power to weight ratios

[Dustydog]

Idling away time at hospital reading Car mag. All their tests show the ratio of BHP per tonne.ignoring fuel type what ratio should us tuggers go for? Dare I mention also the interface with torque?

whoops. Wrong place. Mods please move to tow cars. Thanks

 

[Lappy]

Hi Dustydog,
I can recall this was discussed a few years back and I think it was Prof John L who gave a good detailed feedback.
I think it was around 60bhp per ton for towing, although I may be wrong. This is based on the combined weight of the outfit.
Regards,

 

[ProfJohnL]

Idling away time at hospital reading Car mag. All their tests show the ratio of BHP per tonne.ignoring fuel type what ratio should us tuggers go for? Dare I mention also the interface with torque?

whoops. Wrong place. Mods please move to tow cars. Thanks

:woohoo: How dare you "idle your time away" :woohoo: That's why you have stop start systems for these days :lol:

Seriously, the traditional (Yuk) wisdom was to look for 40BHP per Tonne for an outfit, but that was suggested before the vast increase in diesel tugs, and way before the introduction of widespread turbo charging of petrol engines. Those are game changers, and how you can come up with a new guide figure or method of producing a vehicles optimal towing ability is yet to be established.

 

[Dustydog]

Thanks Prof ,
I was at the Alzheimer’s clinic and forgot your earlier words of wisdom. No joke
I’ve started looking at non diesels to see how they compare. I know we are looking to hybrids and pure electric. The base comparison isn’t easily available yet which is a shame as all four fuels still have a lot to offer.
Now here’s the strange thing. The Car mag rates the new Volvo XC90 5*. Maybe the earlier reports of 16mpg are flawed?
The Lexus 450 hybrid looks a great car but again not frugal.
Surely petrol engines aren’t as bad as we tuggers think :
The ratio you suggest is fine with me but the newer vehicles are way way above that figure.
So maybe there is hope for petrol andalternativesandwewerehood winked years ago to go diesel B)

 

[otherclive]

Thanks Prof ,
I was at the Alzheimer’s clinic and forgot your earlier words of wisdom. No joke
I’ve started looking at non diesels to see how they compare. I know we are looking to hybrids and pure electric. The base comparison isn’t easily available yet which is a shame as all four fuels still have a lot to offer.
Now here’s the strange thing. The Car mag rates the new Volvo XC90 5*. Maybe the earlier reports of 16mpg are flawed?
The Lexus 450 hybrid looks a great car but again not frugal.
Surely petrol engines aren’t as bad as we tuggers think :
The ratio you suggest is fine with me but the newer vehicles are way way above that figure.
So maybe there is hope for petrol andalternativesandwewerehood winked years ago to go diesel B)

I’ve said in several posts that I’ve had some good petrol tow cars, but the market changed when good diesels became more readily available in cars/estates as opposed to vehicles such as Disco, Shogun, etc. There’s no doubt a diesel makes a good tow car but after driving a number of petrol cars with turbos you would be surprised how smooth, quiet and free revving they are. I’m sure that as more petrols and hybrids come onto the market there will be ones suited to towing duties. My current pick would be the 280 Skoda Superb 4x4 estate, it’s a non hybrid and non frugal, so mileage might be constrained

 

[Dustydog]

Thanks Prof ,
I was at the Alzheimer’s clinic and forgot your earlier words of wisdom. No joke
I’ve started looking at non diesels to see how they compare. I know we are looking to hybrids and pure electric. The base comparison isn’t easily available yet which is a shame as all four fuels still have a lot to offer.
Now here’s the strange thing. The Car mag rates the new Volvo XC90 5*. Maybe the earlier reports of 16mpg are flawed?
The Lexus 450 hybrid looks a great car but again not frugal.
Surely petrol engines aren’t as bad as we tuggers think :
The ratio you suggest is fine with me but the newer vehicles are way way above that figure.
So maybe there is hope for petrol andalternativesandwewerehood winked years ago to go diesel B)

I’ve said in several posts that I’ve had some good petrol tow cars, but the market changed when good diesels became more readily available in cars/estates as opposed to vehicles such as Disco, Shogun, etc. There’s no doubt a diesel makes a good tow car but after driving a number of petrol cars with turbos you would be surprised how smooth, quiet and free revving they are. I’m sure that as more petrols and hybrids come onto the market there will be ones suited to towing duties. My current pick would be the 280 Skoda Superb 4x4 estate, it’s a non hybrid and non frugal, so mileage might be constrained

It’s a beast :evil: I’ll have one B)

 

[Raywood]

While bhp is relevant I would be just as intersted in the car producing good low down torque. This is where the diesel excells and petrol manages.

 

[Hutch]

While bhp is relevant I would be just as intersted in the car producing good low down torque. This is where the diesel excells and petrol manages.

The SteamRover

 

[xtrailman]

Advice is 40bhp and 80 pound feet per ton.

I prefer diesel with high torque with adequate power for towing. I've towed with a 180bhp turbo petrol which was ok as well, but very few petrol cars give out more than 250 pound feet IME.

 

[Lutz]

My 3.0 diesel has 413 ft lb of torque. The petrol equivalent, also 3 litre, has 295 ft lb. OK, not as much but still more than 250.
Besides it's still the brake horsepower that gets you over the hill, not the torque. Basically, bhp is torque times engine speed. A low torque at a high engine speed will produce the same results as a high torque at a low engine speed.
Therefore, only when looking at the same time at engine speed does a torque comparison make any sense. The petrol version achieves maximum torque at 1200 to 5000rpm, the diesel at 1500 to 3000rpm, so in that respect, the petrol is even better than the diesel although the net torque figure for the diesel is somewhat higher.

 

[xtrailman]

My 3.0 diesel has 413 ft lb of torque. The petrol equivalent, also 3 litre, has 295 ft lb. OK, not as much but still more than 250.
Besides it's still the brake horsepower that gets you over the hill, not the torque. Basically, bhp is torque times engine speed. A low torque at a high engine speed will produce the same results as a high torque at a low engine speed.
Therefore, only when looking at the same time at engine speed does a torque comparison make any sense. The petrol version achieves maximum torque at 1200 to 5000rpm, the diesel at 1500 to 3000rpm, so in that respect, the petrol is even better than the diesel although the net torque figure for the diesel is somewhat higher.

I agree both are more than adequate, but most people tow with low capacity typically 2L four cylinder cars. That was in my mind when posting.

 

[Gafferbill]

Lutz........I see you have ditched the Lexus hybrid for a big 3 ltr diesel.
It would be interesting if you gave your thoughts as a caravanner on comparisons of ownership.

 

[Lutz]

Lutz........I see you have ditched the Lexus hybrid for a big 3 ltr diesel.
It would be interesting if you gave your thoughts as a caravanner on comparisons of ownership.

Actually, I was very happy with the Lexus. I only sold it because I'd already had it 8 years and I figured that sooner or later I could expect the need to have expensive work done on it like perhaps a new battery pack. It was perfectly reliable while I had it, though. The only criticism I had of the car was its pitifully small starter battery (identical to that of a Nissan Micra) which simply wasn't up to the job, and its torque sensitive steering.
I now have a BMW X4 30d. It's a diesel because I clock up a fair mileage and it's a matter of economics that dictates a diesel. (When I bought the Lexus I did less miles) I probably would still have bought one if the whole diesel emissions saga had happened earlier as it's Euro 6 unit with which I'm not expecting any major restrictions as to its use at least in the short to medium term.
I found that the hybrid only saved appreciable fuel solo and in stop-start city driving, but not on the motorway and even less when towing. Anyway, I'm using 50% less fuel on average with the BMW despite similar engine performance.