New member - Aircraft engine EFI

[Jeremy Harris]

Hi all,

I've just built a modified BMW R100 air cooled motorcycle engine to fit into
a light aircraft.  As an electronic engineer I have been pondering over
whether to go down the EFI route, rather than use the big, heavy Bing carbs
that came with the engine.  My reasoning for EFI has more to do with weight
and freedom from icing than fuelling accuracy.  Responsiveness and
driveability aren't big issues for an engine that only needs to idle at
around 2000rpm or so and spends most of its time running at around 4000 to
5000rpm (it has a reduction gearbox driving the propeller).

My thoughts at the moment run along these lines:

1) Keep the system as simple as possible.
2) Use a single throttle body injection system with one injector
3) Use just a throttle pot as the "air flow" sensor (it's for low altitude
use only)
4) Seperate out the "measuring" part of the system from the "pulse
generation" part

As an outline for a really simple system I am planning to use a small,
cheap, microcontroller to do the measuring and hold the map of throttle
angle/rpm to pulse width.  This will load the required pulse width into a
timer triggered by a crank sensor (I already have a Hall effect sensor that
gives one pulse per crank rev).

Can any of you experienced people see a major flaw in my thinking here?

Many thanks in anticipation.

Jeremy
Salisbury
UK

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