simple analog fuel injection

[Chris Morriss]

In message <14213947142659 at glasscity.net>, John Wickerham
<ibeme at glasscity.net> writes
>A while back, Peter Wales and some others were discussing a simple
>analog fuel injection system using a MAF from a Mitsibishi vehicle
>along with a 555 timer as a one shot..  I believe the name of the
>thread was EFI555.
>
>I am interested in using this system in a couple of applications
>and since every attempt to contact Peter Wales directly has failed,
>I am resorting to asking the group.  My questions are:
>
(original deleted)

MAF isn't such a good idea for a simple analogue EFI (not easy to
implement anyway).  If you use a MAP sensor, and fire the injectors once
per revolution, you will find that a pulse length linearly proportional
to MAP will suffice.  You will need to have a gain and an offset pot.
The gain sets the slope of the pulse-width versus MAP, and the offset
pot shifts the whole curve (or rather, straight line) up and down the y
axis.  You can even use the offset pot as a manual 'choke' equivalent.
The system won't be as good as a real modern EFI, but I have found that
on a small tuned 4 cylinder engine (998cc Hillman Imp) it works better
than the old twin 1.25 carbs ever did. (I only suggest you try this on
vehicles that aren't subjected to stringent emissions checks.
 
BTW, I made up a plenum chamber to bolt onto Weber alpha injector
elbows, which in turn bolted onto a twin-40DCOE aluminium inlet manifold
(not easy to find for an Imp).  The throttle body was of a (UK) Ford
Escort.

The electronics were breadboarded on double sided veroboard.  I intend
to get a proper PCB produced by the time I get the Clan Crusader back on
the road.
-- 
Chris Morriss