Hi Paul -

I understand the concept of how a trigger pulse and pulse width
modulation can be combined to fire an injector and control its fuel
output when the rotors are taking in a fuel / air charge. The 555 clock
chip has been around for a long time.

Here is a thought I have been mulling over... To control the amount of
air when a cycle of fuel pulse is shot into a manifold, the airflow has
to be controlled in coordination with the average amount of fuel going
through the injector. This is necessary to avoid a too rich or too lean
charge condition.

I am thinking that there ought to be a way to manually coordinate the
pulse width per cycle to the amount of airflow opening of the intake
manifold. My thought is to have a left-oriented push-pull lever control
the pulse width, and have a right-oriented push-pull lever control the
position of the manifold air intake restriction plate. Both levers are a
fraction of an inch apart, so one hand can move both simultaneously.
Kind of like the throttle levers of a twin-engine airplane.

The fuel control (pulse width) can be controlled by varying the
resistive value of a wiper potentiometer. The manifold air restriction
plate can be controlled by a conventional sliding cable. If coordinated,
the fuel / air mixture could remain closely the same ratio from idle to
full throttle.

Now, assume a change of air density... either fuel or air could
be manipulated to compensate for the change. Let's choose the fuel flow.
At higher density altitude, pull the fuel lever to decrease the
injector's pulse width, leaning the fuel / air charge. Monitor an EGT
gauge (or gauges) to adjust the fuel mixture to avoid getting the
exhaust gas too cold, indicating a too rich or too lean a mixture.
Moving to a lower density altitude will require reversing the fuel pulse
width, enriching the fuel / air charge. I envision the EGT gauges to
provide feedback to the pilot.

The advantage: An on-board computer or mass airflow sensor circuit will
not be needed. Better fuel distribution.  The disadvantage: more
workload on the pilot to monitor the EGT and make adjustments while in
flight.

I have not tried this yet. But with your 555 timer circuits, I might do
so using an engine in a test stand and while I am standing on the ground.

I'd like to hear from you and others if this may or may not be practical.

Thanks for your time,
Mike


Make sure you try the Ti CMOS TLC555 as it is the only one I found to
be truly linear. So far nobody has fed EGT back into a computer
as far as I know. Tracy looked at it and did not think it would work.
I am not so sure. The secret may be use a smaller thermocouple that has
a faster response time.
O2 sensors go away when confronted with 100 Lots of Lead.
Mass airflow sensors are a dime a dozen as millions are made each year.
When you buy an engine you sometimes get them thrown in for free.
Anything is possible if you spend enough money. I am always thinking
of cutting the cost as that is the primary driver on the implementation
of rotary engines.

http://www.rotaryeng.net/simple-cheap-555.html

Paul Lamar