Towing - Kw or Nm

Submitted: Monday, Mar 01, 2010 at 11:50
ThreadID: 76439 Views:7624 Replies:16 FollowUps:9
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Okay so i just towed something (rented jayco Hawk) for the first time in my non-turbo hilux diesel.

My enquiry is this, what is best for towing, Kw or Nm, and towing up hills?

I did some google searching and forum searching and the clear answer is the highest amount of both kw and nm, but you know, we can't always afford what we want.

Like you have a brand new VW ute coming to market with 90kw and 360nm while the newer brand utes have 135kw and 360nm so it got me wondering, if you had a limited budget and wanted more towing power and uphill towing power, would it be Kw or Nm if that was your only choice?
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Reply By: Battery Value Pty Ltd - Monday, Mar 01, 2010 at 12:05

Monday, Mar 01, 2010 at 12:05
Just generally:

You want max kW for fastest/heaviest uphill towing.

kW is a product of Nm and RPM of your motor, thus at the same RPM higher kW directly translates to higher Nm.

But power and motor torque are not the only factors.

A box offering 6 gears can make up for a lack of kW when comparing to a higher powered 4/5 speeder.

Best regards, Peter
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Reply By: olcoolone - Monday, Mar 01, 2010 at 12:20

Monday, Mar 01, 2010 at 12:20
Do a Google search for torque vs power and all your questions will be answered.


AnswerID: 406647

Reply By: _gmd_pps - Monday, Mar 01, 2010 at 13:26

Monday, Mar 01, 2010 at 13:26
Towing Performance is not just about Power or Torque.
It is about gearing and revs. In order to generate torque you need power
and you need the torque to turn high gearing, which in turn lets you tow
higher loads. There is also the factor of drive axle weight because the highest powered car with huge torque cannot tow effectively when you don't bring the torque onto the road.

Dually wheels on the drive axles with high geared diff and a diesel with max power at 1800-2000 revs will give you best results when towing heavy as long
as the engine has enough power. What is enough power ?

I'd say 70-90hp per tonne GCVM is good 50-70 is just ok and below that it
is getting tedious when you go uphill or want to pass.

So when you have a 4.5t vehicle fully loaded towing a 3t trailer with 250hp
you are on the low side and probably over the GCVM of the vehicle.

Such a rig should be pulled by at least 375 hp to make it less than a traffic hazard or an annoyance on the road. Looking at those figures one can conclude that most bigger caravan rigs are probably underpowered. The camper trailers and light caravans are usually ok.

good luck
gmd
AnswerID: 406667

Reply By: Member - Oldbaz. NSW. - Monday, Mar 01, 2010 at 14:15

Monday, Mar 01, 2010 at 14:15
G'day Porl, I imagine your non turbo towing trip didnt exactly blow you away, & a
Hawk maybe not the heaviest thing you might wish to tow anyway. I'm not
smart enough to know much about Nm or Kw but I do know that most towing is
a different experience to tootling around solo. Generally ,towing results in lower
speeds & higher fuel consumption, probably in direct ratio to the weight towed.
The more power available cures the speed problem, but one must consider the safety aspects of towing, & being able to cruise at 110 kph with a big tow load
may not be the best outcome, for safety or fuel usage. Conversely, being in 2nd
gear pulling 50 kph up a long hill doesnt make you many friends either. I guess the happy medium lies in the middle somewhere. My solution is to pull a light
C/t with a strong V6, it is effortless, the fuel issue is controlled by staying under
100 kph. The whole towing thing is full of compromises...being underpowered
makes the driving hard & tedious, having all the power you need is good, but will
cost you a motza if not controlled, & , as always, weight is your enemy.
cheers....oldbaz.
AnswerID: 406678

Reply By: Maîneÿ . . .- Monday, Mar 01, 2010 at 14:46

Monday, Mar 01, 2010 at 14:46
Porl,
if I had a limited budget and wanted more uphill towing power, I would it be looking at a diesel with high Nm over a wide range.

Maîneÿ . . .
AnswerID: 406687

Reply By: Member - Kiwi Kia - Monday, Mar 01, 2010 at 15:36

Monday, Mar 01, 2010 at 15:36
Nm all the way

KK
AnswerID: 406697

Follow Up By: Member - Michael P (QLD) - Monday, Mar 01, 2010 at 16:08

Monday, Mar 01, 2010 at 16:08
Are Nm's much the same as M&M's
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Reply By: MEMBER - Darian, SA - Monday, Mar 01, 2010 at 17:18

Monday, Mar 01, 2010 at 17:18
Someone qualified is quite welcome to tell me if my thinking is too simplistic on this one, but does it not go like this ? Power is what we tow with - power is measured in KW - a vehicle with more usuable KW is more powerful than one with less KW (even IF the latter has a higher Nm rating) - that is, usable Kw is the key to the subject; Nm are only one of the components in the power figure.
AnswerID: 406716

Reply By: Best Off Road - Monday, Mar 01, 2010 at 17:35

Monday, Mar 01, 2010 at 17:35
Truckies always talk Horsepower (kW) ratings as to how well a truck/prime mover will tow a load.

Cheers,

Jim.

AnswerID: 406722

Follow Up By: get outmore - Saturday, Mar 06, 2010 at 19:09

Saturday, Mar 06, 2010 at 19:09
yea but trucks would be kind of created equal with one goal in mind - to haul a load. So talking horspower would also be talking NMs where they ned them
- but who talks NMs??

its like toyotas petrol sixes - they have been desighned with different things in mind

so you have the older school 4.5 l six from the 80 and early 100 showing about 20kw less than the plado 4.00l 185kw beastie

- but theres no doubt the 4.5l puts its ponies down in a better way for towing and offroading

they now have a 3.5l there using increasingly more with 200killer wasps

again the numbers mean nothing as it is a free reving motor not as suted to 4wding and towing as either of the previos mentioned engines
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Reply By: howesy - Monday, Mar 01, 2010 at 17:56

Monday, Mar 01, 2010 at 17:56
without getting into technical arguments which could see this thread go on forever, the old diesel motor and the prime movers mentioned may have impressive power ratings but as the power goes up so too does the torque.
Torque pulls and torque gets you off the line ask most drag racers.
Prime movers have massive amounts of torque available at very low revs.
My ford pulls like a train and flogs cars in a sprint that have a lot more kilowatts and this is because it makes 530nm of torque 100% avail on tap by 2500 revs and 80% is avail at 1500 revs.
have a look at your prospective vehicles dyno sheet. see where the power comes in. Its no good having a car that is rated with 50kw more if that power is not developed until 5000revs (who tows at 5000 revs) Power curves are what you need to look at.
Go for the car that has the most impressive figures where the power is down low at the revs you drive at. Compare the dyno sheets and on some you will find that the car that has the lower power rating may develop more power avail. at 3000 to 3500 revs than the other and lets face it thats realistically where your revs are going to be.
AnswerID: 406727

Follow Up By: Member - Kiwi Kia - Monday, Mar 01, 2010 at 18:58

Monday, Mar 01, 2010 at 18:58
Spot on. Nm is what you will actually be using to do the work.

KK
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Reply By: Dion - Tuesday, Mar 02, 2010 at 00:02

Tuesday, Mar 02, 2010 at 00:02
Porl,
a Kw with a Cat C15 or a triple 4 Cummins should make easy work of towing your caravan up hills no wurries. If you have an infinity for 2-strokes, there are probably quite a few classic SAR Kw's with Silver 92's in them that would do the job well too.

Cheers,
Dion.
AnswerID: 406802

Follow Up By: Dion - Tuesday, Mar 02, 2010 at 00:05

Tuesday, Mar 02, 2010 at 00:05
Kw's will pull much better than yer Slowlux ;-)

Cheers,
Dion.
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Follow Up By: Dave(NSW) - Tuesday, Mar 02, 2010 at 11:41

Tuesday, Mar 02, 2010 at 11:41
Dion,
This one with an 892T was putting out 560 HP which was huge back then.
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Follow Up By: Dion - Tuesday, Mar 02, 2010 at 11:45

Tuesday, Mar 02, 2010 at 11:45
Hi Dave,
I like, at leats someone cottoned on to my humour. :-)

Cheers,
Dion.
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Reply By: Member No 1- Tuesday, Mar 02, 2010 at 08:20

Tuesday, Mar 02, 2010 at 08:20
you cant beat grunt...if you've got KW then you have torque
torque can be increased (by gearing) from a small kW engine which will get you over the hill but bigger engine with more kw with same torque will get you over it faster
AnswerID: 406826

Reply By: OzTroopy - Tuesday, Mar 02, 2010 at 10:04

Tuesday, Mar 02, 2010 at 10:04
Whatever happened to the good ol days ??? ....

A 4cyl for tootling round town

A 6cyl for doing a bit of everything and

A V8 for towing stuff properly.

Vehicle dimensions were relative to the engine capacity and a diff ratio change let the veh tow even better .... albiet with a drop in the max top end speed available.

Then theres was diesels ..... and a good 4cyl one could out perform a 6cyl petrol.

Seat of the pants driving .... If the engine is revving freely (no - not screaming) in a gear whilst underload ... and road speed is acceptable for the gear selected ... its a good towrig.
AnswerID: 406842

Reply By: Davo_60 - Saturday, Mar 06, 2010 at 15:09

Saturday, Mar 06, 2010 at 15:09
Nm, if you have the gearing. A 600hp truck diesel will have around 2800nm of torque, will pull 100 ton, but with lots of gears to use.
AnswerID: 407520

Reply By: Off-track - Saturday, Mar 06, 2010 at 16:09

Saturday, Mar 06, 2010 at 16:09
Torque for towing, horsepower for hooning.

You can have a 500hp engine (say a Chev small block) with around 500nm of torque. Will it have the same towing abilities if mated to same gearbox/driveline as a say a Cat with 500hp and over 2000nm of torque?

Both have same horses.


simple description
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Reply By: vk1dx - Saturday, Mar 06, 2010 at 21:06

Saturday, Mar 06, 2010 at 21:06
Why is it that trucks (no! not the toy 4wd's - real trucks) semi's etc are diesel? Real trucks and big movers. A bit of a rhetorical question I suppose. But it gets you to thinking doesn't it.

Cost may have been the reason years ago but in recent years I wonder if it is true now. Surely it s not just cost.

Phil
AnswerID: 407555

Follow Up By: Dave(NSW) - Saturday, Mar 06, 2010 at 23:32

Saturday, Mar 06, 2010 at 23:32
Diesel engines produce more torque at lower revs and when your moving big loads over hundreds of kilometers are cheaper to run.
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Follow Up By: vk1dx - Sunday, Mar 07, 2010 at 03:08

Sunday, Mar 07, 2010 at 03:08
True. Then doesn't it follow that the diesel would be better for towing. Not only the better alternative at the time, now, but over time better on the pocket as well. Its so much easier on the hills and steep rocky roads in the Victorian mountains.

That's why our whole family have diesels. Also for the longer term reliability.

I gather by the lack of conflicting arguments that we are correct!

Phil

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Reply By: landseka - Saturday, Mar 06, 2010 at 23:34

Saturday, Mar 06, 2010 at 23:34
To expand terminologies, I was told years ago that a (race) car with understeer will hit a curve wall with the front end first, an OVER steering car hits with the rear end first.
Horsepower (Kw) determines how much damage you do to the car in the crash while Torque (Nm) determines how far you push the wall!

I have never had a problem with the descriptions since. LOL.

Cheers Nei;l
AnswerID: 407569

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