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KW versus NM
Posted: Wed Apr 21, 2010 1:55 pm
by 4ePikanini
Which one does what for you?
What would you want more?
why?
I thought this will be an interesting discussion.
Re: KW versus NM
Posted: Wed Apr 21, 2010 2:32 pm
by 4ePajero
Torque is the twisting force the engine produces.
Power is the speed at which this force is done.
Think about a big wrench attached to a nut.
Torque / force - The longer the arm and the force applied, the higher the twisting force applied to the nut.
Power / work - The quicker the twisting force can be repeated, the higher the 'work'
In an engine, the two are directly related: (
http://www.rri.se/index.php?DN=28#060 )
Power [kW] = Torque [Nm] x Speed [rpm] / 9549
Torque [Nm] = 9549 x Power [kW] / Speed [rpm]
With a gearbox (a torque multiplyer), you can get the required torque by using the right ratio.
For me? Give me torque, as in a good TD! (Large capacity V8 petrol engines give the same, at double the fuel consumption).
Extremes:
Ship (diesel) engines: very high torque, but low revs.
F1 engines: very high revs, but low torque.
Re: KW versus NM
Posted: Wed Apr 21, 2010 8:32 pm
by HBannink
In short it is like race horses compared to cart horses
I have a Calibra that produces 243kw on the wheels enough to get to 267k/h in less than 13 seconds but it is not made for working, the power is at high rpm and shifting the 6speed box is like stirring a cup of coffee. Hook a trailer behind her or load anything more than the day's shopping and she becomes lazy.
A diesel pajero would be happy with half those kw but produces more torque at lower rpm and that is the reason why diesel is in theory better for 4 X 4 applications. It would idle over obstacles that a petrol motor would burn cluches on.
Your petrol 3l produces about 40% of those kw in a 6 cyl monster and would stand no chance in a straight and level race other than to bring the trailer at the end of the meet but try and load the pajero on the trailer and get the calibra with all its kw try and tow it on level surface forget about any incline, you'll have more smoke than Mick's jet car

Re: KW versus NM
Posted: Mon Apr 26, 2010 2:51 pm
by RoelfleRoux
C'mon Pikanini,
You knew what your dad was going to answer here, look at what he bought.
I'm more of a fence sitter and believe that both torque and power is needed to get the job done properly - simply because we operate our cars in extremely varied conditions. A low kw - high nm motor is not going get you through the Namib desert, but really enjoy climbing over obsticles and ofcourse vice versa for a low nm - high kw motor. That is why we sit here on the Pajero site, both the 3.8V6 as well as the 3.2DiD deliver well on both counts. Obviously each one with a bit of a bias towards it's own strong point.
Re: KW versus NM
Posted: Mon Apr 26, 2010 5:19 pm
by 4ePikanini
I'm definitely a torque fan having driven my brother's 1.9 tdi and my dad's v10 tdi.
I'm more interested in the technicalities of what is torque and what is kilowatt with regards to weight, gearing and what each's benefits are?
Re: KW versus NM
Posted: Mon Apr 26, 2010 7:29 pm
by MR2-Blue
We have a nice "saying" in German for exactly that question - but I can't translate it:
"
Hubraum statt Heckspoiler"....but it matches perfectly
Maybe Kai can help in the 3rd word to translate...
Re: KW versus NM
Posted: Mon Apr 26, 2010 11:03 pm
by HBannink
Direct translation = Cubic capacity instead of back spoilers
In South African = " There is no replacement for displacement"

Re: KW versus NM
Posted: Tue Apr 27, 2010 8:02 am
by 4ePajero
HBannink wrote:Direct translation = Cubic capacity instead of back spoilers
In South African = " There is no replacement for displacement"

That phrase was coined in the days of the American V8 engines.
In those days they were the only engines which could produce prodigious amount of torque at low rpm, albeit at the cost of kW and fuel economy.
Today's 3l TD engines produce as much torque at low revs, with the benefit of very good fuel economy.
I had a Chevy 4.3l V-6 in the Gen1 before I fitted the Di-D. Both the torque and kW figures were very similar (the Di-D winning in the torque department).
The Chevy uses just about double the fuel the Di-D does.
No contest.
Re: KW versus NM
Posted: Tue Apr 27, 2010 2:59 pm
by MR2-Blue
4ePajero wrote:...I had a
Chevy 4.3l V-6 in the Gen1 before I fitted the Di-D. Both the torque and kW figures were very similar (the Di-D winning in the torque department).
The Chevy uses just about double the fuel the Di-D does.
Unbelievable - you can just install another engine in a car w/o any official technical proof of compatibility, i.e. that the brakes can handle the increased power ???
The TÜV in Germany would never allow this....not even in Europe such modifications would be allowed w/o an official technical check.
Re: KW versus NM
Posted: Tue Apr 27, 2010 4:13 pm
by 4ePajero
MR2-Blue wrote:4ePajero wrote:...I had a
Chevy 4.3l V-6 in the Gen1 before I fitted the Di-D. Both the torque and kW figures were very similar (the Di-D winning in the torque department).
The Chevy uses just about double the fuel the Di-D does.
Unbelievable - you can just install another engine in a car w/o any official technical proof of compatibility, i.e. that the brakes can handle the increased power ???
The TÜV in Germany would never allow this....not even in Europe such modifications would be allowed w/o an official technical check.
Sorry for the OT digression, but this needs a reply.
Brakes don't handle power, but only speed (or the reduction thereof), which was not higher than previously.
I know what I do, and I would not have done anything which would have been unsafe.
My conversion would have passed any test in any case. It looks like a factory fitted engine.
Leaving intelligence to the government only, can have very negative consequences.
Mark one
against Europe, and one
for 'backward' South Africa, for a change!
