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  • power/torque kfuffle

    Hi,
    This is a question posed to me by my neighbour who is a car fanatic and is looking to purchase his 67th vehicle (for retirement).
    Yes, I know....who the hell could clock up 67 vehicles in a lifetime?? He has a very supporting wife is all I can say.

    Anyway he was looking at the spec for the common rail DID Pajero and noticed that the

    GLX DID has 118kW/3800rpm with 381Nm of torque at 2000rpm

    VRX DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm

    and the

    Exceed DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm

    His question is why the difference in the above considering that they are the same motor and my 2005 DID GLX has 125 kW/3800rpm with buggered if I know how much torque.

    Could anyone explain the discrepancy to me as I cannot give him an answer.

    thanks
    chook

  • #2
    My understanding

    First, note the difference relates to whether you have a manual transmission or Auto.

    Power is about how fast you can get a car to 60 Km/h and Torque is all about the ability of an engine to keep you there. So as the load on the rear wheels (or Front depending on mode) increases, the engine has to match it to maintain say Speed. In the case of a manual, it's a pretty solid connection achieved through a clutch plate to metal contact and the amount of slip is close to zero. In the case of an auto transmission its achieved through a torque converter which is a lossy hydraulic coupling. This is why when you pull up at the lights in an auto there is no need to put it into Neutral but with a manual you do. The amount of loss generally is that which is seen in the difference of the torque figures.

    In the case of the power, it turns out that a torque converter has better ability to transfer power to the wheels at low speeds, my guess is that this is the reason why the power is greater. FRom Wiki http://en.wikipedia.org/wiki/Automatic_transmission
    "Fluid coupling or torque converter: A hydraulic device connecting the engine and the transmission. It takes the place of a mechanical clutch, allowing the engine to remain running at rest without stalling. A torque converter is a fluid coupling that also provides a variable amount of torque multiplication at low engine speeds, increasing "breakaway" acceleration."
    Last edited by danc12; 19-11-07, 09:20 PM.
    Dan C; Stock NS Exceed DID Auto w T'bar, Magellan Explorist XL w DAST topo, Tom Tom One

    Comment


    • #3
      The manual has more torque and less KW than the auto. Your neighbour was probably comparing a manual GLX to an auto VRX.
      Sandgroper.
      NS VRX DiD manual, family pack, tint, 2.5t tow, Smartbar, Firestone airbags, Vision X HID driving lights.

      Comment


      • #4
        So If I have this right it's due to the manual having a better clutch mechanism than an auto and therefore more torque is transferred to the wheels.
        The difference betwen a manual and an auto is the loss of torque an auto has with it's slippery thingamajigi.

        Does all torque get measured at the wheels? or does it get measured at some other point prior to the clutch/thingamajig?

        thanks
        chook

        Comment


        • #5
          But remember, it is not the peak torque figures that matter but the "torque curve".

          Someone did explain it all to me a little while ago (went in one ear and out the other) but it was something like the auto works in a higher rev band and so the motor is tuned accordingly which is why it has more power but sacrifices a bit of torque.
          thanks,

          Adam

          2010 Prado ZR 150 SWB
          1987 Range Rover Ute

          You tried your best and you failed miserably. The lesson is, never try. - Homer Simpson

          Comment


          • #6
            Ok understood that. But why does the auto Exceed and VRX have higher kW and at the same time have the same revs as the manual GLS which has lower kW?

            chook

            p.s. by the time I understand all this i should quit teaching and become a mechanic.

            Comment


            • #7
              Torque by itself is pretty meaningless for powering a car.

              I can apply 500NM of torque with my arm with a long enough lever - but I can't provide any useful drive to a car.

              You need POWER to drive a car - whether it's at 700rpm or 7000rpm - Power is the product of Torque and RPM.
              Mike R. Sydney. Pajero GLS NX Silver Jan15. DiD Auto. STILL grossly disappointed with the errors in Speed Limits on major roads in my TomTom.

              Comment


              • #8
                The fact of having a clutch or a torque converter means nothing, all figures are measure at the 'flywheel'.

                As to your neighbours questions, this sums it up nicely-
                "The manual has more torque and less KW than the auto. Your neighbour was probably comparing a manual GLX to an auto VRX."

                And more specifically why the difference between manual and auto, without workin at mitsy in engineering or soemthign, your guess is as good as mine. What was the difference between the vt and vx for the 6kw gained etc?? Id imagine it has something to do with the DPF, not sure specifically though.

                And the definition of torque and power, this was the best explanation i ever got.

                Torque is the ability to do something, power is the speed in which it occours.

                So like mikes example, without power (NMxRPM) it simply wont happen.

                Comment


                • #9
                  Originally posted by Mike DiD View Post
                  Torque by itself is pretty meaningless for powering a car.

                  I can apply 500NM of torque with my arm with a long enough lever - but I can't provide any useful drive to a car.

                  You need POWER to drive a car - whether it's at 700rpm or 7000rpm - Power is the product of Torque and RPM.

                  Yes you are right but in a strange way power is almost theoretical. You can measure torque and revs but you can only calculate power.

                  The other thing to look at is where it occurs. You want peak torque down low while you want peak power at high revs. At least that was my understanding of a good engine.

                  But I can understand what you are getting at Chook. You would expect the auto torque figure to occur higher in the rev range than the manual but thespecs show them at the same revs. Not sure why???
                  thanks,

                  Adam

                  2010 Prado ZR 150 SWB
                  1987 Range Rover Ute

                  You tried your best and you failed miserably. The lesson is, never try. - Homer Simpson

                  Comment


                  • #10
                    A graph gives the full story of how much power is available at different RPMs.

                    You can't show a graph on a car's specification sheet, so they've all agreed to show two numbers -

                    - Maximum power (and the engine RPM where it happens) - to convey the most power the engine can deliver (usually close to peak RPM, though we spend little time driving with the engine at peak RPM).

                    - Maximum torque (and the engine RPM where it happens) - only to convey some idea of how much power there is at mid-range RPM - but interpret it carefully. Comparing the maximum torque one engine puts out at 2200 RPM with another engine at 3300 RPM is dangerous - if they both put out 200NM max torque, the engine peaking torque at 3300 RPM will be putting out 50% more POWER at mid-RPM ! You must compare Torque at the SAME RPM to make it a valid comparison. Torque will NOT accelerate your car - only power will.

                    It's like trying to compare between a 12 volt and an 18 volt electric drill. The 18 volt sounds more impressive, but if you measure current as well, you might realise why the 18 volt drill can't cope with heavy work.

                    12volt x 2 amps = 24 watts
                    18volt x 1 amp = 18 watts

                    You can't measure electrical power as directly as voltage or current, but it's the ONLY number that indicates how hard the drill can work.
                    Last edited by Mike DiD; 20-11-07, 10:21 AM.
                    Mike R. Sydney. Pajero GLS NX Silver Jan15. DiD Auto. STILL grossly disappointed with the errors in Speed Limits on major roads in my TomTom.

                    Comment


                    • #11
                      the torque spec of each motor is not determined by the transmission type, the power is rated at the flywheel.

                      i can imagine that the torque and power differs for each, for one of the following reasons (or both)
                      1. to achieve emissions
                      2. to not exceed torque spec on transmission/driveline

                      both above are common occurrences


                      power is great!! torque (twisty force lol) determines how quickly you get to max power... that is it gives you a good shunt in the pants
                      SWB NT X DiD its R E D

                      SWB NS X DiD that's double D's !! Retired

                      Comment


                      • #12
                        Don't forget the auto has a variable vane turbo charger and the manual doesn't. Their torque curves are probably quite different.
                        NS GLX DID Auto, MM alloy bar, Kings Springs 35mm Lift, Polyairs, Cooper ATR Tyres 265/70/17, Spider chip.

                        Comment


                        • #13
                          Back again.

                          First of all I would like to thank all of you for your contributions to my education. My neurons have made a few new connections.

                          Now to give you some more headaches...My 05 manual DID pajero has 121kW at 3800rpm with 373Nm at 2000rpm. I would think that the newer model GLX DID which has 118kW/3800rpm with 381Nm of torque at 2000rpm would have more kW than it has especially with common rail. Also puzzling is the fact the the VRX and the Exceed both have 358Nm of torque/ 2000rpm which is less than the GLX.
                          If the vehicles torque is measured at the flywheel we can disregard the fact that a car is an auto or a manual.

                          Being sus at everything under the sun, I have an idea that mitsubishi toned down the kW of later models due to the fact that the added common rail would be a selling point and at some time in the future and they could just increase the kW for future selling points as a "more powerfull" version.

                          What I still don't understand is why the Exceed and the VRX have less torque that the base model pajero. How do you go about adjusting the torque for the same engine anyway. is it the computer??

                          thanks
                          chook


                          VRX DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm

                          and the

                          Exceed DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm

                          Comment


                          • #14
                            Originally posted by chook View Post
                            Back again.

                            First of all I would like to thank all of you for your contributions to my education. My neurons have made a few new connections.

                            Now to give you some more headaches...My 05 manual DID pajero has 121kW at 3800rpm with 373Nm at 2000rpm. I would think that the newer model GLX DID which has 118kW/3800rpm with 381Nm of torque at 2000rpm would have more kW than it has especially with common rail. Also puzzling is the fact the the VRX and the Exceed both have 358Nm of torque/ 2000rpm which is less than the GLX.
                            If the vehicles torque is measured at the flywheel we can disregard the fact that a car is an auto or a manual.

                            Being sus at everything under the sun, I have an idea that mitsubishi toned down the kW of later models due to the fact that the added common rail would be a selling point and at some time in the future and they could just increase the kW for future selling points as a "more powerfull" version.

                            What I still don't understand is why the Exceed and the VRX have less torque that the base model pajero. How do you go about adjusting the torque for the same engine anyway. is it the computer??

                            thanks
                            chook


                            VRX DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm

                            and the

                            Exceed DID has 125 kW/3800rpm with 358Nm of troque at 2000rpm
                            What are you on about? The figures above are the same as they are for auto dids.

                            The base model figures you quoted for the GLX are the manual specs - read them on the MM web site.

                            That is why they are different.

                            If you bought a manual VRX or Exceed (if you can?) the specs would be the same as the manual GLX you quoted.
                            NS GLX DID Auto, MM alloy bar, Kings Springs 35mm Lift, Polyairs, Cooper ATR Tyres 265/70/17, Spider chip.

                            Comment


                            • #15
                              Hi Wilmo,
                              I'm looking at the Overlander 4WD october 2007 edition in which the spec are as I have stated. The question is why is the torque different across the model range at the same revs out of the same motor. especially as the torque is measured at the flywheel.

                              Is it purely as a sales pitch??

                              cheers

                              Comment

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