RPM independence

[James Montebello]

> I have given more than a little thought to the possibility of an EFI
> system that operated completely independently of engine RPM.  The idea
> being that as the injectors are batch fired anyway, the timing is
> irrelevant so long as the injectors fire at engine RPM or more.
>     Such a system could be almost entirely MAF based.

This is, essentially, what CIS (aka K-Jetronic) does.  Airflow
is the ONLY parameter used to adjust fuel flow rate, except for
cold running and WOT operation.  Engine speed isn't a factor at
all.  Designing an EFI system to emulate this is straightforward.

However, if you plan on controlling ignition as well as fuel,
you're going to need crank position and speed, anyway, so
using it as part of the fuel delivery strategy doesn't add
any more complexity.  It also opens up a few new avenues of
overcoming common problems.  A MAF (or MAP or CIS) system is
sensitive to reversion when high-lift, long-overlap cams are
used.  With given exhaust and intake systems, reversion will
only take place at certain engine speed ranges, so it can be compensated for
if the engine speed is known.

More data is almost always better than less.  The frequently
forgotten other half of the KISS principle is: keep it simple,
but not TOO simple.

james montebello