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Date: Mon, 01 Mar 2010 15:14:54 -0500
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From: "Greg Ward" <gregw@onestopdesign.biz>
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Subject: Re: [LML] Re: IV-P Turbo Blanket
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Hi Brent;
I totally agree with the below, and we are at the stage where we have to 
deal with the heat from our turbo, and would like to know where you found 
the Zetex A600.
Regards;
Greg Ward;
Lancair 20B N178RG, in progress

----- Original Message ----- 
From: "Brent Regan" <brent@regandesigns.com>
To: <lml@lancaironline.net>
Sent: Monday, March 01, 2010 9:36 AM
Subject: [LML] Re: IV-P Turbo Blanket


I don't like the idea of insulating a turbocharger turbine housing as it
necessarily restricts heat flow from the housing both during operation
and after shut down. The Continentals have an alarmingly high maximum
TIT of 1650 degrees F, necessitating the use of Inconel for the exhaust
plumbing. Heat is supplied to the turbo via the exhaust gas. Heat is
rejected via the exhaust gas, engine oil, conduction to the bearings and
compressor and radiative cooling. Radiative cooling climbs exponentially
with temperature. Blocking the flow of radiated heat causes the heat to
go elsewhere, requiring that the bearings, compressor and discharge oil
are all incrementally hotter.

After shut down, connective air currents quickly cool the turbine
housing. Keeping it warm in a blanket means the heat has more time to
work on breaking down the oil in the bearings.

Finally, what about the headers? If the logic is that the source of the
radiative heat has to be blocked to prevent having to insulate the
cowling then the headers and crossover must also be insulated as they
are exposed to the same hot gasses and their area is substantially
greater than the turbine housings.

The best answer is to not insulate the turbos and to add a reflective
shield to the lower cowling such as Zetex A600 plus (see attached
picture). This addresses the heat from all sources without focusing it
to sensitive areas.

Automotive, commercial, marine and truck turbos operate at lower TITs,
and diesels are much much lower. What works in one industry may not work
in aircraft applications.

Regards
Brent Regan