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Author Topic: Very interesting site on ignitions and how they work  (Read 3435 times)
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Blake Malkamaki
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« on: December 12, 2011, 11:59:17 PM »

Very interesting site on ignitions and how they work http://www.breakerless.com/igntionfacts.htm

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440roadrunner
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« Reply #1 on: December 18, 2011, 01:23:55 AM »

In  the basics,  he left out a very important point,  no  pun intended.    The condenser  does NOT  only protect the breaker points,  it is NECESSARY   to form the spark.  If you remove the condenser  out of a Kettering  (breaker points battery)  ignition,  it will not start or run.

This is because,  when the points open,  and the coil field collapses,  the voltage generated in the coil is generated in  BOTH  the primary  and secondary.   The primary  voltage  being generated  CHARGES UP  the condenser  (capacitor)  until the coil has completely  discharged it's  magnetism.  At  this  INSTANT,   the capacitor/  condenser  is fully charged,  and now things REVERSE.   The charged capacitor  now discharges it's energy  BACK INTO   the coil,  charging the coil magnetism  (flux) AGAIN.  At the peak of this magnetism,  the capacitor  is discharged once more,  the coil field is at it's peak,  the coil now discharges  AGAIN   and AGAIN  charges up the cap.

This "seesaw" ---known  as  "ringing",  or  "flywheel effect"  continues   until  electrical losses or load on the circuit  (the spark gap at the plug)  finally runs down  the ringing, ----just in time for the points to close  and start all over

Anyone  that has ever seen  a scope ignition pattern   should immediately  recognize  the above description from seeing  that pattern.

In the representative pattern  below,  you can see this oscillation  or ringing.    It  is damped out  by the load of the spark  plug firing,  which is the "flat line"  to the right  of the initial  pulse.   The reason  that the spark  jumps up so high at first,  is that it takes   some  "overshoot"   so to speak  to ionize  the plug gap  and get  "The fire going."    After the plug fires,  conditions,  IE  fuel mixture,  compression,  causes  a load  which  "pulls down"  the spark voltage.     Finally,  the coil and cap  "run out of soup"  and the voltage power supplied by the coil can no longer maintain the spark.   The  SECOND  high spike  at the end of the plug firing  is caused because  when the plug finally stops firing,   the coil  has JUST  enough energy,  and is now  "unloaded"   it's voltage jumps up for a momentary spike,   Finally,  the final  ringing at the end  is where the energy  in the coil/  cap  is finally petering out,   and further to the right, you can see the points  closing,  to start things all over again.

Some electronic  (breakerless)  ignitions   such as the older   NOT  HEI  GM  stuff  and the Mopar  ECU  used in the early 70's  into the 80's  essentially worked exactly the same way  as breaker points,  and the scope patterns  look very similar.

80s  GM  HEI,   however does NOT work  quite the same way.  To put it simply,  HEI  is designed to operate   withOUT  a condenser in the system

(Incidently,  GM  4 terminal HEI  modules are VERY  adaptable,  can be used with many  mis-matched breakerless distributors,  as well as adapted  with a simple circuit   to a points  distributor.      I'm using  a GM  HEI  on my  Toyota powered crawler,  with the factory  Toy  breakerless dist.      I'm also using  HEI  on my 67 Dart,  with a factory  equivalent Mopar breakerless dist.



A  "real world"  scope pattern,  stolen  from  "that other place"

« Last Edit: December 18, 2011, 01:33:58 AM by 440roadrunner » Logged

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« Reply #2 on: December 18, 2011, 10:58:49 AM »

Nice! I think the original article may have intentionally left this out because is was a basic explanation. Your post elaborated on more of the technical aspect. Good additional info.
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Blake Malkamaki
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« Reply #3 on: December 18, 2011, 02:07:46 PM »

Thanks for adding the details. Great explanation!

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My gramps Howard van Driest was Experimental Engineer at Cletrac and Oliver Corporation. After the plant closed, he and my uncle started an excavating business, initially using Cletrac and Oliver Crawler tractors. Please help Support This Site and give your business exposure by buying a business card sized ad.
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