flip flops to drive ignition

[Bob Wooten]

Chris,

any chance that you have copy of the print, I would love to check it out
for sanity sake.

Bob Wooten



> [Original Message]
> From: Chris Conlon <synchris at speakeasy.org>
> To: <diy_efi at diy-efi.org>
> Date: 1/15/01 12:36:05 PM
> Subject: Re: flip flops to drive ignition
>
> At 04:28 PM 1/15/01 +0800, Dan Zorde wrote:
> 
> >How about using the ignition outputs to drive a couple of Flip Flops,
then
> >you could tie opposite cylinders to the Q and Q(not) outputs, thus every
> >time the ignition driver fires it toggles the FF to alternatively drive
the
> >coils.  You'd just need to figure out some way to overcome this 1/10 sec
> >auto fire Orin was talking about.
> 
> A friend of mine has a system that works along these lines.
> 
> You need some kind of crank or cam position signal. If you only want to
> do wasted spark (on his 4 cyl at least), crank position would be enough.
> If you want to do coil per/on plug, you need cam position.
> 
> His system taps into the stock dizzy reluctor. In this case (Toyota
> SW20) there are signals for TDC compression on #1 and #4. There is a
> simple flip flop counter circuit that figures out what cylinder is
> next. It free runs, based on ignition pulses, and the dizzy signals
> essentially reset it to a known state.
> 
> The stock Toyota ignition driver runs off a logic level signal, +5
> to charge the coil, drop to 0v to fire. I *think* at one point he
> was using 3rd gen RX-7 coil packs, which are apparently waste fire
> but with the same type of drive signal. Supposedly they have a
> pretty hot spark too.
> 
> >coils.  You'd just need to figure out some way to overcome this 1/10 sec
> >auto fire Orin was talking about.
> 
> The simple version of his circuit had this potential issue too, but in
> his case it did not seem like the RX-7 coil packs objected to having
> the trigger held high that long. I'm sure that power dissipation went
> up undesirably at lower rpms though. One easy fix to this is to AND the
> factory ignition driver sigal with each flip flop output, or use a
> multiplexer. This way the coil pack will only charge when the ECU wants
> it to, not over a whole 1/4 (or whatever) rotation.
> 
> Another issue he ran into at one point was conditioning the reluctor
> signals. This caused some hassles. Also since the reluctors were still
> needed by the stock ECU, it was important that the circuit didn't
> interfere with that operation. 2 parts that may be helpful: the LM1815
> (Nat Semi), which is an IC designed to deal with reluctor signals, and
> MSD's p/n 8209 ignition stabilizer, which is probably not much more
> than an LM1815 in a box, with a digital output.
> 
>    Chris C.
> 
>
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--- Bob Wooten
--- r71chevy at earthlink.net
--- www.r71camaro.homestead.com 


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