Alan Tolle wrote:

There have recently been some interesting notes about fuel injector
location.  I will add my $0.02 worth.

Both of the Powersport engines which I ran used a Bendix type ( proved by
millions of hours of operation in aircraft) fuel injection.  Like in any
other fuel injected aircraft engine, the fuel pressure ran 30 psi at the
gauge, and regardless of the fuel flow, the pressure relief valve at the
fuel pump kept the pressure constant by returning excess to the tank in use.

The Bendix system is air flow controlled.  The fuel flow is matched to the
air flow into the engine to maintain the proper fuel/air ratio.   Air alone
comes through the induction system.  The fuel is continuously flowed in
right behind the intake valve where the fuel/air mixing occurs.  Crude, but
it is simple and it works.  Except on a hot start.

Many of the electronic fuel injection systems in the last thirty years have
been patterned after various Bosch patents.  Air flow is measured for volume
and temperature, rpm and engine temperature are measured, and the black box
electrically opens the injectors to dump fuel close to the intake valve.  I
think of the Bosch AFC system used by Porsche, Toyota, Nissan, BMW, Volvo,
and a host of others.

>From the above we can derive some ideas to adapt to the rotary engine.

First, only air goes down the induction runners, the amount of air being
determined by the throttle plate opening.  You can run a fuel/air mixture
through an Intake manifold only if it is well heated.  Otherwise you get
induction icing big time.  Think of all the heated induction systems through
which a fuel/air mixture travels, from  a Chevy V8 to a 4 banger Lycoming.

Second, if you run a fuel/air mixture through a cold induction tube which
makes a 180 degree bend, not only will you get  induction ice, you will get
fuel plating out of the mixture on the outside of the bend, which can lean
out the mixture something fierce and lead to some hard to figure out flat
spots in the power curve.

So Powersport put their fuel injection nozzles either into the port through
which the oil injection into the trochoid housing normally occurred, or into
the intake runner right at its entrance into the trochoid  housing, aimed
right at the throttle plate.  (You will recall that the Powersport engines
were peripheral ported with the throttle plates right at the trochoid
housing.)  While both locations seemed to work well, the latter location
seemed to idle a little better.  Two nozzles into each trochoid housing gave
redundancy in case of a fouled injector, but gave no improvement in overall
performance.

I suspect that the injectors in a fuel injection system will work best if
they are pretty close to the trochoid housing.  I also wonder how an Ellison
throttle body dumping a  fuel/air mixture into cold intake runners is going
to work out.

Finally, I am still not sure how much I trust black boxes.  My Porsche 928
is a great car, but I am on my third ECU.  Bullet proof reliability is a
primary consideration in any aircraft engine.  I can park my Porsche and
call a tow truck.

Sorry this message is so simplistic.  Many of you already know all of this.
Maybe the newcomers can benefit.

 
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