[Diy_efi] Several basic questions from a newcomer to EFI

[Merchant, Adnan]

Hi,

For a while now I've toyed with the idea of building an EFI system for my
Austin-Healey 3000, a vehicle that I'm doing a complete restoration on.   It
has a 3-liter straight six with twin semi-downdraught SU carbs.   While the
engine is a terrific one, with loads of low-end torque, the intake manifold
design leaves a lot to be desired.   Mixture uniformity is poor as there are
a few right-angle turns that the mixture has to endure.

I am leaning towards using a MAP sensor to measure load.   While I'd love to
go MAF, I don't really want to get into redesigning the intake manifold
right now.   With injectors and the existing plenum, I think most of the
mixture issues will go away.   Now the questions:

1)	Is fuel metering to MAP purely an empirical process?   How would I
go about making at least first-approximation calculations to determine fuel
needs based on MAP, RPM and inlet air temp?

2)	Do I need an ambient pressure sensor (BAP)?   Would a Gauge Pressure
Sensor do the job of MAP + BAP?   Is it best to plumb the MAP directly into
the intake or keep it remote?

3)	Is there any value in adding TPS?   Would it allow for better
enrichment algorithms or is MAP quick enough?

I also have a few ignition-related questions:

4)	I see that some off-the-shelf systems use a Bosch ignition module.
If I use a darlington switch, can I not perform all dwell control through
the software?

5)	With a distributor system, dwell is angle dependent; what's the rule
of thumb for dwell time as with a processor I can now have fixed dwell,
regardless of RPM?   I plan on using a direct ignition system with three
coils and wasted-spark.

6)	What's the best (and easiest) way to figure out the advance curve
for the existing distributor?   The vacuum advance is probably going to be
more difficult, I'd guess.

Is there a fuel pump system that does not need a return line to the tank?

Lastly, I am considering the Motorola 68HC16Y1 microcontroller as it has an
on-board TPU with software built in for detecting missing teeth and
generating angle-angle and angle-time pulses.   Have any of you used it and
would care to comment on it?   Does anyone offer a pcb that uses this
controller plus has EPROM added in?

Sorry for the long message, folks.   I look forward to your input.

Thanks,
Adnan

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