Re: 5KCSTQ Exhaust system mods

[PDQSHIP@aol.com]

In a message dated 96-05-03 09:07:20 EDT, you write:

>Scott, I was squintin at the downpipe on the Ur-Q a few days ago and thinkin
>about your 3" upgrade...... The downpipe diam on the Ur-Q is 65mm and is
>already like ~1/4 to 1/2" larger than the exit port in the turbo. Two
>questions:
1/3 of an inch would be most accurate.....
>
>1) Is going from 65mm/2 + 1/2" to 3" really worth it when the biggest
>restriction is the size of the exit
>    port in the turbo?

That's not really true....  The exit size of the turbo is part of TURBO
design, not the EXHAUST design....  In fact, for example, the RS2 hot side
diameter on the outlet is LESS than a stock k26....   The exhaust starts at
the downpipe where it meets the turbo, so the restriction starts there as
well....  a three inch system is 20% larger than a 2 1/2, in terms of volume
of air this becomes very significant....  I wouldn't do a 3inch after the
stock downpipe, it ain';t worth the trouble...  a three inch system must go
to the turbo, which means you have as much $ into the downpipe as you do in
the rest of the system....  And things are VERY tight in that turbo frame
rail area, so it's a major PITA....   If you are doing a 2 1/2 system, the
cat back is fine, your gains in the downpipe prolly aren't worth the
expense.....  The ur q actually has a slightly larger downpipe than the 5ktq,
so prolly better there anyhow.....   However, one of the restrictions in the
downpipe is actually the cast downpipe at the turbo (where the O2 and CO
ports are) cuz audi designed a pinch into the casting for the downpipe nuts
that really pinches the inside of that pipe....  Me, I would cut off the
casting and fabricate a plate and pipe that has less of a pinch (btdt with
mine), or none, and fabricate a better wrench for those nuts....  Then weld
onto the stock downpipe, and bingo, lots less hassle and expense....

>
>2) How did you implement the 3" system? Custom-fabd piece to replace the
cast
>flange on the downpipe
>    that bolts to the turbo hot-side outlet? Just welded a 3" pipe onto the
>stock cast downpipe flange and
>    suffered the high impedance of the stock flange in light of the fact
that
>the outlet on the turbo is so
>    much more restrictive anyhows?

1/2 inch plate stock with a 3inch pipe welded to it about 4 inches long....
 Then used a donor WG downpipe for the fabricated downpipe, but it took my
guy 5 tries to get the 6-8 bends correct, not an easy project.....

Scott