How does it idle on secondaries?

Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed

From: Mark Steitle
Sent: Tuesday, May 29, 2012 5:54 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Injector balancing

Ernest,

With my current setup, this p-port engine idles better than my side-port
motor ever did.  It will idle down to 750-800 rpm if asked, although I
normally idle at 1500-1600.  Still, it might be an interesting experiment to
add temporary dividers in the airbox to see what effect it would have on
tuning.

If you take a close look at the picture I posted you can see the blue fuel
rail.  This is the primary fuel rail feeding the primary injectors.  They're
located downstream of the butterflies, very close to the intake ports and
pointed directly at the rotor faces.  I can't imagine how the fuel could
find its way 18" back down the runner and back into the other runners.  I've
never found any residual fuel in the airbox either.  I don't see how the
fuel could be pooling so close to the ports, especially at 4500 rpm.  But
then I'm not an expert in fuel injection design either.

Alleviating fuel pooling in the runners was one of the design goals with
this latest intake.  My previous slide throttle had both the primary and
secondary injectors located upstream of the slide.  This caused fuel
pooling, especially at very low throttle settings.  Needless to say, this
made low throttle tuning almost impossible.  So, the new intake has the
primary injectors downstream of the butterflies, and it idles great.

Mark




On Tue, May 29, 2012 at 4:32 PM, Ernest Christley <echristley@att.net>
wrote:

  Mark Steitle wrote:
  > Ernest,
  >
  > I don't understand how that could happen if my injectors are after the
  > airbox (see attached pic).
  >
  > Mark


  At idle, the intakes coming off the airbox can set up some serious
standing waves that will suspend fuel droplets and
  let it stick to the walls.  You're set-up is very similar to mine, in that
the fuel can run downhill and air has to pass
  in front of one runner before reaching the others.  Some of that suspended
fuel will coalesce on the wall and drivel
  down the runner, and any coming out of the middle will get pushed back to
the rear (which will then be running over rich).

  It would also be interesting to watch individual MAPs across the runners.
Dollars to donuts that the first runner's
  inlet is at a partial vacuum compared to the rear one.

  I may be wrong about the mechanism, but I know my fix fixed whatever was
wrong.  I inserted a plate so that the runners
  could not "see" the air intake.  The air hits the plate and spreads out
before heading to the runners directly, instead
  of flying past the first on the way to the second.

  Going off of what I think I know, I would use a handsaw to cut a slot
halfway through the plenum between the runners.
  Then I would slide a partition between them.  It would essentially create
three stalls that the runners originate from.
  The point being that air would not be able to go past one runner on the
way to the second.


  --
  Homepage:  http://www.flyrotary.com/
  Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html