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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
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