Converting HP to Kw
  • Register
  • Help
Results 1 to 25 of 25
  1. #1
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Sydney
    Posts
    212

    Converting HP to Kw

    Hey

    1. how do you convert hp to kw?
    2. what is the formula for the wheel hp?

    Advertisement


    Ashley
    ashleyt

    --------
    1993 205GTI Sorrento Green
    1990 205GTI Red - Track Car ("431")

    EC:2:02.18, WP:1:16.07, OP 54.27, OPGP 1:28.83, Huntley 32.34

  2. #2
    Simon's Avatar
    Join Date
    Jul 2000
    Location
    Adelaide
    Posts
    6,097
    1 hp is equivalent to 0.74570kW
    1963 Renault R4 Van
    1964 Renault R4
    1967 Volkswagen 1300 Deluxe
    1969 Renault 8 Gordini 1300
    2005 Renaultsport Clio 182 Cup

  3. #3
    Fellow Frogger!
    Join Date
    Mar 2003
    Location
    Sydney
    Posts
    212
    ta cheers!
    ashleyt

    --------
    1993 205GTI Sorrento Green
    1990 205GTI Red - Track Car ("431")

    EC:2:02.18, WP:1:16.07, OP 54.27, OPGP 1:28.83, Huntley 32.34

  4. #4
    Fellow Frogger! MYT205's Avatar
    Join Date
    Sep 2001
    Location
    NSW
    Posts
    1,063
    Ashley.

    Pretty much hp at the wheels is the same as engine kw.

    Darren

  5. #5
    1000+ Posts parry's Avatar
    Join Date
    Sep 2002
    Location
    Sydney Australia
    Posts
    1,323
    Forget about HP! Its all about Power to weight ratios.
    90 205 Gti Cherry Red(Track Car)
    2009 207gti
    1985 505gti (Shitbox Rally) Sold

    PBs:

    Oran Park: 1:27:9
    Wakefield: 1:05.6 (July 2015)
    Eastern Creek: 1:54 (8v) 1:48 (16V)
    Mt Huntley: 34.44 (2004 stock 205)
    Ringwood: 35.06 (30/10/2005)
    Winton: 1:33.6 (2017)

  6. #6
    Fellow Frogger! MYT205's Avatar
    Join Date
    Sep 2001
    Location
    NSW
    Posts
    1,063
    And the cheapest gain you can make is strip the car out. head_ban roll_lau

    Darren

  7. #7
    1000+ Posts Warwick's Avatar
    Join Date
    Nov 2002
    Location
    Melbourne
    Posts
    2,664
    Formula is on <a href="http://www.pumaracing.co.uk" target="_blank">www.pumaracing.co.uk</a> site. This seems accurate. Seems.
    "Now my dream lies shattered like the shards of a broken dream"

  8. #8
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    parry:
    Forget about HP! Its all about Power to weight ratios.
    Actually it's all about torque to weight, and gear ratios which match the torque curve to give the most usable torque at the wheels, and thus the greatest and most consistent force thrusting the car along (the weight and thus inertia of rotating mechanical components also plays its fair share). This is why some cars with certain power to weight ratios are slower than other cars with "inferior" power to weight ratios.

    Acceleration=force/mass

    As for Hp at the wheels, people argue over various values between 65% and 85% of flywheel Hp. I think it's closer to 85%, although a Dyno day we had in the NSW Pug club showed that most cars had a wheel Hp figure about 72% of their manufacturer quoted flywheel Hp. I think this just shows that manufacturers tend to overquote their flywheel figures (probably becasue they are measured on engines which are put together with more care than the general ones of the assembly line).

    Dave

    <small>[ 11 April 2003, 03:38 PM: Message edited by: davemcbean ]</small>
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  9. #9
    Fellow Frogger! AlsPug504's Avatar
    Join Date
    Jul 2002
    Posts
    310
    Some say around 15hp driveline loss in a manual and 20hp odd in an auto. That is deducted from the full power delivered from the engine. At least that is what I have read in 21st century perfomance.

    Al

  10. #10
    Fellow Frogger! MYT205's Avatar
    Join Date
    Sep 2001
    Location
    NSW
    Posts
    1,063
    21st Century Performance was written by Julian Edgar. Wouldn't believe much of what he says.

    Many many people think this of him. moon

    Those from Autospeed and Performance Forums will know what I mean. roll_lau

  11. #11
    Fellow Frogger! AlsPug504's Avatar
    Join Date
    Jul 2002
    Posts
    310
    Just curious, did Edgar offend you at some point?
    I know he certainly is controversial. And does stuff up a few facts.
    question
    I have heard other figures Hp quoted elsewere that are simular!

  12. #12
    Fellow Frogger! PUG309's Avatar
    Join Date
    Feb 2001
    Location
    Sydney, Australia
    Posts
    231
    So a 1000BHP Skyline GT-R is going to lose 5BHP when going from a manual to an auto :p

    Not flamin I just think every car is diffrent, as in there is no global formula

    Daniel
    Daniel Djuracic

    Ex UK spec 89 309
    206 XT 1.6 16V (Diablo Red)with Peugeot Lion in back windows

  13. #13
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    PUG309:
    So a 1000BHP Skyline GT-R is going to lose 5BHP when going from a manual to an auto :p

    Not flamin I just think every car is diffrent, as in there is no global formula

    Daniel
    Yeah, gear tooth helix angles and profiles have alot to do with transmission losses, as do bearings. This is why racing cars use straight cut gears. They're noisy, but they don't loose so much power as helical cut gears.

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  14. #14
    1000+ Posts CHRI'S16's Avatar
    Join Date
    Jun 2002
    Location
    Sydney
    Posts
    3,298
    PUG309:
    So a 1000BHP Skyline GT-R is going to lose 5BHP when going from a manual to an auto :p

    Not flamin I just think every car is diffrent, as in there is no global formula

    Daniel
    not really, it will still be a 1000BHP GTR, just an auto one, final @the wheels figures can be easily bodged by puting under driven wheels, or Smaller rotating diameter, etc.... so TOO may variables to count for.. not just the auto box.
    cheers
    Xq
    ... ptui!

  15. #15
    Sense Pug307's Avatar
    Join Date
    Mar 2002
    Location
    Australia
    Posts
    4,355
    If the 307 1.6M vs 2.0A figures are anything to go by, the auto costs you 20kW!!!

    I still believe power to weight is more important than torque to weight. You can increase torque via gearing - you can't do so via power.

    There is an interesting Autospeed article on this. Using various formulas, graphs and R values, it shows how power to weight is far more important than torque to weight. I've put down some simple stats here.

    Ford 4.1 Cortina - 1220kg, 288Nm and 92kW.
    0-100: 10.0 seconds
    0-400: 17.4 seconds (128 km/h)

    Honda S2000 - 1350kg, 208Nm, 176kW
    0-100: 6.6 seconds
    0-400m: 14.8 seconds (155 km/h)

    Now there are extra factors here, such as the efficiency of gearboxes (aerodynamics really aren't that much of an issue for things like 0-100), but the S2000 is way and truly ahead. This doesn't talk about real world driveability.

    Let's compare 2 Peugeots - simple figures here. One is clearly superior in power, once is clearly superior in torque.

    A: 307 1.6 16V - 80kW, 147Nm, 1193kg
    B: 307 2.0 HDi - 66kW, 205Nm, 1260kg

    Power to Weight

    A: 14.91kg/kW
    B: 19.09kg/kW (28% worse off)

    Torque to Weight

    A: 8.12kg/Nm (32% worse off)
    B: 6.15kg/Nm

    0-100km/h

    A: 11.7 (real world seems to be less)
    B: 13.8 (real world tests seem to be higher).

    Despite being far superior in torque, the HDi is at least 18% slower (factory figures). Based on the reviews I'm reading, I'd say that's closer to 25-30% in real life. You'll find that this is repeated with the 1.4 (+ 10% power) vs the 1.4 HDi (+ 33% torque) - the 1.4 is 11.5% faster 0-100km/h.

    Any examples to the contrary?

    Cheers,

    Justin

    Peugeot 307 XS 1.6
    Aussiefrogged in MEL, PER, SYD, BNE & ADL.
    Rendezvous Adelaide 2005

  16. #16
    Fellow Frogger! AlsPug504's Avatar
    Join Date
    Jul 2002
    Posts
    310
    Sorry I have made an error. 15% to 20% of the total figure not hp! Or though even that does not sound right?

  17. #17
    1000+ Posts dino's Avatar
    Join Date
    Nov 2002
    Location
    melbourne
    Posts
    4,504
    surely comparing the s2000 and the cortina is a bit like comparing a P76 to a ferrari...???no??
    i d be interested to find what u think of lets say a 4cyl na sri (astra) against a LETS SAY a V6 vn commodore???yes their weights differ, yes one is rear drive and the other is front and i m sure their suspension geometry/handling differs as well...it d be interseting what 0-100 time the s2000 would do with a cortina motor under the bonnet and s2000 gearing...???(if it was possible!)

    cheers
    dino

  18. #18
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    Pug307:

    Despite being far superior in torque, the HDi is at least 18% slower (factory figures). Based on the reviews I'm reading, I'd say that's closer to 25-30% in real life. You'll find that this is repeated with the 1.4 (+ 10% power) vs the 1.4 HDi (+ 33% torque) - the 1.4 is 11.5% faster 0-100km/h.
    The reason the HDi is slower is probably because the torque (at the wheels) to weight ratio is lower (because of the taller gearing), which is what I was getting at in my post. I also mentioned inertia. Diesel engines often have alot of inertia due to heavier conrods, flywheel, etc, which inhibits acceleration to some extent.

    Quoting torque to weight ratios, without taking into account gearing (and thus torque at the wheels) are as useless as quoting power to weight ratios. You also have to take into account the weight of the driver when calculating the figures.

    Dave

    <small>[ 12 April 2003, 10:57 PM: Message edited by: davemcbean ]</small>
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  19. #19
    Sense Pug307's Avatar
    Join Date
    Mar 2002
    Location
    Australia
    Posts
    4,355
    The gearing of the HDi is only 15 to 20% taller than the 1.6 in the lower gears, and similar to that of the 2.0. The HDi has more torque than the 2.0, but is much, much slower - weighs 3% more, but is 41% slower, 34% less power, but 8% more torque).

    In all honesty, I don't think driver's weight is that much of a real issue, given that when testing, you'd have the same person doing the testing, and any difference can hardly be that significant (it's not like we're comparing a 50kg driver and a 200kg driver).

    Let's compare two cars. Same weight, same gearing, same internals, both NA, etc.

    Volvo S60 2.4 Automatic.

    A: 103kW/220Nm 11.1s (0-100km/h)
    B: 125kW/230Nm 9.6s (0-100km/h)

    B has 21% more power, 5% more torque.
    A is 16% slower.

    Considering how small the torque increase is, I find it hard to argue that the small torque increase is responsible for the improvement in acceleration - it's chiefly power.

    I've asked once before, and I'll ask again - find an example that proves the contrary.

    As I'll say again. You can increse torque via gearing, but you can't increase power via gearing.

    Simple -

    Got power, little torque - you can create more torque.

    Got torque, little power - you can't create more power.

    Cheers,

    Justin

    Peugeot 307 XS 1.6
    Aussiefrogged in MEL, PER, SYD, BNE & ADL.
    Rendezvous Adelaide 2005

  20. #20
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    Pug307:
    As I'll say again. You can increse torque via gearing,
    That was exactly my point when I said torque at the wheels (which is a function of gearing).

    As for driver weight, the lighter the car, the more the weight of the driver makes a difference.

    Now when it comes to power, an increase in power is an increase in torque at a given revs (the two are directly related from the equation Power=torque X angular velocity). You can't get more power at a certain revs without creating more torque. A given torque at low revs creates less power than the same torque at high revs, but I guess you already know these finer details.

    Now if you really want an example of a higher power to weight ratio giving less acceleration:

    Hyundai Elantra 5 dr manual
    Weight 1240kg
    power 104kW
    weight/power ratio = 11.92 kg/kW
    0-100km/h 11.3 sec

    BMW 318 Ti manual
    Weight 1390kg
    power 105kW
    weight/power ratio = 13.23 kg/kW
    0-100km/h 10.2 sec

    OR

    Ford Escort 2 litre MkII manual (Australian spec)
    Weight 970kg
    Power 70kW DIN
    weight/power ratio = 13.85
    0-100km/h 12 sec

    Peugeot 504 Ti manual
    Weight 1230kg
    power 77.5kW DIN
    weight/power ratio = 15.87kW
    0-100km/h 11 sec

    The tall 3.54:1 diff and 1.97:1 second gear are what kills the acceleration of the Escort. When fitted with a 3.89:1 diff these cars fly. eek!

    Likewise early six cylinder Cortinas (TC model)are actually slower 0-100km/h than their 2 litre counterparts, depite their better power/weight ratios.

    I can quote more if you like

    Dave

    <small>[ 13 April 2003, 01:37 AM: Message edited by: davemcbean ]</small>
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  21. #21
    Sense Pug307's Avatar
    Join Date
    Mar 2002
    Location
    Australia
    Posts
    4,355
    The current figures I have say that the Elantra is faster than the 318i. Figures are from the respective websites.

    0-100km/h
    Elantra: 9.1s
    318ti: 9.8s

    Also bear in mind, Hyundai was caught out overstating power figures.

    Generally speaking, I believe that power to weight ratios are a better indicator than torque to weight ratios. Unless you have a car with really stuffed up gearing that should hold - most cars generally do get it right.

    You rarely have gearing info handy and in more cases you'll find a car with higher power to weight will have better acceleration than torque to weight.

    Regards,

    Justin

    Peugeot 307 XS 1.6
    Aussiefrogged in MEL, PER, SYD, BNE & ADL.
    Rendezvous Adelaide 2005

  22. #22
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    Pug307:
    You rarely have gearing info handy and in more cases you'll find a car with higher power to weight will have better acceleration than torque to weight.
    Please don't misinterpret what I wrote. I was refering to torque at the wheels, not torque at the flywheel, which means I agree with most of what you're saying. I have also noticed that with newer cars the power to weight ratio seems to be a better indication than it once was, but there are always exceptions (especially when manufacturers don't give accurate power figures).

    The 504 TI is a case in point where the weight to power ratio of over 15 is not a good indication of its performance. As anyone who has driven one will know, they clearly go just as well as many cars with a far better power to weight ratio. How many new cars with a 0-100km/h sprint time below 11.5 seconds have a weight/power ratio on the wrong side of 15?

    Dave

    <small>[ 15 April 2003, 02:07 PM: Message edited by: davemcbean ]</small>
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

  23. #23
    Sense Pug307's Avatar
    Join Date
    Mar 2002
    Location
    Australia
    Posts
    4,355
    Yep,

    I think we're not too different on this one

    But in regards to your question, based on German results, I'll suggest the 307 1.6M.

    Peugeot 307 XS 1.6
    Aussiefrogged in MEL, PER, SYD, BNE & ADL.
    Rendezvous Adelaide 2005

  24. #24
    Fellow Frogger! two-oh-philic's Avatar
    Join Date
    Feb 2003
    Location
    Glen Waverley, Melbourne
    Posts
    419
    Anyone here who knows about engineering or physics can correct me if i'm wrong but if i am looking at a graph with torque in Nm (at the wheels) on the vertical axis and revs ( would need to be in Hz to be strictly accurate) on the horizontal axis. Isn't the power calculated by doing the integral, or summing up the area under the curve? Doesn't that mean power depends entirely on torque and revs? If i'm still right wouldn't it be more practical show weight to torque and then then redline?
    205 GTi (S2 ) rolled

    '96 306XR "Sex" Black

  25. #25
    Guru davemcbean's Avatar
    Join Date
    Apr 2001
    Location
    Camden NSW & Selwyn NZ
    Posts
    2,333
    two-oh-philic:
    Doesn't that mean power depends entirely on torque and revs? ?
    Yes, this is right and I touched on it in a previous post.

    Also as discussed before the gearing and mechanical inertia are large factors in the torque at the wheels during acceleration, so it's quite a complex equation.

    Dave
    NZ Fleet
    1976 504 Ti
    1984 205 GT twin carb
    1991 205 SI 1.6GTI motor
    1994 106 Xsi
    1996 Mondeo V6
    Aus Fleet
    1955 203C
    1997 Civic Cxi (great allrounder- revy, flexible, nimble, comfortable , economical, simple and durable )

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •