Why turbo normalizer?

"Big John" wrote in message
...
[...]
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

"Peter Duniho" wrote in message
...

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 ).


Actually a constant speed prop converts HP into thrust about the same at all
(reasonable) altitudes. That is one of the great advantages of a CS prop.

Mike
MU-2

"Mike Rapoport" wrote in message
ink.net...
Actually a constant speed prop converts HP into thrust about the same at
all (reasonable) altitudes. That is one of the great advantages of a CS
prop.

Really? I just assumed that with air density lower, the prop (CS or
otherwise) had less air available to move, and thus could not produce
sea-level thrust.

I guess in that case, my longer take-off runs are solely due to the higher
true speed required. Still, that's a significant effect. I just don't want
anyone thinking that a turbocharger makes high-altitude takeoffs just like
sea-level.

Pete

"Peter Duniho" wrote in message
...
"Mike Rapoport" wrote in message
ink.net...
Actually a constant speed prop converts HP into thrust about the same at
all (reasonable) altitudes. That is one of the great advantages of a CS
prop.

Really? I just assumed that with air density lower, the prop (CS or
otherwise) had less air available to move, and thus could not produce
sea-level thrust.

I guess in that case, my longer take-off runs are solely due to the higher
true speed required. Still, that's a significant effect. I just don't
want anyone thinking that a turbocharger makes high-altitude takeoffs just
like sea-level.

Pete

The CS prop simply changes its angle of attack in response to the lower
density..

Mike
MU-2

"Mike Rapoport" wrote in message
ink.net...

"Peter Duniho" wrote in message
...

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 ).


Actually a constant speed prop converts HP into thrust about the same at
all
(reasonable) altitudes. That is one of the great advantages of a CS prop.

Some of them.

In the Bonanza conversions, you would need a new prop or else your engine is
placarded to limit MP.


Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

On Wed, 18 May 2005 17:33:58 -0700, "Peter Duniho"
wrote:

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.

There was a website devoted to the wear of Lycoming valve guides that
went into design and development of Lycoming engines, and also what
they think is the actual problem causing the premature wear in certain
models of Lycomings.

You probably can find it by Googling "lycoming valve guide wear".

To synopsize, the mechanics who took it upon themselves to research
the problem feel that it is Lycoming's use of a particular type of cam
follower or lifter, that has created the situation (of accelerated
valve guide wear).

Lycoming patterned their original lifter after those used by flathead
engines. Since flathead engines have the valves in the block, not the
head, the lifter design, which was not intended to flow much oil
through it, worked fine.

But when this lifter was used in Lycoming's overhead designs, there
were problems because not much oil was getting to the valve guides and
they suffered premature wear.

Many of the fixes for those engines that suffered the most are fixes
that bring more oil to the valve guide area, according to this well
documented and extensive three or four part article.

But the conclusion of the article is that Lycoming does not have the
in-house engineers to come up with a real fix at this point.

Corky Scott