MautoK
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| posted on 11/9/09 at 04:28 PM |
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The imperial unit of torque is 'ft lb'.
Tq is the product of force and distance.
It most definitely NOT ft/lb as is so often seen.  Pet hate #1!
John.
He's whittling on a piece of wood. I got a feeling that when he stops whittling, something's gonna happen. (OUATITW/Cheyenne)
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Ninehigh
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| posted on 12/9/09 at 07:07 AM |
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Torque is what women do all day, and you can spot the amateurs they have to stop to breathe (seriously I watched 2 girls blah at each other for 50
mins non-stop, and I mean NON stop).
My version of the layman's explanation would be this:
The higher the torque the better you accelerate at 1500-3000rpm, ther higher the bhp (the amount of power to break a horse  ) the better you
accelerate at 3000+rpm
Torque is nicer cos you're not screaming the crap out of your engine and you can laugh at Saxo boy and his mates as you glide past
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Ivan
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| posted on 12/9/09 at 07:40 AM |
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It's a common misconception that torque dictates acceleration - if that where true then turbo diesel cars with their massive torque would p1ss
all over F1 and BEC cars with minimal torque. So torque dictates things like climbing or towing but not acceleration.
What dictates acceleration is rate of work, i.e. horsepower which for the same torque is lower at low revs and higher at high revs, which is
why BEC's and F1's that rev high to get good horsepower from low torque accelerate like stink.
To belabour a point - what would accelerate faster - a Busa in a Locost or a VW turbo diesel in a locost presuming the BEC is weighted to match the
deisel 7 - the one makes most probably 3 X the torque and the other 50% more HP. I'm willing to bet its the Bussa motored car.
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Ninehigh
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| posted on 12/9/09 at 07:43 AM |
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quote:
Originally posted by Ivan
To belabour a point - what would accelerate faster - a Busa in a Locost or a VW turbo diesel in a locost presuming the BEC is weighted to match the
deisel 7 - the one makes most probably 3 X the torque and the other 50% more HP. I'm willing to bet its the Bussa motored car.
Most probably, but then if you limit both cars revs to the peak torque limit?
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The Black Flash
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| posted on 13/9/09 at 08:35 PM |
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quote:
Originally posted by Ivan
It's a common misconception that torque dictates acceleration - if that where true then turbo diesel cars with their massive torque would p1ss
all over F1 and BEC cars with minimal torque. So torque dictates things like climbing or towing but not acceleration.
Quite wrong I'm afraid.
Torque at the wheels determines acceleration. Nothing else.
You are right that power is a better measure of performance, but that's because it takes rpm into account.
Edit: Someone had already explained it better.
A really good discussion of torque vs power here: http://www.vettenet.org/torquehp.html. Well worth reading.
[Edited on 13/9/09 by The Black Flash]
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prawnabie
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| posted on 13/9/09 at 08:43 PM |
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Im with the brick wall!
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nigel.hillier
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| posted on 14/9/09 at 03:11 AM |
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Torque
In simple terms - What it actually means to you as a driver (rather than a complicated mathmatical White Paper)
Torque is the only thing the engine produces. This varies during the RPM range.
At any given RPM more Torque is Better (more Power).
You as a driver you want Power/Kilowatts.
Power (Kilowatts/Horsepower) is simply the amount of Torque multiplied by the RPM of the engine divided by a Constant (5252 from memory this is a
mathmatically generated number from last century)
Torque x RPM / Constant = Kilowatts
If you want to make more Power you must do one of 2 things (or both is even better)
1) Produce more torque at any given RPM
2) Rev your engine to higher RPM (so long as torque does not drop off significantly)
Example 1 - High reving engine (low torque)
You engine produces 100 units of Torque at 8,000 RPM = 152 kilowatts
Example 2 - Low reving engine (high torque)
You engine produces 1000 units of Torque at 800 RPM = 152 kilowatts
Both examples will deliver to you the same power. It is just how they get there that is different.
High torque low rpm is better for engine life but that is another discussion.
[Edited on 14/9/09 by nigel.hillier]
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Ivan
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| posted on 14/9/09 at 07:41 AM |
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quote:
Originally posted by The Black Flash
Quite wrong I'm afraid.
Torque at the wheels determines acceleration. Nothing else.
You are right that power is a better measure of performance, but that's because it takes rpm into account.
Quite right - but torque is a very poor measure of a car's potential performance whilst horsepower (which takes into account peak torque
location and spread) is an excellent indicator - that's why it's dangerous to choose a motor for performance based purely on torque - if
you did that there would be no BEC's and every racing car would be running low revving turbo diesels.
Your refference articles are good but tend to basically support the HP argument for assessing performance. (Given that it's all about
gearing)
[Edited on 14/9/09 by Ivan]
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Antnicuk
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| posted on 14/9/09 at 05:07 PM |
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i think its explained above but i dont understand it, why does the bhp and torque curve cross at 5250 rpm on every car i have had dynoed,???
I have 350 torques and its more than enough  it certainly takes the wall a ong way!!!
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
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MikeRJ
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| posted on 14/9/09 at 05:52 PM |
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quote:
Originally posted by Antnicuk
i think its explained above but i dont understand it, why does the bhp and torque curve cross at 5250 rpm on every car i have had
dynoed,???
Because for power in bhp and torque in lbft:
Power = ( RPM * Torque ) / 5250
Rearranging gives:
RPM = ( Power / Torque ) * 5250
So, when Power(bhp)=Torque(ftlb) the right hand side of the equation equates to 5250.
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simonk
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| posted on 14/9/09 at 08:19 PM |
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Hi all
It was posted further up the thread but I also found this same torque / horsepower primer some years ago and it really is a good explanation. If you
read it carefully it should only take 15 minutes and the writer has put it in 'car' language and as such it's very readable - solves
and answers all the arguments and questions in this thread...
http://www.vettenet.org/torquehp.html.
Cheers
Simon
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iti_uk
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| posted on 14/9/09 at 08:41 PM |
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Torque isn't a Force!!! It's a moment!
M = F*d
(F being force applied, d is perpendicular distance from the rotational axis at which the force is applied)
The fact is, it's the shape of and area under the torque curve which is important. Peak numbers are only for impressing people with.
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MikeRJ
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| posted on 14/9/09 at 08:58 PM |
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quote:
Originally posted by iti_uk
The fact is, it's the shape of and area under the torque curve which is important. Peak numbers are only for impressing people with.
As I mentioned above, the only reason it is important is due to the limitations of the transmission system.
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liam.mccaffrey
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| posted on 15/9/09 at 09:21 AM |
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torque is rotational force (moment  )-full stop end of story
power is a rate at which work is done due to force-full stop end of story
I didn't mean this to sound curt, sorry
[Edited on 15/9/09 by liam.mccaffrey]
Build Blog
Build Photo Album
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flak monkey
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| posted on 15/9/09 at 09:23 AM |
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quote:
Originally posted by liam.mccaffrey
torque is rotational force (moment )-full stop end of story
power is a rate at which work is done due to force-full stop end of story
Nicely put
Sera
http://www.motosera.com
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02GF74
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| posted on 15/9/09 at 10:01 AM |
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quote:
Originally posted by nigel.hillier
Example 1 - High reving engine (low torque)
You engine produces 100 units of Torque at 8,000 RPM = 152 kilowatts
Example 2 - Low reving engine (high torque)
You engine produces 1000 units of Torque at 800 RPM = 152 kilowatts
Both examples will deliver to you the same power.
let's say you have these two engines in identical cars and you want to drive them up an increasingly steep hill, keeping rpm the nbad torque the
same, if that is possible.
which one wil get further?
which one will get there faster?
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alistairolsen
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| posted on 15/9/09 at 10:10 AM |
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do you mean constant, or the same?
if you mean constant then you would use different gear ratios so that the torque and speed at the wheels was the same and hence both would be
identical.
My Build Thread
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phelpsa
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| posted on 18/9/09 at 11:49 AM |
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It's all to do with power, torque means fook all once gear ratios are involved.
Power is the amount of energy transferred in a certain time period. You apply more energy per second and you will accelerate faster.
Area under the power graph is how much energy is transferred as you rev the car from 0-the rev limit. This is what makes the difference, the more
energy you can transfer in that period the more speed you will gain.
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