[TR] TR3 coil question

[Jason Sukey]

Tony, you might not be familiar with the 123 ignition dizzys, but they
recommend 1 ohm or greater- no worries on that.

Jason
On Sep 19, 2015 7:52 PM, "Anthony Rhodes" <spamiam at comcast.net> wrote:

> 1.5 ohm coils are typically used with a ballast resistor to make the
> overall resistance about 3 ohms except when starting the engine.  A total
> resistance of less than 3 ohms may damage an electronic distributor
> switching unit unless it is specifically designed for low resistance coils.
>
>
> I think that some racing applications, particularly 8 cylinder engines may
> use a lower resistance ballast, or none at all.  But at low revs like 2500
> on a 4-cly, the peak current is too high for points and the usual
> electronic distributor.
>
> -Tony
>
> Sent from my iPhone
>
> On Sep 19, 2015, at 2:45 PM, Jason Sukey <jsukey at gmail.com> wrote:
>
> I don't have all the specs on me at the moment, but from memory, the
> "hotter" red coil has a primary resistance of about 1.5 ohm, and the
> "colder" coil had a primary resistance of 3 or 3.5 ohm.  My understanding
> is this is the typical situation where the lesser coil can't develop enough
> voltage at high rpm when the charge time is the shortest, thus needing the
> increased voltage of the lower resistance coil.
> Jason
> On Sep 19, 2015 2:35 PM, "Anthony Rhodes" <spamiam at comcast.net> wrote:
>
>> That is can interesting question of why one coil was failing at high RPM
>> while the other didn't.
>>
>> Assuming both are in proper operating condition, then I would expect that
>> the one that can't sustain high RPM has a lot more inductance than the one
>> that worked ok
>>
>> As a matter of fact, the "high voltage" coils probably get that extra
>> oomph by having higher inductance.  The price you pay for high inductance
>> is that it takes longer to "charge" the magnetic field of the coil.  So,
>> there is a steeper drop off of output voltage vs RPM.
>>
>> Do you have the specs on the two coils?  Btw the resistance of the
>> secondary windings also has an influence.  So does the resistance of the
>> primary windings though I am assuming both are 3 ohm.
>>
>> -Tony
>>
>> Sent from my iPhone
>>
>> > On Sep 19, 2015, at 1:00 PM, triumphs-request at autox.team.net wrote:
>> >
>> > Message: 1
>> > Date: Fri, 18 Sep 2015 14:26:04 -0400
>> > From: Jason Sukey <jsukey at gmail.com>
>> > To: auprichard at uprichard.net, triumphs at autox.team.net
>> > Subject: Re: [TR] TR3 coil question
>> > Message-ID:
>> >    <CAMmo4o-UUO+VMFaKgUCjZiOEQHs1zfsV6fArUq9C+eKQ8s-Mzw at mail.gmail.com>
>> > Content-Type: text/plain; charset="utf-8"
>> >
>> > Andrew,
>> >    Not TR3 related, but I've had to play around with coils on my
>> modified
>> > GT6 using the 123 distributor (USB tune model).  After a lot of
>> fiddling, I
>> > found that with the recommended Bosch "blue" coil, it would "go flat" at
>> > high rpms when I was accelerating hard.  (this is compared to points
>> dizzy
>> > with a hot coil).
>> > I ended up with the Bosch "red" coil (made in Brazil model, I'm told the
>> > made in Mexico version is of lesser quality).  This solved my problems
>> and
>> > it once again is happy to pull strong up to 7,000 RPM's.
>> >
>> > My theory is that the lower voltage "Blue" coil is fine for stock
>> > applications, but isn't enough for higher performance use.
>> >
>> > Jason
>>
>
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