why are car's measured in bhp? and if my car is 120bhp - how/why/what is it measured that i have 120 horses under the bonnet?!
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Dave,
I'm sure someone will be along soon with a detailed explanation, in the meantime, this page covers the basics of horsepower, apparently 1HP equals the 150% of the work done by an average pit pony!
auto.howstuffworks.com/horsepower.htm
IIRC the metric equivalent of HP is PS (Pferdestärken), which appears to be used on most european cars.
To covert from PS to HP, HP=PS/1.0139 (from www.vw.co.uk)
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To covert from PS to HP, HP=PS/1.0139 (from www.vw.co.uk )
Or forget the exact figure and remember that its about 1:1, thereby getting a falsely optimistic impression of the power of VW group cars.
If they can translate the brochure from German to English then they can convert the PS figure to BHP. Everyone else does, but they don't. I wonder why not? I wonder if they would bother if the conversion was to multiply instead of divide?
Covert indeed!
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PferdStarken isnt that just German for Horse Strength ?
Does this mean that those damned european horses are just lazy ?
Mark
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Indeed, its all just other measures of horse power. There is another one (I think) not used anymore, but I forget what it is. Either there's a scientific explanation for the difference, or someone over here just wanted to say "our horses are more powerful than your horses, so there! :-P"
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These alternative definitions of power are all similar, but different in the detail. Some standards specifiy that the engine doesn't have to drive a fan or water pump, whereas others specify that the engine has to be almost as installed. Other differences involve the way that corrections are made for air temperature and pressure during the test. Obviously, manufacturers tend, whenever they can get away with it, to quote the figures that make their engines look superior.
number_cruncher
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Correct the vag group 2ltdi is quoted at 140, yes ps that is but 138bhp doesn’t quite ring the right bell does it? also the lasted 200ps petrol turbo sounds great, but 198 bhp not the same message is it? Also not that vw doesn’t shout the fact that 98 octane is required to achieved these figures. Still both good engines, but Joe blogs I sure is not aware of these small but important facts.
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Well said NC..going back years ago I do remember standards that were never met..Mind you I come out of the trade for a while..Poor pay for those that knew what they were talking about or did..better pay for those that had no Idea.Think that was due to fast fit no training/very little ......I wonder about Techs now
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Steve
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AFAIR 1 HP will lift 550LBS 1 foot in 1 second... the various abbreviations are to do with where the power of the engine is measured. BHP and SAE are the same, being measured by the dynamometer at the final output (wheels); DIN = PS is measured at the crankshaft. A 100 (DIN) car will come out at (say) 92 BHP due to losses in the power train. There're also various theoretical calculations based on capacity, but the best measurement is BHP or the equivalent in KW, as that's what your machine actually has available to use *on the road*.
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AFAIR 1 HP will lift 550LBS 1 foot in 1 second...>>
A great little engine though it is, I can't imagine my 4.5hp Honda lawnmower being able to lift 2425lbs 1ft in 1 sec.
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Sometimes a cars power output is stated in Kilo Watts, so its helpful to know that 1horse power=746 Watts.
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1 HP *is* the equivalent of 746 watts, or 33,000 ft pounds of work per minute.
The latter figure is the same as 550 pounds feet of work per second -- as quoted above.
>can't imagine 4.5 HP lifting . . .<
Let us consider just a 1 horse power motor rotating at 3000 rpm -- not a high speed for a lawnmower motor. That is 50 revs per second.
So what diameter shaft could we wrap a 'string' round such that it would roll up the string at 1 foot per second? The answer is, 12 inches, divided by 50 and then again by Pi (3.142). Thus the shaft diameter is less than one tenth of and inch (0.076 inches).
Begins to look pheasible that it *would* have quite a powerful pull, I suggest. And you would need to be able to pull at 550 pounds to stop it.
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(Third time lucky?)
This goes back to James Watt's time, when lifting 33,000 pounds in one minute was stated to be the capacity of a stout horse; as many of the early applications of engines were in lifting water this idea of a horse power gave an understandable picture of what one could do. (Disappointment was to be avoided, and it would in practise have needed to be a strong horse and not working for long to give such a figure.)
Today in cars I believe sometimes the figures given are often high to impress custmers who will never test them, or sometimes low not to upset do-gooders.
Supra is given somewhere to have only 270 horses, but this I think must be at the back wheels (and before superchip). At any rate 0 to 60 has been timed at just on five seconds, roughly equating to vehicles of similar weight and quite a lot more horse power.
How long is a piece of string?
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