What is the basis of computation for automotive engine horsepower?
enrico p asked:
Automotive manufacturers indicate specific horsepower ratings for their engines/vehicles. How do they measure these? Is the weight of the vehicle relevant to the computation?
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Automotive manufacturers indicate specific horsepower ratings for their engines/vehicles. How do they measure these? Is the weight of the vehicle relevant to the computation?
June 4th, 2010 at 9:21 am
How do they measure these?
It’s basically an imaginary number. All it is, is Torque, multiplied and divided. If you want to talk about a REAL unit of force, look at torque.
Horsepower is great for advertising, but that’s about it.
Here’s an example. Let’s say you have Car A, advertised at 300 hp at 6,500rpm. And Car B at 210hp at 5000rpm. Which is the more powerful car?
Impossible to say from that comparison, because you’re not measuring the two cars at the same rpm. The 210hp car might actually make 350hp at 6500. And the 300hp car might only make 140hp at 5000.
As a comparison, imagine one person says they run a mile in 6 minutes. Another says they run 1.5 miles in 9 minutes. Who’s faster? Hard to say, since you’re comparing different things.
Is the weight of the vehicle relevant to the computation?
Not in the slightest. But it is relevant to the vehicle’s performance. So are things like gearing, traction, aerodynamics, etc. Simply saying a 300hp car, does not immediately mean it’s faster than a 250hp car. Or that it’s more powerful. Vipassana
June 7th, 2010 at 6:45 am
vip is almost right.they come up with the advertised hp and torque by running them on a dyno.they run several,then avg the numbers.as for rpm,they always list peak hp and rpm.so if the engine is running less or more rpm, the hp drops from peak,thats its sweet spot.as for torque,it also has a sweet spot,but seldom follows the hp curve. idontgivafork