A downpipe is one of the first modifications that should be done on your car, as the OEM downpipe contains two very restrictive catalytic converters. Replacing these with our single high-flow unit will dramatically improve performance potential while maintaining the use of a catalytic converter. Within our complete lineup of downpipes, you have the option to add a high-flow, 300 cell catalytic converter, fully machined and contoured flanges with beautiful brushed tubes and black ceramic coating. Whether you're racing time attack or to work and back, we've got the perfect downpipe for you.
We use 3D scans of 10-15 OEM downpipes to identify the variances within stock parts and ensure that our fitment is perfect across the board. We then pull those scans in 3D CAD and design our downpipe with flange locations, transmission tab locations, O2 bung locations, firewall clearances and material selection in mind. Bend locations, tube lengths and divorced wastegate re-entry point are all checked for healthy flow using CFD (computational fluid dynamics) simulations in CAD. With even the largest stock location turbine outlets utilizing factory exhaust gaskets, we used a reduction process to smoothly transition from the 2.5" turbine outlet to our 3" downpipe material. The outlet of the downpipe has a standard 3", 2-bolt flange that will mate up with most aftermarket Cat-Back exhaust systems and the secondary O2 bung that we've added will save you time and money when you decide to use a wideband O2 sensor/gauge in the future. As engineers and enthusiasts, we take great pride in the work that we put into our design process and it shows in the finished product.
Material selection is a very important, but often overlooked, part of an aftermarket exhaust system. The tubing we chose is a thick 3in, 16ga 304L Stainless Steel tubing and our meaty 1/2" flanges will resist warping and leaks in even the most extreme environments. Stainless steel, particularly 300-series alloys, have terrific durability and corrosion resistance but are still quite cost-effective for fabrication of this type. Lower grade alloys (400 series, for example) may be more prone to corrosion over time, reducing the life and beauty of your parts while higher grade alloys introduce unnecessary cost. All flanges use a fully-machined bolt pattern to ensure very tight tolerances and flawless fitment. Each tube is CNC mandrel bent and CNC laser cut for perfectly repetitive fitment and accuracy. The catalytic convertor that we've selected is custom sized and utilizes a metallic substrate for increased effectiveness, higher flow and better durability than other, lesser units. We selected a 300 cell count mantel for a perfect compromise of performance and function.
This is where the rubber meets the road. Every single 02-07 downpipe is welded in the exact same master fixture. Our competitors build their welding fixtures around a single OEM downpipe. We build our fixtures to the average (found using the CAD data mentioned above) of a number of OEM downpipes and turbo/Cat-Back flange locations. We periodically re-check our fixtures using our FARO arm to ensure that heavy use and heat cycling don't affect their accuracy. Each downpipe is TIG welded by one of our two expert welders, Chuck and Andrew. Don't be fooled by shiny immitations where a robitic TIG pass has been made over a wire-fed MIG weld; real TIG welding takes the skilled hand of a true craftsman. Chuck and Andrew take the structural integrity and beauty of their work very seriously and when you handle your new GrimmSpeed downpipe, you'll know it.
- 2008-2014 Subaru WRX
- 2008-2016 Subaru STI
- 2005-2009 Subaru Legacy GT (Non-VF46, Manual Trans Only)
- 2009-2013 Subaru Forester XT