Ceramic impellers are used generally becuse they are LIGHT and therefore
the acclerate quicker than incinel. The temperature in a turbine housing, if
all is right, with the mixture is about 1650F. Nothing at all to see the
exhaust pipe down stream from the turbo become a very nice bright yellow,
so hot they looked as if you could push a screwdriver right through them. I
made hundreds of turbo kits for the RX-7 rotary engine years ago and the
temperature would go over 1800 as those engines do have a terrific exhaust
temperature just normally. I furnished kits to the NASA research center in
Cleveland Ohio and they sent me photos of their studies in the dyno that
were just spectacular for color. They ran things harder than I did in my
dyno. they used those engines for pilotless high altitude drones.
The problem with the hot turbo when you shut off is that the turbo is now
without oil pressure and the heat sink to the bearing ruins the bearing then
on start up as the shaft is coated with oil varnish from the cooked oil and
the shaft is rough and scaley. You idle for about 1 minute and the temp
will drop from 1200 to 400 degrees which is safe. Easiest thing to do is
just idle along on the street for one block before shutting down.
----- Original Message -----
From: <portermd@zianet.com>
To: <dmitchel@sbcglobal.net>
Cc: <MJSUKEY@cs.com>; <fot@autox.team.net>
Sent: Friday, July 02, 2004 12:17 PM
Subject: Re: Hot manifold question
> Doug Mitchell writes:
>
> > If you want to see something neat, look at a turbo when it is
> > running at full rpms. Glows a beautiful color. When I worked
> > in the engine dynos at Ford, we used to run tractor and heavy
> > truck engines at full load, wide open throttle to check them
> > out. The turbos were glowing cherry red. Understood why it was
> > necessary to keep the engine running for a few minutes after
> > a hard run with the boost on.
>
> Probably the reason why so many manufacturers have been moving to
ceramic
> impellers (those seem to have their own set of problems, though, such as
> cracking at stress concentration points--for a while in the mid-90s,
Detroit
> Diesels were shelling them fairly regularly).
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