"Kent, Russell" wrote:

John Slade wrote:

[snip]

As I passed through 5800 with 36 MAP I noticed something

interesting.

[snip]

At 5900 rpm and 38 MAP it was even smoother.

[snip]

I backed off - ok chickened out - at 6100 rpm and 185 kts

indicated with a 44 MAP.

[snip]

By the way, perhaps I should mention that the manual wastegate was

wide open for the entire flight."

Russell Kent commented:

????
How can he get such MAPs with the waste gate wide open?  I would

expect

that a *properly working* waste gate should yield MAPs close to

atmospheric when fully open.

Paul Lamar replied:

The waste gate on the stock turbo is too small. The stock turbo

relies somewhat on turbine inertia and the back pressure of the
muffler to limit boost.

So what you're saying is the stock waste gate is not working properly,
in that it is undersized for continuous high power operation.

Russell Kent

I think so Russell. The flapper is limited to about 15 degrees open as
it hits the turbo charger back panel.

Here are my suggestions for improving it.

Paul Lamar

-Matt Prather wrote:

John Slade is running a modified waste gate.

Regards,

Matt-

I know and I am kind of surprised it is not working better than it is.
I am struck by the analogy of a radiator placed too close to a blocking
object such as an engine, oil pan or firewall. Apparently the fact that the back panel
of the turbo charger limits the opening angle of the flapper to 15 degrees
or so has a lot to do with it IMHO. There needs to be a large 3 inch diameter
tube welded into the steel back panel so the gate can open fully IMHO. 

One may need two 3 inch tubes. One directly behind the turbine and another
directly behind the waste gate.

Paul Lamar
 
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