[s-cars] Turbo Trim

[Richard Tanimura]

I am trying to select a new turbo. I think I have a pretty firm grip on the
definition of turbo trim. It seems basically to be the relation between the
swept area of the minor to the cross sectional area of the opening. But I am
curious about the practical aspects.

To simplify, lets look at the compressor side. 60 trim means that the swept
area of the minor is 60% of the inducer area.

1. In terms of turbo performance, what are we doing when we alter trim?
Intuitively, 0 trim means we don't suck much air obviously. So why not run
as close to 100 trim as possible? I.e. why trim?

2. Dumb question. To decrease trim, do you just hog out the inducer bore?
That seems easier than trimming the blades.

3. Can it be that we trim to establish the P(out)/P(in) ratio? I.e. we trim
to hold operation within the most efficient areas of the compressor map?

Now lets broaden the discussion to include the hot side.

4. Is it common to also trim the hot side?


Some numbers from the "Colorado Instumentation and Measurement Laboratories"
would be interesting :-)


Help me here,

Rich
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