Re: triggered gap idea

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi All, Jim!

  Been there, did it ;)  I grabbed the IGN unit out of a VW Jetta
(80-something).  It's a little black 7-pin doolie on a plain aluminum sheet
(heat sink) under the hood on the driver's side, right back under the rain
tray.  It's driven by a Hall sensor on the distributor, so all you have to
do is feed it pulses from a 555 based timer.  I used a small switching
xsistor (sorry, no number, was in the junk box) to keep current on the 555
within sane levels, and I ran 12v pulses to the IGN module.  The 555 circuit
was the standard, running at ~200hz to some nasty high-pitched level.  The
use of a low (I used a 2 ohm) value resistor in the +12v feed of the IGN
module is recommended.  VW does this by means of a ~38" wire of a specific
gauge in the engine compartment.  Sorry, but no Chiltons here at work for my
VW.     Does it work?  You betcha!!!  The IGN unit is built like a little
tank!
        Is it useful?  Ummm...all mine really did was give me a convenient,
easy to trigger IGN coil driver that I *knew* would handle the abuse. I blew
mine up from stupidity.  It drove a GM coil with no problem, though I never
tried running it on a flyback.


    Just my $.02



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, December 13, 2001 7:46 PM
Subject: triggered gap idea


> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
>
> There has been much discussion on various and sundry triggering circuits
> for a triggered gap.  Since most of us are using auto ignition coils,
> rather than cobbling up something from dimmers, etc., why not just use the
> electronic ignition amplifier that typically accompanies that HEI coil.
>
> In several systems I've built, I've used various MSD ignitions to fire an
> auto coil from a TTL timing source.
>
> Wretchedly expensive if bought new, but, if you're scrounging coils at the
> junk yard, you might be able to grab the solid state driver as well, since
> it's all encapsulated in the distributor.  Maybe a good source would be
the
> ones that Ford is replacing in the big recall?  They don't meet car spec
> (temperature related failures, I believe), but they'd be more than good
> enough for triggered gap use.
>
> These amplifiers typically trigger of a very small pulse from a magnetic
> pickup, and should be readily adaptable to being triggered of an
> optoisolator or 555 or something sync'd to the power line.  Modern
> ignitions need to time the spark to better than 1 degree of crank rotation
> at 6000 RPM (= 100 RPS = 10 mSec/360 = 27 microseconds) to meet emissions
> requirements.  All you'd need is a beefy(probably 5A minimum...)12V supply
> to run them.
>
>
>
>