Paul,
Lately, I've been contemplating the decision to turbo charge my 20B this
time.
The main reason that I haven't considered this in the past is because I
know absolutely nothing about matching a turbocharger to an engine.
Where would you suggest I start looking for information to help me
figure this out? I would like to produce a consistent 350 hp that is
maintained to 18K ft. altitude, but still idles well and is not
ridiculously loud. I don't care to port and hotrod this thing to a
ridiculous level because reliability is of utmost importance to me. The
350 hp doesn't seem like it would be hard to do with a 20B. I was
thinking that it might be best to go with a large street port and open
the exhaust up. Then select a good quality turbo that is well matched
for my intended use.
When I read about turbos, all the stuff they describe as desirable for
auto applications doesn't seem all that important for aircraft use. I
could care less if it takes 0.25 seconds or 2.0 seconds to spool up
since I will mostly be running at constant speed anyway. Also, a BOV
doesn't seem that important since I wont be jacking the throttle up and
down like in shifting a car. The wastegate and setting up the boost is
a total mystery to me. It seems like an aircraft engine running a
75-80% power and 6500 rpm almost constantly would be bypassing the
wastegate all the time, but I'm not sure. If that's true, it seems
that
an integral wastegate is a better option, but is it as reliable as an
external wastegate? I have no idea!! What about oil cooled
versus water cooled bearing housing? I've always heard of turbos
failing because of coked oil clogging the bearing holes from high heat.
And as far as setting the boost for aircraft application, how does one
do that and manage it during flight?? I've never flown a turbocharged
aircraft. Does it add to the complexity of flying, or is it something
that can be set and left alone (or computer managed)?
As you can see, I have plenty of questions!! Where can I look for
answers??
Thanks again!!
Don
---------------------------------------------------------
Yes it does add to the complexity of flying unless you want to
get into microcomputer control of waste gates. So far I know
of nothing like that off the shelf that will work with a turbo
rotary in aircraft use.
I think Gordon and maybe a few others on here have a turbo selection
spread sheet for A/C use.
Gordon, could you upload your spread sheet again?
The thing to watch out for is turbine over speed. That makes
car turbochargers the wrong choice for aircraft use as the car turbo
charger turbine has too much HP for the compressor. This is done
so the turbo charger will accelerate rapidly. In steady state
use the turbo charger will over speed and the turbine will be
destroyed. Several people have blown up stock turbo chargers in turbo
rotary engines in aircraft use.
Usually the turbo charged used is a TO4 for the 3 rotor but the
compressor should be chosen to be larger than what one would find
in car use. This slows the maximum RPM of the turbo charger to keep
it within RPM limits for the given EGT. Another way of putting it
from the turbine point of view is you want an A/R greater
than one. This slows the air flow going into the turbine
blades.
A way of measuring this is record the temperature
drop across the turbine. The higher the temperature drop
the more powerful the turbine. Also it is a good idea to
get a turbine tachometer to check and make sure the turbine
RPM is within limits. This will pay off in the long run
as your turbine will last longer.
Here is a spread sheet from Dave Leonard.
Also get a copy of this book.
"Turbochargers" by Hugh MacInnes HP Books ISBN 0-89586-135-6
To minimize oil coking use a synthetic oil like Idemitsu
rotary engine oil or Mobile One. Also try to get a water cooled
turbocharger housing. They are available for the TO4. The stock
Mazda turbos are water cooled.
Paul Lamar ...No rotor no motor.
Paul, Obviously the 20B will need a bigger turbo with its bigger
displacement. That is a whole different class than the T04.
Turbonetics T70 series seems to be about right. I put some 20B numbers
into my calculator. A 20B at 14k' running 35"MAP would be smack in the
middle of the T70 and T72 turbos. Garrett would have similar large
turbos.
Here is my calculator with the numbers plugged in for the 20B and the
T70 compressor map. The T72 and T76 compressor maps are also there.
Just click and carry. No data on turbine section, but it should be
appropriately big!
BTW, notice I have finally purchased a domain name for the rotary
roster. Time to stop using AOL. :-)
David Leonard
Turbo Rotary RV-6 N4VY
N4VY.RotaryRoster.net
<http://N4VY.RotaryRoster.net>
www.RotaryRoster.net <http://www.RotaryRoster.net>
leonardiniraq.blogspot.com
<http://leonardiniraq.blogspot.com>
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