In a message dated 96-07-26 04:35:10 EDT, verbeek@the-hague.stbv.slb.com
(brian verbeek) writes:

>If you are determined to build your own, you'd have to: calculate/test
>correct header lenght, make sure they are all exactly the same lenght,

While this is good reccommended practice, VW didn't follow it on the 2.1L
exhaust.  Each of the right side exhausts travel over to the left side of the
engine before mating with the left side exhausts and are probably about 14"
longer than the lefts.  It doesn't seem that VW attempted any correction of
this by altering tube diameters, they appear to be the same diameters.

>that the bends are as smooth as possible, that the bends remain the same
>dia after bending them into shape, collector shape and lenght etc., that
>if you want to go from 2 x 2in1 and then these two into one you join 1 and 3
>and 2 and 4 before these combinations join together, adjust the tube dia
>to the exhaust valve dia. i'm sure other people can come up with other
>things to consider, make sure that your exhaust system flows at least
>the same as stock, if not, it will reduce volumetric efficiency,

If I were building one from scratch, I'd consider combining both exhausts
from one side and routing them through a small cat & muffler for each side.
 You might be able to find some tiny cat & muffler intended for a little 1.1L
or 1.3L  3-cylinder car to fit in-line along each side of the engine.  I
don't know what resonance (or other) effect this would have by collecting
both cylinders from one side together, but dual exhausts would seem the way
to go to reduce backpressure.  Just a thought.

Jim Davis
87 GL Syncro
88 GL Wolfsburg