Speedo reads double in Gt4 with 328 engine fitted? | FerrariChat
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Speedo reads double in Gt4 with 328 engine fitted?

Discussion in '308/328' started by Stimbow, Feb 12, 2022.

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  1. Stimbow

    Stimbow Rookie

    Sep 3, 2020
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    #1 Stimbow, Feb 12, 2022
    Hi,
    I’ve bought a 308 gt4 with a 328 engine and box fitted. The Speedo reads double the actual speed.
    Ie. phone gps reads 50mph and Speedo reads 100mph!

    Am I right in thinking it’s to do with the speed sensor on the gearbox as they’re listed differently between 308 & 328(Mondial)?

    Also the mileometre doesn’t work? Not sure if it’s connected to the Speedo in some way?

    Has anyone done this conversation? or come across this problem?

    many help would be much appreciated.

    justin
     
  2. BigTex

    BigTex Seven Time F1 World Champ
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    #2 BigTex, Feb 12, 2022
    It absolutely is, the odometer problem.

    There's "early" and "late" speedo sensors, first of all, so spend some time in the Part Numbers.
    But I have no idea if an early 308 can be somehow modified to accept the 328 sender signal, or vice versa.

    maybe a call to PaloAlto Speedometer would shed light??
     
  3. BigTex

    BigTex Seven Time F1 World Champ
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    #3 BigTex, Feb 12, 2022
    ..and Welcome!!

    That sounds like SOME example of a GT4!!!

    Post up some pics and the VIN info..

    It's hard to imagine a salvage yard where they said:
    "Hey man!! Get the engine out of that red/tan car, and bring it around to stuff in the Series 2 Sunroof GT4!!"

    Hard to imagine but obviously it happened!!
     
    dinogt4guy likes this.
  4. BigTex

    BigTex Seven Time F1 World Champ
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    #4 BigTex, Feb 12, 2022
    Saving you some recon, the speedo sensor creates a square sine wave, that is then translated in an IC chip board (now obsolete) in the Speedo, that makes the needle go around!!!

    Wheeee!

    And the odometer of course is the cumulative measure of these gearbox rotations.
    You can almost see Fred Flintstone feet under the car!!
     
    greg328 likes this.
  5. BigTex

    BigTex Seven Time F1 World Champ
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    #5 BigTex, Feb 12, 2022
    Thinking it thru further, the simplest fix might be an age appropriate 328 Speedometer.

    Palo Alto will know,
    TRutlands might be able to help too..
     
    Brian Harper likes this.
  6. Stimbow

    Stimbow Rookie

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    #6 Stimbow, Feb 13, 2022
    Thanks BigTex for your reply.
    Definitely a lot to think about.
    So, the early one sends out a different signal than the later ones. From what I can see the two types are physically different?
    So, is there an earlier type which is physically the same as the later type but sends out the early compatible signal? Or is there just the two earlier/later to choose from?

    Not sure how who the two people mentioned are?
     
  7. MFlanagan

    MFlanagan Karting

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    #7 MFlanagan, Feb 13, 2022
  8. ragtop1

    ragtop1 F1 Veteran
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    #8 ragtop1, Feb 13, 2022
    Big tex said
     
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  9. Stimbow

    Stimbow Rookie

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    #9 Stimbow, Feb 13, 2022
    Thanks for the links. I’ll send them a message.

    I haven’t owned the car long. Most of the work was carried out before my ownership. If anyone’s interested I can put photos and the info I know about the car on the forum. Not sure where though?
    It’s a work in progress running project.
     
  10. ragtop1

    ragtop1 F1 Veteran
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    #10 ragtop1, Feb 13, 2022
    Post them here. You have to subscribe though. $15 is cheap for a whole new level of information
     
  11. Mark C Harvey

    Mark C Harvey Formula Junior

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    #11 Mark C Harvey, Feb 14, 2022
    Congrats, sounds like a fun car. Is it the white GT4 from a Los Angeles collection?
     
  12. smg2

    smg2 F1 World Champ
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    #12 smg2, Feb 14, 2022
    GT4 uses a worm gear assy, shaft etc to turn the speedo sensor. QV and later is a reluctor wheel with magnetic sensor. No interchange possible at the gearbox end.
     
  13. Stimbow

    Stimbow Rookie

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    #13 Stimbow, Feb 15, 2022
    No, it’s not white. My one is red, based in the Uk and is a ex-formula classic race car. Nothing fancy, except the 3.2 qv engine came from Marenello UK as a crate engine a few years back and has still only done 1000 miles!!
     
    Mark C Harvey likes this.
  14. Vonbarron

    Vonbarron Formula 3
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    #14 Vonbarron, Feb 15, 2022
    I remember your car when I still had instagram, was following it along. Very cool machine
     
  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #15 Steve Magnusson, Feb 15, 2022
    Do a search on "speedometer" posted by Member "alhbln" -- there will be a lot of information about this issue for you in those threads. Adrian (alhbln) is truly the demonstrated expert on speedometer, odometer, speed sensor issues.
     
  16. BigTex

    BigTex Seven Time F1 World Champ
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    #16 BigTex, Feb 15, 2022
    alhbin has also reverse engineered the replacement IC boards within the gauge.

    Perhaps "knowing the target" he could build your gauge into the later style of signal interface.
    Good luck!!
     
  17. Stimbow

    Stimbow Rookie

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    #17 Stimbow, Feb 16, 2022
    That’s great thanks. I really appreciate all your help. I’ll do a speedometer and alhbin search. Hopefully I can get it fixed.

    Vonbarran, yes that’s me on Instagram.
    I started the page on Instagram to document the cars journey and to make friends with similar cars to mine.
    If anyone wants to follow its: ferrari_308_gt4_qv
     
  18. dinogt4guy

    dinogt4guy F1 Rookie

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    #18 dinogt4guy, Feb 18, 2022
  19. derekw

    derekw Formula 3

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    #19 derekw, Feb 18, 2022
    Ask Adrian if he can make you a simple circuit with a flip flop to halve the pulses. I may also need one when I switch to the single coil MSD programmable ignition.
     
  20. smg2

    smg2 F1 World Champ
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    #20 smg2, Feb 18, 2022
    Just add MSD 8920 for the tach signal.
     
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  21. greyboxer

    greyboxer F1 World Champ

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    #21 greyboxer, Feb 18, 2022
    which/whose if I may ask
     
  22. Stimbow

    Stimbow Rookie

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    #22 Stimbow, Feb 22, 2022
    Hi, I’m still trying to find out as much history on the car as possible. Any help of results, owners etc. would be much appreciated. What I do know I bought it from Atchill Thorpe who bought it of Ben or Alan Cosby.
     
  23. Stimbow

    Stimbow Rookie

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    #23 Stimbow, Feb 22, 2022
    I may end up going 355 throttle bodies and independent ECU so I can loose the EFi so won’t be going the MSD route.
     
  24. Stimbow

    Stimbow Rookie

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    #24 Stimbow, Feb 22, 2022
    I haven’t chased anything or looked up Adrian will do soon. The joys of having a you a family.
    Thanks for the advice, much appreciated. I’ll be on it soon.
     
  25. Stimbow

    Stimbow Rookie

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    #25 Stimbow, Feb 22, 2022
    I mentioned my Instagram post on the car. I’ll try and put a few photos up soon. Don’t expect too much.
     
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