ECU's and HEI

[Ken Kelly]

Out of curiosity, I've been trying to think of ways to manage an engine by
building my own ECU. Obviously, this is an arduous task, but one I'm not
afraid to embark on.

I started off by figuring out the inputs and outputs and determined that I
could do it with a few of the new high-speed BASIC Stamps from Parallax, but
lately I'm beginning to wonder if it can't be done (easier) with an analog
system - i.e. transistors/diodes/resistors/capacitors and have pots for
tuning? I believe this is the way Holley does most of their systems aside
from their 4D and 4Di systems.

My main big question, however, is HOW do the HEI electronic systems work?
How does the computer adjust retard and advance? Is it a signal varied by
voltage, frequency, or what? I'm at a total loss for this concept. The other
parts of the engine I have figured out (injectors, MAP, TPS, O2, etc.) but I
can't quite see how the timing works on the electronic versions of the HEI.
(I see it has a seperate 4 wire interface?)

Part of my reasoning for making my own ECU is simply for the fun of it and
partly because I'm going to be making some of my own components - I'm
looking into making a VFI (Venturi Fuel Injection) unit out of a Quadrajet
(similar to the Barry Grant VFI unit made from a Holley carburetor body.)
I'm also looking into how to control and monitor other aspects of engine
management - i.e. fuel pressure.

Thanks for any help..

The "Other" Ken Kelly

ken73 at houston.rr.com
home.houston.rr.com/ken73