Horse power - why is it used in this age?

As penski says, which I think is the issue that confused you. RPM and torque are measured to create the power curve.

The peak value on this curve is the 'power output'.

See my sig for an example of the graph - Torque in Red, power in Blue
 
I don't understand how you can ask / see why it's uselesss, perhaps peak power on its own may be not the best thing to know, as you do want to know what the power delivery is like across the rev range, as that'll help understand how well it can accelerate etc, along with correct gearing etc.

Edit, penski has summed it up, along with others.

Edit2, I guess the way I see your confusion is why we use the term horsepower or something like that, horsepower, like any other measurement of powers has the same units, which is a rate of Force x Distance per second, so Nm/s (Watts) etc.
 
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Ford Focus TDCi: -


206lb ft @ 1850rpm = 2472 lb/inch


POWER = 1850 * 2472 = 4573200


BHP = 4573200/63025 = 72.56bhp


so @ 1850RPM the Focus would be generating 72.56bhp? (It's Max power: 115bhp @ 3800rpm).


Or am I totally wrong?


Sorry I'm bored after playing CS:S. :D
 
OK, horsepower is making sense now. I was really baffled why it mattered when torque gave you the actual pulling power of the engine, but I see that it is how many times the engine is pushing at that given moment. (I hope that is right?)

And yes, I do prefer the power delivery of a diesel. :p
 
OK if I'm right..


Max power: 115bhp @ 3800rpm


HP = Torque (lb. -in.) x RPM
___________________
63,025

115*63025= 7247875 POWER

7247875/3800RPM


= 1907 lb/i

/12

=158 lb/ft


So it's producing 158 lb/ft @ its max power of 115BHP @ 3800RPM.

Lmao. :D


Do I get a gold star?
 
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I did my corrections Sir. Do I still have to attend detention?



In laymans terms...


If you have a diesel engine and a petrol engine both producing 100bhp at the same time.


The diesel will be turning over but with more torque.

The petrol will be turning over faster but with less torque.



OcUk Mathmatics course on BHP.


Kthxbye. :D
 
penski said:
Oh dear God, please let it be a wind up...

snippety snip

RPM DOES NOT MATTER IN ANY WAY. IT IS SIMPLY USED TO CALCULATE THE HORSEPOWER BY VIRTUE OF THE AMOUNT OF TORQUE PRODUCED AT THAT SPECIFIC ENGINE SPEED.

*n
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Thanks penski, you just saved me the effort.

;)
 
why is it used?

Because its what were used to and its easy to compare to our older cars

another one is

mpg.. but yet we dont buy fuel in gallons but yet we still use that..
 
GlasgowTitan said:
Okay, how about horsepower and brake horsepower. If the original idea was to compare steam engine's to horses, where does the B in bhp come from and why? :confused:
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brake horsepower will be cause it is measured by braking the engine. Rather than pulling some horses :p

Don't really know the reason but both are the same
 
Tesla said:
What's the difference between HP, BHP and PS?
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Nothing between HP and BHP, both imperial. All the B means is "brake". The old word for a dyno. PS is metric and very slightly different
 
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From the Wiki link Simon posted:

SAE-certified horsepower

In 2005, the Society of Automotive Engineers introduced a new test procedure (J2723) for engine horsepower and torque. The procedure eliminates some of the areas of flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified".

Many manufacturers began switching to the new rating immediately, often with surprising results. The rated output of Cadillac's supercharged Northstar V8 jumped from 440 hp (328 kW) to 469 hp (350 kW) under the new tests, while the rating for Toyota's Camry 3.0 L 1MZ-FE V6 fell from 210 hp (157 kW) to 190 hp (142 kW). The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette Z06. Certified power rose slightly from 500 hp (373 kW) to 505 hp (377 kW).
Click to expand...

I like that....GM had been under-rating one of their engines, Toyota had been lying (apparently, at least as far as one of their main markets was concerned) about one of theirs :D *

Does remind me somewhat of the muscle car era when Chrysler, GM and Ford had to rate some of their engines lower than they actually were. For example, the Chrysler Hemi was rated at 425hp when in reality it invariably produced up over 500.


***edit***


* = alright, lying was maybe too strong a term. Under certain measurments their rating was probably accurate. Still amuses me though!
 
Why is horsepower used?

Well, I, for one, want to know how much sooner my four-hundred horsepower Aston Martin will deliver me to my audience with buxom Miss Farquah at The Manor, than if I were to take the carriage with but six horses.

I had thought we were all the same, although after reading this thread I fear that you are all a complete shower.
 
Nozzer said:
Why is horsepower used?
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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.....:)
 
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