Do you plan on testing the ignition system that you designed as well
 as the
 555 EFI?  Any time frame?

 Joe Berki
 Limo EZ

 Yes. I have everything I need to test that. I am not sure when I'll
 get to it. Here is the idea for the new guys.

 These are inductive coils and they normally require a computer.
 Inductive coils are turned on for a period of time and then
 they fire when the current is suddenly turned off. This off time
 is called dwell. If the dwell is too long the coils over heat.
 If too short you don't get full spark energy.

 The breakthrough on how to make this stand alone and work without
 a computer just occurred to me. The trick is to slot the trigger
 wheel and use a  IR photo transistor, an IR emitter LED and FET switch
 instead of a magnetic pickup or Hall Effect sensor. These devices
 put out a single narrow pulse. Not what we need.

 When the IR photo transistor sees the infra red emissions from the
 IR LED it turns the coil current on using a high voltage FET solid
 state switch. In the case of the GM coil the FET is built in. I used
 something like this for years on my computerized road test equipment
 and it is very reliable and durable. Also tolerant of dirt and dust.

 It will work with just about any stock inductive plug on coil system
 including the Corvette GM coils. The length of the slot controls the
 dwell time. The end of the slot controls when the coil fires.

 I have been thinking about this problem ever since the stand alone
 coil on plug systems first appeared. How do we get rid of
 the computer?

 If you want to fire the leading and trailing plugs at different
 times you can use four slots with four photo TX's and four
 LED's other wise each photo TX fires both leading and trailing
 plug coils at the same time.

 Now some of you electronic types might say "why not just
 use a 555 one shot with a fixed pulse width to turn on
 the current in the coil for a fixed period of time triggered
 by a magnetic sensor or Hall Effect "?

 The problem with that is the spark timing will vary with RPM.
 You want the plugs to fire at 22 degrees TDC over a wide range of
 RPM's so that approach will not work.

 Basically this thing works like distributer points.

Aircraft engines run in a very narrow load band so a 22 deg fixed advance
is typically used. Aircraft engines run in cruise mode 99% of
the time with a fixed prop load unlike an auto engine that runs
at 40 HP while driving down the freeway  and variable load during
acceleration and hill climbing.

Once the current in the coil (charging) reaches a peak the spark energy
is independent of the time it takes to fully charge the coil.
The GM coils are fully charged in 5 ms.

We are not looking for ultimate sophistication here. We are looking
for a simple cheap ignition system to use with a carburetor.

 I have the GM DS580 part number 12558948 coil.

That works. I got it to fire every 2 seconds or 30 RPM with a dwell
time of 1 second. Also at a voltage of only 6 volts. I am impressed.

It does not automatically fire at 100 ms. That was a false alarm.

This thing is working so well I can't believe it.
I won't need a slot or movable segment  in the trigger wheel at all.
Just a 180 deg tab sticking out which will lower the cost of a laser
or water jet cut disk. As you can see from this scope picture
(img 1023) it fires on the rising edge. The tab is 180 degrees.
The spark last for about 1/2 msecond.

Super simple and super cheap for an ignition system.

I'll redraw the disk after Christmas as I am leaving for
Robin's cousin's hous for a few days.

Merry Christmas

Paul Lamar


Paul if Fixed ignition would work why not consider stand alone EDIS?
Simply advance the sensor 12 degrees and you have it permanently in 22
degree "limp home mode" no computer....

Is there a searcahble database so I could review if the EDIS option
has been vetted out in the past?


Matt

It can be made to work but it is a bit tricky. Something about
the waste spark coils. We discussed it at length so I would have to look
that up. The easiest thing is go on the Magasquirt web site and see what
they have to say about it. Also the stock Ford trigger wheel is very
very heavy. This new system is easy to build without relying on junk
yard or expensive new parts. It is also not waste spark and using low
cost one coil per plug GM or RX8 parts. Some times you can get the
coils when you get the engine.

Paul Lamar