16v ECU raised rev limiter - pics inside

Discussion in '16-valve' started by barny, Oct 14, 2006.

  1. JonnyPhenomenon New Member

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    man, I wish we had more pics of it.. its possible they replaced more than the crystal. im still trying to track one of those down.
     
  2. markone2L16v Forum Member

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    I'm not sure if this is true or just some babble i heard, but a while ago i was told that if the little nob bit on the side of the ecu is green, then it has a better map or something... Not to sure tbh, anybody any the wiser than me?
     
  3. Joe_G Forum Member

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    If you want the crystal you can get one here.

    Think it's 15 minimum order quantity so buy yourself some batteries or something else at the same time.

    Joe
     
  4. JonnyPhenomenon New Member

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    :)
    thanks fo the tip Joe, Im over here in the USA and Farnell likes to charge a lot of money for shipping, so I am looking for a vendor in this country. - of course, having that crystal available to you guys might encourage onf of you to grab one up and test this out..
    (hint hint)
    :)
    maybe grab more than one and mail one over to me here in the US, would only be about a buck or two for stamps if you stuck it in a padded envelope. (hint hint)
     
  5. barny Forum Member

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  6. barny Forum Member

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    If you use the part no from the web joe posted all sorts comes up ! LF A125C
     
  7. JonnyPhenomenon New Member

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  8. mark25 Forum Junkie

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    Is the lower power throughout the rev range due to (not the cam) but the fact that the standard ignition map has now been superimposed over a bigger rev range? ie to 7800rpm. The rev limit software has been fooled, but so has the cranking retard, tickover advance and advance throughout the rev range (which is all now retarded!!!)

    I think the dwell period will be effected too[:s]
     
    Last edited: Nov 8, 2006
  9. seanlazyass Forum Member

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    Very interesting point Mark. I remember a thread from a while back when Barny was complaining about his engines lack of torque compared to his mate Speedo's engine, (which now happens to be mine) and trying to figure out why this was as they're almost identical spec. The max power outputs were the same but the torque curves were quite different. If what you have said is true this could well explain it.

    Sean
     
  10. seanlazyass Forum Member

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  11. barny Forum Member

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    Good point .... but - I have a Dastek uni-chip on mine - so remapped ignition - and i think ( memory fades here ) Paul had a K-star 5th injector thingy.
     
  12. seanlazyass Forum Member

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    I didn't realise you had any sort of chip Barny. Yeah the engine does have K-star and a 5th injector.

    Thanx for all the info you've posted mate, it may well be useful in the future.

    Sean
     
  13. barny Forum Member

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    No worries, have lots of fond memories of chasing that jetta and still speak to paul so if you need to know anything about it just ask
     
  14. Trev16v

    Trev16v Paid Member Paid Member

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    I guess that there's very little else modified other than the microprocessor's crystal, right? I guess that's the only thing you would need to change in order to (very crudely, for the reasons that mark25 pointed out) get an increased rev limit, because you've changed the microprocessor's clock frequency.

    JonnyPhenomenon posted the frequency of what I assume is the original crystal frequency, 4.194304MHz. Am I right - is that the original one? Superchips crystal is 4.608MHz. So this increases the clock frequency by a factor of 4.608/4.194304 = 1.099. The rev limit would increase by the same factor.

    I can't remember what the stock 16V limit is. Is it 7200? If it's 7200 then 7200 * 1.099 gives a new limit of 7912ish.

    Make sense?

    I also would have thought that it isn't critical that you obtain the exact crystal frequency that Superchips originally used, either. The frequency you'd want is: New crystal frequency = (New rev limit / Stock rev limit) * Old crystal frequency. So you could buy various frequencies and try them out. If you can't get the Crystal that Superchips used, just get the next highest one you can find easily.

    I don't know what that other wire is that has been connected between the snipped connector pin to the PCB, but the pin it's going to on the pressure sensor could just be a convenient ground pin.

    Take what I say with a pinch of salt, just banging ideas about in a sitting-in-a-pub, boozed up, drawing on a back of a beermat fashion.


    Uninterestingly, I recall the microcontroller in the Digifiz also uses a 4.194304MHz crystal.
     
    Last edited: Jan 7, 2007
  15. Trev16v

    Trev16v Paid Member Paid Member

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    Just thinking about this... if my above waffle is right and you do just simply change the clock frequency to alter the rev limit (and I can't see why you'd have to do anything more than that), then maybe there's a way to do this but without messing up the map over the stock rev range. Do this by having a little circuit that provides a clock signal to the microcontroller that can change as a function of the tacho input. Over the 'stock' rev range (0 to 7800 or 6800 or whatever it is) the circuit provides 4.194 to the micro, but above around 6500rpm it starts to incrementally increase the clock output towards 4.6MHz... so for most of the rev range you don't upset the stock ignition map, dwell etc.

    Actually surely an easier way to do it is to just intercept the tacho input and start to divide it by a value of slightly less than 1 as it approaches 6800. Do this using a PIC microcontroller.

    Anyway, I'll shut up now.
     
  16. GVK

    GVK Paid Member Paid Member

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    VR6 don't need one ;) :p
     
  17. A.N. Other Banned after significant club disruption Dec 5th 2

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    4.608 gives 7200 rpm limit IIRC, so you could check that back to the formula Trev
     
  18. Trev16v

    Trev16v Paid Member Paid Member

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    Ah, what's the standard 16V rev limit then Chris?
     
  19. mk1. Forum Junkie

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    7200 is std 16v limit:)
     
  20. Trev16v

    Trev16v Paid Member Paid Member

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    Ah ok, just a little confused because Chris is suggesting that the Superchips crystal is giving 7200.
     

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