Quantcast Transistor Ignition System

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here continues with the basic types of transistor ignition systems   (breaker-point   and   magnetic-pulse),   the capacitor  discharge  ignition  system,  the  Chrysler electronic  ignition  system,  the  Delco-Remy  unitized ignition system, and the Ford computerized ignition system. TRANSISTOR IGNITION SYSTEM (BREAKER-POINT  TYPE) The  breaker-point  type  of  transistor  ignition  system was  developed  to  replace  the  standard  or  conventional ignition system. To obtain the maximum power and speed that this engine can produce, you must install an ignition system that outperforms the conventional one. Electronic type of ignition systems provide a hotter, more uniform spark at a more precise interval. This promotes more efficient burning of the air/fuel mixture in the combustion chamber, producing less exhaust emissions,  and  resulting  in  better  engine  performance and  increased  mileage.  The  increased  reliability  of electronic ignition allows less frequent maintenance by increasing  parts  life.  At  high  speeds,  the  breaker  points of a conventional ignition system cannot handle the increased  current  flowing  across  them  without  pitting too much. Also, the dwell angle of the breaker points is too small for complete saturation of the ignition coil. The transistorized ignition system takes care of both drawbacks. By comparing figures 4-28 and 4-29, you can see how  the  transistor  ignition  system  differs  from  the conventional.  When  the  breaker  points  are  connected  to the  transistor,  as  shown  in  figure  4-29,  it  nearly eliminates arcing across them since the current flow is small (about one-half ampere). However, the current flow in the primary windings of the coil is about 6 amperes. This amount is enough to saturate the coil completely at high engine speeds, and results in a higher output to the secondary circuit. Therefore, the transistor ignition system is superior to the conventional system at high  engine  speeds  because  there  is  less  arcing  across Figure  4-28.-Conventional  ignition  system. Figure  4-29.-Transistor  ignition  system  (breaker-point  type). the breaker points and higher and steadier voltage in the secondary  circuit. TRANSISTOR IGNITION SYSTEM (MAGNETIC-PULSE  TYPE) The drawbacks of a conventional ignition system operating  at  high  engine  speeds  can  also  be  overcome with  the  magnetic-pulse  type  of  transistor  ignition system  (fig.  4-30).  Notice  that  a  magnetic  pulse distributor,  which  resembles  a  conventional  distributor, is used instead of a breaker-point type of distributor. An iron  timer  core  in  this  distributor  replaces  the  standard breaker  cam.  The  timer  core  has  equally  spaced projections (one for each cylinder of the engine) and rotates inside a magnetic pickup assembly. This pickup assembly replaces the breaker plate assembly of the conventional distributor. Since there are no breaker points and there is no condenser, there can be no arcing across them. Capacitors in this system are for noise suppression.  This  overcomes  one  of  the  drawbacks already mentioned. The other drawback is overcome by controlling the amount of current that flows through the primary windings of the ignition coil and to ground. Transistors  in  the  ignition  pulse  amplifier  do  the controlling.  Another  feature  of  this  transistor  ignition system is its coil, which has fewer and heavier primary windings  and  a  higher  turns  ratio  of  primary  to secondary  windings  than  the  conventional  coil. Controlling the current flow and using a special coil Figure  4-30.-Magnetic-pulse  type  transistor  ignition  system. 4-16



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