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582 Power Settings

 
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bnn(at)nethere.com
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PostPosted: Fri Apr 21, 2006 8:40 pm    Post subject: 582 Power Settings Reply with quote
I went back through the archives and discovered that the cruise RPM for a
582 is recommended to be 5800-6000 RPM. Looking at the HP/RPM chart I
calculate this to be about 95% power. Now, when I cruise my Lycoming or
Continental I use a maximum of 75% power. That would equate to 5300 RPM for
the 582. I also calculate 65% and 55% RPM's of 4800 and 4450, respectively.
Do we run such high RPM's because we're anxious to get somewhere? And is
that why the TBO is so low? If I ran 75% power, (5300 RPM,) at cruise could
I expect a much higher TBO? Are there problems with running around at 5300?

Thanks for the help.
Guy Buchanan
K-IV 1200 / 582 / 99.9% done, thanks mostly to Bob Ducar.

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bmwebb(at)cox.net
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PostPosted: Sat Apr 22, 2006 5:20 am    Post subject: 582 Power Settings Reply with quote
Guy,
One thing to think about is the power curve of the 582. Torque drops off
sharply below 5800 rpm. It also rises sharply from 6000 to 6500. Mine, for
example, is pitched more for cruise, so I only see 6200 on climb out at
70mph. But this means that at 5800 rpm, I'm moving a bit faster, about
85mph.

You can't really equate % power between a four-stroke and a two-stroke. You
could if the torque curves were similar, but they're not. I would be willing
to bet that 5800 rpm is about 75%, or maybe a little lower.

I read an article a few months back, that running below cruise power, was
somehow "false-economy". I can't remember where it was, maybe a CPS article?

Another thing, in a two-stroke, the fuel is used to cool the combustion
chamber and provide lubrication. By throttling back, you reduce both
qualities. But then, you are reducing the heat produced and the internal
engine pressures as well. Maybe it's a wash? It's also liquid-cooled, and
maybe it doesn't make a difference here.

I run mine a lot at about 5100rpm, and get about 3-4gph. This is mostly for
just roaming around, looking down on the little people (!). Maybe this is
50% power? This puts my 'fox at about 60mph, and makes for a good flight
with the doors open.

Bradley

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bnn(at)nethere.com
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PostPosted: Sat Apr 22, 2006 5:52 am    Post subject: 582 Power Settings Reply with quote
At 06:17 AM 4/22/2006, you wrote:
Quote:


Guy,
One thing to think about is the power curve of the 582. Torque drops off
sharply below 5800 rpm. It also rises sharply from 6000 to 6500. Mine, for
example, is pitched more for cruise, so I only see 6200 on climb out at
70mph. But this means that at 5800 rpm, I'm moving a bit faster, about
85mph.

You can't really equate % power between a four-stroke and a two-stroke. You
could if the torque curves were similar, but they're not. I would be willing
to bet that 5800 rpm is about 75%, or maybe a little lower.

Looking at the torque curve in the CPS catalogue, 5800-6000 is about peak
torque.
Quote:
I run mine a lot at about 5100rpm, and get about 3-4gph. This is mostly for
just roaming around, looking down on the little people (!). Maybe this is
50% power? This puts my 'fox at about 60mph, and makes for a good flight
with the doors open.

If you believe the charts, 5100 puts you at about 70% power, 88% torque,
and you should be burning right around 3 gph. My big question with these
curves is what effect the gearbox has. Right off the bat it should almost
triple torque, but horsepower should stay the same. The torque curve will
be amplified, but not shifted in RPM, so I guess it makes no difference to
the operating RPM. If the prop is designed for the 3:1 box, then I presume
it's torque and power requirements will fall along the curves shown, as well.
Guy

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