[Healeys] coilt induction ingition

Richard Ewald richard.ewald at gmail.com
Thu Dec 29 21:47:26 MST 2016 

No. you have it backwards.  The rise in the coil primary (100-300V AC) is the result of the coil firing NOT the cause. 
When the points are closed current flows in the coil primary. This creates a magnetic field. When the points open that field collapses and moves across the secondary windings inducing the high voltage that fires the plug probably about 9-10KV at idle. 
As the plug fires the magnetic field in the secondary winding collapses and induces AC voltage back in the primary which collapses inducing voltage into the secondary and back again. As this voltage bounces back and forth it decays  AC voltage. Then the points close and lather rinse repeat.  
If you doubt this go out to the garage remove the coil primary wire to the coil. Run on the key and measure voltage at coil primary. 12V. Now ground that coil primary lead and disconnect it. Two things will happen
1. A large zap from the HT terminal
And 
2. You will get shocked from the induced voltage in the wire you just disconnected. 
Rick
Sent from my iPhone

> On Dec 29, 2016, at 12:31, Austin Healeys List <austinhealeyslist at gmail.com> wrote:
> 
> No. A Transil across ignition points will result in little or no spark
> at the plugs. The coil primary voltage needs to rise up to somewhere
> around 400V, depending on the coil, in order to drive the HT voltage
> across the plug gap (firing voltage). If it is clamped at 20V by the
> Transil then the plug firing voltage will be 20V * the turns ratio of
> typically 100:1 so 2000V which won't do anything useful. A capacitor
> is the perfect solution here as it protects the points for a few nano
> seconds as they open, then allows the voltage to rise up and drive the
> spark across the gap.
> 
> Modern electronic ignitions don't need the capacitor as transistors
> can easily handle 400V.
> 
> Andy.
> 
> 
>> On 12/29/16, Oudesluys <coudesluijs at chello.nl> wrote:
>> I presume a larger capacitor might influence the speed of the collapse
>> of the magnetic field, reducing the voltage produced in the secondary coil.
>> To prevent arcing as much as possible in the Lucas fuel pump I now
>> install a "transil" across the points instead of the earlier used and
>> less effective capacitor or diode. This could probably also be done on
>> the distributor points. As I do not run points any more so I cannot try
>> it out myself.
>> A transil is very cheap, $1-$5 depending on where you get them. I got a
>> larger quantity for less than $1 a piece on eBay. I use a bidirectional
>> one in the fuel pump to make them positive and negative earth:
>> /1.5KE24CA,/ CA indicating it is bidirectional.
>> May be worth a try?
>> 
>> Kees Oudesluijs
>> 
>> //
>> Op 28-12-2016 om 22:56 schreef Ed O'Neal:
>>> 
>>> Gents,
>>> 
>>> By way of recap:  When the points close current flows through the
>>> primary (12 volt) side of the coil.  When they open the magnetic field
>>> around the coil collapses across the secondary coil windings (high
>>> voltage) driving a high voltage current across the plug gap and firing
>>> the cylinder.  At the same time the magnetic field also across the
>>> primary windings attempting to drive a current across the open points
>>> and creating a relatively high voltage (perhaps 400 volts) which will
>>> want to arc across the open points and wearing them out quickly.  To
>>> mitigate this a condenser (capacitor) is places between the points
>>> coil connection and ground which absorbs the “shock” of the current
>>> being driven towards the open points and reducing the potential for
>>> arcing across the points allowing them to last longer.
>>> 
>>> Question:  Why would a larger condenser (capacitor) not reduce the
>>> potential for arcing across the points even more?  What might be the
>>> down side of such an attempt???
>>> 
>>> Thanks for your expertise in advance.
>>> 
>>> Ed
>>> 
>>> *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of
>>> *Al Fuller
>>> *Sent:* Wednesday, December 28, 2016 2:40 PM
>>> *To:* 'Healeys, Forum'
>>> *Subject:* Re: [Healeys] Mount a coil on an alternator.
>>> 
>>> Josef:
>>> 
>>> Petty broad brush you are painting some of us with there… [Quote:
>>> “People who swap a generator for an alternator like to modify in any
>>> way.”] Without further comment to your over-statement, I WILL say the
>>> following:
>>> 
>>> I drive my car on multi-day cross-country trips and see the value in
>>> installing a modern alternator.  The generators on our cars were
>>> installed 50 years ago, and designed way before that to provide a
>>> fairly modest output [~20 amps, if memory serves].  The generator was
>>> barely able to supply the car’s needs as supplied, and modern use
>>> calls for additional and more power-hungry apliances in the car, such
>>> as headlights that actually light up the road ahead…
>>> 
>>> I now have an alternator that will power the car, headlghts, the CB
>>> radio I consider a necessity when driving in a multi car caravan,
>>> etc.  An added bonus is if it happens to fail, rebuild or repar are
>>> readily available.  Note that none of this drives me necessiarily to
>>> any other modifications.
>>> 
>>> Al Fuller
>>> 
>>> al at bighealey dot org
>>> 
>>> '65 BJ-8
>>> 
>>> '85 Rx-7
>>> 
>>> *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of
>>> *josef-eckert at t-online.de <mailto:josef-eckert at t-online.de>
>>> *Sent:* Friday, December 23, 2016 4:07 PM
>>> *To:* Simon Lachlan <simon.lachlan at homecall.co.uk
>>> <mailto:simon.lachlan at homecall.co.uk>>; Healeys, Forum
>>> <Healeys at autox.team.net <mailto:Healeys at autox.team.net>>
>>> *Subject:* Re: [Healeys] Mount a coil on an alternator.
>>> 
>>> People who swap a generator for an alternator like to modify in any
>>> way. Anybody who knows more about electrics know there is no need for
>>> an alternator at all on Healeys. its only to adjust the rehulator to
>>> work as it should.  But that´s to difficult for most I suspect.
>>> 
>>> those selling these alternators are quite happy to sell them as people
>>> like to modify and they also sell you one of these performance coils
>>> and they need to be kept cool and best is to put the coil in the boot
>>> to keep it cool. Haven´t seen that so far but can´t await to see it.
>>> 
>>> Josef Eckert
>>> 
>>> Konigswinter/Germany
>>> 
>>> -----Original-Nachricht-----
>>> 
>>> Betreff: [Healeys] Mount a coil on an alternator.
>>> 
>>> Datum: 2016-12-23T21:57:44+0100
>>> 
>>> Von: "Simon Lachlan" <simon.lachlan at homecall.co.uk
>>> <mailto:simon.lachlan at homecall.co.uk>>
>>> 
>>> An: "'Healey Group'" <healeys at autox.team.net
>>> <mailto:healeys at autox.team.net>>
>>> 
>>> I’ve had an alternator in my BT7 for a while now.
>>> 
>>> So, when I was doing the job, I looked at pictures of other people’s
>>> installations. Nobody’s coil was mounted on the alternator as coils
>>> were/are mounted on the generators.
>>> 
>>> I didn’t mount mine on the alternator either.
>>> 
>>> Now, I’m wondering why everybody found ingenious places to put the
>>> coils and nobody ingeniously adapted their brackets to fit onto their
>>> alternator.
>>> 
>>> Do alternators get too hot? Do they give off some kind of magic death
>>> ray that fries coils or what??
>>> 
>>> Any reasons not to do it??
>>> 
>>> Thanks,
>>> 
>>> Simon
>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
>> 
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