[Diy_efi] Low tech fuel injection system

[Geoff Harrison]

Hi all. I too have been contemplating such a system. I am not afraid of 
computer controlled
stuff, just think in can be done analogue, easier.
My thoughts so far have been to use a monoshot LM555, triggered by ignition. 
The pulse width preset
to the shortest required pulse, i.e. normal warm idle. MAP, Manifold temp, 
water temp, throttle position,
mixed (and inverted if required) to increase pulse duration. The O2 sensor 
needs to processed through
a time delay. When it switches to "rich", triggers a slope generator, to 
lean off the mix. When the unit
is set-up properly, the O2 sensor would switch several times a second, with 
a 50% duty cycle. That signal
could become the "fuel OK" indicator.
If the ignition pulse of any cylinder can be determined, a divider can be 
used to switch the injectors, if
sequential injection is desired.
Some I have spoken to say it would take to long to set-up. These guys seem 
to spend every other weekend
remapping their Haltechs.
Has anyone ventured down this path?

Regards,
Geoff
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