Advanced Turbo Questions

[FauxZ]

My Turbo knowledge of A/R is far from perfect, but I understand it like
this.. The A/R is the ratio between the housing and the wheel, not the
opening...    This explains why a tighter (smaller) A/R (exhaust side) will
spool faster than a bigger A/R...  Small volume, velocity rises so does
pressure... So with little gas you can get the wheel up to speed, but as you
try to cram more air past it becomes a restriction.....   Conversely, an
open A/R, .80 or example, may have a lower velocity, but you can flow more
air past it allowing the motor to breath better...

VANOS, or variable turbo like on the VW TDI motors, have a variable A/R by
using a series of vanes around the wheel..  You can probably find more info
about that online since it's too much to type here...  Also check out Corky
Bell's book  "Maximum Boost"... It's a great resource, if a bit dated, for
the amateur  Turbo enthusiast...

Zaron

From: <cjburn_2 at yahoo.com>
To: <se-r at lists.deskmedia.com>
Sent: Thursday, March 25, 2004 5:58 PM
Subject: Advanced Turbo Questions

I've always been a lurker on the list and post more on
the forum but if anyone can help me out here, I'd
really appreciate it:
I really don't understand the A/R concept too much. If
the A/R ratio describes an area ratio relative to the
opening of the turbo to the general area inside the
housing, how is it possible to have A/R change with
wheel diameter? Does this happen? I'm guessing it does
since there are different part numbers for different
housings given for a different wheel. Lastly, has
anyone ever mounted a T04S housing in the front of an
SR, being mounted on a GTi-R manifold? Is it possible
with enough grinding on the block? Or would I be
better off getting a T04E housing cut for the wheel
I'm going to be using. Nobody who runs a business who
sells turbos has a clue to what I'm trying to get to.
It's absolutely hilarious.  Thanks in advance....