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Ok guys this has been doing my head all morning.....

What is torque?... I was talking to a guy at work and he seems to think having lots of torque doesnt make a difference, for example down the quarter. He reckons that its your rwkw that makes the car fast.... I believe him in a sence cause look at the rice burners they dont seem to make much torque but they are quick.. What is the difference between outright power (rwkw) and torque in a 'practical' sence??

Hope someone clears my head soon...

Cheers Mike

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the old saying torque wins races kws sells cars is true.ricers would still have decent torque if there running heaps of boost.torque is the twisting power of the engine.the more torque the quicker you offset the weight of the car.

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What makes our cars fast it torque. You need big torque to move a heavy car and get it off the line.

Torque is generally what the motor produces down low, and usually max's out around 4500.

If you look around at a few dyno graphs on here you'll see some cars are tuned with alot more torque than others but all may end up with similar peak power results... like, they all say 300wkws but have a completely different looking curve on the graph.

More torque can feel like a lag free tune compared to the same peak power (300wkws) on a car with less torque, which is why some poeple think they have laggy tunes. They just have less torque tuned in ( safer on rods! ) so when top end power hits, there is a bigger difference compered to down low in the torque range.

A good example of torque, is over taking on the freeway in 5th or 6th and having it pull strongly... a 200sx with 300wkws wont do that due to its much reduced torque.

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Thanks for the info dudes clears it up heaps.... I did google it and your responses mirror what I have found out... So my 650nm of torque is what makes my 227rwkw T 'feel' so quick ey!!

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Mike,

KW is how fast you can accelerate you car for a given weight.

Torque is a force or push, in a circle - it is half the picture.

This is the difference between KW and torque.

Imagine accelerating of a trolley of a certain weight and you are the engine – you are pushing.

For any given power output you can.

1 -Do a few big pushes infrequently.

(In a car engine this is high torque low revs.)

2- Do lots of little pushes frequently.

(In a car engine this is low torque high revs)

That’s it. Your power output and the weight of the trolley determine the acceleration.

Some other points

Gears are levers, in circles.

Levers allow you to change a fast little push into a slow hard push, and visa versa.

Gears do the same in circles, they allow you to change a high rpm low torque to low rpm hi torque.

So the rev monster and the torque monster can produce the same KW. The rev monster makes half the torque but twice the revs of the torque monster.

The RWKW for any rear wheel speed is also the same, the gearing is different.

Some more point.

In an acceleration run the car motor is constantly changing speed - which is obvious.

A complexity is that nearly all car motors constantly change max torque with RPM - which is not obvious. The factory tune XRT is one of the new breed low boost types that don’t - the 335i/135i is another. Their torque curves at max throttle and full boost are flat - straight lines. In many ways this is the ideal for an everyday car.

If your torque varies with RPM this means that in any given gear, the cars the acceleration is constantly changing with RPM – you experience this as a a surge of acceleration. So whilst you may have a great torque spike at a certain RPM, where the acceleration is staggering, the moment you move your RPM away from that spike your acceleration drops. The racer comment about torque winning racers is speaking to how complex and difficult it is for a driver to keep a particular engine spinning where the torque is high, at just the right speed, just when you want it. An engine may produce staggering power, but is it spinning at 8,000 rpm when you launch...

A simple way to work out the average power of your car in a run, in a particular gear, is to look at the area under the torque curve the RPM range of interest.

Regards,

aa

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well most of you seem to take alot of words to explain it, and you miss the point. so here it is...

torque is the TURNING force applied to the crank. it is this force that is transmitted thru the driveline to the wheels and gives you acceleration that you can feel by PUSHING YOU BACK IN THE SEAT or the ability to spin the wheels.

RWKW can be simplified as torque mulitiplied by RPM. Therefore (simplified) it is how many times per minute, a given amount of torque can be applied. An engine with high KW therefore must maintain as much torque for as long as possible as high into the rev range as possible to achive a high RWKW. its no good to make massive torque for a short rev range (like a prime mover truck) and likewise, you cannot achive big RWKW with lots of revs and no torque (like in a high revving motorcycle engine) - you need both. A piston engine inherrantly has a rpm point at which its ability to generate toque starts to diminish and continues to do so the harder it revs...

so, RWKW is also total POWER because its a measure of BOTH, and ultimatley defines how fast you can accelerate a given mass.

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  • 6 months later...

I like torque.. its simple.

ok torque for dummies

so torque = kw x 9550 divided by rpm . roger that captains??

ok so say a rota makes peak power of 400fwkw at 8000 rpm ---- 400x9550/8000 = 477.5nm

xr6t makes peak power of 400fwkw at 5000rpm -----400x9550/5000 = 764nm

stock xr6t makes 240fwkw at 5400rpm------------- 240x9550/5400= 424.444nm

big ole diesel truck has 300fwkw@1500rpm--------------- 300x9550/1500=1910nm

sound about right??

please note, I dont have an effn clue where a stock t makes its peak power.

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Thanks for the info dudes clears it up heaps.... I did google it and your responses mirror what I have found out... So my 650nm of torque is what makes my 227rwkw T 'feel' so quick ey!!

ok so ummmm 227 + 22% = 272.4 so im guessing mabey your dyno sheet says you made peak power at 4002rpm?? (using the 22% rule anyway)

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  • 2 months later...

I think an important thing to remember as well is that RWKW is not a measurement. A chassis dyno cannot measure RWKW as such, its actually a calculation that it makes by measuring the TORQUE of the engine compared to the speed of the REAR WHEELS at a given ENGINE speed (RPM). This is why you may get different results on a dyno run if your using different dyno's, depending on how the dyno is set up and the calibration you may get varying power results.

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  • 1 month later...

Simply Torque is the twisting force an engine produces, power is the work resulting from it.

Example: power equals (torque * rpm)/ a constant

The constant is either 9549 (where torque is Nm) and 5252 (where torque is lb/ft)

A car can produce a heap of torque little power I.e diesel engine because it doesnt rev alot and peak torque happens very low and declines when the revs increase.

A really good example is a Mazda RX8 which produces around 177kw but only produces a crappy 216 nm of torque, why? because it revs very high and peak power and torque is produced at very high engine speeds around 5500rpm for max torque and 8500rpm for peak power.

You can either rev an engine faster to make power or keep it reving the same speed and increase the torque, both increases peak power.

A dyno graph measures torque created at the wheels and uses the above formula to calculate power at the wheels in relation to the rpm the engine is running at.

Like someone above said torque is what gets you there and power is what keeps you there

Hope that helped

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I like torque.. its simple.

ok torque for dummies

so torque = kw x 9550 divided by rpm . roger that captains??

ok so say a rota makes peak power of 400fwkw at 8000 rpm ---- 400x9550/8000 = 477.5nm

xr6t makes peak power of 400fwkw at 5000rpm -----400x9550/5000 = 764nm

stock xr6t makes 240fwkw at 5400rpm------------- 240x9550/5400= 424.444nm

big ole diesel truck has 300fwkw@1500rpm--------------- 300x9550/1500=1910nm

sound about right??

please note, I dont have an effn clue where a stock t makes its peak power.

Mate that is the best explanation of torque so far, straight to the point!

Cheers Alf

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  • 1 year later...

Peak rwkw figures are fine for bragging rights, but it is the way your engine produces torque that matters most.

A nice torque curve is what we all should be chasing, not just a massive peaky rwkw figure. Torque is very much the king.

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torque is what matters most, but being able to use torque over a wide RPM band will make it more useful. torque is what you feel pushing you along as technically you can't 'feel' 300rwkw as its a peak value only.

below is a link to an old article but very worth the read, even if you aren't good at maths - get to the car bits:

http://www.vettenet.org/torquehp.html

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  • 2 weeks later...

Strange how alot of dynos read inaccurate torque peaks.

Can anyone explain as to why this happens? ie: 300rwkw xr6t at about 5750rpm which supposedly reads 1100nm of torque.

Does it have anything to do with the way they enter the cars values into the computer?

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  • 1 year later...

Strange how alot of dynos read inaccurate torque peaks.

Can anyone explain as to why this happens? ie: 300rwkw xr6t at about 5750rpm which supposedly reads 1100nm of torque.

Does it have anything to do with the way they enter the cars values into the computer?

I think it may have more to do with what gear the car was in when it was tested. To get the most accurate results the car should be in a 1:1 gear (4th in ours?) and then the total torque divided by the diff ratio to get an idea of what is happening at the flywheel. It's all got to do with gear ratios - every time the torque goes through a set of gears (torque converter included for autos) the torque gets multiplied by that ratio (ie - flywheel x torque converter ratio x gear ratio x diff ratio / wheel circumference). that's where say 300Nm at the engine can become over 1000Nm at the wheels. Put smaller wheels on if you want more torque lol

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I also often wonder what our power figures would look like if we measured useing the BHP method that English dyno tuners use where they use the breaking effect that the cars drive line has on the rollers after they back off to calculate the drive line losses which then gets added to the power they measured at the wheels to give the suposed flywheel hp.

BHP stands for Brake horse power.

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  • 3 weeks later...

You cant have heaps of KW's (Hp)of power.

Without much Nm's (ftlbs) of torque.

IMO just find a big hill drive a small car up it.

Then go back with a diesel 4wd.

This is the first time I really saw torque in action and fully understood it's importance.

Drag racing these two cars in a straight line the small pertol would flog the pants off the 4wd.

But up the mountain range it had no chance.

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  • 2 months later...

hey sorry to smash up an old thread I would like to know does a mainline dyno convert wheel torque figure to flywheel value or is everything read at the wheels?

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Everything is read at the wheels, the only accurate way to get flywheel power or Torque is to use an engine dyno rather than a chassis dyno, some maths types could probably get a close figure based on what the dyno has reported and they know every ratio, tyre height, roller diameter, slip etc

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