Capacitor Discharge (CD) Ignition?

Discussion in 'Electrical and Ignition' started by Richard Sweet, Oct 24, 2018.

  1. Richard Sweet

    Richard Sweet Well-Known Member

    Messages:
    97
    Likes Received:
    11
    Joined:
    Oct 15, 2013
    Location:
    Ventura, CA
    Local Time:
    3:02 AM
    I'm considering replacing my points ignition system in my '65 Dodge 273 V8. I'm looking at what's available in electronic distributors & systems. I've seen CD systems mentioned but don't know what they are or which one are considered CD's. What do they include and how do they work? I've heard that they work well.
    Thanks, Richard Sweet
     
  2. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

    Messages:
    31,794
    Likes Received:
    13712
    Joined:
    Jan 18, 2006
    Location:
    Iowa
    View My Photos
    Local Time:
    5:02 AM
    What's the rest of your build? 2barrel or Charger/Commando?
     
  3. Tooljunkie

    Tooljunkie King of cobble/master of the broken bolt FABO Gold Member

    Messages:
    6,109
    Likes Received:
    4570
    Joined:
    Jul 22, 2017
    Location:
    Manitoba
    Local Time:
    5:02 AM
    I ran a cdi many years ago.
    If i had a choice,electronic all the way. The cdi system i had still used the existing point ignition,so dependability was still no better than points. Electronic ignition to me is a simple system.
     
  4. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

    Messages:
    14,450
    Likes Received:
    3770
    Joined:
    Jan 19, 2014
    Location:
    South-Central Manitoba,Canada, 900ftelevation
    View My Photos
    Local Time:
    5:02 AM
    CDI is the most powerful system out there, and MSD has parlayed it into an extremely useful builder-system, in the racing world.
    But for a streeter,IMO,at up to ~1.2 hp/cid,there is nothing wrong with a Kettering Ignition System electronically triggered. And I prefer a magnetic pick-up myself.
    Your ignition coil is already correct.If you want to upgrade your coil, I have had excellent results with the Accell Square top SuperCoil. It's pricey, but it will likely be the last coil you will ever buy.
    So; all you need is a pick-up and the amp/translator to run it.
    Unfortunately that usually means a new distributor with the proper guts in it,and the translator is commonly called an ECU. You can snag these used as they are known to work over a half a million miles. Or you can buy a Kit that includes the wiring you will need.
    The magnetic trigger eliminates the points and their associated limitations and maintenance schedule. And that is all it does.
    But I gotta tell ya; " if your current ignition lights all of the cylinders all of the time, nothing can be gained by switching to another type of ignition." quote from Smokey Yunich.
    "Type"; in this context is referring to Kettering vs CDI.
     
    Last edited: Oct 24, 2018
    • Thanks! Thanks! x 1
    • toolmanmike

      toolmanmike FABO Staff Staff Member FABO Gold Member

      Messages:
      31,794
      Likes Received:
      13712
      Joined:
      Jan 18, 2006
      Location:
      Iowa
      View My Photos
      Local Time:
      5:02 AM
      If you have a stocker and don't want to hassle with points, Pertronix is a good choice.
       
      • Agree Agree x 5
      • Like Like x 1
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

        Messages:
        3,729
        Likes Received:
        1790
        Joined:
        Feb 7, 2013
        Location:
        Phila. Pa
        Local Time:
        6:02 AM
        Advantage of the stock distributor, esp. if a 4 bbl equiped 273, is the timing curve.

        CD ignition advantage is if trying to run larger spark gaps or other situations where higher voltage is needed. The actual voltage needed to cause a spark to jump across the gap in the spark plug depends on the gap and cylinder conditions at that moment. If it sparks at 10,000 Volts, then it doesn't matter if the system can only produce 15 kV. Multi spark is helpful in preventing misfires - more prevelant in 'hot cammed' engines with exhaust dilution at low rpm. Another reason for multi spark is the coil and CD ignitions are usually optimized for high rpm, and multi-strike is used at lower rpms.

        Inductive ignitions tend to have longer spark duration than CD. That's not a bad thing on today's pump fuel.
         
        • Agree Agree x 3
        • Thanks! Thanks! x 2
        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

          Messages:
          3,729
          Likes Received:
          1790
          Joined:
          Feb 7, 2013
          Location:
          Phila. Pa
          Local Time:
          6:02 AM
          Mine leaked oil. :(
          Was running it with a chrome box, and I can't remember now if it went before or after the chrome box. I'd have to dig out my log notes. The windings were still intact, so it didn't die, it was just seeping. Smelled it first.
           
        • AJ/FormS

          AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

          Messages:
          14,450
          Likes Received:
          3770
          Joined:
          Jan 19, 2014
          Location:
          South-Central Manitoba,Canada, 900ftelevation
          View My Photos
          Local Time:
          5:02 AM
          IIRC the instructions were to mount it on it's side, which is what I did, in about 2004, on the apron, with a really long coil-wire,lol. Yeah it's ugly, but if someone comes to steal it, he better bring a long wire.
           
        • 67Dart273

          67Dart273 Well-Known Member

          Messages:
          37,738
          Likes Received:
          5391
          Joined:
          Oct 14, 2010
          Location:
          Idaho
          View My Photos
          Local Time:
          3:02 AM
          Something that seems to have been ignored::

          MOST factory ignitons work somewhat like old breaker points, except the electronics turns the coil on and off rather than the points.

          GM HEI is a bit different but it is still, in the end, "a switch."

          Kettering, loosely, covers breaker points and the above

          CD means "capacitive discharge" and it works sorto' like a photo flash. A high voltage power supply (inverter) charges up a relatively large condenser/ capacitor, and the spark trigger discharges that cap across the ignition coil.

          CD does NOT have DC current through the coil like the previous units. MSD stands for "multiple spark discharge" (at some operating RPM)

          There is some opinion, that in certain conditions, the very "sharp" spike of a conventional CDI may not fire fouled plugs, where, the broader, more powerful HEI spike might. In other words voltage along might not be the only thing.

          Many of us here use a GM HEI module. When my car was together, the HEI even fired a factory Mopar coil.

          Pertronix is not CD. It is similar to Kettering. Many like them. Only downside I see to them is parts. If it dies, you better keep spares in the glove box, as most parts stores don't carry them.
           
          • Thanks! Thanks! x 2
          • RustyRatRod

            RustyRatRod Just another dumbass. FABO Gold Member

            Messages:
            46,501
            Likes Received:
            11042
            Joined:
            Jun 7, 2010
            Location:
            Georgia
            View My Photos
            Local Time:
            6:02 AM
            I have a CDI box used for firing the electric turnout motors on the turnouts on my model railroad. 25V out to the turnout insures a loud and decisive "SNAP" and assures the turnout is thrown in the proper direction, all but eliminating derailments due to an improperly thrown turnout. Works very well, but it'll knock the shit outta you in the right circumstances.
             
            • Thanks! Thanks! x 1
            • Richard Sweet

              Richard Sweet Well-Known Member

              Messages:
              97
              Likes Received:
              11
              Joined:
              Oct 15, 2013
              Location:
              Ventura, CA
              Local Time:
              3:02 AM
              I have an A100, automatic, van with a 4 barrel, just driven on the street. I'm just considering my options. CDI looks kind of expensive.
              Thanks all. Richard
               
            • Claudius

              Claudius Well-Known Member

              Messages:
              268
              Likes Received:
              54
              Joined:
              Feb 6, 2010
              Location:
              Greensboro, NC
              View My Photos
              Local Time:
              6:02 AM
              I used a Summit Racing 850027 distributor with a MSD 6AL (#6425) in the 318 block used to build my 392 stroker. The MSD distributors are much more expensive so I am happy with my decision.
              FYI, I originally had acquired a MSD Stacker 7000 box long before getting the distributor but that was a mismatch. This box would work with your stock ignition and support any tachometer you might already have. Send a PM if interested.
               
            • rumblefish360

              rumblefish360 so close yet so far away

              Messages:
              32,467
              Likes Received:
              4677
              Joined:
              Jun 21, 2005
              Location:
              New York, on a Island
              View My Photos
              Local Time:
              6:02 AM
              Don’t listen to anybody here except tool junky, mattex, rusty rat rod and 67dart273.
              FWIW, Claudius is is a good fella! He gets a thumbs up from me.
              Talk with him

              Now on to the subject at hand and my personal experiences with the MSD brand. When I swapped in the box alone it did all they claimed. The addition of there coil helped a bit more since it was a better more power unit than stock. I used a electronic distributor. The MSD bid can be run with the points distributor. Not a problem. IDK about your coil though. I’d up graded it in a flash.
               
            • Abodybomber

              Abodybomber Breaking street machines , since 1983.....:)

              Messages:
              31,881
              Likes Received:
              10199
              Joined:
              May 21, 2011
              Location:
              Arroyo grande ca
              Local Time:
              3:02 AM
              Run a analog ,non digital old school MSD box .It works ,can be touchy on installation.
              Agreement with Rusty Rat Rod ,and 67 Dart 273... who actually explains the last century of ignition.
              Think all three , out ....if you're a hot rodder ,study all three... (points ,HEI and Capacitive Discharge, and digital boxes ,as a fourth option).
              To be honest, a Pertronix...fits a stock distributor. ..
              The HEI option, fits a stock points distributor:
              designedtodrive..gmail.com...
              Have one ,on the shelf....
               
            • Richard Sweet

              Richard Sweet Well-Known Member

              Messages:
              97
              Likes Received:
              11
              Joined:
              Oct 15, 2013
              Location:
              Ventura, CA
              Local Time:
              3:02 AM
              So what about tunability? An easy to tune system would have a big advantage. Which is the easiest to get a good tune with?
               
            • rumblefish360

              rumblefish360 so close yet so far away

              Messages:
              32,467
              Likes Received:
              4677
              Joined:
              Jun 21, 2005
              Location:
              New York, on a Island
              View My Photos
              Local Time:
              6:02 AM
              Which ignition system is easiest to get a good tune on?

              That shouldn’t matter an iota. If it does, take it to someone who can tune an old school ride. Watch, ask questions, learn, DIY next time.

              A multiple spark system will run best all things being equal.
               
            • cavisco

              cavisco New Member

              Messages:
              4
              Likes Received:
              6
              Joined:
              Dec 2, 2015
              Location:
              south carolina
              Local Time:
              5:02 AM
              Hi Richard,
              Unless you are having trouble firing oil fouled plugs I think a Magnetic discharge (Kettering Ignition) will deliver more enegy to fire the plugs. The energy storage capacity of a CDI setup is limited by the charge time of the capacitor. In most cases a 1 - 2uF capacitor is the max that will work. For a comparison of the two have a look at the magnetic vs capacitive discharge ignition article on this page:
              Home
              A really nice HEI electronic ignition setup can be put together using OEM replacement parts or junkyard parts by following this guide from the Slant Six dot org site. Of course you will need a mopar V8 electronic ignition distributor instead of the slant six part:
              HEI Electronic Ignition Retrofit How-To - Slant Six Forum
              If you want to keep your original points setup, you can trigger a Ford TFI module and coil as shown in this article over on the HAMB:
              TFI using points how to
              The MSD CDI products work well and have a proven track record, but I think an HEI or TFI setup has a slight edge on a stock or mild street engine and certainly has the cost advantage.

              Good luck,
              Scott McAuley
               
              • Like Like x 2
              • Thanks! Thanks! x 1
              • mopar head

                mopar head Well-Known Member

                Messages:
                2,571
                Likes Received:
                316
                Joined:
                Oct 21, 2008
                Location:
                Cooneysville
                View My Photos
                Local Time:
                6:02 AM
                Scott, lurk for 3 years and finally post something? Welcome to the forum! LOL:D
                 
                • Like Like x 2
                • cavisco

                  cavisco New Member

                  Messages:
                  4
                  Likes Received:
                  6
                  Joined:
                  Dec 2, 2015
                  Location:
                  south carolina
                  Local Time:
                  5:02 AM
                  I enjoy reading more than posting. Is there a time-out function for lurking? Thanks for the welcome.

                  Scott.
                   
                  • Like Like x 1
                  • AJ/FormS

                    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

                    Messages:
                    14,450
                    Likes Received:
                    3770
                    Joined:
                    Jan 19, 2014
                    Location:
                    South-Central Manitoba,Canada, 900ftelevation
                    View My Photos
                    Local Time:
                    5:02 AM
                    Nice reading right there, thx for posting, and Hello!
                     
                    • Thanks! Thanks! x 1
                    • Agree Agree x 1
                    • rumblefish360

                      rumblefish360 so close yet so far away

                      Messages:
                      32,467
                      Likes Received:
                      4677
                      Joined:
                      Jun 21, 2005
                      Location:
                      New York, on a Island
                      View My Photos
                      Local Time:
                      6:02 AM
                      More like time in and that is normally between the hours of 1am - 4am. Prime time lurker time!
                      :rofl:

                      FWIW, I love my chrome box ignition!
                       
                      • Like Like x 1
                      • cavisco

                        cavisco New Member

                        Messages:
                        4
                        Likes Received:
                        6
                        Joined:
                        Dec 2, 2015
                        Location:
                        south carolina
                        Local Time:
                        5:02 AM
                        I'm glad you enjoyed it.
                        Scott.
                         
                      • AJ/FormS

                        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

                        Messages:
                        14,450
                        Likes Received:
                        3770
                        Joined:
                        Jan 19, 2014
                        Location:
                        South-Central Manitoba,Canada, 900ftelevation
                        View My Photos
                        Local Time:
                        5:02 AM
                        What else you got up your sleeve,lol?
                         
                      • cavisco

                        cavisco New Member

                        Messages:
                        4
                        Likes Received:
                        6
                        Joined:
                        Dec 2, 2015
                        Location:
                        south carolina
                        Local Time:
                        5:02 AM
                        Make sure you charging system is working well and use an electronic voltage regulator. Electronic ignition does not like low voltage and may result in module failure with 4-pin HEI modules. The 7 and 8-pin HEI modules are more tolerant of low voltage. Resistor plugs and wires are also a good idea.

                        Scott.
                         
                        • Thanks! Thanks! x 2
                        • BillGrissom

                          BillGrissom Well-Known Member

                          Messages:
                          7,184
                          Likes Received:
                          319
                          Joined:
                          May 10, 2009
                          Location:
                          Sacramento
                          Local Time:
                          3:02 AM
                          The GM 8-pin HEI is simplest and best. It was in 1985-95 V-8 trucks. Grab the module (inside distributor), connector & wire to pickup, coil & cable to it, and cut the red & wht supply wires as long as you can. TrailBeast here sells as a kit. You can leave the 6-pin connector open, or use it for spark timing control (from Holley Commander 950 or such). The Megasquirt site has more info. A Mopar distributor pickup can trigger it, but you need the polarity right for most stable spark.
                           
                          • Thanks! Thanks! x 1