Last thursday, Subaru of Dallas hosted what they called a "High Performance Tuning" session with keynote speaker Trey Cobb of COBB Tuning.
The event started with the obligatory pizza and beer; then moved to an introduction of the staff, some history of the new dealership, and a hint at where the dealership is heading. The most notable new information is that Subaru of Dallas is expanding to add an STi showroom, which will stock the entire line of STi parts. This will be the first STi showroom in the Americas.
Trey's presentation focused entirely on COBB Tuning's R&D process and the new parts they are offering for the Impreza and Legacy. While this wasn't quite what I was hoping for, it was rather informative. Trey spent a significant percentage of time discussing their new downpipe and the thinking behind its fabrication. His first point was about the casting process for the bellmouth housing. Its two notable features are a taper design that doesn't interrupt flow coming from the turbo exhaust port (the taper is on the waste-gate side) and a casting made from stainless steel instead of iron (using an investment cast instead of a sand cast for a smoother surface.) The bellmouth housing is then slipped over a 304 stainless steel pipe (with a small internal gap to leave room for metal expansion) which is joined in a zig-zag patterned fusion weld (a TIG weld with no filler metal.) The odd shaped joint was designed for increased strength, which should allow this section to hold up to exhaust heat abuse better than a traditional pipe weld. The bellmouth also features a top-mounted O2 bung, which is conveniently located if you're not using heat shields.
The new COBB downpipe also features a very small catalytic converter. Trey wouldn't disclose the brand, but emphasized that this is a modern catalytic converter design more popular in Europe then North America. The device is more expensive than traditional high-flow cats, but more efficient and features a lower profile. The downpipe bolts to the factory mid-pipe using the same donut flex joint used by Subaru.
After addressing audience questions about the downpipe, Trey moved on to their new uppipe. An uppipe is a pretty simple part, so instead of simply copying the factory design and removing the cat, COBB focused on optimizing air flow through this section with extensive CAD and fluid-dynamics modeling. The end result is a 100% investment cast stainless steel part. As a fully-cast part, the piece requires no welding, thus avoiding the common joint failure seen in other uppipes. The uppipe is available in 304 stainless, or Inconel 625. Inconel is a more exotic metal that is stronger and more heat resistant then regular stainless. The qualities of Inconel make it a great choice for exhaust headers, but also make it very expensive to tool. Given the higher manufacturing costs, the Inconel part is about $150 more then the stainless piece.
Trey also pointed out the use of non-stainless, coated studs in their uppipe. He claimed that stainless studs combined with non-stainless nuts are a recipe for seized bolts. COBB also uses a custom made stud that properly matches the factory bolt lengths to ease installation and reduce the chance of the studs hitting an after-market downpipe.
After discussing fluctuations in the raw metals market, Trey moved to the highly controversial (in the WRX world) topic of after-market intakes. After holding out for many years, COBB will soon introduce a short pod intake for the Impreza. While Trey is still a strong believer in keeping the stock air-box unless pushing over 400hp, he's recognized that customers want the sound of a pod intake and are willing to purchase a part just for that.
The common problem with after-market intakes for the WRX is a disruption in airflow over the Mass Airflow [MAF] Sensor, which then requires extensive ECU tuning to correct. To avoid this, COBB designed a short intake featuring internal air stabilization channels. While describing the design, Trey mentioned that the new Subaru Legacy GT uses a very similar design in its factory intake. Trey only had a 3D printed model of the intake to show, but indicated that the final parts are in production.
While running short on time, Trey quickly introduced the Access Port. The Access Port is a simple ECU map storage device (which connects to the factory OBDII port) capable of storing and loading alternate ECU maps for the stock ECU. After this short explanation, Trey quickly moved to a demonstration of his upcoming StreetTuner software. StreetTuner is an engine management solution which enables end users to modify every data point in the factory ECU in real time. Unlike piggyback or replacement ECUs, using StreetTuner with an AccessPort gives direct control over the existing ECU, and the ability to modify every tuning aspect available in the factory ECU (ex., low-det and high-det timing maps; the boost map; OLF cutover point; MAF correction; target air/fuel ratios; etc.) The modifications to the ECU are undetectable by the Subaru diagnostic tools used at dealers and don't require any rewiring.
The event wrapped up with a door-prize raffle that unfortunately didn't include any actual car parts. However, I won a Hot Subaru T-Shirt which was pretty cool. Hot Subaru also has a short blurb about the event.
Thanks to Trey Cobb, COBB Tuning, and Subaru of Dallas for hosting the event!