Ed Anderson wrote:

Hi Paul,

    New topic for the group.  How do you tell if you have a "stalled

Prop"

on static run up.  I know if you start take-off roll and as speed picks

up

the engine loads up and the rpm drops then you probably had a "stalled
Prop". But are there indications sitting still?

   The reason I would like to know is that my newly rebuilt 91 is

turning my

prop (same prop specs/make as Tracy uses) 2670 rpm (5800 engine rpm).

Old

engine turned static at 5000-5100 rpm.  I took out a prop tach this AM

and

it and the engine tach were in agreement to within the eyeball

resolution of

the engine tach (100 rpm).

   If this is indeed a reflection of the HP the engine is producing then
great, but if the rpm has increased because the prop is "stalled" then I
would like to know that if possible before first take off.  I figure
somebody on the list may be able to answer the question.

Best Regards

Ed Anderson

You got me there Ed. Sounds like you need more pitch if your engine is

strong

enough to turn that prop at 5800 RPM static. BTW I will bet your exhaust

is less

restrictive than Tracy's so you have more power. I also think your intake
manifold is better. Your engine is also ported is it not Ed?
I hope you can run your airplane in the Sun 100 this year.

Paul Lamar

Well, after all the past year has put on my platter, perhaps this is payback
of the nice kind.  I agree about needing more pitch, I ran a little prop
program that indicates that if the engine produces 6350 rpm WOT in-flight,
I would need a prop with 75" pitch to hit 207 mph.  I will have a better
idea once I get airborne.

 I measured my exhaust path and from the exhaust port to the tip of the
holey exhaust pipes it is 33".  The holes might functionally shorten the
effective length somewhat. The pipes are 2" in dia so a little larger than
recommended.

 There are  only a couple of  differences between Tracy's manifold ( which I
based mine on it and appreciate Tracy sharing his idea in his news letter)
and mine.

  1.  I used separate and dedicated throttle body openings for the primary
and secondary pipes which requires me to use the entire throttle body so
mine definitely weights considerable more than Tracy's.  However, I believe
it may cause the air to flow slightly  better.

2.  I also used fiberglass plenums to smooth the 90 deg turn from the
throttle body into the manifold pipes.  While the air velocity through the
throttle body might be relatively slow compared to its velocity in the
tubes, we are asking the molecules to make a right angle turn.  So I
reasoned that even a small radius would assist.

3.  I extended the inner primary path through the use of the taller primary
fiberglass plenum so that the physical path lengths of the primary and
secondary intakes are identical.  I had this vision that if one were shorter
than the other then the pulse would blow in the inner port, cross the
chamber and out the other side of the closing port.  This way I envision
that the pulses arrive at each side of the chamber at the same instant and
squeeze more mixture in from both sides.  Of course, I don't have clue if
any of this is really  happening.

The only other thing I can think of is that I ported the center housing
myself and did not port the outer housing intakes.  This made the center
housing ports almost identical to the outer housing ports.

I am working on a fuel flow meter (again one borrowed for Tracy) in order to
measure fuel flow and get a better feel for the power being produced.

Hope to be in the air by the end of next week.

Best Regards

Ed Anderson

 
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