meaningless.

An engine needs to be able to apply a force while maintaining a velocity, just force isn’t enough (see: breaker bar example). High torque doesn’t mean an engine can do both. Thus....torque doesn’t indicate how quickly a vehicle will be moved from point A to B. It just indicates how much force can be applied STATICALLY, not while the engine is turning.

McLarry > DeWayneV8 05/12/2015 at 12:01

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Well yes, you need something to apply the torque, but torque is still what’s pushing the car forward at any given moment.

I agree torque doesn’t make you cover ground quickly (ie torque != speed, as per your title), but it does make you accelerate quickly (arguably still not by itself), and that’s usually what people are concerned about IMO. I think it was Enzo Ferrari who said “Horsepower sells cars, torque wins races.” I’d agree with you that his statement is perhaps incomplete, but I think we can give the old man the benefit of the doubt that he’s not saying torque to the exclusion of HP.

DeWayneV8 > TJDMAX 05/12/2015 at 12:03

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High torque just means it can have an instanteous acceleration rate that is high. It doesn’t mean the engine can apply force and have velocity at the same time....that’s horsepower.

I mean, cool, you have a ton of torque so your instantaneous acceleration value will be high, but it doesn’t mean you’ll ever have any wheel speed.

Covering ground is about power. Energy.

DeWayneV8 > McLarry 05/12/2015 at 12:06

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It doesn’t win races....if geared correctly the higher horsepower engine will make more wheel torque because horsepower is what matters. When you race your buddy at a stoplight, you don’t take a g-meter and say “look I had the most acceleration of the line!”, you see who gets to point B first. Horsepower.

Rusty Vandura - www.tinyurl.com/keepoppo > DeWayneV8 05/12/2015 at 12:11

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Thanks. Would you consider shooting me an email? oliphant.chuckerbutty@gmail.com

TJDMAX > DeWayneV8 05/12/2015 at 12:11

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For the sake of not arguing the same point....Read this.

https://danielmiessler.com/study/horsepow…

Horsepower is a factor of torque...among other things....RPM’s being critical too. But horsepower is a made up figure. And its derived by measuring the torque. So if you don’t understand torque you don’t understand horsepower and on the flip side if you know what horsepower is (or so you think) then you should also realize that its a factor of torque and essentially its a number to quantify the torque of the engine after its gone through the transmission and drive train and wheels.