I believe you may have missed the point of the 12v to 6V setup
The 12v coil stock setup had 12V going to it all the time.
That is ...during cranking and during normal running.
The latter systems using a 6v coil, while cranking, gets a straight
shot of +12V to help start the car (overdrives the coil a bit). After
the solenoid de-energizes,( when you release the key after starting)
the 12V signal is disconnected and V+ power is fed to the 6V coil via
a ballast wire in the harness and or through a fixed ballast resistor
wired in series with the coil (usually mounted right near the coil on the fire
wall.)
The newer (oem) elec ign. systems were designed around a roughly
3-5 amp draw though the modules to power the coil. So a constant
running condition of 12V / 1.8 ohm = roughly 6.66 amps wouldn't cut it.
A resistance is placed in series with the coil. do the resistance value of the
ballast,
voltage is 'dropped' across the ballast, bringing the level the coil+ side sees
to something closer to 6-9 volts. This power level was conducive to the type
of electronics used in the day.
Neither has any advantage over the other in spark power delivered.....except
maybe the 'high output' during cold startup.
This is also the real problem some people have with converting to elec ign.
Some of the aftermarket setups don't take kindly to only being fed by 6-9 volts
when the systems are plugged directly across the old coil and wiring.
So do... and some only work right if you tap +12V for the 'hot' side of the
module.
Paul Tegler ptegler@gouldfo.com www.teglerizer.com
----- Original Message -----
From: "flinters" <flinters@picarefy.com>
To: <sfgator2@juno.com>
Cc: <spitfires@autox.team.net>
Sent: Monday, February 04, 2002 2:31 PM
Subject: Re: 6V or 12V coil ??
Starting with Mk III's, Triumph went to 12 volts negative ground. To my
knowledge, there has never been a 6 volt Spitfire. Using a 6 volt coil
in a 12 volt system only causes excessive heating and stress on the coil
and won't necessarily give you a 'hotter' spark.
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