This has got to be the place to ask this question. I am thinking of changing my tug and am getting totally bewildered by the amount of info available when assessing a new tow car. What should be the optimum numbers I should be looking for, re torque , horse power , litres, weight of car/4x4/van...or is it a more emotional thing.
H.P v Torque v Litres
- Thread starter barrychas
- Start date
More is better - only you can decide how much is enough, or more likely how much you can afford to buy/run.
- Mar 14, 2005
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Litres is fairly irrelevant and there's no horsepower if there's no torque. Horsepower gives you the power that you need, for instance to climb a hill, and plenty of torque makes towing more pleasant because you don't have to rev the engine or change gear as much.
Therefore, horsepower AND torque are both needed. As Roger says, as much of both as you can afford.
Therefore, horsepower AND torque are both needed. As Roger says, as much of both as you can afford.
It is argued that a vehicle with torque rather than a flighty engine is better.
Therefore it would stand that a diesel vehicle would be best suited, as it produces its torque lower down the rev range, hence it will pull easier at lower speeds and less revs.
Ideally it should be around its peak torque when you are traveling whilst maintaing your speed at or around 60 mph, for eg my car has peak torque at 2000 rpm which is 58 mph.
Automatics are also believed to be better, as you have more control, especially at lower speed, with no clutch to burn out when manoevering.
Driving wheels are also something to think about, front may loose grip on wet grass or when attempting a hill start in the wet, perminant 4x4 are more costly due to the mechanics and associated extra weight, where inteligent 4x4 (fwd until traction loss then drive automatically goes to the rear as well) are possibly the best all round.
As for weight the heavier the greater the safety margins (85% guide line). If your vehicle has a mass in service/ kerb weight of around 2000 kg then unless prevented by manufacturer, renault for example then any caravan under 1700 kgs MTPLM will be fine, which would open up the market should you change your caravan.
That said the only real decideing factors are your funds and wish list.
Mat
Therefore it would stand that a diesel vehicle would be best suited, as it produces its torque lower down the rev range, hence it will pull easier at lower speeds and less revs.
Ideally it should be around its peak torque when you are traveling whilst maintaing your speed at or around 60 mph, for eg my car has peak torque at 2000 rpm which is 58 mph.
Automatics are also believed to be better, as you have more control, especially at lower speed, with no clutch to burn out when manoevering.
Driving wheels are also something to think about, front may loose grip on wet grass or when attempting a hill start in the wet, perminant 4x4 are more costly due to the mechanics and associated extra weight, where inteligent 4x4 (fwd until traction loss then drive automatically goes to the rear as well) are possibly the best all round.
As for weight the heavier the greater the safety margins (85% guide line). If your vehicle has a mass in service/ kerb weight of around 2000 kg then unless prevented by manufacturer, renault for example then any caravan under 1700 kgs MTPLM will be fine, which would open up the market should you change your caravan.
That said the only real decideing factors are your funds and wish list.
Mat
For towing the more torque the better & bhp doesn't necessarily mean more torques
A 2.4 litre Formula 1 engine produces about 720 bhp but only 200 ft/lbs of torque whereas my diesel 2.0 Jaguar produces 128 bhp with 240 ft/lbs torque, I know which I would rather tow with
A 2.4 litre Formula 1 engine produces about 720 bhp but only 200 ft/lbs of torque whereas my diesel 2.0 Jaguar produces 128 bhp with 240 ft/lbs torque, I know which I would rather tow with
If you can afford a lot of literage that is the way to go.A larger engine is more reliable,less strained,has lower engine speeds and will last a lot longer.Generally the larger the engine the more the torque.Larger engines rely less on things like boost pressure.As the old saying goes "theres no substitute for cc's" and its true.Second on my list would be a vehicle with plenty of torque.
I thought it was 'there's no replacement for displacement' unfortunately displacement equals low fuel economy & high emissions.seth said:
As i said if you can afford large thats the way to go.But yes there is a price to pay.As regards to fuel consumption not allways the case,my larger engined car is better on fuel compared with the smaller engined car when towing the van due to the fact its not working as hard.
It's a case of YMMV, I get better economy towing with my 2.0 jaguar than our 2.7 Nissan (both diesel).
There's no simple answer to the OP apart from as Roger said, as big as you can afford to buy & run.
There's no simple answer to the OP apart from as Roger said, as big as you can afford to buy & run.
On all machines HP is proportional to torque x rpm
For towing you need the best torque at as low an rpm as possible.
For towing you need the best torque at as low an rpm as possible.
That's only true as stated if the engine directly drives the wheels - adding a gearbox makes the statement only true in one single specific gear which is different between car models.ChrisUK said:
You can measure the power-to-weight ratio of a car (HP divided by tonnes) but you can't measure the torque-to-weight ratio because of the measurement units, whether metric, imperial or US.
RogerL said:
I thought that manufacturers torque and bhp figures quoted were for the engine output. Not an at the wheels figure.
Anyway more torque at lowest rpm will be best for towing.
OK, a quick recap on this then.
Understeer is where you hit the fence with the front of the car.
Oversteer is where you hit the fence with the back of the car.
Horsepower is how fast you hit the fence
Torque is how far you take the fence with you.
Well that's my understanding anyway.
Oh and my RR is a 3.6 V8 diesel with 300HP and 650NM of torque in a car which weighs 2600 kilos. It pulls like a train.
. So anything over 100HP per tonne and over 200nm of torque is going to be more than adequate.
Dom.
Understeer is where you hit the fence with the front of the car.
Oversteer is where you hit the fence with the back of the car.
Horsepower is how fast you hit the fence
Torque is how far you take the fence with you.
Well that's my understanding anyway.
Oh and my RR is a 3.6 V8 diesel with 300HP and 650NM of torque in a car which weighs 2600 kilos. It pulls like a train.
Dom.
200Nm per tonne ?DomDom said:OK, a quick recap on this then.
Understeer is where you hit the fence with the front of the car.
Oversteer is where you hit the fence with the back of the car.
Horsepower is how fast you hit the fence
Torque is how far you take the fence with you.
Well that's my understanding anyway.
Oh and my RR is a 3.6 V8 diesel with 300HP and 650NM of torque in a car which weighs 2600 kilos. It pulls like a train.. So anything over 100HP per tonne and over 200nm of torque is going to be more than adequate.
Dom.
200 Nm = 20.39 kg metre so dividing that by 1000 kg gives 0.2039 metres because units have to balance in physics calculations.
HP is proportional to torque and rpm?
Perhaps in the old days when engines were mechanically controlled but certainly not now with electronic engines.
Just to prove a point we regularly see Diesel engines with exactly identical cubic capacity(the same unit) with a substancial power difference,yet the lower powered unit delievers a substancial amount more torque.
The governing factor now is the calibration data file.
Perhaps in the old days when engines were mechanically controlled but certainly not now with electronic engines.
Just to prove a point we regularly see Diesel engines with exactly identical cubic capacity(the same unit) with a substancial power difference,yet the lower powered unit delievers a substancial amount more torque.
The governing factor now is the calibration data file.
- Mar 14, 2005
- 10,030
- 859
- 40,935
Chris is right. Horsepower is defined as torque times rpm. Therefore, to get the necessary performance (horsepower) you need a combination of torque and rpm. If the engine is low on torque one can make up for it with bags of rpm, although, on the whole, that would be very tiring as the engine would have to be kept screaming its guts out all the time.
So in other words torque is what matters unless you what an extremely stressful day constantly changing gear at the slightest sight of an incline and reving the bowels out of your vehicle with very little torque and using extreme amounts of fuel.Not ideal.
Yep, it is. But I said 200NM of torque. No mention of mass in this part of my reckoning.RogerL said:200Nm per tonne ?It's a nonsense unit
But yeah, torque. Cos too much is not quite enough.
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