"Big John" wrote in message
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I have a turbo normalized engine. Going cross country I cruise at 5K
and 65% power. Turbo is off.

I then go on another XC and cruise at 15K and use turbo to pull 65%.

Are you saying that cruising at 65% with turbo on will do more damage
to engine than pulling 65% with turbo off??????

You'll have to define "more damage".

Yes, as Mike said there are at least a couple of issues that cause the same
power to result in hotter operating temperatures at higher altitudes than at
lower.

However, the increased temperatures may or may not result in damage, or even
increased wear. There's just the *potential* for increase in wear.
However, as far as I know, increased operating temperatures almost always
translate into decreased lifetime.

I'll agree that the turbo will require more maintenance it used but
engine no if run within engine manufacturers specs.

I'm having a hard time parsing that sentence.

IMHO, the bottom line here is that no one ought to expect a turbocharged
engine, turbonormalized or not, to require just as little maintenance as a
normally aspirated engine. But that's not an indictment of turbocharging.
It just means that with the significant benefit of turbo-charging, there
comes a cost.

As it happens, I feel that turbonormalization strikes a pretty good
compromise. Even more so when the installation isn't strictly
"normalization". Again, looking at my airplane as an example, the
turbocharged installation has 20hp more than the normally-aspirated version.
This isn't a lot of extra power, but it's enough to help compensate for the
extra weight of the turbocharger and give a little extra "oomph", without
significantly increasing the wear on the engine due to the power the engine
is making.

Yes, at altitude the engine runs hotter. It runs hotter than it would at
the same power setting down low, and it certainly runs hotter than a
normally-aspirated engine would at that altitude. But guess what? I go a
lot faster too, to the tune of about 20 knots compared to what my best
cruise speed at 8000' would be without a turbo. It's really nice being able
to maintain cruise power up into the oxygen altitudes, and I get a nice
true-airspeed boost as a result. As long as I'm not bucking a big headwind,
it's all good.

In addition, mountain flying is less dangerous. Ground speeds are still
higher, and the prop can't convert the horsepower to quite as much thrust as
it would at sea-level. But it's not nearly as much a reduction as I'd get
without the turbocharger. Acceleration, even at max gross, is good as is
the climb rate (handy when you are surrounded by high terrain ).

What's the cost? Well, I can't speak for the average. But in my own case,
I have had a "mini top overhaul" (replaced one piston, due to leaking rings
on that piston, causing erosion of the piston head), and have had to replace
all of the exhaust valves and guides. I don't even know that this was due
to the turbo-charger, but certainly it seems that the extra heat may have
accelerated the wear, if not caused it entirely.

The turbo-charger itself has been remarkably maintenance free, especially
considering it uses an automatic wastegate. As an added bonus, it acts as a
muffler, so my airplane is somewhat quieter than similar-powered airplanes,
and noticeably quieter than the normally-aspirated version. Since it's a
seaplane, and since I do often operate in "well-habited" areas, this is a
nice side-benefit.

There is, of course, the acquisition cost too. Turbocharged airplanes seem
to run anywhere from $20-50K more than the normally-aspirated equivalent.

But given that airplanes are intentionally operated at above-sea-level
altitudes on a regular basis, I can't imagine owning another airplane
without turbocharging. Turbonormalized or otherwise.

IMHO, it's much more important to look at the maintenance history for a
given installation, than to try to paint all turbocharged aircraft with the
same brush. The effects of turbocharging have as much to do with how the
manufacturer recommends the engine is operated and the design of the
installation (especially with respect to cooling), as they do with
generalities about all turbochargers broadly.

Pete