This downpipe (down pipe) with flange has been designed for all A4 chassis TDIs with both ALH and BEW engines.
Our pipe uses mandrel bends to maintain full diameter at the turbo exit. An extra long flex section in the stock location to allow engine movement without transmitting vibration to the vehicle or stressing the pipe. Precisely fit hanger for easy installation.
2.5 Inch vs. 2.0 Inch
The factory exhaust system is roughly 2 inches in diameter, though smaller at the downpipe bend. Choose the 2-inch for a factory replacement. Choose the 2.5 inch system for upgraded flow that can increase boost response and horsepower.
2.5 Inch Exclusive Upgrades
The upgraded 2.5 inch system has two very useful upgrades. First, the flange that attaches to the turbocharger is custom cast, 1/2 inch thick, port matched and is then beveled out to the full 2.5 inch diameter. This lessens back pressure due to turbulence.
The exhaust flange on the 2.5" pipe is 1/2" thick, and has an opening that matches the turbo exit, beveling to the 2.5" pipe diameter. This provides a smoother transition from turbo to down pipe, improving flow. The flange on the 2" downpipe is similar thickness and is port-matched to the turbo.
The 2.5 inch downpipe also features a high quality, dual-layered flex section. The flex has both an inner and outer layer. The outer layer is the traditional stainless steel weave seen on the OE flex and traditional flex sections. The inner layer is a unique "interlock" layer that limits turbulence and resists exhaust leaks better than the weave alone. We think it is the best flex section in the industry.
These pipes are made exclusively for IDParts by K&B Fabrication, a local stainless and aluminum fabricator with over 30 years of fabrication experience in high performance automobile parts. These pipes are made from 304 Stainless and will not rust. OEM material is 409 stainless which does rust over time. We think you'll agree the workmanship is excellent, and we will warranty all products against defects for one year after purchase.
Downpipe Exit Options
For those choosing the 2.5 inch downpipe there are two different exit options. If you are upgrading the rest of your exhaust system (CAT-back & muffler) to a 2.5 system, you should keep the 2.5 inch exit. However, if you are keeping your OEM muffler and midpipe, choose the option for "Stock Exit Size" and we will weld on an adapter bringing the 2.5 downpipe down to the stock midpipe diameter.
With the stock exit adapter you can re-use the OE exhaust clamp, though it is typically too rusty to re-use.
Catalytic converters are available in both 2.0 inch and 2.5 inch downpipe sizes. Both versions are high-flow designs.
Includes down pipe gasket and three copper pinch nuts. Do not order these separately unless you need an extra gasket or pinch nuts.
Selecting a CAT or Resonator will delay shipping as the downpipe will be sent out for fabrication.