[Diy_efi] This turbo assist stuff, suggestions

[Grant Beaty]

> Ball-bearings indeed do have lower friction than under-lubricated
> hydrodynamic bearings.

Yes, we are aware of that. I think more people are worried about friction
during opperating conditions. Or are you implying that cold-starts can
eventually take their toll on plain bearing turbos?

FWIW Turbonetics now uses 713C Inconel turbine wheels. Not any lighter I
guess, just stronger? I wonder why they would want them stonger, I've never
heard of a failure, except of course for those molten EGT probes....
http://www.turboneticsinc.com/713CInconel.html

Grant Beaty

----- Original Message -----
From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, January 01, 2003 5:23 AM
Subject: Re: [Diy_efi] This turbo assist stuff, suggestions


> On Tue, Dec 31, 2002 at 09:17:15PM -0800, efi student wrote:
> > Got data?  I can get all the anecdotal evidence I want from lots of
> > testimonies, but I can get the same thing for Prolong or Slick 50.
>
> Ball-bearings indeed do have lower friction than under-lubricated
> hydrodynamic bearings.
>
>
> > If you think ball bearings have less friction than a properly
> > oiled plain bearing, you're kidding yourself.
>
> Unless you're running some sort of "oiler", the turbo spinning down
> after the engine is turned off will be withough circulating oil - so
> the bearing friction will be high and wear will also be high. A ball
> bearing requires very little oil in comparison; it only needs the
> oil to wet the surface of the races.
>
> And when starting, you have a similar situation; hydrodynamic
> bearings dry until enough oil flows through the bearing to allow it
> to work.
>
> > Plain bearings have some pretty significant advantages over ball
> > bearings.
>
> The main reasons being that they are more quiet, cheaper to build
> and maintain.
>
> The use of ceramics BTW reduces expansion and hence the loading on
> the balls and races... that's the main advantage for a turbocharger;
> the housing and bearings typically being made from different
> materials.
>
> Oil-flow can, OTOH be used to minimise temperature fluctuations when
> the engine (and oil pump) is running; but is doesn't resolve the
> isssue of bearing pre-load to accommodate cold, warming, hot and
> cooling conditions - so the design of the bearing housing is
> critical.
>
> --
> /"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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