All, testing the motor to find that it is running smoothest
at an A/F ration of almost 13 at 2200 rpm. This is on a PLX meter and
appears a little lean. What say the experts?? Neil.
That's about right for p-port idle. What is the manifold
pressure. I assume engine RPM. All engines like to run a bit rich
at idle.
The p-port is no great shakes at idle. What is it for WOT with the
airplane well tied down? Mixture, manifold pressure, EGT, and
RPM? That is the real proof of the pudding.
Paul Lamar
For a car at idle of 800-900 RPM that is about right. Slightly
rich warmed up. Then as the revs come up they should lean a bit.
Light throttle cruise may let it go lean to 15-16:1. Note: that is
light throttle in a car!. For the AC engine at idle (2000 or so RPM)
I would think that is OK. Now with the prop spinning it is not going
to be light load as in a car so will not go lean the same until you
lean it. Us the info Paul asked for above to determine where it
should be. Idle is not a big concern as long as it is fairly smooth.
During takeoff, I would expect 11.5-12:1 for power. Then when you
get to economy cruise you can lean like the car engine or even more
as long as it stays running smooth.
Dale Davies
Dale, the prop gear ratio is 2.85:1
The prop RPM is only 770.
Paul Lamar
The 2200 RPM I gather is the output shaft RPM, the rotor is at 1100
. My interest is a 13b single rotor and I want up to 140?HP out of
it. The P port is basically an enhanced air intake duct. Those ducts
seems to be very bulky, like V8 high rise manifolds, hot roders have
to cut a hole in the hood for them.If I do not mind the extra mechanical
complexity, can I get the enhanced air flow by turbo or a supercharger.
I only want the extra power when I select it, so a manual waste gate
is what I will have, just for those heavily loaded hot and high situations.
The turbo will also act as a muffler, for I want a very quiet engine,
even with some power losses.
The supercharger may use something like a magnetic clutch, use on
demand. It will have to have some sort of spring one way air damper
to make sure the engine will get air if the charger is not working. The
engine would idle better without the P port. Not that it is that
important, as this is aircraft application, as Paul already taught
me. I also save the cost of the P port mods and the bulk. I am aware
the force feeding will cost more. Weight wise, I think P port and
turbo would be similar.
The ideal would be to have a regular ported 13b at 95 HP, then add
the force feeding later. I wanted fuel injection from the start.
Indirect or direct?? Leave the carbs on those model T Fords. I just
want to know all the alternate ways are.
A quiet engine, with more gear reduction, using a bigger prop with more
blades, at 2200 rpm or less, it might even be quiet enough for European
standard. Comments anyone??
Tony
Tony,
What rotor are you talking about at 1100 RPM when the output shaft is at
2200RPM? I think you are speaking of the engine rotor. If that is the case,
the rotor will be turning at 1/3 of the e-shaft RPM or about 733RPM. This is a
matter of the internal design and the rotor timing gears.
If you want 140HP and a quiet engine, p-port a single. It is the easiest and
least expensive way. The intake wraps around the top of the engine and is
fairly tight to it and compact. Not at all like automotive V8 high rise
manifolds. If you want a turbo for density altitude situations, the manifold
can be shorter. It is the easiest to plumb in. If weight is a problem, Richard
Sohn's or Racing Beat end housings will do the trick. The 2.85 ratio PSRU will
allow the RPM required.
EFI as Paul has been writing about for a single will be obscenely simple to
do.
If you are looking at using a single, KISS is the principle you need to keep
in mind. Simple design, simple to repair and maintain. May also be lighter.
Dale Davies
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