Programmeable CDI?

Home Forums Technical Programmeable CDI?

This topic contains 6 replies, has 4 voices, and was last updated by  pmb5 2 weeks, 1 day ago.

  • Author
    Posts
  • #3057

    FAHR451
    Participant

    Hi Chaps and Chapesses
    A newby here and have just read through the regs (2014) and enjoyed the journey back in time with the ‘Tuning Guide’ and this is looking like the kind of racing that has just what I remember from the 70’s ,fun and minimum cost. It would seem that there are huge holes in the published regs and the guide doesn’t wander to deeply into ignition either . Can ignition systems be considered ‘free’ ?Considering most if not all are using kart ignition coil packs with fixed advance/ retard curves, would it be possible to use ones own programmeable CDI systems as these can be built extremely cheaply and simply programmed with software based on spreadsheet programmes available on everbodies laptop , to tailor the advance curve and the necessary amount of retard at high RPM to suit each particular engine built and its projected powerband.This also has the added benfit of safe guarding an engine from one of the main causes of piston failures due to unknown amounts of advance throughout the useable spread.Considering the cost of a programmeable CDI is less than that of a replacement piston ,this does not detract from the spirit of this form of racing .
    Thanks for any input .

  • #3059
    Brian Rogers
    Brian Rogers
    Participant

    I have just published our revised Technical Regulations on this forum and you will see that ignition systems are free choice. Several guys have played with programmable ignitions in the past, Chris and I included, and one tuner has used them all season. Our experience was not good but I recognise that things have moved on since then. So it maybe its time to give them another try. Probably you are aware that no extra power can be derived from programmable systems but our aim was to give us a better spread of power, Chris was never certain he could detect any improvement on the track.

    • #3061

      FAHR451
      Participant

      Hello again Brian ,
      Thanks for the reply and answer to my question and your response to the Mikuni question which I have just replied to .I hope the information is useful and amusing .
      I assume that the systems used have been the PIC or Atmel based programmeable types or perhaps the more expensive types that can cost an excessive amount with no apparent benefit of the cheap kit types ? As you know most bikes these days have some form of tailored advance curve in the coil pack or seperate emu very similar to that I have used on karts many years past and these have been used to regulate performance of many bikes of identical design to suit the regulations of a particular country but the curve being burnt permanently onto the eprom so unless you obtain an emu from Italy to slap on your UK Aprilia Cagiva or whatever 125, all the aftermarket goodies in the world would not reap the optimum or maximum performance from the machine as the first thing to eliminate is the rev limiter.I very much doubt that the advance curve in a kart ignition pack is suitable for a simple piston ported engine like the MZ . I am building a Honda NSR 125 ( perhaps not the best choice but certainly the cheapest of the 3 well known Italian built boy racer machines) as a bit of a challenge by my son to ring around 35 bhp at around 12500-13000 rpm out or the machine again at absolute minimum cost and the parts bin , so not surprisingly it has programmeable ignition and is full of CR125 parts ,reed block ,38mm Mikuni etc as this is my enjoyment.
      The idea of its use in the low cost formula is not that it is an advantage but that it can be used as a means to keep costs under control as some competitors will have more funds available than others, and if there is a means available where a programmeable can be used to an advantage it is in avoiding excessive advance by progressive retardardation at hi rpm where most damage occurs.It can be used to fix an ignition curve for all competitors so that the racing is more competitive to develop closer racing and encourage,hopefully,greater participation and possibly other people taking podium positions than the norm . There is no doubt that tailoring an ignition curve is highly beneficial as I have used these systems with great results if only simply to move the power band around to suit a circuit, but to know that the possibility of having an ignition curve to suit a circuit with the change of a £1.50 PIC up/Eeprom with the insurance that no destructive overadvance has been programmed in,to all competing for whatever purpose is surely of benfit.It also adds another dimension as big kids love to play computer games too ! Again if it is limited to the simple PICkit type that uses simple Excel based firmware that is well used by everyone that would cost around £40 with reader/programmer this would make it fair for all competitors present and future and with commonly available sensors and is much cheaper than a kart ignition system too.If your quick I am selling a Yamaha KT100 kart engine complete with ignition system on ebay for £100 !
      Look forward to meeting you at Brands next year .

  • #3112
    ChrisMZ78
    ChrisMZ78
    Participant

    Hi I have used both Hpi and zeeltronic ignitions, but peak power is still the same as pvl fix curve kart ignition as we set them up for optimum adv at max rpm. Gains can however we achieve at low rpm extra 2hp seen @ 6000rpm on dyno. The down side was reliability of the programmable ignitions and cost, so i ended up the season back with a pvl kart igntion, on track its generally the rider that makes the difference in mz racing not a great deal of difference in the power of any of them

  • #3113
    Brian Rogers
    Brian Rogers
    Participant

    Yes Chris what you have described was exactly our experience, in fact was a large factor in our coming second once again. Peak power can never be affected by ignition systems but the number of DNFs can be.

  • #3119

    FAHR451
    Participant

    Hi
    Apologies for slow input but I am presently involved in designing and building an F2 Sidecar for next season ,which has put the MZ thing on hold.I am now modifying and reprogramming an ECU for a 3 cylinder 675R Triumph engine .These things just don’t like odd numbers of cylnders especially with 3 pairs of staged injectors !
    As you know the common PVL type kart ignition is a coil with CDI built in and has a fixed curve ( although some people still believe the red thing is just a coil!) ,with rapid advance to somewhere around 28* @ around 2K and then retards after a certain peak in revs well above that of an MZ engine .As karts rev to almost twice the rpm as these machines you are basically setting your ignition timing for peak power/rpm as you have said without regard to the advance/retard curve fixed in the Motoplat or whatever your running .As the MZ engine will never see the rpm point where ignition retardation begins ,points would be as reliable and effective in performing this function and having been involved in karting ( I have been asked by a very famous karting family to prepare an engine for next season ) , nearly a hundred times cheaper than a Motoplat or equivalent.The ability to retard the ignition at a particular engines max rpm can extend the usable band without the severe drop off that would normally occur after peak .28* might be fine @ 9k but 26* or whatever at 9500 24* at 10k , may be more effective when used in conjuction with restricted breathing and the limitations of the exhaust when the CDI system is still delivering 28* up to 11k.Many people blame an engines inability to rev and hold a broad powerband on porting ,exhaust or carburettor and rarely consider the retardation requirement at peak rpm when the 2 stroke relies on all these factors to work harmoniously. There are those that would believe that as an ignition system is good for 15k on a 100cc rotary engine its got to be OK for 9 or 10k on a piston or reed ported motor, but this is not generally the case.The gains you saw lower down with the programmable system is mainly due to the fixed advance in the PVL , if you watch the karting boys at this point in the rev range they hand choke the airbox to get the mix slightly rich of actual (not theoretical) stoichiometric to make up for the fixed advance .
    The system I am testing at the moment is based on the ever reliable PIC16 up, as found in many other devices such WBO2 controllers etc , uses simple Excel based spreadsheet programming, and costs £30 complete in a simple DIY kit with a pcb the size of a credit card .The PicKit 3 interface/programmer and burner for your laptop or anything else that runs the current version of MS Excel can be had for around £10 or £11 off auction sites.The programme is a free download off the website .Results are pretty good so far and I have run the test one all day at 15k rpm from a simulator.This is for my sons roadgoing NSR 125 on a 38mm Mikuni which makes around 34 bhp,so it has to be reliable running off the alternator, but the chap also sells a total loss dc race version for a little more.The pcbs on their own ,if you want to supply your own components are £7.The PIC16 up ( the bit that sometimes goes wrong) £1.50 ! Most people are familiar with Excel ,but I suppose it depends how good you are with a soldering iron and a few electronic components whether you are able to go this route or not.
    I am not suggesting the more exotic and therefore expensive versions here as that is not in the spirit of this form of racing and excludes those on a very tight budget, but £40 and a bit of fun with a soldering iron for what appears to be a totally reliable system with the added bonus of having built it yourself!

  • #3510

    pmb5
    Participant

    We used the programmable red PVL units, which were very expensive. You can (well could back in 2006) get a custom curve burnt into the non-programmable digital red units. Our plan was to figure out a decent curve and then get an “MZ” curve burnt for everyone to use, but there was push back.

    Viper racing also have a custom curve for the 250 gearbox karts which is close enough to what MZ wants (but timed up differently), it just doesnt fit in with the peak power as they peak at 13k

    Ultimately the programmable unit made the bike pull cleaner below 7000rpm, i had about an extra 500-700rpm low down that was usable and it stopped the power dropping off so dramatically, but not by much. I could never feel the extra revs, but i’d swear I could feel the low down boost…although maybe it was because it just ran cleaner, less boggy?

    I stopped using mine at a Snetterton round when it was implied i only won a race because of the ignition. Although the bike was a little harder to ride, i still won the next race and put in the same laptimes.

    I’d pick a reliable PVL. There are enough other things that break MZ’s already… unless the thing your proposing works without a battery?

    All the curves i tried got sold with the bike… i might still have the spreadsheets on an old PC, i did a lot of dyno work on ignitions.

    FYI – I also found wrapping the front cone gave me an extra 200rpm over-rev, i see that’s something people no longer do.

You must be logged in to reply to this topic.