DIY_EFI Digest V5 #79

[John Dammeyer]

Hi Jack,

I just completed and engine controller for 4Cyl Honda Engines.   A custom controller was
desired because: a) The reduction drive for propellors was in the way of the stock
distributor; b) the customer wanted dual ignition for aircraft redundancy; c) the customer
needed fuel injection and wanted to use as many Honda parts as possible.

A prior version involved a carburator and just dual ignition and used a couple of Hall
sensors with two PIC micros on one circuit board.

The first Injection version has everything except dual ignition so addresses the
controller side of things you mention.

Fascinating question though.  If absolute position information is available for each
cylinder then designing a single PIC or ATMEL processor on a per cylinder basis would be
an interesting project and certainly scalable up to V12 engines.  It gets more complicated
if you wish to use the newer 'waste spark' coils because now you need to work with two
cylinders at a time and handle overlapped injector timing.

i.e. With a one cylinder engine and a 720 degree cycle you have a total of 4 events to
manage; Injector on/off and coil current on/off.  A two cyl. engine doubles this along
with overlapping injector times depending on engine load and the complexity at that point
isn't any more difficult than 4 or 6 or 8 or 12 assuming the processor is fast enough
relative to engine speeds.

Now let's talk cost.  The four cyl. controller I designed drives two coils through a
Capacitive Discharge technique and also drives 4 injectors using two VND05 devices.  So
this could be scaled back to a two cylinder project at the cost of doubling up the Coil
and Capacitor storage section which is shared.

But... The cost of the processor, EPROM and RAM are insignificant compared to the cost of
the interface circuitry, circuit board, the box, the connectors and the CAN network used
for debugging.

Just throwing two MAP sensors into the engine for two controllers raises the price far to
much compared to what you would gain.  Even with single quantity pricing,  a single C167
or Motorola 16/32 bit processor on one circuit board is still less expensive than bank of
8 individual processor boards.

Good idea but not economically viable - especially for a hobby.

Cheers,

John

>------------------------------
>
>Date: Tue, 29 Feb 2000 10:43:19 -0500
>From: "Jack E. James" <indyjj at indy.net>
>Subject: Atmel & List Stirring
>
>Hi Bernd,
>

[snip]
>controllers becomes available, it would seem that there might be an
>advantage to
>separating cylinders, like two identical 4 cylinder controller's for
>a V8.  Two ignition sensors (like Pertronix modules switching resistor
>loads to provide position logic) and parallel mass air flow or 2- MAF
>units for less air flow loss.  Or one controller for part throttle
>and another for full throttle.  Just curious about multiple processors,
>having thought about using some of the faster PIC,s for each
>cylinder.

[snip]
>Jack
>


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