"Robert M. Gary" wrote in message
oups.com...
I"m still confused...
1) Why not just put a regular turbo on and agree to not over boost it?

Why do you think that's not what they do?

In fact, my airplane was originally sold with "turbo-normalization". After
the type was certified, the manufacturer went back and tested at higher
horsepower, allowing for recertification at 20 hp higher. All they changed
was an adjustment on the turbo controller. The planes built prior were all
retroactively given the benefit of this change. I still have "250" stitched
into the interior, even though the airplane is 270hp (and says so in big
letters on the engine cowl ).

Turbo-normalization is JUST LIKE regular turbo-charging, except that the
maximum induction pressure is limited to 30".

2) If compression increases inside cylinder pressure about 8 times
wouldn't taking MP up to 30" cause a MUCH higher inside cylinder
pressure than 20" (its a mutiple scale). If the outside of the cylinder
is 20" its going to have a significantly higher difference in pressure
than running out the outside 20" in MP.

Well, first of all, the difference between even 240" and either 20" or 30"
ambient is hardly significant (220" vs 210"). I don't understand why you
are comparing 30" times 8 with 20" times 8, while at the same time arguing
that the pressure differential between the inside and outside of the
cylinder is important (it's not).

As Dave explained quite well, differential pressure isn't relevant. It's
like worrying about your soda can exploding at altitude. The can is capable
of dealing with far greater pressures than it might experience, and the
difference between 15 psi (sea level) and even 0 psi is insignificant
compared to the pressures the can is designed to tolerate. A 15 psi change
in that case just doesn't mean anything, nor would a 10" or even 30"
difference matter for an airplane engine (or any engine, for that matter).

What does matter are all of the load-bearing components in the engine, but
that load is determined not by the difference between internal and external
cylinder pressure, but rather simply by how much horsepower the engine is
making.

I just don't see how a cylinder
could crack and stress relative to 30" when its only 20" outside.

Who says it could? No one here has, and prior to the above statement, you
haven't even implied anyone else has.

Isn't
the cabin of the space shuttle under more stress when in space than
when sitting on the ground at sea lever?

What's that got to do with the price of tea in China?

Pete