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From YourSITE.com Technical Features Upping the performance, or rather measuring the increased performance, of our Project TT Coupe has been trying at times. Considering changes in dyno facilities and various mechanical gremlins, seeing just how a part effects the car hasn’t always been clear cut. As luck would have it, such difficulties are not-to-be-found during our latest installation – a performance downpipe from 42 Draft Designs. The Maryland-based company’s latest offering looked very interesting to us - a 3” downpipe for the 225 TT quattro.
While there are a number of cat-back exhaust systems available for the TT 225 quattro, there have only been a limited number of downpipes available (generally custom units or very limited production units that were pushing $1000), and one only available with a full turbo back exhaust system from APR. While the complete APR exhaust a very nice unit, most owners who have already installed a cat-back system are looking for a reasonably priced unit that would mate up with our existing system. Another alternative worthy of mention is Milltek’s twin high flow catalytic converters, which replace the factory units but leave the stock downpipe in place and are also north of $1000. Lucky for us, Evan Dent at 42 Draft Designs decided that he’d venture into this relatively untapped market by designing and fabricating a quality downpipe that would meet the needs of the large number of TT enthusiasts out there and remain reasonably priced. The TT’s stock downpipe is a marvel of engineering in the way that it twists and contorts within a very cramped space - a space limited by the TT’s quattro driveshaft and subframe design. The stock downpipe starts out with a severe 90 degree bend and then splits into two smaller 47 mm (1.85-inch) pipes which then mate up with the twin catalytic converters before converging back into a 2.55” opening at the end of a Y pipe from the twin cats.
Most of the cat-back systems out there are 2.75” or 3” in diameter. While they do a good job of opening up some of the restrictions of the stock exhaust system, most notably the crimp in the piping by the rear subframe, the don’t address the biggest restriction in the system - the downpipe and twin catalytic converters. As with all 42 Draft Designs products, we received the unit nicely packaged along with all the necessary bolts and gaskets necessary for the install. 42 Draft’s attention to detail is not only evident in the construction of the unit, but also in the complete kit which was assembled, including everything you need to install the downpipe - an adaptor to allow the system to be bolted up to the factory OEM sleeve which connects the downpipe to the cat-back system. 42 Draft can also provide additional CNC machined 3/8" steel flanges for a small charge if you want to have your local shop do a custom connection of your existing system to the downpipe, eliminating the 2.55” OEM clamp. Unit received, a call was placed to our friends at STaSIS Engineering at Infineon Raceway to schedule an appointment for the downpipe install. Although well-known for their SPEEDworld Challenge Audi A4 racing team, and more recently their Signature Series Audi A3 and A4 vehicles, STaSIS also provides all types of installation and maintenance work for a variety of vehicles. The TT was dropped of and its return eagerly awaited. Chatting with Evan from 42 Draft, he said to expect an estimated time for install at about 3 to 4 hours. On pick-up of the car, STaSIS indicated that it took about three hours to install, and while it was a bit involved, they had no trouble getting the downpipe in and adjusted correctly.
Now for the moment of truth - turning the key, the car rumbled to life. The exhaust note is a bit deeper and with a bit more of a burble to it, but was not much louder than it was before the install. We attribute this to the fact that we had STaSIS install the high flow cat, instead of the test pipe. We wanted to dyno the car with the cat to see what it would do, as a test pipe would almost guarantee pretty significant gain over stock. Logging some miles on Project TT over the next couple of weeks before the dyno, the car seemed to adapt quickly to the new freer flowing exhaust. In addition to more power being felt in the top end of the rpm range, a significant increase could also be felt in low rpm torque. Cross-checking before and after boost levels with the VAGCOM it should be noted that the TT did pick up a couple PSI of boost after the downpipe install, something that will probably be noticeable on the dyno. A dyno session was scheduled with Streetwerke on their Mustang Dyno. Trying to identify simply the gains from the newly installed downpipe and catalytic converters, no additional changes of parts or settings to the TT were made between our previous dyno session and this new session. After strapping Project TT down, a number of runs were made, producing impressive results. The best run of the day netted a 9.3 hp and 19.3 ft. lb. peak gain at the wheels. Not only did it yield these peak gains, but power was increased over the entire RPM range. Torque and horsepower was now being made much sooner in the rpm range. The car is now making about 125 ft. lbs. of torque at 1,900 rpms, as opposed to 2,400 RPMs before the downpipe install. Peak horsepower was also occurring at 5,500 RPMs, rather than 6,250 RPMs as previously recorded. Upper range power was also markedly better, with an approximate 15 wheel horsepower gain at 5800 RPMs over the previous run.
Considering these numbers were done with the cat setup in place and on 91 octane, we were extremely happy with the results. Likely, the 2.55” OEM clamp used to mate the downpipe with our existing Forge exhaust robbed us of a couple horsepower. With the test pipe in place the car probably could have picked up another 5 or more wheel horsepower and who knows how much more torque. Owners with easy access to 93 octane might pick up even more power. In fact, we can’t wait to see what difference the downpipe makes when we top off the tank with 100 octane. We continue to be impressed with the 42 Draft Designs 3-inh downpipe on a daily basis. Every time you get into the throttle, hear the turbo spool up more quickly and feel that slug of torque, you can’t help but get a big grin on our face. Rumor has it that Evan Dent of 42 Draft is looking into producing a full 3-inch cat-back exhaust for the TT 225 quattro that will mate up directly with his new downpipe. Based upon our dyno results, one would expect even greater gains with the full 3-inch system. Project TT has come so far, and the checklist of must-do modifications is shortening check-by-check. While there are still a few more engine-related modifications to go, the car will most likely only be heading to the dyno one or two more times. In the middle of all these modifications, we’ve also managed to have the 60,000 mile service done and hit the track with the Audi Club of North American Golden Gate chapter at Thunderhill Raceway and Reno/Fernley Raceway and will be reporting back on our experiences. Along the way, we’re likely to find a few new upgrades as well as wrinkles before calling this project complete.
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