Larry,
I'm playing with my own design ideas ( slide carb) and one of the variables
is an adjustable ( in height via screw thread) needle to lean and richen the
mixture and the other problem of different seat jets sizes, I feel  could be
solved with a variable pressure fuel pump ( from 1.5 psi +). This could be
managed with an idle jet under the jet/seat.

I envisage the variable pressure pump an idle screw as the course
adjustment, with the needle ( into seat/jet) as the fine adjustment.
What do you think.
George ( down under)



George,
The best way to manually control the fuel flow is a barrel valve type
system. Needle valve systems are known to have problems with thermal growth
of the components changing the mixture as well as being very prone to
contamination errors.

The easiest way to vary the fuel pressure is to pulse width modulate the
supply voltage to the pump. I do have an easy way to do this, I just have to
get my software/electronis friend to change the control signal from
temperature to pressure. My friend makes a dual fan controller for
automotive use that pulse width modulates the fans based on engine
temperature. I had him design this for hot rod stuff years ago. Works very
nice. The design could be changed to control a fuel pump. We could drive the
pump based on a combined signal of throttle position, manifold pressure and
rpm. One advantage is now the fuel pump only uses the electric power
required to obtain the required pressure. Now leaning can be done with a
trim pot on the panel changing the overall trim of the system.
You can check out the original I-FAN2 at
http://www.hms-electronics.com/fan/index.htm

Let me know it this is something we want to pursue, I and will talk to Dick
about what it will take to make one for our purpose. This may actually be
the easiest way to make the low cost injection work.
Larry


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