Re: 5000 & 200 turbo hoses & perf. mods

[MHLIGGINS <MHLIGGINS@aol.com>]

<<For as long as I have been on this list, it seems that most of the mods to
increase hp/torque have focused soley on boost pressure. >>
There have been other things discussed, such as tweaking the timing, changing
cams, using a gear to vary the cam timing, different wastegate springs, etc.
Check the archives for greater detail.

<<I was wondering, if any listers have found some aftermarket (or other parts
from later model turbo cars) intercoolers, or intercooler tubes, intake,
exhaust manifolds.. downpipes, and of course, exhaust.>>
Some of this is also in the archives, but you should check the Intended
Acceleration and T.A.P. web sites for go-fast goodies  -- including mods to
boost.

<<I am about to buy a '89 or '90 200TQ, and am looking into the best mods to
put on my new baby. Minor pre-tuning things : K&N and a boost gauge. First of
all, I'm looking into a more efficient intercooler, and the tube that connects
the intercooler to the intake manifold. Then, I'm considering a 2.5" downpipe,
and larger (not louder!!) exhaust...Say 2.5 or 3". >>
To address the last part, the stock Audi exhaust system is approximately
2.25".  If you go to 2.5" using normally available parts and labor (i.e.
muffler shop) you will probably be going backwards in performance.  I suspect
that only a mandrel bend 2.5" exhaust will show any statistically significant
improvement over stock.  The 3" stuff will change the performance parameters
measureably.  Graydon Stuckey (and those who have used exhaust systems he has
built) have explained these changes.  If I'm not mistaken his systems are
built with traditional muffler shop equipment.  (GDS, please correct if this
is not correct.)

     The reason there has not much discussion re: things other than boost is
cost.  Most of the go fast-parts are made in Germany in limited quantities.
The parts that are sold must be approved by certain German authorities so that
they are "T.U.V. approved" before they are allowed on european highways.  This
means tests done to government standards, plus whatever additional taxes need
to be paid once approval is received.   This all becomes part of the cost to
the end user.  High initial cost, plus low volume, tend to make the per-piece
price exorbitant.  
     And the pay-back for some of these parts is not especially high.
Consider $500+ for a euro after-market cam for the I-5 engine.  It will not
significantly alter the capability when compared to other options.  Such as
increasing the boost.  A cam will not allow a gain of 50-80 h.p., increasing
boost will.  (Ned Ritchie's web site will go into more detail.  T.A.P. might
also, but I haven't checked it lately.)
     But suffice it to say that the reason boost is the most common change
discussed is because it is the most cost effective.  There is not a more cost
efficient path to increased h.p. for the turbo-charged I-5 engine.  BUT, once
you've gone this route, you are then forced to spend the big bucks to make
further gains -- no options.
     Most of the members of the list love these cars, but are underwhelmed by
the power available in the stock form.  And we like to increase where we can
afford to.  We choose the cost effective way as the first step, then do
additional stuff when (usually IF) funds are available.  If you have the
finances available to work it in reverse, please keep us up-to-date as you go.
Enquiring minds want to know....

     Later.
     Marty Liggins
     Imperial Potentate, Bucksnort Quattro Club (Un-Inc.)