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Towcar Guide Website Query.


martin1512
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I have been looking at several towcar matching guides, and something has me confused. For some reason, they all seem to base how well a car will tow a certain weight of van based on the towcars max BHP. As far as towing is concerned, a cars max BHP is pretty much irrelevant, as a car usually produces it's max power at an RPM range much higher than the engine is driven at when towing. What would be a much indicator would be to use the 1500-3000 rpm torque figures. For example, my V8 Land Rover produces a maximum of 190 BHP at 5000 rpm, and the Ford Galaxy 2. 0 ecoboost produces 203 BHP at 5500 rpm, and based on these figures the galaxy scores much higher than my Landy. When you compare torque figures however, things are very different My Land Rover produces 297 lb-ft at 1700rpm compared to the Galaxy's 221 lb-ft at 1750 rpm. This means my Land Rover actually has almost 35% more pulling power than the Galaxy at the same engine speed.

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I'm afraid you've got your terms mixed up. Pulling power, as the name suggests, determined by horsepower, not torque. Lots of low end torque makes for relaxed driving, but in the end it's power (torque times revs) that determines whether the outfit can make it up the hill or not.

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I'm afraid you've got your terms mixed up. Pulling power, as the name suggests, determined by horsepower, not torque. Lots of low end torque makes for relaxed driving, but in the end it's power (torque times revs) that determines whether the outfit can make it up the hill or not.

Torque is the amount of turning force the engine produces, Horsepower is like you said, torque x RPM. Torque determines the maximum amount of tractive effort the vehicle can provide, horse power determines how fast it can apply that force. Which is why a HGV with only 350 BHP but 1000 lb-ft of torque will pull a 30 ton trailer but if you were to put an engine in with 750 BHP and 400 lb-ft of torque in the same truck, it would not pull 30 tons but would be an awful lot quicker when unloaded. Basically, Torque determines how much a vehicle will pull, whereas BHP will determine how fast the vehicle can go.

Edited by martin1512
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Torque is the amount of turning force the engine produces, Horsepower is like you said, torque x RPM. Torque determines the maximum amount of tractive effort the vehicle can provide, horse power determines how fast it can apply that force. Which is why a HGV with only 350 BHP but 1000 lb-ft of torque will pull a 30 ton trailer but if you were to put an engine in with 750 BHP and 400 lb-ft of torque in the same truck, it would not pull 30 tons but would be an awful lot quicker when unloaded. Basically, Torque determines how much a vehicle will pull, whereas BHP will determine how fast the vehicle can go.

 

Your comparison is a bit meaningless as you haven't said at which engine speed the 1000ftlb or the 750ftlb of torque are developed. If the 1000ftlb are developed at 1500rpm and the 750ftlb at 2000rpm then both trucks will pull a 30 ton trailer up the same hill at the respective engine speeds. The one with the lower torque will just have to rev faster.

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I agree it some times not easy working it all out keeping in mind the power to weight ratio. The old ratio was simpler ie 'the biggest car you can afford pulling the smallest caravan you can manage with' . Hope you find something you like and enjoy.

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