"Robert M. Gary" wrote in message
oups.com...
This started on a Mooney list. I cannot for the life of me (and an
engineering degree) figure out why a turbo normalizer would be any
easier on an engine than a regular turbo. Is this just marketing crap
from the turbo normalizer people? Turbo'd engines cost more to run
because of the increased stress on the cylinders, rings, etc do to the
pressure. Running an engine at 30MP when outside is 20" is just as much
pressure difference as running at 40MP when outside is 30".

It's not the 10" difference that matters. It's the new number after it's
been multiplied to take into account compression and combustion pressures.
Compression alone multiplies the number by about 8 (typically), but because
the turbo is packing so much more air and fuel into the cylinder, the
combustion pressures go up at a much greater rate.

After considering the multiplicative effects, the ambient baseline is
irrelevant. It's the absolute pressure that's the big deal, and it's higher
when you turbocharge.

Of course, for some engines, even a 30" MP while the engine is running could
be an issue, at least for long periods of time. There's a reason some
engines are limited to full power for some period of time (5 minutes, for
example). Comparing turbo-normalization and turbocharging above sea level
pressure only makes sense when you are comparing apples-to-apples (ie same
basic engine).

It seems like the turbo norm crowd is trying to confuse people.

What statement by the "turbo norm crowd" do you find confusing?

Unless the
entire engine was pressurized to 30", you should expect turbo style
stressed on your engine when running 30" when outside is 20".

Wrong. See above.

This is
*much* different than running 30" when outside is 30" (down low). Am I
missing something?

It appears that what you are missing is that the ambient air pressure
doesn't really matter, not in this context.

Now, all that said, it's not entirely true that turbonormalization is no
harder on an engine than running the engine at sea level. At altitude, the
ambient air may be cooler, but there's a lot less of it for cooling. In
addition, compresing the induction air heats it up. So even a
turbonormalized engine may run hotter than a normally aspirated engine would
at the same MP.

But it is true that turbo-normalization doesn't stress a given engine as
much as turbo-charging above sea level pressure.

Pete