Cdi choices

Discussion in '2-Stroke Engines' started by Rob H, May 15, 2016.

  1. Rob H

    Rob H Member

    Looking for past and present experiences with best cdi' out there seen jaguar,huffy davidsons and some other cheapie a looking for an adjustable any help out there?
     

  2. FurryOnTheInside

    FurryOnTheInside Active Member

    Good question, Rob! I have really seen barely any info on the functionality/adjustability of the upgrade CDIs apart from the Jaguar which is internally adjustable.. I have not seen anything like a comparative review of CDIs yet.
     
    Rob H likes this.
  3. butre

    butre Well-Known Member

    I don't know about the rocket racing cdi (the pill bottle case turns me off. don't know how he gets away with that in a marketed product). the jaguar and hd lightning are based on the same circuit but the jaguar is internally adjustable. the hd lightning has a slightly more aggressive timing curve than the jaguar's most aggressive curve.

    the stock CDI has no timing curve but in my experience is very reliable if you get a good one (though it sure doesn't help the engine's reliability). I also know from experience that it can handle beyond 10000 RPM, which none of the aftermarket CDIs can do.
     
    Last edited: May 16, 2016
  4. jaguar

    jaguar Well-Known Member

    My CDI works best with engines that have had the compression increased, which is a mod most people do who want more power.
    Why want more power? To not get laughed at if you are pedaling a motored bike to help it get uphill.
     
  5. Rob H

    Rob H Member

     
  6. Rob H

    Rob H Member

    Which cdi is that
     
  7. FurryOnTheInside

    FurryOnTheInside Active Member

    Well I would like to pedal uphill very fast. With the engine RPM to pedal RPM ratio nicely sorted (I'm thinking of 45.92:1 which is easy to arrange) so I can be under 100rpm pedalling cadence, and get it just the right RPM to blend the engine sound with the nasty neurofunk blasting out from my portable speakers so that it appears I'm just pedalling with superhuman strength. :D

    I'm not sure what "aggressive" means in the context of CDI curve. In fact I don't have a clue. Does it mean it's for high rpm screaming race engines?
    I am sure of one thing.. only one of the CDI creators is actually on here contributing to the thread, and on forum week in week out and bothering to tell us about his product as well as offering advice and support for the mb community.
    Just where are the other CDI makers when threads like this come up?
    I'm pretty sure I know where my money's going.. That is, as soon as I can actually leave enough in the piggy bank to do the big order of parts I need from the USA. :")
     
    Timbone likes this.
  8. FurryOnTheInside

    FurryOnTheInside Active Member

    That, is the Jaguar CDI. Can get em from SBP (and probably other places by now too..)
     
  9. butre

    butre Well-Known Member

    aggressive as in the timing is more advanced. can be a good thing or a bad thing depending on how it's tuned, what the compression ratio is, what fuel you're using, what spark plug you're using, how you ride it, etc.
     
  10. jaguar

    jaguar Well-Known Member

    the weaker the compression, the more advanced the ignition needs to be. (but the stock CDI is too advanced even for the low compression of 90psi and its spark is weak and it's unreliable)
    and the spark is weak, and it's unreliable. and the spark is weak and its unreliable)
    the stock timing is too advanced even for its low compression (90psi)
    the stock timing is too advanced even for its low compression (90psi)
    the stock timing is too advanced even for its low compression (90psi))
    the higher the compression, the more retarded the ignition needs to be.
    a graph of the timing curves for the Jaguar and the Lightning CDI is on my site. (click on my signature link)
    the Jaguar high performance CDI is even better for rides with expansion chambers to get the best power/speed at top RPM.
    the Jaguar is the only adjustable one and the only one tested on a true CDI tester (to see its timing change thru the RPM range)
    it is available from JNMotors, Sick Bike Parts, and directly from me here in South America. the disadvantage of ordering from me is waiting 2 weeks to receive it. The advantage is that the high voltage coil is the best available for this CDI and it comes with a snap-on spark plug cap (for spark plugs with nipples such as the Iridium plug) that is made of rubber so it seals tight on the plug.
     
    FurryOnTheInside likes this.
  11. FurryOnTheInside

    FurryOnTheInside Active Member

    @ butre:
    Jees! For the layman that's a lot of factors to account for when you only get one setting and one chance to get it right. I'd be scared to pull the trigger on a purchase like that..
    As far as this layman can understand from the forums, more advance means it suits either a slower burn (from lower compression) or a faster rpm (piston downstroke to get it away from the battering). I had really already made my mind up based on the other issues, but that (if I'm even understanding correctly) confirms it for me about the technical side anyway. :)
     
  12. jaguar

    jaguar Well-Known Member

    yeah, the topic of CDI is truly technical.
    actually because of increased turbulence at high RPM the timing needs to change from advanced to retarded because the mixture burns faster. that also takes into account that at high rpm the time from TDC to exhaust opening is less.
    an expansion chamber increases the dynamic compression at high rpm so that the timing needs to be even more delayed (retarded) whilst the reverse pressure waves are stuffing the escaping fuel mixture back into the cylinder.
     
  13. FurryOnTheInside

    FurryOnTheInside Active Member

    (another Jeesh!)
    I don't fancy tuning an engine to suit the needs of a single unchangeable CDI setting. Forget that. Makes sense to tune the CDI to the individual engine. (and talking to the man who designed it, how much better is that?!) :)
     
  14. butre

    butre Well-Known Member

    that's why I use the jaguar on bikes that turn under 10k RPM (which really is too much for the stock needle bearing anyway, and unless you really know your way around a 2 stroke the most you might hit is 8500)

    for race bikes that turn over 10k (mine turns 11,500-ish) I use the stock CDI in conjunction with an adjustable timing magnet. tune it for high RPM because it doesn't spend much time down low. it's cheaper than a good CDI anyway, though power down low can be a bit on the miserable side, but pedaling makes more torque than the motor does so you don't lose too much that way. if you feather the clutch right you can hold it in the power band until you're up to speed as well.
     
  15. Rob H

    Rob H Member

    Wow now we got us some info thanks fellas I guess maybe I was on to something I looked into it but was way to complicated for this Yankee so I'll go with the jaguar
     
  16. Rob H

    Rob H Member

    I like the idea of changing the timing curve as I keep experimenting with different carbs heads pipes and piston designs oh and gearing I finally got to put the triple range stack together I took it for a couple spins now I have to fine tune the shifting on front derailier
     
    FurryOnTheInside likes this.
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