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Speedometer Differences in GSR/LS cluster

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Speedometer Differences in GSR/LS cluster

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    Speedometer Differences in GSR/LS cluster

    Hey all,

    So I just purchased a GSR cluster from a member here and it occurred to me that there may be different calibrations for the two clusters. So I did a little research and this is what I found, the GSR Speedometer component is different compared to an LS one. Yet they have the same power steering /vehicle speed sensor.

    Speedometer
    GSR: 78120-SK7-A21
    LS: 78120-SK7-41

    VSS
    GSR/LS: 56500-PR3-010

    I also looked at the differences between the Tachometers, they are different, obviously, cosmetically yes but mechanically? Who knows.

    GSR: 78125-SK7-A91
    LS: 78125-SK7-A12

    So until I receive my GSR cluster I won't know for sure, so in the mean time I need some assistance. If you have a 90-93 GS/LS/RS with a 92-93 GSR cluster what is your RPM reading at 50 MPH? Also if anyone has an open cluster with the speedometer part out, look on the back of it, there should be a number like 1258rpm/km or something like that. This should be the calibration number used to match the gearing of the car to the speedometer, I am curious if these are the same or not.

    Once I open these two up in the coming weeks I will let everyone know my findings.

    #2
    They are different part numbers because they are different parts! The Speedometer / odometer is silk screened with "premium fuel only" on the GSR the LS does not have this. The tach is also different due to higher RPM on the GSR.

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      #3
      Dont worry you can use it like Plug and Play.

      I installed GSR cluster in to my LS and I checked out the speed with GPS. Its calibrated very well and it has no deflection.

      Cheers Burak

      Comment


        #4
        Originally posted by 2ndJenn View Post
        They are different part numbers because they are different parts! The Speedometer / odometer is silk screened with "premium fuel only" on the GSR the LS does not have this. The tach is also different due to higher RPM on the GSR.
        Ahh yes I forgot about the premium fuel on the speedometer.

        Originally posted by Serencebey
        Dont worry you can use it like Plug and Play.

        I installed GSR cluster in to my LS and I checked out the speed with GPS. Its calibrated very well and it has no deflection.

        Cheers Burak
        Well I know it is plug and play its the differences in RPM that I am worried about. By my calculations I get a 72 RPM difference between the GSR and the LS because of final drives. Also it is interesting to note that the GSR/LS have the exact same differential part, which also means they have the same gear to drive the VSS.

        Differential:
        GSR/LS/RS/GS: 41100-P21-000

        So that means the only difference is the final drive and the speedometer. My hunch is that the speedometer is calibrated for the 4.4 gearing and by putting it in the LS with 4.266 gearing you will be at 72 higher RPMs and thus be speeding.

        The difference is small yes, but its a 1.6 MPH difference, and a 72 RPM difference by my calculations. But I still have to test that.

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          #5
          http://www.honda-tech.com/showthread.php?t=593564

          Comment


            #6
            Ok so I was thinking backwards with respect to this whole conundrum of mine. I was falsely assuming that the final drive affects what speed you are at, true for an RPM dependence; not so the other way around.

            Let honda-tech learn us all.

            Originally posted by 94eg!
            VSS monitors the rotations of the wheels cause the VSS gear is attached to the diff housing. This means altering gear ratios or final drives does not alter VSS signal. The only thing that alters the VSS signal in relation to actual speed, is the diameter of the tire. If you run a larger tire, the car is traveling further than intruments are indicating (speedo reads low). If you run a smaller tire, the car thinks it's going faster than it actually is (speedo reads higher).

            My 205/40/16 tires are 4% smaller than stock ITR tires. Therefore My speedo reads 4% higher (at 100mph on the speedo, I'm actually only doing 96).

            ...

            VSS measures the speed of the rotating differential.

            By changing the final drive, you are altering the relation of engine rpm vs diff rotation. Not diff rotation vs tire rotation. TO MEASURE SPEED, YOU NEED TO KNOW TIRE DIAMETER & DIFF RPM. It has nothing to do with engine rpm, mainshaft rpm, or countershaft rpm...

            It doesn't matter what motor, gearbox etc. The only thing that matters is that you use the correct size tires for the VSS & diff...

            EXAMPLE/PROOF: If you took the ring-gear off the diff and pushed the car down a hill, would the speedometer read the vehicles speed?
            So I think we can all agree that the differences are purely cosmetic.
            Last edited by capn; 06 Aug 2009, 09:09:12. Reason: left out something...

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