[Vwdiesel] Choosing a turbo

[Gary Shea]

I spent last weekend digging into turbo info.  Based on my reading,
turbo selection is fairly simple (basically read it off a graph) if you
know a bunch of difficult-to-measure and difficult-to-guess information
about your engine... so, it seems to be a hit and miss business for
those of us without major measurement equipment.

Here's what appears to be a decent intro to the terminology and tools:
http://www.hotrod.com/techarticles/engine/113_0312_turbo/index.html

Quite a few useful bits of information at this site, including
compressor maps and a 'turbo calculator' (I haven't used this particular
one but it looks promising):
http://not2fast.wryday.com/

This site also has a decent selection of compressor maps:
http://www.rbracing-rsr.com/turbotech.html

The Garret catalog (towards the back) has sections on technical topics
like compressor maps (Garrett has been eaten by Honeywell, I haven't
found any actual information on any of their pages, just marketing crap,
but a variety of turbo businesses have their own local copies of this
pdf):
http://www.jimwolftechnology.com/wolfpdf/GARRETTCATOLOGUE.pdf

Each half of the turbo has two main parameters, a/r (area to radius
ratio) and trim (ratio of the sizes of the two kinds of blades on the
wheel).  This information is sometimes available online but not easy to
find.  Usually you can find the A/R and trim of the compressor side, but
not the turbine side.  I have never found that info online for the '84
Quantum TD engine that I have (a Garrett TA0304).

Have fun!

    Gary

On Mon, 2005-07-18 at 23:49 -0400, Libbybapa at wmconnect.com wrote:
> I have heard of a/r ratio.  Can someone explain what that means?  Are there 
> other things to consider when choosing a turbo for a particular engine other 
> than flange pattern and making sure it will physically fit where you want it?  
> Does anyone have a source for the a/r ratios of the stock 1.6 TD turbos?  
> Thanks.
> 
> Andrew
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