Author Topic: Ignition coil question ..Is a condenser necessary?  (Read 7611 times)

Online bigbikerrick

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Ignition coil question ..Is a condenser necessary?
« on: January 17, 2015, 12:42:21 AM »
Hello Folks, I am replacing the oem ignition coil on my Eldo with a Pertronix "Flamethrower" 3.0 ohm epoxy filled coil. I still have the points distributor. When removing the old stock bosch coil, I noticed there is a condenser attached to the negative coil terminal. I s this necessary? Im wondering if I should reinstall this condenser with the new coil, or leave it off? I wonder what function the condenser played ?  My distributor has the normal condenser on the side, which I replaced a few months ago.
I thought I would wait to hear from someone that knows more about ignitions than myself, before I re-install the gas tank, and other accouterments.
Thanks alot!
Rick.
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Offline JoeW

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #1 on: January 17, 2015, 01:37:25 AM »
That condenser on the coil is for noise suppression. So you don't get static on the radio. Not that necessary for a bike but, they were used a lot on cars back in the day.
Joe Walano

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #2 on: January 17, 2015, 02:01:06 AM »
Thats interesting, Joe. I wonder why the original owner put one on the bike? Maybe because it was a customary thing to do on cars, etc. back in the 70s..... ??? unless someone knows of a reason, for having it,in this case, I think i am going to leave it off.
Thanks ,Rick.
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Offline rodekyll

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #3 on: January 17, 2015, 03:49:12 AM »
It's to suppress noise and interference to receivers (not necessarily radios) near the bike.  Some ignitions can blast noise for a hundred feet or so.  I can see it in my computer screen when some vehicles go by.  So maybe the PO discovered that he has a noisy ignition.

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #3 on: January 17, 2015, 03:49:12 AM »

Offline Kiwi_Roy

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #4 on: January 17, 2015, 04:41:54 AM »
Some coils will not produce a spark without the condenser aka capacitor or at least a strong spark.
While the points are closed the current flows through the coil saturating the magnetic field. When the points open the field collapses causing a spark and the Voltage across the coil charges the condenser in the opposite direction which builds up the magnetic field again so the energy swaps between the magnetic field in the coil to the electrostatic field in the capacitor
The condenser and coil ring (oscillate) together causing several sparks in a quick succession.
Yes it does suppress the spark at the points but without it the spark will be very weak if at all.

http://www.ratwell.com/mirror/users.mrbean.net.au/~rover/ketterin.htm

Considering his great contribution to motoring there's not a lot of good information on the web about Charles Kettering.
http://inventors.about.com/library/inventors/blignition.htm

BTW the magneto which preceded the coil also had the capacitor to cause the ringing effect, it's in the rotating part.
« Last Edit: January 17, 2015, 05:12:35 AM by Kiwi_Roy »
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Re: Ignition coil question ..Is a condenser necessary?
« Reply #5 on: January 17, 2015, 08:28:56 AM »
Some coils will not produce a spark without the condenser aka capacitor or at least a strong spark.
While the points are closed the current flows through the coil saturating the magnetic field. When the points open the field collapses causing a spark and the Voltage across the coil charges the condenser in the opposite direction which builds up the magnetic field again so the energy swaps between the magnetic field in the coil to the electrostatic field in the capacitor
The condenser and coil ring (oscillate) together causing several sparks in a quick succession.
Yes it does suppress the spark at the points but without it the spark will be very weak if at all.

http://www.ratwell.com/mirror/users.mrbean.net.au/~rover/ketterin.htm

Considering his great contribution to motoring there's not a lot of good information on the web about Charles Kettering.
http://inventors.about.com/library/inventors/blignition.htm

BTW the magneto which preceded the coil also had the capacitor to cause the ringing effect, it's in the rotating part.

I believe this is correct.  The points are normally on the ground side of the coil and the condenser is in parallel with them with both the points and condenser having one side tied to ground and the other sides tied to the coil - post.  Usually the condenser is inside the distributor, but could be placed at the ground terminal of the coil.  Been too many years since I worked on the T3 I had with coil ignition, but I believe you'll get a very weak to no spark without the condenser connected as described.  Had a condenser go open on a '74 Ford pickup and it wouldn't get above about 30 mph and missed. Points were burnt badly.

Offline Chuck in Indiana

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #6 on: January 17, 2015, 09:03:51 AM »
I'm late to the party, but yeah even magnetos have condensers..
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Offline Wayne Orwig

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #7 on: January 17, 2015, 09:09:39 AM »
One condenser is of course needed. The second one at the coil like that would likely just be for RF suppression. That is what they were for in autos anyway.
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Offline twhitaker

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #8 on: January 17, 2015, 09:15:57 AM »
Charles Kettering, the inventor of the automotive self starter, was a native of Dayton and started the company DELCO.
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Offline JoeW

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #9 on: January 17, 2015, 09:59:45 AM »
Thats interesting, Joe. I wonder why the original owner put one on the bike? Maybe because it was a customary thing to do on cars, etc. back in the 70s..... ??? unless someone knows of a reason, for having it,in this case, I think i am going to leave it off.
Thanks ,Rick.
I assume that there is still the condenser on the distributor. Maybe this coil was added and had the condenser on it already and the installer figured either it was necessary or it couldn't hurt?
Joe Walano

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #10 on: January 17, 2015, 01:04:58 PM »
Hello Folks, some very interesting information here, thanks! I just spent an hour studying the links Kiwi Roy provided. Excellent!! Maybe my simple mind is easy to impress, but statements like this in Kiwis link to the "Kettering Ignition"  just blow my mind! I never had any idea the points worked so fast!!  Wow!
   "At ordinary engine operating speeds, the points open and close a couple of hundred times per second, the exact number depending on the number of cylinders and the engine RPM. The points need to be closed for a appreciable time in order to build up the maximum magnetic flux in the ignition coil core."
This is one of the things I love about this forum, you can get an education in mechanics, and a history lesson here! After reading my personal email, this forum is the next place I always visit, with my morning coffee in hand.

Thank You all Fellow Guzzisti for providing that quality experience.

So what I gather, is that the second condenser placed at the coil neg. terminal doesnt do the necessary function the other condenser on the distributor does, and its function would be just noise suppression, and unnecessary for the running of the bike.

There is no way the second condenser is to provide "backup" to the the condenser by the points, is it? They are hooked up to the same circuit, as the wire from the negative side of the coil is the one that goes down to the distributor, right?

I got the gas tank back on the bike, and it started up normally, without the second condenser,I plan to take it for a test ride in a bit, and see how the new Flamethrower coil performs....Of course with a name like flamethrower, its supposed to "Feel faster" ! ;D

Will report back,Thanks,
Rick.
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BigDave in PA

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #11 on: January 17, 2015, 02:14:17 PM »
I'm pretty sure this one has a "flame thrower coil" too.
« Last Edit: January 17, 2015, 02:15:18 PM by BigDave in PA »

Offline rodekyll

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #12 on: January 17, 2015, 02:31:39 PM »
Hello Folks, some very interesting information here, thanks! I just spent an hour studying the links Kiwi Roy provided. Excellent!! Maybe my simple mind is easy to impress, but statements like this in Kiwis link to the "Kettering Ignition"  just blow my mind! I never had any idea the points worked so fast!!  Wow!
   "At ordinary engine operating speeds, the points open and close a couple of hundred times per second, the exact number depending on the number of cylinders and the engine RPM. The points need to be closed for a appreciable time in order to build up the maximum magnetic flux in the ignition coil core."
This is one of the things I love about this forum, you can get an education in mechanics, and a history lesson here! After reading my personal email, this forum is the next place I always visit, with my morning coffee in hand.

Thank You all Fellow Guzzisti for providing that quality experience.

So what I gather, is that the second condenser placed at the coil neg. terminal doesnt do the necessary function the other condenser on the distributor does, and its function would be just noise suppression, and unnecessary for the running of the bike.

There is no way the second condenser is to provide "backup" to the the condenser by the points, is it? They are hooked up to the same circuit, as the wire from the negative side of the coil is the one that goes down to the distributor, right?

I got the gas tank back on the bike, and it started up normally, without the second condenser,I plan to take it for a test ride in a bit, and see how the new Flamethrower coil performs....Of course with a name like flamethrower, its supposed to "Feel faster" ! ;D

Will report back,Thanks,
Rick.

Yes.  You got it.

The second condenser may also be necessary to reliably run your pacemaker.  ymmv.

Offline 1Sourdough

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #13 on: January 17, 2015, 09:57:48 PM »
Maybe a P-O received complaints from a neighbor or spouse about making the TV flicker when the motorcycle was out front?
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Offline Muzz

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #14 on: January 17, 2015, 10:29:04 PM »
Now shoot me if I am wrong.

If the capacitor is on the -ve side of the coil it is doing the job of the capacitor in the dizzy, and is very necessary to the running of the spark.

If it is on the +ve side of the coil it is for suppression of interference.

(Assuming a -ve earth system.)
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Offline Kiwi_Roy

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Re: Ignition coil question ..Is a condenser necessary?
« Reply #15 on: January 18, 2015, 04:36:55 AM »
Now shoot me if I am wrong.

If the capacitor is on the -ve side of the coil it is doing the job of the capacitor in the dizzy, and is very necessary to the running of the spark.

If it is on the +ve side of the coil it is for suppression of interference.

(Assuming a -ve earth system.)
As Muzz says
I think having 2 condensers on the point's side would be detrimental, the coil and condenser are matched to make a tuned circuit.
If it's for suppression on the battery side of coil I suspect it is to overcome the effect of any resistance in the ignition wiring causing Radio Frequency Interference. you could add as many as you like after all what's the battery but a dirty great condenser (capacitor).

I remember when TV was introduced to NZ, that's when they started adding resistors to the HT leads and extra condensers to eliminate the sparkle lines on reception.
These days with everyone tied to cable suppression it's probably not so vital.
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