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What are Torque and Horsepower really?

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Killrob

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Post Thu May 01, 2014 6:15 am

Re: What are Torque and Horsepower really?

V10I10ilove10cyl wrote:Isn't torque pretty much how much force is generated to push A car in a given direction?

No it isn't. Please check the resources provided in this thread to get a better understanding of what torque is.
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Post Thu May 01, 2014 10:38 am

Re: What are Torque and Horsepower really?

Killrob wrote:
V10I10ilove10cyl wrote:Isn't torque pretty much how much force is generated to push A car in a given direction?

No it isn't. Please check the resources provided in this thread to get a better understanding of what torque is.



Well, Torque at the wheels kind of is, but torque at the engine is an entirely different matter. Gear ratios matter, yo.
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Killrob

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Post Thu May 01, 2014 5:20 pm

Re: What are Torque and Horsepower really?

Daffyflyer wrote:Well, Torque at the wheels kind of is, but torque at the engine is an entirely different matter. Gear ratios matter, yo.

Torque is not a force, so it doesn't push anything, not even at the wheels. At the wheels, torque is converted back to a force, which then pushes the car forward, confusing those things is at the core of the general misconceptions surrounding this topic.
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Post Thu May 01, 2014 5:54 pm

Re: What are Torque and Horsepower really?

Killrob wrote:
Daffyflyer wrote:Well, Torque at the wheels kind of is, but torque at the engine is an entirely different matter. Gear ratios matter, yo.

Torque is not a force, so it doesn't push anything, not even at the wheels. At the wheels, torque is converted back to a force, which then pushes the car forward, confusing those things is at the core of the general misconceptions surrounding this topic.



Ahh, yes once you go through the final step of Torque at the wheels = Force at the outside of the wheel, true that.
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Post Fri May 02, 2014 3:50 am

Re: What are Torque and Horsepower really?

As far as i know Horsepower is happiness you can buy, Torque just means you wait less for it :D
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Post Fri May 02, 2014 9:35 am

Re: What are Torque and Horsepower really?

Killrob wrote:
V10I10ilove10cyl wrote:Isn't torque pretty much how much force is generated to push A car in a given direction?

No it isn't. Please check the resources provided in this thread to get a better understanding of what torque is.

Will do but I didn't claim to be an expert on it I just in a sense threw my understanding of it out there.
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Post Wed May 14, 2014 1:40 pm

Re: What are Torque and Horsepower really?

I am still wondering what an engines dyno should look like. Is the torque supposed to run with the power? What if it stays flat the whole time (within 100 units?
When adding a turbo what do you want the boost pressure chart to look like. Do you want it to be a plateau or a hill? Peak at the last third or can you have the turbo limited to have a line that extends past the redline?
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Post Wed May 14, 2014 2:01 pm

Re: What are Torque and Horsepower really?

KielEire wrote:I am still wondering what an engines dyno should look like. Is the torque supposed to run with the power? What if it stays flat the whole time (within 100 units?
When adding a turbo what do you want the boost pressure chart to look like. Do you want it to be a plateau or a hill? Peak at the last third or can you have the turbo limited to have a line that extends past the redline?

This probably does not belong in this thread.
Post pictures of the dyno chart, and there will be many people to analyze your engine.
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Post Tue Jul 01, 2014 7:33 am

Re: What are Torque and Horsepower really?

Killrob wrote:Hey guys!

I did go on a little explanatory rant in the beta forum some time ago... and now that its clean-up time there, I'd like to post it here instead:

The only thing you feel while driving a car (affecting acceleration) is power at the wheels. Torque is convertible, power is not and can only be lost while finding it's way to the wheels. Thus, for measuring performance, torque is a useless, insanely overrated stat which almost everyone gets wrong - including car magazines and people who should know better. Hell, we got some of the most well car-educated people here on these forums and even most of them don't get it right, being brainwashed by the torque-nonsense.

My normal example for showing the point is the following example: which engine makes a car accelerate faster?
A: An engine that makes 800 Nm at 2000 RPM
B: An engine that makes 200 Nm at 8000 RPM

It is a triple trick question of course! First you say: hell, I'm not stupid, they are the same of course. But you are still not quite right if you say that...
How much capacity do you need to make 800 Nm of torque? Well, say 8L. How much for 200 Nm? In this analogy, probably 2L.
Which engine would weigh more? Probably the 8L engine. So which engine would make a car accelerate faster? The lighter one with the same performance...
or would it? No, definitely not in the hands of an unskilled or even average driver.

If you put your foot down while cruising with engine A, hell breaks loose. If you do the same with engine B, basically nothing happens.
It is a question of how accessible the engine's power is, which doesn't matter if you are Michael Schumacher, but does for the average, torque-brainwashed Joe.

In the car designer we will have a stat related to "ease of driving", and this whole thing above will affect that stat. Should the engine be held responsible for the lack of driver skill? No, at least I don't think so - which also explains why I don't really want to see torque matter in the engine designer scenarios. Should it matter once you design the car? Absolutely!

With a gearbox being an additional layer of abstraction and most people not understanding the underlying principles, I can see why people equate torque with power... although it does make as much sense as equating Mussolini with porridge.

Cheers guys!
/Killrob

anyway, both are 300HP-producing banger, no?
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Post Fri Jul 04, 2014 6:53 pm

Re: What are Torque and Horsepower really?

darkjedi wrote:basically the electric motor is the easiest to drive :D. constant torque from 0-6000 rpm


zero to infinity!

only limited by amperage!

oh do i love electricity... mmmmm...

the average gasoline vehicle is about 20% efficient, while the average all=electric vehicle can bu up to 90% efficient!

myself, I am working on building a hybrid-electric vehicle, which should be about %50 efficient...
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Post Sat Jul 05, 2014 4:39 am

Re: What are Torque and Horsepower really?

Which is totally wrong ;)

Electric engines dont have constant torque - they have constant power. A 3kW electric asynchronous engine always has 3kW, and the most used type of electric engine is the asynchronous 3-phase AC induction motor. Its the one with the best torque curve - the reason they have constant torque in cars is that induction motors have a kinda high starting torque that can rip the gearbox apart - it can be 3x higher than the normally rated torque.

I think the Tesla S 60 uses a max 225kW Engine - thats the power it has from 5000-8000RPM - which is the maximum power the engine has. As i already said, AC motors have constant power... and 225kW@2000RPM results in... 1070Nm Torque! And at a normal "idle" it would be twice as high, so do you really want to construct a gearbox that can withstand the massive torque, or just take a way cheaper power limiting unit ? Trust me, its easier to take a frequency converter that has a power limiting feature instead of a normal frequency converter and a ultra-durable gearbox.


Cheers :)
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Post Sat Jul 05, 2014 8:23 am

Re: What are Torque and Horsepower really?

pyrlix wrote:Which is totally wrong ;)

Electric engines dont have constant torque - they have constant power. A 3kW electric asynchronous engine always has 3kW, and the most used type of electric engine is the asynchronous 3-phase AC induction motor. Its the one with the best torque curve - the reason they have constant torque in cars is that induction motors have a kinda high starting torque that can rip the gearbox apart - it can be 3x higher than the normally rated torque.

I think the Tesla S 60 uses a max 225kW Engine - thats the power it has from 5000-8000RPM - which is the maximum power the engine has. As i already said, AC motors have constant power... and 225kW@2000RPM results in... 1070Nm Torque! And at a normal "idle" it would be twice as high, so do you really want to construct a gearbox that can withstand the massive torque, or just take a way cheaper power limiting unit ? Trust me, its easier to take a frequency converter that has a power limiting feature instead of a normal frequency converter and a ultra-durable gearbox.


Cheers :)

Indeed. Continuing with the Tesla example (uh oh, you got me started on Tesla!), what people constantly make a mistake about is that they think that the car has max horsepower from 0 RPM, whereas it actually has max torque from 0 RPM. If you look at the dino run they did of a P85+ here (https://www.youtube.com/watch?v=xVmdr5nUArQ), by looking at the chart you can see how the horsepower builds continuously. Torque is not displayed, but I believe it is at maximum from 0-5200 RPM.

Also, fun fact about these Tesla cars (Roadster and Model S): Both were supposed to have a two speed rather than one (which would massively increase the top speed), but the instant torque kept breaking the gearbox.
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Post Sat Jul 05, 2014 8:53 am

Re: What are Torque and Horsepower really?

Electric Motors are a bit complicated, in my apprenticeship we pretty much talked about them for almost two months... and even then some people did not fully understand them :)

However, yeah the power has to be limited a lot, but if you do some calculations you see that the torque is pretty much constant until 5200, then it drops. And the fun fact is infact the problem you may encounter when you simply change your lets say 5.8L V8 to a 225kW 3-phase AC motor - that thing WILL break your gearbox. Starting torque is massive... upto 220% of the rated torque at rated RPMs. Basically: 4300NM@500RPM - but at the moment of starting it, it can have over 9000NM@500PRM for some seconds. Electric Motors are crazy and Teslas awesome!

Here just a small article about the AC induction motors: http://en.wikipedia.org/wiki/Induction_motor It may blow your head, but its kinda interesting :)
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Post Sat Jul 05, 2014 9:26 am

Re: What are Torque and Horsepower really?

I went up against a p85+ at a drag strip in my Mustang. Were it a quarter mile, there would obviously be no comparison, but in an eighth, and with me on cold tires, he actually beat me through the 60 footer. I do believe that I could beat him given a second chance in the same measurement, but every time? No. He was just way too consistent.
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Post Wed Jul 30, 2014 6:02 pm

Re: What are Torque and Horsepower really?

cheers
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