Dual Exhaust

Upon deciding to go forward with a purchase of aftermarket downpipes I also decided I would replace my 70mm Supersprint exhaust with a dual 2.25″ system. I decided upon a dual pipe system over the single 3″ options due to the greater flow capacity of two 2.25″ pipes. At the time I reasoned that the increase in total carrying capacity above my 70mm system (around 45% by my calculations) would be a good thing and I would be able to sell my old exhaust for close to the cost of a new dual, and thus it would not be an expensive upgrade in the end.
As with my first exhaust upgrade I was looking for a system that would improve upon performance while maintaining a livable sound. Cost as always was something to consider. With the dual systems fit was an even bigger factor since there was less space to accommodate the exhaust.
Options Available:
I had a small number of options for consideration, they were as follows:

  • AWE TWIN2: Reported good fit but the most expensive of the group. Also likely to be slightly louder than what I was looking for. I was looking to sell my Supersprint when a Twin2 owner who was looking for a quieter exhaust and was interested in my Supersprint contacted me. Upon learning that the Twin2 might not be as quiet as I was hoping, I ruled it out.
  • FORGE TWIN BORE: Very limited information about this exhaust. Based upon the Forge/Milltek exhausts that I had heard about I expected this to sound close to what I was hoping for but I had no information about how well it fit.
  • UUC VM3: Decent price but has a reputation for being quite loud.
  • Milltek SuperDual: Milltek has a reputation for making quieter systems and reports on the SuperDual supported this. I was somewhat concerned by the fact that numerous owners of Milltek’s had found the fit of the system less than good. Stratmosphere was having a 15% off sale and a conversation with them about the fit of the systems they had sold eased my concerns.
I reasoned that the performance benefits to be gained by any of these systems would be roughly equivalent, and thus discarded performance as a criteria. With the UUC and Twin2 eliminated due to volume it came down to the Forge and Milltek systems. I decided to go with the Milltek because there was more information about it and I was assured by Stratmosphere that if it did not fit I would be able to return it.

I placed my order for the Milltek on February 25. I received my system on March 10th,and on the 12th made preparations to install the system. I commenced with a dry run in my garage to ensure the components would fit together before I took the car to a lift. To my disappointment, I found that the resonator pipes would not line up with the muffler pipes. In fact, after measuring the error I found that the pipes were 1.6 cm off.

I placed a call to Stratmosphere and they worked to get a replacement system sent to me direct from Milltek. After that system arrived I checked it out in my garage and was happy to find that the two halves fit together. I then went to a garage to use a lift for the installation.

Upon raising the system on to the car it became apparent that I would need to scrunch the exhaust down a bit to get it to fit since it was rubbing against the fuel return line. My efforts to push the pipes into more of an over lap were fruitless, and it was apparent that it would not be fitting on my car. I took the system down and began to remove the rubber hangers. This is when I discovered that Milltek uses huge flanges to keep the rubber hangars on the posts. It was a pain removing the hangars and once I got to the forward most hanger, which is made of a harder rubber, I was in for a real battle. Fifteen minutes, lots of dish soap, and two screw drivers, plus a good bit of sweat and profanity were needed to get it off.

I wrote to Stratmosphere and explained what happened. I was called by a Milltek rep and discussed the problem. The determination was that the system should fit on the car but just needed to have the front extension pipes trimmed enough so that the system would hang correctly. I spoke with Stratmosphere and we agreed that I would have the system installed with the extension pipes being trimmed as necessary.

For this work I took the car to an Audi dealership that was mod friendly. Once installed I noticed right away an unusual sound. Upon looking under the car I discovered that the exhaust pipe was pressed against the control arm for one of the rear wheels. If the exhaust system vibrated, the sound was directed into the car through this contact point.

By this point I had my fill with the Milltek system and put my Supersprint back on. After contemplating my alternatives I decided to remain with the Supersprint. The Supersprint uses the same diameter pipe as the MTM exhaust, which is part of their Stage 5 setup producing 400+ HP and I concluded that the Supersprint would be more than adequate for my Stage 2+ setup.

Audi B5 S4 Information and Testing