Mark Waldron wrote:
Paul,
I've been concentrating on the NA version of the 13B for my
eventual
project (due to cost and weight), but it seems worth at least
considering a
turbo. I don't need more HP for sea level conditions, but the
extra
power
at alt (especialy for low density altitude takeoffs) might be
useful.
So, some questions for those in the know:
- If I recall, many have written that with the turbo they
believe
they
can get by with no muffler. If so, what's the approx weight diff
(turbo+no
muffler vs. NA and swiss or tangential muffler)
I would say it is on the order of ten or twenty pounds in favor of
no
turbo.
- Pluses/minuses of the stock turbos
Low cost.
Could over speed due to the small size of the turbine. Strict
attention
to the turbine inlet temp as the material may not be Inconel
as is available with certain after market turbo's from Garrett.
- Cost, recommendations in the aftermarket turbos
$750 and up for the turbo. $250 and up for a manifold. Then you
will
need a intercooler and piping. You might get away with a stock
Mazda
intercooler if you have room.
- Set-up considerations (waste gate, etc).
We are rapidly coming to the conclusion that a waste gate is not
essential with a Mazda as the engine is very robust indeed.
Fly it by the boost gage. No cylinders heads to blow off through
the sides of the cowling. The stock second gen 89-91 (best years
to
use)
has a built in waste gate.
- Reliability issues:
-- What are the typical turbo failure modes, esp relative
to
safe
continued flight under power.
The big thing to avoid is knock. That can crack an apex seal.
Other than blowing them up from over speed turbo's have a benign
failure mode. The blades slowly melt or erode off the turbine
wheel
reducing
the boost and the power and the heat energy applied to the turbine
wheel.
-- Just how often do they fail (If used primarily for
turbo
normalizing vs boost above SL/standard day conditions)
If you limit the power they could last thousands of hours.
On the other hand we have no hard and fast data. It will take 20
years to get enough turbo rotaries flying to come up with some
average life. No question about it. You will be in the
experimental
stage in every sense of the word. PL
Thanks to you or any who care to reply.
Mark Waldron
Mark,
I keep wondering along the same lines and come back to KISS. From
what I
have seen here a two rotor should reliably produce 200 hp. My a/c
only
needs
150, so if I build a 200 hp 2 rotor I can use the extra power
lifting
floats out of the water and I can maintain 150 to 5000'-6000' ( a
guess ).
The rest of the time I fly it with lower power and fuel burn. No
turbo,
inter-cooler etc. and still lighter. Build light.
Cheers,
John
I'm not an expert on engine performance. Having said that, I think
200 hp from the n/a 13-B is just a dream unless you go to P.
Porting.
That is the real answer to more power in an aircraft installation
because it is light and simple. And, by keeping the tiny footprint
of
the 13-B, the PP engine will fit easily inside any cowl. Jerry
You might also get it with careful porting and a 2.85 to one gear box
good
for another 1000 RPM or so.
Paul Lamar
John Gibbons wrote:
Yeh Jerry that is sort of what I was thinking. A first gen two
rotor (
availability ) p-ported. With a 2.17:1 ratio 6000 rpm would be 2764
rpm at
the prop which would be about right for take-off, 2000 rpm at the prop
would
give 4340 rpm at the engine which I would think would make a good
economy
cruise and loads of reliabilty. I've heard the p-port won't idle below
2000
rpm but at the prop that would only be 920 rpm. There was talk a while
back
about using side ports for idle and then open the p-ports for power
above
2000 rpm. If they're not too heavy you might be able to use the
auxillary
port actuators to do this. I think i'm going to try and find a cheap
running
first gen to try this out on, I already have a couple of junker 13B
housings
I could test grind. It would be nice to test on a stand, any
suggestions on
how I could load an engine on a stand without the expense of a PSRU ?
John, based on the bearing load data, there is no reason to cruise at
4340rpm. I am hoping to CRUISE at
6000 rpm unless the fuel consumption is prohibitive. Jerry
You can say that again Jerry. Lets do the numbers to
put things in real perspective.
Fixed pitch prop load straight and level
is also a square law function at least. Lets say you have max HP of 200
at 6000 RPM. That squared is 36,000,000. 4340 RPM squared is 91,000,000
roughly. 36-19 is 17 or 47% of peak power. Lets also say the BSFC is .6
at 200 HP and .5 at 100 HP. Typical numbers for a rotary. Tracy claims .47.
So the fuel burn is 120 pounds per hour or 20 GPH at 200 HP and .5 times
100 or 50 pounds per hour or 8 GPH at 100 HP. Even if the P port engine
goes up to .55 BSFC at 100 HP the fuel burn is still only 55 pounds
per hour or about 9 gallons per hour. Hardly breaking the bank.
A good air craft performance measure comparison formula is speed divided
by ten.... times MPG. The way that works is lets say your speed is 150 MPH and
your miles per gallon is 20. 20 times 15 would give you a performance
number of 300. Klause Savier claims about 200 MPH at about 50 MPG for his
modified O-200 Varieze so his performance number would be about 1000.
Truly remarkable performance. Nobody else comes close. Four gallons
an hour. At $2 a gallon $8 dollars an hour. 9 gallons an hour.. $18 an hour.
Speed has a powerful effect on HP required so if you want more MPG
slow down just a little bit. Or work on the drag of your airplane.
I just bought a JPI fuel flow meter at Sun & Fun that takes GPS input
from my $79.95 hand held Magellan GPS. It outputs MPG so when I get
that installed I will be able to give you some real world MPG verses MPH
data for a C182.
Paul Lamar
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