A few data points that may help... or not.. in answering your question.
I have no specific expertise in this area from a practical standpoint.
My point of reference is the research I have been, and currently am
doing to utilize a Mazda 13B 2nd generation Turbo II rotary engine in a
Velocity Fixed gear application. The engine is without a turbo core at
the moment and will have a custom turbo sized for the intended operating
range of the engine.

1) If the normally aspirated aircraft engine is being converted to
turboCHARGED versus turboNORMALIZED, then you are probably exceeding the
rated power of the powerplant.

To a purist, turbo-normalization is simply turbocharging the intake
system to no more than sea-level pressure. This offers no benefit on the
ground but offers sea level power up to altitude. Since this offers
little benefit to the auto-street rodders, this term is not common in
the street crowd.

Turbocharging in the traditional sense involves applying many psi over
ambient.. I've read that aviation applications may use 45" on some of
the TSIO prefixed engines.. that comes out to about 22-23 PSIA (PSI
absolute). Some of the street rodders are running 30-40-50 PSI of boost.
This type of power output can dramatically increase wear and decrease
durability of the engine. Some of the guys who drag race with 60 PSI end
up rebuilding after each or every other race. Also, horsepower
production is DIRECTLY related to fuel consumption. Increasing the power
output will increase the fuel flow. In a smaller airframe that only
carries, say, 50 gallons, you might end up producing power that would
drain your tanks in 2.5 hours rather than 4-5.. The increase in speed
will NOT make up for the fuel burn.. drag increases exponentially, so
for a linear increase in fuel burn/HP you will NOT see a corresponding
linear increase in speed. One thing that WILL help is using surplus HP
to get to altitude, then producing sea level power values at high
altitude to take advantage of higher true air speeds.

2) Car turbo assemblies in general are simpler. Car turbos on car
engines have an internal wastegate assembly that is referenced to
ambient pressure, usually through a diaphragm/spring/pushrod setup. In a
car this is fine.. that majority of street rodders ply their trade at
less than 5000 ft MSL. Turbo's work their magic through values called
pressure ratio's.. If the wastegate springs open at a PR of 3, at sea
level that would be 45 PSI. At about 25,000 feet, a PR of 3 would be 15
PSI of boost. Those numbers are rough, and for example only but lead to
the next point.

Aviation turbo's have one of 3 types of wastegate assemblies: a) a
fixed, nonadjustable wastegate (pilot has to watch his MP's carefully
down low) b) a manual wastegate (a second throttle, if you will, and the
pilot has to pay attention to it on descent and down low) c) an
automatic wastegate (the more pilot-proof of the three). The automatic
wastegate manages the boost output of the turbo up to the point the
wastegate is fully closed, at which point, max attainable power
decreases with altitude. I considered such a beast for the
auto-conversion I was working on, until I researched what was out there.
The wastegates appear to be fairly complex mechanically, and if I
remember right may require engine oil as a hydraulic fluid.

A further level of complexity is the need for a scavenger pump in most
aviation turbo setups. In auto engines, the turbo gets its oil feed
under pressure then it passively drains by gravity into the sump through
a height differential of several inches. In the aviation turbo setup on
a horizontally opposed engine you typically have the turbo's oil outflow
BELOW the oil sump, which requires a scavenging oil pump to return this
vital turbo cooling oil from the turbo to the sump.

3) You wont really want to use high compression cylinders on any turbo'd
engine. The margins of safety between normal operation and detonation
can disappear quickly, resulting in an expensive overhaul. Car engines
DO run turbo's on autogas, but the stock arrangements tend to have boost
limiters that keep the boost under 2.0. They also use premium autogas to
slow the combustion flame front. I am not privy to the common auto
engine piston compression ratios, but in the mazda engines, the turbo's
CR is less than ANY of the normally aspirated motors, to avoid
detonation. This isn't so much a problem RIGHT NOW, but keep in mind
that all the huss and fuss about 100LL goin away... is going to hit the
turbocharged aviation (true aviation engines, Lycs and Conts) engines
the hardest.. Those high powered turbo engines use the majority of the
high octane fuel, and they have no effective replacement WHEN 100LL goes
bye bye. The options are to reduce available power to avoid detonation,
or change the powerplant altogether.

4) While you dont have to be a rocket scientist, it does help to be
meticulous about engine management when using higher HP/Turbo engines.
Allowing adequate warmup and cooldown periods. Every redblooded pilot
would have to pay good attention to operating the powerplant properly to
improve longevity. I dont think turbocharged engines are a sound idea in
rental fleets (and I am a renter pilot at this time). There is the
notion that turboed aircraft if not managed properly can easily become
hangar queens/maintenance hogs.

If you look at the Continental chart at
http://www.tcmlink.com/producthighlights/ENGTBL.PDF) you can see that
with the exception of the liquid cooled engines, many of the TBO's are
just as low, or lower than normally aspirated engines, and also you can
see the bit about compression ratio I spoke of earlier.

Finally, cost may be artificially inflated, but Tornado Alley Turbo's,
the guys with bolt-on turbonormalized STC's... are charging 25-30 grand
for the priveledge of using their product. There has to be a significant
R&D hurdle there, coupled with small market, coupled with the
traditional aviation premium on product costs.

If anyone gives a rip about the experimental end of it, the engine I am
rebuilding now, I have a Mazda 13B torn down into its individual
components and am ready to reassemble once I purchase the seals/gaskets.
The stock engine will develop around 160-180 hp. We are guessing 250 hp
with a mild turbocharging of 23psi/45"hg, and using a turbosmart
(www.turbosmart.au) brand Eboost "absolute pressure controller", a $500
electronic/servo car version of aviation's automatic wastegates. Neat
thing is, its programmable, so you can set multiple levels of boost (not
truly needed, but may be useful). The utility behind that is opening the
wastegate fully on descent so that the turbo gets unloaded while you are
a ways out, cooling it off, and allowing it to be even cooler at
shutdown and extending bearing/turbo life.

We will be using a Real World Solutions PSRU (www.rotaryaviation.com)
and also an EFI from them. Turbo wise, well that remains to be seen, but
I have been crunching numbers (mass air flow, rpm, etc) to size a turbo
properly (plotting these values on compressor maps) for the airflow this
engine should generate. I think at the time being we are going to be in
something like a Garrett T04Super60. I say "think" because I have yet to
get good data on what the engine REALLY flows with regards to airflow.
The rotary engine's theory of operation is slightly different from a
piston's, with regards to stroke volume/power strokes/rpm so I have
based it on one value and been told of another, which fudges up all the
numbers. I am going to see how some of the flying guys are doing (we
have one of the rotary guys who blew two stock mazda turbos, and now has
a T04-V1 and waiting to fly again)

Dave


The Weiss Family wrote:

Let me restate my question:

Why haven't more companies sought to get STC's for turbocharger/supercharger
upgrades?
Is it THAT difficult to get an STC?

It seems to me that every red-blooded pilot would love a reaonably priced
turbo upgrade (in other words, the market demand is there). Automotive
turbochargers/superchargers are extremely inexpensive (by aviation
standards), so it is reasonable to assume that they could be built and
priced relatively cheaply (compared to an engine upgrade, if one even
exists).
So, why can't I easily find these upgrades?

Adam

"The Weiss Family" wrote in message
...

Has anyone heard of either a turbo or supercharger STC for an IO-360?
In particular, an IO-360-A2B?

It seems that there would be a HUGE market for a turbo upgrade.

Adam
PP-ASEL