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Thread: Article: BHP vs HP vs kW and other power conversions

  1. #1
    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Article: BHP vs HP vs kW and other power conversions

    This article arose out of my own curiosity with respect to the difference between Brake Horse Power (BHP) and Horse Power (HP). I figured I'd research it myself and write a little article on the differences.

    It then grew a bit as I decided to whack in the other Power Conversion Factors.

    Firstly, the difference between BHP and HP.

    Technically there is NO difference short of the fact that you won't find power ratings for BHP at the wheels. The reason for this is the concept of BHP was born out of the old way of measuring engine power output.

    A resistance (brake) was applied to the end in test to determine how much power it was putting out, as opposed to today's methods where an electronic Dynometer or Torque Converter is put on the engine. Hence BRAKE Horse Power. A 'brake' is applied to the engine to provide the resistance to measure the power output. The output is still measured in Horse Power, so there is hence no difference between BHP and HP.

    BHP is an old unit of measurement and only get's used in places where 'old' forms of measurement are common place (read UK & US).

    One other common mis-conception is the PS. It has been listed in a few supposedly reputable magazines as "Power Stroke".... Clearly they were "Power Stroking" something because it DOESN'T stand for power stroke.

    PS stands for PferdeStarke which is the German word for Horsepower. It's also commonly know in France as the CV or Cheval Vapeur. Both words are the translation for Horsepower. These are used across Europe because they provide a reasonable metric conversion for a Horse Power.

    Where a HorsePower is measured in Imperial Units (50 foot pounds per second), the PS is measured in comparable metric units (75 kilogramme metres per second). Clearly the numbers don't exactly match up, so there's a conversion factor of PS to HP. One PS is approximately 98.6% of on HP.

    Of course we all know the KiloWatt. This is purely a measure of energy transfer (a Watt being Joules transfered Per Second) and doesn't have to have any relation to an engines power output, it ofcourse can be used for any appliance or device that consumes or creates energy. There is however an application for it in the automotive sense, and it does help to 'standardize' the automotive power quotation convention.

    Now while the kW doesn't have roots leading to a torque based calculation, the other two do. I have the information on where torque fits into all of this but I don't have time to explain it all now, so I'll leave it for next time..

    I will however leave you with a neat little conversion table that lays out the differences between the ratings.

    Source -> To -> Conversion Factor

    kW -> PS -> 1.360

    kW -> BHP -> 1.341

    PS -> Kg M/second -> 75

    PS -> Ft Lbs/second -> 542.476

    PS -> Watts -> 735.5

    BHP -> PS -> 1.01387

    BHP -> Ft Lbs/second -> 550

    BHP -> Watts -> 745.7

    Lb Ft -> Nm -> 1.356


    PS: Because this won't let me post HTML, I can't do a table to make it look nice, sorry..
    Damn hard to read, I know.
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    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
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    Junior Member Carport Converter SL666's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    PS stands for PferdeStarke which is the German word for Horsepower
    i thought it meant 'power stroke'

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    Toymods Pimp Chief Engine Builder Norbie's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Good info stradlater, +rep.

    Quote Originally Posted by SL666
    i thought it meant 'power stroke'
    Go and stand in the corner.

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    Toymods Club Member Too Much Toyota RONA's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Great thread any chance of a sticky for it, i'm always looking for the lb ft/Nm conversion
    If in doubt power out

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    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Hehe. No, it doesn't mean Power Stroke... I found it interesting that the French call it CV...
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    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
    2007 BMW 3.0Si Z4 Coupe - 195kW 0-100 5.7.....
    1996 VR Lexcen - Let the gearbox slippage begin...

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    Junior Member Too Much Toyota YLD-16L's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Good work Strad +rep.

    I will add a few of these conversion factors to the converter in my phone It's a killer at parties and for picking up chicks. Also reasonably handy at dyno days

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    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Killer for picking up chicks? I thought you were a chick>?
    www.stradlater.com | Facebook | LinkedIn

    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
    2007 BMW 3.0Si Z4 Coupe - 195kW 0-100 5.7.....
    1996 VR Lexcen - Let the gearbox slippage begin...

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    Junior Member Carport Converter SL666's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Norbs: believe it or not.. im 100% sure thats what it says in this book i have at home, a book on rotaries... i agree the literal translation is horse-strong through

    strad: the bloody french.... does explain the citroen 2CV though..

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    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    2CV.. Hehe. I like that...
    that's one powerful car.
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    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
    2007 BMW 3.0Si Z4 Coupe - 195kW 0-100 5.7.....
    1996 VR Lexcen - Let the gearbox slippage begin...

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    My Wife says I have Too Much Toyota o_man_ra23's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Quote Originally Posted by YLD-16L
    Good work Strad +rep.

    I will add a few of these conversion factors to the converter in my phone It's a killer at parties and for picking up chicks. Also reasonably handy at dyno days
    I have NFI how you would pick up chicks with a power conversion table...

    On topic tho, Power is derived by multiplying torque with rotational velocity in RPM and then multiplying by a constant. Ill see if i can dig all the formulae out of my old lecture notes. If i remember correctly, Horsepower is gained by multiplying Foot Pounds directly by RPM... ie conversion factor of 1... but i would have to confirm that. Ill see if i can find these old notes and let everyone know.

    Props to Stradlater for putting this stuff up, I was always wondering WTF the difference was between BHP, HP and PS... Oh, and if anybody wants to believe that PS stands for Power Stroke, they are more than welcome to continue Power Stroking as much as they like... just please dont do it anywhere I may witness.

    Cheers, Owen
    Cheers, Owen
    1977 RA28 with 18R-GTE
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    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Horsepower = Torque x 2 pi x rpm / 33000

    So sort of what your talking about, yes.
    www.stradlater.com | Facebook | LinkedIn

    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
    2007 BMW 3.0Si Z4 Coupe - 195kW 0-100 5.7.....
    1996 VR Lexcen - Let the gearbox slippage begin...

  12. #12
    Junior Member Carport Converter SL666's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Owen: I think you are power-stroking right now power is a measure of work done, torque is a measure of force. and i think the multiplier is something like 5454 or something.. i suppose i could ACTUALLY look it up.

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    Junior Member Backyard Mechanic
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Google has a fairly good translater. You simply type -
    "200 foot pounds in newton meters" in the search bar and enter, and it outputs -
    "200 foot pounds = 271.16359 newton meters"
    or basically any conversion you can think of
    if you didnt already know.....

    and yeah, good info stradlater

  14. #14
    Experience shows I'm no Chief Engine Builder Roundy's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    5252 is the multiplier

    hp = torque x rpm / 5252
    "If you try to fail, and succeed, which have you done?"
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    Junior Member Too Much Toyota YLD-16L's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Google has a fairly good translater. You simply type -
    "200 foot pounds in newton meters" in the search bar and enter, and it outputs -
    "200 foot pounds = 271.16359 newton meters"
    or basically any conversion you can think of
    if you didnt already know.....
    Thanks, didn't know about that one.


    I have NFI how you would pick up chicks with a power conversion table...
    .....and that is why you will be power stroking yourself to sleep each night

  16. #16
    Official Off Topic KING! Conversion King stradlater's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Correct, 5252 is the multiplier.

    Funnily enough, if you see a dyno graph in foot pounds and HP, graphing torque against power, you'll see that they ALWAYS cross over at 5252 if the graph is done properly.

    An interesting thing..
    www.stradlater.com | Facebook | LinkedIn

    1976 RA23 Celica - 1UZFTE ???rwkw - Earlier: 11.6 @ 116.9mph But Now: ??
    2007 BMW 3.0Si Z4 Coupe - 195kW 0-100 5.7.....
    1996 VR Lexcen - Let the gearbox slippage begin...

  17. #17
    Cunning Linguist Domestic Engineer The Last Streetfighter's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    http://en.wikipedia.org/wiki/Horsepower

    Cheval (horse) Vapeur (Steam)

    Also, haven't you got those little conversion files Conversion.exe and Sapfile.exe.? They are both great.
    AE90 Silvertop - GONE; 2001 ST215W GT-T Manual - SOLD; EP82 Starlet GT - Sold
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    My Wife says I have Too Much Toyota o_man_ra23's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions



    .....and that is why you will be power stroking yourself to sleep each night
    Hmm... interesting concept... Ive got a missus to powerstroke me to sleep... but i dont know any chicks (even the geeks from uni days) who are impressed by a conversion table... just cant think of a way that it would come up in conversation.
    Chicks seem to prefer a smile, a compliment and an offer of an enjoyable evening alone around here... dont know how it is in other parts of the world tho.
    Cheers, Owen
    1977 RA28 with 18R-GTE
    Lancer EVO Brakes into old Celica/Corolla/Corona
    2013 86 GTS Aero Daily
    1976 RA23 - waiting to one day get a 3S...

  19. #19
    Purple is the new black! Automotive Encyclopaedia sillycar chick's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    This thread is great, and I will add to it with this link to download an awesome program....

    http://joshmadison.net/software/convert/

    It doesnt have all the power conversions that have been listed, but it is handy when you have torque settings in a workshop manual which are in a different form to the torque wrench you have!! And I use it at work as well (because engineers are lazy) Enjoy....
    51LII - 1972 TA22 Celica | Morpheous Metallic | 4AGE 20v Silvertop | Razorback ECU | W58
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    There is not much hotter than a Freshly painted Celica, Unless its the reflection of a freshly painted Celica on a freshly painted Celica

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    Purple is the new black! Automotive Encyclopaedia sillycar chick's Avatar
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    Default Re: Article: BHP vs HP vs kW and other power conversions

    Quote Originally Posted by o_man_ra23
    ... but i dont know any chicks (even the geeks from uni days) who are impressed by a conversion table... just cant think of a way that it would come up in conversation.
    Chicks seem to prefer a smile, a compliment and an offer of an enjoyable evening alone around here... dont know how it is in other parts of the world tho.
    hahahahaha I always think I am the only chick who would be/is impressed by a conversion table LOL!! But im just a phreak anyways being so into fixing cars and all
    51LII - 1972 TA22 Celica | Morpheous Metallic | 4AGE 20v Silvertop | Razorback ECU | W58
    Toyota Car Club (Qld)

    Quote Originally Posted by TheToyman75 View Post
    There is not much hotter than a Freshly painted Celica, Unless its the reflection of a freshly painted Celica on a freshly painted Celica

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