Horse power - why is it used in this age?
- Thread starter Trifid
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DRZ said:
If you are using ft-lbf as the unit for torque then the only time that peak torque and peak revs will ever meet is when they are both achieved at 5252 revs.
Peak horsepower in it self means nothing, it is a nice big number to brag about but in real world conditions it means little.
JRS said:I still prefer to use a slightly different method of calculating the power that the Seicento puts out - Brake Shetland Pony Power....much more respectable to say that my car produces 120BSPP than 39BHP.....
rofl
As I understand it, the useful way to interpret the stats are:
- Torque is the ability to accelerate something at specific point in the rev range. Hence why diesels do accelerate well at lower revs than a petrol equivalent, but then die somewhere post 4k
- Peak power is a measure of overall workload that can be completed. As such it shows that if you continued to rev the car to it's peak, just how well it will do it over the full rev range
- The power and torque curves. Now these are the really useful things, as they show how "useable" and effective an engine is across it's full rev range.
For example, normally aspirated petrol engines tend to have a fairly linear acceleration across a wide range, meaning that they're not going to have massive flat spots, then suddenly a huge glut of power that'll stick you in a hedge (which is what some early turbos did).
- Torque is the ability to accelerate something at specific point in the rev range. Hence why diesels do accelerate well at lower revs than a petrol equivalent, but then die somewhere post 4k
- Peak power is a measure of overall workload that can be completed. As such it shows that if you continued to rev the car to it's peak, just how well it will do it over the full rev range
- The power and torque curves. Now these are the really useful things, as they show how "useable" and effective an engine is across it's full rev range.
For example, normally aspirated petrol engines tend to have a fairly linear acceleration across a wide range, meaning that they're not going to have massive flat spots, then suddenly a huge glut of power that'll stick you in a hedge (which is what some early turbos did).
This confuses the hell out of me.
For example, a 500 HP truck will easily pull 44+ tonnes without complaint, yet a 500 HP car such as an e60 M5 would struggle to pull a tenth of that weight despite the same power output.
I know with diesels its all down to torque, as I say, what confuses me is how two engines with the same output are capable of completely different things.
Aye, I'm thick!
For example, a 500 HP truck will easily pull 44+ tonnes without complaint, yet a 500 HP car such as an e60 M5 would struggle to pull a tenth of that weight despite the same power output.
I know with diesels its all down to torque, as I say, what confuses me is how two engines with the same output are capable of completely different things.
Aye, I'm thick!
R124/LA420 said:This confuses the hell out of me.
For example, a 500 HP truck will easily pull 44+ tonnes without complaint, yet a 500 HP car such as an e60 M5 would struggle to pull a tenth of that weight despite the same power output.
I know with diesels its all down to torque, as I say, what confuses me is how two engines with the same output are capable of completely different things.
Aye, I'm thick!
The truck will have 3,000Nm of torque.
The M5 has 520Nm.
As it has been explained above by myself (and others...), bhp is a BYPRODUCT OF TORQUE AT A GIVEN RPM.
Irrespective of whether it runs on petrol, diesel, chip fat or the shattered dreams of children on christmas morning, torque is required to calculate bhp.
*n
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People seem to be missing an important point. Torque at the engine (i.e. flywheel) is not important, it's torque at the road wheels and this is determined by both engine torque and gearing. With suitable gearing the M5 engine could pull 100 Tons with no problem, albeit not very quickly.
Diesels lose a lot of their torque advantage at the wheels as the gearing has to be higher to compensate for the relatively slow speed of the engine.
Diesels lose a lot of their torque advantage at the wheels as the gearing has to be higher to compensate for the relatively slow speed of the engine.