IGNITION PROJECT

[John Brewer]

Mark,  This sounds, almost verbatim, like what I am working on for my '78
FJ40 LandCruiser.  I initially wanted to start with EFI but have decided to
start with ignition since my electronics skills are lacking; like many
engineers I have plenty of theoretical grounding in dynamics, controls,
thermo, etc, but I can't build anything!  (Decided to use my mechanical
ability and love of automobiles to get something going.)

>Objective: Replace the distributor and points with a blob with some
>inteligence.

Amen brother, the thing is so incredibly obselete!  I thought perhaps an
optical system using a semiconductor laser combined with appropriate lookup
tables.  Either that, or a reference point, perhaps optical, in the
distributor to give me TDC on #1 and a toothed wheel on the crank pulley.
Maybe even use painted teeth on the flywheel (hhmmmmm.)  Get rid of the
high tension leads completely and go with spark plug mounted coils
controlled by a central computer: ostensibly a central computer powerful
enough to do full state variable control and have it control my EFI when
the time comes.

>Desired sensors: Combined engine speed/crank angle, MAP, water temp,
>knock, and possibly air temp.

This is about what I was thinking as well.

>Desired outputs: 'points' output for as many coils as required. 1,2 or 4.
>Cooling fan out put. RS232 monitor port. High speed interface for sensor
>output to possible further extension blocks.

Definitely got to go with plug mounted coils so at least 6 outputs for me.

>Reasons: My engine is a 4 pot normally aspirated 1.5 liter engine. Its
>distributor is shot, and needs replacing. It eats points, and condensers
>and coils, and no there is no fault, all spitfires do this!

Classical distributors just stink, what more needs to be said!

>Sensing: Speed and position from a machined chain sprocket bolted to the
>front pulley (which in my case is keyed in one position to the end of the
>crank), with 36 or 24 teeth. Pickup is to be the digital magnetic pickup
>from RS components , it costs 16 UK Pounds or about 35 bucks to anybody
>over there if I have to send them (if you guys cant buy them). MAP to be
>measure using MPX4250A, about 30 bucks (up to 36 psi, so that allows
>turbos up to about 22 psi boost. Knock: haven't even thought about this
>one yet, all suggestions welcome . Water temp, million and one ways of
>doing this.

I like it, a turbocharger is in my dreams as well... that's one of the
better dreams.

>Processor: 68 something (but only if I'm doing the programming, if you
>want to join, and do the software, I'll adapt to what you like)
>On the fly re mapping, in flash.
>All information to be made available to other systems on request, by
>serial >coms.
>High speed programmable pulse chains indicating TDCs, firing points etc
>for accurate timing by other systems (possible fuel inj?) and scope
>diagnostics.
>Remote controll of ignition events by other systems (eg, revlimiter,
>traction control etc)

I can certainly design a controller for this sort of thing though
programming a chip is a skill which I hope to get out of this little
endeavour.

>Extra sensor input from current points, to allow initial map to be built
>from currently working mechanical system.
>
>CUT TO THE CHASE:
>
>Order of development:
>
>
>Sensors first.
>
>Chose sensors, and design their interfaces, then test.
>Design software.
>Chose uP
>Design system.
>Test system and refine.
>
>Up shot.. publish the sensors and interfaces , so that other scratch
>builders can just do a building block design on their own hardware. If at
>the point I go 68xx(x) they want to go PC or Z80 or anything else, they
>can, and the software design can be followed and implemented, even if they
>cant use the code.
>
>Things needed imediatly:
>
>Suitable temp sensor, and a knock sensor, and preferably their interface
>schematics if anybody has a suitable solution to these two questions, I
>would dearly like to hear from them.
>
>Does anybody want to join this idea.. or am I on my own for this one?
>
>A good programmer would be a bonus, I can do it, but I would prefer to let
>somebody else do it. I am prepared to add dedicated hardware for doing
>timing, and interrupt control, and stuff like that. Anything that makes
>the programming easier. ;-)
>
>Mark
>
>(Who has decided to stop messing around and get on with it)

Like the NIKE commercial says, "Just Do It."

John Brewer


"Any man who would trade liberty for security deserves neither." -  Ben
Franklin