David,  check with Tracy on the EM3.  The 20B powered RV8 does use the
electronic throttle. Tracy mentioned he  didn't want to release any
details until he had flown with some hours on  the system. With an
electronic throttle controller, I could build a simple  one in a few
hours, as I have done this before. Building is one thing,  validating and
testing is quite another. Add support and it suddenly  becomes a 500 hour
project. :) For a vehicle it reduces a number of  subcomponents (aux air
valve, cruise control, cable and linkage - NVH  reduction, in additon to
emission or engine saving mode (i.e. built into  the Corvettes to prevent
your 16 you old son from borrowing the car and  spinning high-G donuts
until the engine is starved of oil... hence in that  case it will reduce
throttle slowly as few onramps have more than 360  degree turns!) Older
systems used an idle control valve. Simple PWM or  stepper motor to
control the amount of air bypassing the throttle plate to  keep a steady
idle. I did make a system to replace the BMW VDO module, but  didn't want
to mess with liability, so it was simplier to repair the OEM  system than
replace it with my own controller. With aircraft and a throttle  control
cable, there isn't much need as we only are at idle a few times  before
and after flight. One thing I recommend is that if the cable is  detached
or slips out of place, is for the throttle go to WOT (Wide Open  Throttle
). Much easier to return to an airport at WOT, and just kill the  engine
once in the pattern. :)  I was looking at a few Rotary Powered  planes
and noticed the stock spring for "return to idle", when I asked  the
pilot about it he commented "never had an issue, so it is fine that  way"

Tom Walter

--

Tracy said effectively the same to me  - that was over 15 months ago I
have reached a point where while I would  like to use it, it appears that
it is still not available. I have to do  something in the next few weeks
so I can progress further.

Tracy's -  Has something changed recently?

Hey Tom, I'll take the Circuit you  mentioned I'll deal with the support
as it is a one off anyway :)  Otherwise,

I guess I'm at cable conversion.

WOT on a Gyro would  be very BAD, rather somewhere around cruise would
be the better  choice.

Regards David

--

David, another thing to keep me  awake a night... planning the perfect
electronic throttle controller, with  every detail thought of. Once
soundly asleep I'll wake up with "Gyro,  gyro.... I never even thought of
it being mounted on a gyro" For aircraft  is does bring up an interesting
thought...if you are approaching VNE,  should the throttle start closing?
Personally I like the big red knob  (other than when it comes off in my
hand!) to open and close the throttle  on the plane.

The Circuit is a simple uC with a PID loop. Part of the  reason I never
took it too far was little things like the weight of a  flywheel, or flex
plate, had to be considered. A simple "resistor" was a  neat way of
programming the "weighted value" of such, but the more I messed  with it
the more I became convinced of the nightmare. On my production  vehicles,
if you leave the idle switch closed, the engine will sense high  rpms and
realize something is wrong... shutting off fuel control. So for  a
electronic throttle to be fairly fool proof, it needs should be part  of
a larger system.

Irony is the BMW write up (from 1992) about my  neighbors BMW with the
crazy idle is still on the  'net.
http://www.unofficialbmw.com/repair_faqs/idle.html


Tom


Most  airplanes have a Red Mixture nob, a Blue Prop Control, and a  Black
Throttle..  :)

Matt-

Right after I posted that....  doh! :)

Tom