[Diy_efi] Ignition/coil

[Charles M Slack, III]

Mark, Generally not. Just have a 8 to maybe 24 inch of undersized fuse 
link type
resistance wire in line.
Usually a high iron content or other material ( some % nichrome) to give 
higher resistance
per foot. Then the High current , say 6 to 10 amps, drawn through the 
wire will drop the
12-14 volt ignition source down to 9V or so on the coil.  Also, when 
starting, this inline
ballast resistance (older cars had a wire wound( nichrome) ceramic unit 
mounted near the coil.)
is bypassed during the start to give full 12-14 volts at the coil until 
the car starts, then back to the lower voltage in run position. Many of 
the high current fuse links are made this way also.
They can melt the internal wire and not even noticeably harm the 
insulation. Then you have an open
in the circuit to the starter or wherever that is had to locate.

Charlie Slack
65 TBird
Austin / Bastrop, TX


mark krawczuk wrote:

>hi, i thought that the wire  used for ballast resistor is a    special
>nichrome / resistance wire ?
>
>mark k
>
>
>----- Original Message -----
>From: "Bill Washington" <bill.washington at nec.com.au>
>To: <diy_efi at diy-efi.org>
>Sent: Friday, March 24, 2006 5:45 PM
>Subject: [Diy_efi] Ignition/coil
>
>
>  
>
>>David,
>>Most coils are 9V fed thru a ballast resistor during normal running to
>>    
>>
>drop the
>  
>
>>12V(nominal 14V really) to about 9V. During cranking the ballast resistor
>>    
>>
>is
>  
>
>>shorted out to provide extra 'oomph' because the battery voltage sags
>>    
>>
>during
>  
>
>>cranking.
>>If you go looking for this 'Ballast' resistor in most cars you will not
>>    
>>
>find it
>  
>
>>because the actual wiring is sized (small) to provide the resistance, and
>>    
>>
>during
>  
>
>>cranking a lower resistance path is connected in parallel either by the
>>    
>>
>ignition
>  
>
>>switch or by a relay.
>>In a ballast resistor system, if the supply side has been modified (ie the
>>resistive wire bypassed) or the relay has failed with the contacts
>>    
>>
>permanently
>  
>
>>closed you will have lots of spark but a short coil life....
>>If the car was designed for a 12V coil, ie it does not have a ballast
>>    
>>
>resistor
>  
>
>>and a 9V coil is fitted the result is the same - lots of spark, short coil
>>    
>>
>life.
>  
>
>>Some years ago an "auto electrician" without my knowledge fitted a Bosch
>>    
>>
>GT40R
>  
>
>>(9V) coil in place of my GT40 (12V) coil when a workshop had trouble
>>    
>>
>starting my
>  
>
>>car (I had told them that they would not be able to start it and to call
>>    
>>
>me, but
>  
>
>>they "knew" better) - My car had a 12V coil standard - and no ballast
>>    
>>
>resistor -
>  
>
>>the coil only lasted a few weeks!!! and I had to replace it - the workshop
>>refused to accept any responsibility - needless to say they have never
>>    
>>
>seen any
>  
>
>>of my cars again!!!!
>>
>>Just some thoughts
>>Best Regards
>>Bill
>>
>>
>>
>>Subject:
>>Re: [Diy_efi] Bosch ignition coil
>>From:
>>"David Allen" <davida1 at hiwaay.net>
>>Date:
>>Thu, 23 Mar 2006 21:12:22 -0800
>>To:
>><diy_efi at diy-efi.org>
>>
>>   Thanks for the info on DIN 72552.
>>   As for the iginition system in general; it's a remote-coil HEI.  The
>>resistance of the coil-to-cap lead is 12K, and the plug leads range from
>>    
>>
>10K
>  
>
>>to 13K depending on length. The cap and rotor had evidence of cap/ rotor
>>interference but the contacts were clean and the rotor tip wasn't broken
>>off.  I replaced both as a set.  The plugs are Bosch Platinum (original;
>>    
>>
>not
>  
>
>>multi-tip etc..) gapped at .045". Engine is a 305 running about 10:1
>>compression normally aspirated.  There haven't been performance issues
>>betwen coil failures.
>>   With each coil I replaced the cap and rotor shortly after and tested
>>    
>>
>the
>  
>
>>wires, suspecting the high secondary resistance issue you describe. I've
>>never had a module outright fail on this car. The new one on there now was
>>purchased as a replacement for one I had to "borrow" to get my other car
>>running.
>>   I think the coil quality may be the problem.  The last couple times the
>>coil has died I have been on the road and had to locate a local parts
>>    
>>
>place
>  
>
>>to buy a coil. The choices have been limited.  Will see how this one holds
>>up.
>>   Thanks for the ideas. I do have a great apetite for adventure and no
>>    
>>
>wife
>  
>
>>to worry about so I will let the module stay for now!  :-)
>>   I plan to measure the peak primary voltage and see how this is affected
>>    
>>
>by
>  
>
>>changing to non-platinum plugs.  I remember a thread where someone was
>>concerned they were damaging plug wires by use of platinum spark plugs. It
>>sounded far-fetched but you never know.
>>Later,
>>David
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>>    
>>
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