[Vwdiesel] Choosing a turbo

Shirley, Mark R MarkRShirley at eaton.com
Tue Jul 19 14:49:23 EDT 2005

If you want to do more than pick off a graph, pick up a copy
of Hugh MacInnes's book, Turbochargers.  He goes through the
equations for turbo selection.  In simple enough terms a 
non-engineer can handle it.  You do need to know a bit about
your engine though.  

> -----Original Message-----
> From: vwdiesel-bounces at vwfans.com 
> [mailto:vwdiesel-bounces at vwfans.com]On
> Behalf Of Gary Shea
> Sent: Tuesday, July 19, 2005 2:44 PM
> Cc: VW Diesels Mailing List
> Subject: Re: [Vwdiesel] Choosing a turbo
> 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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