[Diy_efi] This turbo assist stuff, suggestions

Bernd Felsche bernie at innovative.iinet.net.au
Thu Jan 2 00:59:40 GMT 2003


On Wed, Jan 01, 2003 at 02:35:20PM -0500, Grant Beaty wrote:
> > 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?

They do; as do other transient consitions where there is
insufficient oil flow or shaft speed to sustain a hydrodynamic film.

Ball-bearings are much less susceptible under those circumstances
and have low turning resistance from static.

It might be instructive to look at the high-performance engines of
the 1930's and 1940's built in Europe. The Auto Union race cars had
ball-bearing conrod ends; as did the DB601-engines (IIRC) used in
tens of thousands of aircraft - until ball bearings could no longer
be obtained. Only then did they change to plain bearings.

-- 
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