hi Marc, mistral has tested the mazda turbo, but they weren't satisfied
with it. Mistral is very safety minded. They have a lot of demand for
turbo's, and will proceed to develop them at a later stage. I agree that
that will help a lot, and for a Glasair, a turbo is a good idea.
Paul janssens
I've looked at a lot of turbo maps and have not found one that would
work for a 3-rotor at both sea level and at 18,000 msl.
Mark S.
Lancair ES, N/A 20b
Could you explain that a little more? How is the 3 rotor different in
that regard than any aircraft engine?
Paul Lamar
The real question is why boost this engine at SL at all (if we want
reliability)? All I've ever wanted to do is 'turbonormalize' it, IOW
maintain SL pressure, hence engine output, at 25,000 or so-a typical
certified application on many light aircraft. We only need to boost it
when we begin loosing pressure as we ascend. Turbo maps have me a bit
flummoxed as well because they are made mostly for cars and trucks
operating at SL or close to it. I am sure an aircraft turbo spec would
be much better than any Mazda turbo....... matched it to the output of
the 3 rotor. An intercooler would be necessary as well. The controls to
close the wastegate as you ascent could get bit tricky.....aircraft that
are turbonormalized and FI (deck pressure injector shrouds, pressurized
magnetos, etc) have many oil fed parts, but the new diesels (all
turbo'd) and many never aircraft now have electronically controlled
wastegates, PRVs, and deck compensators.
Marc
The last turbo aircraft that I worked on was a couple of months ago, and
was a Seneca 2, with 6 cyl Cont TIO360s. The turbos were mounted behind
the engines where the exhaust piping came together (about
2 feet behind the engine in the back of the cowling) and had manual
waste gates, no pressurized mags, no intercooler, no extraneous parts.
Flying the plane is a workout, especially during takeoff where you have
to closely monitor temps, pressures and everything else normal pilots
have to monitor. It proved very easy to over pressurize the engines
during takeoff, even with the waste gate "closed". If the MP went over
30", you had to pull the throttle back a bit to keep it under control.
The turbos were small Garretts, not much larger than the stock Mazda
turbos. There was about 2 feet of piping between the closest cylinder
and the turbos, more distance to the front cylinders from the turbo. The
oil line came off the back of the engine, into the top of the turbo, and
out the bottom just like one on a car and drained back into the oil pan.
Nothing special. I did notice that the oil filter was twice as tall as
one on a non turbo engine.
Adding turbo normalization to a plane doesn't have to be that
complicated. A manual waste gate that is left open for takeoff and
gradually closed to maintain 30" MP as we climb or in cruise would be
sufficient. I would argue that an inter cooler isnt mandatory, if you
only plan to use the turbo at high altitudes where the air is
considerably cooler than at SL. I have seen more than one turbocharged
certified plane without inter coolers.
Can we expect an altitude of 25k feet? Not realistically IMHO. I think a
ceiling of 18k would be more than plenty. Just like in an automobile
application, turbos are matched based on what you want performance to
be. If you want a killer stop light to stop light response with little
turbo lag, a low AR and small diameter impeller will get you there, but
it will choke out at high RPM/pressures. For a diesel or continuous duty
application, an AR closer to 1 would be better. A larger diameter
turbine/impeller, larger gas chambers for better flow, and of course
turbo lag. Match the flow of the turbo with the flow of the engine at
the intended RPM and work load range. I went with a modified Garrett
T04, optimized for the flow of a 5 liter diesel at 3000 RPM. In this
application, it produced 16 psi continuous. I plan to mount it like the
Seneca, behind the engine with around 2 feet of exhaust pipe between the
engine and the turbo. I will install a cooling cuff around the pipe at
the extension piece that dumps overboard to cool the pipe before it gets
to the turbo. This addresses these problems-
1. Hot exhaust- the exhaust is cooled for a bit between the engine and
the turbo-
2. Noise- I still get my turbo, which is known to quieten the engine.
3. Turbo-charging- I will set it at around 8psi to start with with a
mechanical spring loaded waste gate actuator. I am expecting that 8psi
spring pressure will remain fairly constant since it doesn't rely on
differential air pressure to work.
My NA viking had a ceiling of 15k, and with 300 hp would get there no
problem. There are vikings with turbo IO540s and now 550s that are
normalized with ceilings of 17k. My Viking cruised at 160 knots at 12.5
gph at 12500 ft, the turbo version gets 180 knots at 15000 on 15 gph. A
little faster, but lots more fuel burn. Again, manual waste gates for
the vikings. Procedure is to set the wastegate to open for takeoff at
SL, and if you are at higher elevations do not exceed 30" MP. Again, one
more thing to monitor during a busy time.
With an EFI, automatic operation could be achieved, just read the
outside pressure, and the MP, and make sure that the MP stayed within
limits. And temps, and RPM, etc.
I am working on this to be implemented in the EFI system.
Kevin Alderman
Kevin,
Glad you are working it out. I have worked on various TC aircraft, right
now a C337G-T with boosted 210/225 hp Continental engines. Lots and lots
of plumbing. Given, manual wastegates and no intercoolers is workable
(re the Rayjay twin Commanches?) but the engines did not live long. Too
prone to overboosting and ham fisted pilots that caused lots of issues,
and then there was bootstrapping and other troubles. Same with the
Skylanes that were turbo-a manual cam closed the wastegate as the
throttle was pushed in..........never did like it. Anyway, good luck.
PS: this is a good site, lots of info. I refer to them often, but they
do not suffer fools. Same people as Gami.
http://www.taturbo.com/frames.html
Marc
Might this be time to install a turbocharger to see if that could lower
the sound (and provide other benefits, once the cooling is sorted out)?
Marc
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