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Torque? HP? usefulness?

Discussion in 'General Tech and Maintenance' started by SolPWR, Feb 27, 2004.

  1. SolPWR

    SolPWR Senior Member

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    Ok I know this has been asked more times than those sightings of rice on ebay but I just need some clearing in terms where ID10TS could understand.

    What is the relation of torque and HP to speed/accel?

    Example:
    Car A- 210hp 315tq 3600lbs
    Car B- 162hp 195tq 3300lbs
    Car C- 130hp 108tq 2300lbs
    Car D- 140hp 130tq 2800lbs

    These are figures from real cars. Cars A & B are FI and the others are NA. I see with FI there is more tq than hp. Can someone put this into english for me. Also I would like to know which out of these would be the best performer.
     
  2. tab

    tab Super Moderator

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    Horsepower=(Torque x rpm's) / 5200

    On EVERY car, the horsepower is equal to torque at 5200 rpms.

    Torque is the REAL number that matters. Horsepower is inferred by means of the equation above. Depending on the means of FI, the peak torque number may fall below 5200 rpms. This means that the HP number is not amplified by the rpm level.

    My toronado is NA. From the factory, it had 500 ft/lbs of torque and 400 HP. Obviously the peak torque is lower than 5200 rpms.

    IF the peak torque were to happen at 6000 rpms:

    the horsepower number would be (500 x 6000) / 5200
    =3,000,000/ 5200
    =577HP

    So, Horsepower to me does no more than relate the torque curve in another way. Torque is torque, at any rpm.

    Useable power across a wide rpm range is the goal. It's easy to be led astray by "wow" horsepower numbers.
     
  3. SolPWR

    SolPWR Senior Member

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    so your saying that Car A and B are better performers than the other two performance wise.
     
  4. tab

    tab Super Moderator

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    They definitely have more power. They also weigh more. I don't know how many variables go into figuring out which would win in a race, but I'd chose A or B

    If a car makes a lot of torque for a short time, the power would be less useable. I doubt that this is the case. A car with a lower peak could win if the torque curve stayed flatter over a large rpm range. This is why people say they won't pick a winner in a " X vs. Y race". Peak numbers can be misleading.
     
  5. jamesA

    jamesA Well known pissed off telephone guy VIP

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    That should actually be 5252 rpm. torque=horsepower at 5252 rpm. No matter what car, what engine. Torque is the ability to do work, horsepower is the amount of wattage (electricity) the engine can generate. (1 hp equals about 746.7 watts)

    Higher torque cars like small block chevy V8s will generally have a better, more usable power band than a high hp FI sub-2.0L honda motor, BUT weight is the enemy.
     
  6. NoJokE

    NoJokE Senior Member

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    Gearing is one of the biggest factors if not THE biggest factor. You can have an engine producing tons of torque but it needs gearing, not enough gearing and it'll go nowhere fast. Get gearing that matches your power output, and keeps you in your powerband for the most amount of time.

    EDIT: That would be in a perfect world but we dont get to pick and choose the gearing to optimize engine performance. :shrug:
     
  7. odnet

    odnet Member

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    Or in redneck terms:

    Horsepower is how fast you hit the wall,
    Torque is how far you take the wall with you.
     
  8. jamesA

    jamesA Well known pissed off telephone guy VIP

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    :withstupid: all the way.


    If you had a Mustang or Camaro or Corvette, you could choose your rearend gearing... 3.23, 3.43, 3.73, 4.10, etc etc. :)
     
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