Thursday, April 07, 2005

Conversion formulas to help with foreign websites

OK, I have been very frustrated myself trying to figure out the difference between power ratings in the US and abroad. So I did a little checking on the net and have some relief.

In the US we rate cars power in Horsepower and lb ft of Torque, but in Australia they rate cars power in Kw or Kilo Watts and Nm / Newton Meters. So to make it a little easier for myself and others I found the following;

1 hp = .746 kw , so if you want to convert from hp to Kw multiply by .746
example; 300 hp X .746 = 223.8 Kw , if you want to convert from Kw to hp then multiply by 1.34, example; 223.8 X 1.34 = 299.892 . Now it obviously doesn't give exact number but should be close enough for you to get an understanding.

Real world example; Ford of Australia has a Fairlane rated at 220 Kw, we in the US would rate that car around 294 hp.

Now for torque, this one is not as simple. We rate torque in lb ft and in Australia and other places it is Nm or Newton Meters. So I was able to find a conversion from lb ft to Nm;
lb ft / .736 = Nm , so you take your lb ft torque rating and divide it by .736 giving you the torque in Newton meters. An example 300 lb ft of torque would equate to 402.14477 Nm or 402 Nm.

Now going the other way wasn't as clear to me so to help here is how you get lb ft of torque from horsepower; hp x 5252 / rpm or your rated or calculated horsepower multipled by the number 5,252 then divided by the rpm stated for the horsepower.

So if a car has 300 hp at 5750 rpm ; 300 X 5252 / 5750 = 274 lb ft of torque at that rpm.
I know this isn't perfect, the new Mustang is rated at 300 hp at 5750 and 320 lb ft at 4500 rpm.
So in the Mustang peak torque is at a lower rpm than peak horsepower. But if I find a better conversion formula I'll let you know. I'm not a math major so don't hold your breath.

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