Evolution Racewerks:

The factory catalytic converter is very restrictive on the exhaust flow in the exhaust system. Exhaust gas must pass through tiny honeycomb passages in the cat which restrict flow and causes turbulence which in turn hinder performance. By removing the OEM cat and replacing it with the Evolution Racewerks Test Pipe noticeable gains in horsepower and torque can be felt.

The K03/K04 turbine outlet is almost 3" in diameter. That is why Evolution Racewerks' test pipe features a 3" diameter that reduces to 2.5" (to bolt up to OEM and most aftermarket downpipe/exhaust systems). The Test Pipe uses a flare type reducer over a step reducer for reduced turbulence and greater flow. Also, having the transition as far as possible away from the turbo improves performance as well.

The Evolution Racewerks Test Pipe's 3" to 2.5" design is superior over other test pipes that are 2.5" in diameter from inlet to outlet because the 2.5" test pipes will have a "step" right at the outlet. Since the OEM K03/K04 turbos have a turbine (exhaust) outlet of almost 3", the flange of the 2.5" test pipes will actually make a "step" right at the turbo outlet. This step acts like a wall against exhaust flow and when the exhaust hits it, major exhaust turbulence is created, at the worst spot possible, right at the outlet of the turbo. If you have a 2.5" test pipe, check it out. Look at the inlet flange and you will see a "ring" of carbon deposits on the flange. This is the "step" that the exhaust flow is hitting.

Applications

• 1996-2005 Audi A4 1.8T
• 1998-2005 VW Passat 1.8T

Construction
The Evolution Racewerks Test Pipe is completely constructed from quality 304 stainless steel and is polished to a mirror finish.  The pipe, flanges, o2 sensor bungs EVERYTHING is 304 stainless steel, even the welding rod we use.  The piping is also fully mandrel bent.  True to Evolution Racewerks' standards, EVERYTHING needed for installation is included.  That includes BOTH turbo outlet gasket and downpipe inlet gasket.  EVERY bolt, nut and washer that is on the catalytic converter/test pipe is replaced with high quality full stainless steel bolts, nuts, and washers.  Yes that's right FULL stainless steel, down to even the hardware.

For offroad use only