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 ?
Use a homemade dyno. Hook the engine up to an auto trans, lock the output shaft,
cool, cool, cool, the oil. You have an oil filled waterbrake.
Royce
Another great idea Royce. Use a hydraulic cylinder and a pressure gage
to measure the torque. When you know the torque and the RPM you know
the HP. HP = Torque (ft lbs) X RPM / 5252 as I recall.
Mount a bracket to the engine with a 1/2" square hole in it inline with the E-shaft.
Install a beam type torque wrench, fix the handle end to the mount frame at right
angles to the shaft. Direct read the torque on the wrench. :-)
<When you know the torque and the RPM you know
the HP. HP = Torque (ft lbs) X RPM / 5252 as I recall.>
Exactly.
You can control the stall speed of the torque converter doing all
the HP absorption by controlling how much fluid it has in it.
You will need a really big rad with a really big fan to cool the
oil.
Paul Lamar
Water spray on the rad while running, will take away a lot of the heat also..
Royce
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