Is Power (rwkw) Figure Everything? Why Are People So Hung Up On Kw Figures

[Wacky Dee]

here's more food for thought: WTF? I don't get what you're saying or inferring and I don't think anyone else does either. Or did you just want to post your VL times?

[zebra]

He is saying that having less power with the 3040 made a better drive compared to the big one he put on.

[Birds]

As already said a hundred times, peak power isn't everything. Nothing is everything. Neither is torque, neither is brakes, or suspension, or gearing, or aerodynamics. There are too many variables at hand and too many situations. This is why engineers have jobs...because there is no one setup best for everything. Your evidence here is that even V8 Supercar teams change an entire vehicle's dynamic settings to suit certain racetracks. I see alot of neglect for mention of gearboxes and diffs in this thread, with regard to explaining power delivery, and that's just one major variable out of hundreds. Anyone wanting to understand why peak power isn't everything should do some reading on fundamentals of torque and power...and the workings of the complete vehicle package in general, because it's too hard to explain it all within the confines of a post. It doesn't take long and you will be much better for it, understanding the physics (that way you can answer all these questions for yourself later instead of rote learning the answers). Wikipedia is a good start

[PM-R33]

Agreed. This is a far, FAR to complicated matter to be discussing in posts and trying to explain in detail. Hence why people write books on it.

[zebra]

While what the 2 guys above said is very true, the lack of available diff gears or gearbox ratios (that dont cost a squillion dollars)

Means we are kinda stuck with trying to have the best all round engine package. (talking about engines only here)

Unless we go stick a Ford 9" diff under the bum, where ratios are on the shelf from 2:1 all the way to 7:1 in 0.01:1 increments.

[Harey]

For a fast car you want exactly what I said, torque to hit its maximum as early as possible and to hold flat for as long as possible (for as many rpms as possible).

Vehicles good for towing have a similar characteristic, they reach maximum torque very early in the RPM range, however they don't hold flat for a long rpm and drop off very quickly as revs climb. (Think of a diesel van that loses all power at 3500rpm).

So have a look at this very quick dodgy paint graph I did. In no way is this accurate or based on anything, it's mearly to help understand it all and to get a visualisation. (I swear, if this graph starts an argument....)

You can kind of see a basic relationship of what certain "general" cars have. Obviously every car is different and therefore every torque graph will be different. But the basics still remain similar.

That best possible scenario in red would also make a bajillion kw of power. You are separating them too much imo

[PM-R33]

Hahaha yeah I know, it was a very unrealistic graph. Just wanted to show a "ceiling value" so to speak.

From some quick maths it appears to make 1925kw

Edited October 26, 2010 by PM-R33

[Rolls]

PM-R33 is right. dyno's torque measurement is highly suspect. and the simple fact is power = torque. yes the exact numbers can vary but there is a very fixed relationship between power, torque and RPM. so unless your car makes it's 170kw at 2,500rpm it's torque production will not be fantastic. given all our skylines rev to somewhere between 7500 and 8500rpm and all make peak power somewhere above 6,000rpm the amount of torque produced wont vary massively form car to car with similar amounts of power. ie. if power is the same, rpm is the same. torque will be pretty close. you can move the curve around a bit with different tuning techniques and different parts but the peak won't change too much.

Such a misleading statement! The relationship between power, torque & speed is fixed, I'll take the one that creates the greatest tractive effort (force at the wheels) over the operating rev range courtesy of that thing that sits behind the motor.

It is refreshing to read posts like this were people actually understand the relationship between power and torque and know what they are talking about. So many people seem to think torque and power are different unrelated things, where you can have the same power but massively varying levels of torque, as mentioned this is a load of crap, if you have x power at y rpm, you will always have z torque.

That quote about torque winning races is a load of shit, if you make 900000nM of torque at 2rpm and it drops off to 100nm by a very low redline (lets say 2000rpm) you will still only make something like 50kw at the wheels and you wont win the race, if you make only 100nM of torque but you can rev the engine to 18,000rpm you will make something like 500hp and will clearly win the race. Power wins every single time, torque only wins if you make it at high rpm.

"The only reason I lost was because currently my maximum torque is at around 4000rpm, however next week I'll alter my setup and get it 1500rpm sooner and smoke you fool!"

Hmmm doesn't have the same ring to it as others lol.

This is wrong, if you made the same maximum torque 1500rpm earlier you would make LESS power and be SLOWER, more torque = more power, same torque at higher rpm = more power.

You want to make as much torque as possible, and hold it for as long as possible, but being as torque is so obviously confusing for everyone it is far simpler to just say make the most power possible and for the largest spread of rpm as possible. Torque can be completely disregarded from the conversation as all it does is serve to confuse people, power is all you need to know.

its also what breaks diffs and gearboxes...

Also if torque is the be all end all, how come a v8 supercar WITH 5-600NM is faster than a xr6t with 1200NM @ 2000

Because people are stupid and torque isn't the be all and end all, F1 cars have even less torque and are even faster.

Edited October 26, 2010 by Rolls

[PM-R33]

This is wrong, if you made the same maximum torque 1500rpm earlier you would make LESS power and be SLOWER, more torque = more power, same torque at higher rpm = more power.

That is assuming the torque curve has shifted completely to the left. My silly comment was meaning that the torque curve has remained the same, only now rises and reaches its maximum sooner - Think about adding a square to the front or a rectangle

But I know what you mean. I should have worded it better.

You want to make as much torque as possible, and hold it for as long as possible, but being as torque is so obviously confusing for everyone it is far simpler to just say make the most power possible and for the largest spread of rpm as possible. Torque can be completely disregarded from the conversation as all it does is serve to confuse people, power is all you need to know.

Hence my little graph showing torque reaching its maximum for as long as possible and than holding that maximum value for as long as possible

Edited October 26, 2010 by PM-R33

[zebra]

Because people are stupid and torque isn't the be all and end all, F1 cars have even less torque and are even faster.

Now you are changing the game, F1 cars weigh 600kgs.

Not nearly 2 Tonne

Put a 2.4L F1 V8 in your 1700kg skyline and see how fast you go.

[andymoocow]

a heard a saying many years ago from my Dads mate,

"Horsepower sells cars, torque wins races"

Didnt really think much of it at the time as i drove a 1988 Celica, and it had neither HAHAHA

[Rolls]

That is assuming the torque curve has shifted completely to the left. My silly comment was meaning that the torque curve has remained the same, only now rises and reaches its maximum sooner - Think about adding a square to the front or a rectangle

But I know what you mean. I should have worded it better.

Yep if you hold the same torque for longer and only change how quickly you reach it it would certainly be faster.

Now you are changing the game, F1 cars weigh 600kgs.

Not nearly 2 Tonne

Put a 2.4L F1 V8 in your 1700kg skyline and see how fast you go.

Is this a joke? It would be an absolute weapon and would be extremely fast lol....

there is a reason they are faster than v8 super cars and a 1200nm XR6 turbo, sure weighing half the weight is part of it but even if it weighed 2 tonne it would still be faster as it had dickloads more power. More average power = faster, torque has nothing to do with it.

Another example is if I made a whopping total of 5nM of torque but I could spin my motor to 50,000rpm then I would still make loads of power and be very fast, reason is power = torque*rpm, actual torque figures mean nothing on their own, power figures however take rpm into account so they are always far better to describe the performance of a motor.

Edited October 26, 2010 by Rolls

[SimonR32]

a heard a saying many years ago from my Dads mate,

"Horsepower sells cars, torque wins races"

Didnt really think much of it at the time as i drove a 1988 Celica, and it had neither HAHAHA

My opinion of someones car knowledge drops to about zero when someone uses that phrase!

[PM-R33]

Another example is if I made a whopping total of 5nM of torque but I could spin my motor to 50,000rpm then I would still make loads of power and be very fast, reason is power = torque*rpm, actual torque figures mean nothing on their own, power figures however take rpm into account so they are always far better to describe the performance of a motor.

Just to be exact, so people that don't know much about this know exactly how to calculate it:

HP = [Torque (ft.lb) x RPM] / 5252

In other words:

Power = [Force x Distance] / Time

Edited October 26, 2010 by PM-R33

[Rolls]

My opinion of someones car knowledge drops to about zero when someone uses that phrase!

same

Just to be exact, so people that don't know much about this know exactly how to calculate it:

HP = [Torque (ft.lb) x RPM] / 5252

In other words:

Power = [Force x Distance] / Time

Yeah I should have said is directly proportional, not =

Edited October 26, 2010 by Rolls

[zebra]

Yep if you hold the same torque for longer and only change how quickly you reach it it would certainly be faster.

Is this a joke? It would be an absolute weapon and would be extremely fast lol....

there is a reason they are faster than v8 super cars and a 1200nm XR6 turbo, sure weighing half the weight is part of it but even if it weighed 2 tonne it would still be faster as it had dickloads more power. More average power = faster, torque has nothing to do with it.

Another example is if I made a whopping total of 5nM of torque but I could spin my motor to 50,000rpm then I would still make loads of power and be very fast, reason is power = torque*rpm, actual torque figures mean nothing on their own, power figures however take rpm into account so they are always far better to describe the performance of a motor.

FFS Power is a by-product of Torque x RPM, more torque + more rpm = more power

So you expect an engine with f**k all torque to be able to pull a heavy car through the gears?

might be quick if it had 20 gears so it could stay in the power band.

Go put your 50,000rpm motor in anything and i will race you in something the same weight with a 2 cylinder diesel from 0-40km/h, using the same gearing.

So You keep telling yourself that you are right mate.

[Rolls]

So you expect an engine with f**k all torque to be able to pull a heavy car through the gears?

Almost certainly would be able to pull a heavy car if it had enough power and was geared appropriately, don't need 20 gears unless you have a tiny 1000rpm power band like a diesel, F1 engine have a wide 4-5k power band with something like 6-800hp and would easily be able to a 2 tonne car if geared appropriately with a 6-8:1 diff

Go put your 50,000rpm motor in anything and i will race you in something the same weight with a 2 cylinder diesel from 0-40km/h, using the same gearing.

I don't really know why you are making stupid comparisons, all I was demonstrating is that the torque figure is meaningless and power spread is all that matters, obviously the vehicle has to be geared appropriately for the power band. Hell look at those electric cars with 2 speed gearboxes, the engines rev to 50-100,000rpm so it is obviously possible to set up a gearbox for it.

The example I gave was how an F1 car has almost a third of the torque of say an xr6t and is far far faster even if it weighed the same. You attempted to say that this was wrong, but failed to show how, resorting to fallacious comparisons and getting your knickers in a knot isn't helping to prove your (wrong) point.

Edited October 26, 2010 by Rolls

[zebra]

Almost certainly would be able to pull a heavy car if it had enough power and was geared appropriately, don't need 20 gears unless you have a tiny 1000rpm power band like a diesel, F1 engine have a wide 4-5k power band with something like 6-800hp and would easily be able to a 2 tonne car if geared appropriately with a 6-8:1 diff

I don't really know why you are making stupid comparisons, all I was demonstrating is that the torque figure is meaningless and power spread is all that matters, obviously the vehicle has to be geared appropriately for the power band. Hell look at those electric cars with 2 speed gearboxes, the engines rev to 50-100,000rpm so it is obviously possible to set up a gearbox for it.

The example I gave was how an F1 car has almost a third of the torque of say an xr6t and is far far faster even if it weighed the same. You attempted to say that this was wrong, but failed to show how, resorting to fallacious comparisons and getting your knickers in a knot isn't helping to prove your (wrong) point.

They might have a decent power band, but you have to get it there, so a car that weighs 1700kgs has to have some bottom end torque to be able to pull it to the power band (think of a 2-stroke single cylinder race bike, horrible slow until they are in the right rev range), where then it would take off, so while it would be quick while in the power band (which doesnt start to about 10000rpm) it has to get there in the 1st place and would be rather slow untill it did.

My example is then a Diesel Le mans prototype, they only rev to 5500 but are still plenty quick, dont make a heap of power but have a stupid amount of torque, as you say they are geared for it.

No point in having an engine that revs to 17,200 like an f1 car if you have to anything other than drive for 300km in a 600kg car with more aero aids than an F-117

[juggernaut1]

Also if torque is the be all end all, how come a v8 supercar WITH 5-600NM is faster than a xr6t with 1200NM @ 2000

Because the v8 is gutless (OK has more progressive torque curve ) and thefore easier to drive on the limit.

Have a look at the recent time attack. The Fernandes Falcon supercar had the V8 ripped out and the turbo 6 put in. It was slower than the v8 Commodore supercar. Fernandes said it produced too much power/torque and was a handfull - couldn't get traction in 4th gear....and that the v8 was an easier car to drive because of its more progressive nature.

So not only is torque important - but the way its delivered.

Link to results - note the Falcon was nearly 1 sec slower than the Mal Rose Commodore.

http://www.natsoft.com.au/cgi-bin/results..../2010.EAST.S2.Y

Also note the 1st 6 positions were filled by 4 cylinders or rotaries - probably becuase they are a bit "softer" when coming onto boost when on the limit.

Edited October 26, 2010 by juggernaut1

[Rolls]

They might have a decent power band, but you have to get it there, so a car that weighs 1700kgs has to have some bottom end torque to be able to pull it to the power band (think of a 2-stroke single cylinder race bike, horrible slow until they are in the right rev range), where then it would take off, so while it would be quick while in the power band (which doesnt start to about 10000rpm) it has to get there in the 1st place and would be rather slow untill it did.

It is called slipping the clutch, there are many ways to get it into the power band fast, either way my example was extreme to prove a point, that it is the power level and spread that defines how fast a car is not the amount of torque.

My example is then a Diesel Le mans prototype, they only rev to 5500 but are still plenty quick, dont make a heap of power but have a stupid amount of torque, as you say they are geared for it.

Actually they make just as much power which is why they are just as fast, which was my entire point, they have to make far more torque to produce the same power due to the fact that they dont rev, large difference in torque levels but same power results in them being just as fast, ergo torque levels are not important in discussion, it is only the power level and spread.