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  1. #1

    DIY 300x speed de-limiter

    Hi guy's, I am new to riding jetski's but I am not too bad with electronics. As a bit of a challenge I'm thinking of making my own speed delimiter like the current ones on the market. I just got my 300x/300lx service manual today so I have had abit of a read on how the speedo works and I'm pretty sure I can do it.
    Speedo puts out a square wave proportional to the mph/kph, reference point for 40MPH = 203.7Hz
    Therefor the frequency for 1MPH = (203.7 / 40) equals (5.0925HZ)
    ECU limits the RPM "I think at 68MPH "therefor once the ECU receives a frequency greater than (68 X 5.0925) 346.29HZ than the ECU will throttle back the RPM to limit the ski to 68MPH " I think thats how it works anyway".
    What I plan to do is program a microcontroller to do the following, Warning "programming slang included"

    LOOP:
    READ input frequency and save value as "X"
    IF value "X" is greater than 346.29hz then
    "X" = 346hz "if it is not the chip skips this line"
    send out "X" to ECU
    GOTO LOOP

    OK before all the guy's with programming experience bust in on this and tear the coding apart please remember that I am trying to keep it simple for the other guys with no coding experience eg, HPWM will be used etc blah blah blah.

    Can someone confirm if the riva module does anything more than this ?

    I predict that the parts for this unit will cost about $8 maximum so I think we can all gain from this if it works but the code needs to be written which I'm happy to do but any guidance from the guru's would be cool "But don't shoot me down"


  2. #2
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    Quote Originally Posted by cphillips1982 View Post
    Hi guy's, I am new to riding jetski's but I am not too bad with electronics. As a bit of a challenge I'm thinking of making my own speed delimiter like the current ones on the market. I just got my 300x/300lx service manual today so I have had abit of a read on how the speedo works and I'm pretty sure I can do it.
    Speedo puts out a square wave proportional to the mph/kph, reference point for 40MPH = 203.7Hz
    Therefor the frequency for 1MPH = (203.7 / 40) equals (5.0925HZ)
    ECU limits the RPM "I think at 68MPH "therefor once the ECU receives a frequency greater than (68 X 5.0925) 346.29HZ than the ECU will throttle back the RPM to limit the ski to 68MPH " I think thats how it works anyway".
    What I plan to do is program a microcontroller to do the following, Warning "programming slang included"

    LOOP:
    READ input frequency and save value as "X"
    IF value "X" is greater than 346.29hz then
    "X" = 346hz "if it is not the chip skips this line"
    send out "X" to ECU
    GOTO LOOP

    OK before all the guy's with programming experience bust in on this and tear the coding apart please remember that I am trying to keep it simple for the other guys with no coding experience eg, HPWM will be used etc blah blah blah.

    Can someone confirm if the riva module does anything more than this ?

    I predict that the parts for this unit will cost about $8 maximum so I think we can all gain from this if it works but the code needs to be written which I'm happy to do but any guidance from the guru's would be cool "But don't shoot me down"
    oh and no riva is doing nothing special. But charging 200+ $ for a box of 12$ parts.

    You are on the right track it does not take much to do it and sounds like you know what you are doing. I made a very stupid simple one that worked for a while. But did not hold up I'm def no electrical guru.I think your will work fine.

  3. #3
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    build it and they will come.....

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