i'm not sure megasquirt does dual point - you may want to check the info
on that before proceeding any further.  if you're going to the trouble
of retrofitting, either go 4-point and make life easy /or/ just use the
whole dpfi system from an 88-91 civic.  if you need to re-map the dpfi
ecu for a different volumetric profile, there are some "2-ner" projects
out there that show you how to do it.  google is your friend.

regarding specific questions, lower is primary and upper is
"enrichment".  it will inject over the full rev range if conditions
warrant.  it also injects as a function of tandem valve position because
the tandem valve is designed to increase air flow velocity [at the
expense of volume] and hence better fuel droplet evaporation.

They're called "main" and "auxiliary" at online parts sites and in Chilton
manuals.

The main injector is on top. The auxiliary is on the bottom.

For a drawing, click on "Throttle Body" 1.5 L, at
http://www.honda.co.uk/owner/ConcertoManual/index.html

This info is not in my Chilton's manual; nor at Autozone.com; nor at the UK
Honda manual site. There is very little detail at these sites re injection
rates, switching, etc.

+++++++++++++++++++++++++++++++++++++++++++++++++++
While trying to find a way to monitor the FI on time tobe able
to monitor fule use real time I had a dual channel oscillsocpe
connected to botht eh main adn aux FI.

There is no simple way to discribe the "firing" events.
The main cylcled pretty much the way I expected.
But the aux didn't behave in what I would consider to be
any logical manor. During cold starts the main and aux are
both one about the same times. As the engine warms up the
aux on cycles are reduced except for odd cyles that do not
relate to acceration or engine speed. For instgance,
while driving on a level stretch of highway, keeping speed
and throttle postion constant, the main chugss away more or
less like I expected. But at odd intervals the aux would cyle
on for no apparent reason.

In general any demand for increased engine RPM, ie opening
the throttle, will result in the aux opening for variable
periods. Deceleration using the engine had the aux cycling
more then the main.  I finally found this link,
<http://www.ggimages.com/rx7/pwm.html>, and I use 2 of them
to monitor both main and aux. I had thought about trying to
combine the outputs so I only had to deal with one disply,
but after some practice I can now minmise my fuel consumption.

I was intrigued by the lowest intake manifold vacuum does
not translate to best fuel economy.

I am sure that a real micro computer whiz could read the data
from the ECM EPROMS and build a table that shows on ratio for
engine temp, MAP, O2, RPM and BAR but this is way beyond my
skill set.

Terry