Al/ Chris,
I'm certainly no expert on Turbo,
nor are some who purport to be experts. There are those who are
genuinely very knowledgeable in car turbo, but for aircraft use it's
another matter entirely.
From discussions on here and other
sites, it would appear to me that Turbos fail because of the high heat
at high rpm over extended periods and the overspinning in thin air at
altitudes. All that sounds fair and reasonable to me.
Some builders have overcome these
problems by trimming internal blades and making the waste gate as big
as possible - in other words making the internals so that the exhaust
has more room to escape, placing less stress on the turbo.
I notice that some car applications
have remote turbo allowing the exhaust gasses to slow and cool before
entering the turbo. For our application we don't need all the energy
from the exhaust, so we don't need all that heat and exhaust pulses
hammering the turbo, as it does
continuously if it's in close proximity to the engine.
For my application, if I need turbo,
I will place the turbo remotely and only bypass enough exhaust energy,
by way of a 'Y' section in the exhaust pipe, to the turbo. The bypass
should be cockpit adjustable for different applications requiring
different energy requirements - as in the wategate..
Hope you see some merit in my
thinking.
George ( down under)
I know you're fairly entrenched in the 13B
approach, but for the sake of
discussion, I'm not sure that's a valid
reason.
How high do you want to go? I think
Tracy's been over 15k with an NA
13B. I'd be willing to bet that a Velocity
with an NA 20B could get well
over 18k without a problem.
As I
recall my analysis those many years ago; the cross over point on power
for a turbo-normalized 13B and a NA 20B is at about 13,500’ msl. Above
that altitude the torbo 13B will do better. Of course you can boost
the 13B to more than 30” and get more power.
Al