Torque formula question
Discussion
I think I've asked this before and it's been answered, but I either pretended to understand or I've just forgotten, but can someone please explain to my tired head...
I'm sure I read an article recently comparing two cars that were from the same manufacturer, one was petrol and one was diesel. Let's say, for example, that they both produce 300bhp. I'm sure I read that the diesel car produced more torque, and the article actually compared two figures. I understand that the diesel car will produce maximum torque at a different rev range, but the max figure should still be the same.
Given that torque is a factor of HP, how can this be?
If a cars maximum HP is at say 5000rpm, then at this point it is producing 315 ((5252xHP)/rpm) 'torques' regardless of the fuel powering it. Therefore, the maximum torque is the same for both cars?
Confused.
Hi
Power is torque x rpm. So if 2 engines produce the same amount of power at X rpm then they also both produce the same torque at that rpm.
Diesels tend not to rev anything like as high, so make power by producing more torque at lower revs while the petrol engine produces less torque but at higher revs. That on its own makes no real difference as the petrol engine is just geared to use more revs at the same road speed resulting in similar torque at the wheels (torque at the wheels being engine torque x gearing).
However it gets confusing when people think of torque as flexibility (ie, they refer to an engine as torquey when it has a flexible power delivery), when flexibility has little to do with peak torque that is the reported figure. Obvious example of this is a performance 2 stroke motorcycle which will have quite a bit more peak torque than a 4 stroke of the same capacity, but few would claim a performance 2 stroke is torquey.
All the best
Keith
Power is torque x rpm. So if 2 engines produce the same amount of power at X rpm then they also both produce the same torque at that rpm.
Diesels tend not to rev anything like as high, so make power by producing more torque at lower revs while the petrol engine produces less torque but at higher revs. That on its own makes no real difference as the petrol engine is just geared to use more revs at the same road speed resulting in similar torque at the wheels (torque at the wheels being engine torque x gearing).
However it gets confusing when people think of torque as flexibility (ie, they refer to an engine as torquey when it has a flexible power delivery), when flexibility has little to do with peak torque that is the reported figure. Obvious example of this is a performance 2 stroke motorcycle which will have quite a bit more peak torque than a 4 stroke of the same capacity, but few would claim a performance 2 stroke is torquey.
All the best
Keith
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