GrimmSpeed 02-07 WRX/STi / 04-08 FXT Downpipe 3in Catted (grm007082)
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One of the first changes you should make to your car is a downpipe because the OEM downpipe has two fairly constrained catalytic converters. While still using a catalytic converter, replacing these with our single high-flow unit will significantly increase performance potential. A high-flow, 300-cell catalytic converter, completely machined and contoured flanges, and the choice to add black ceramic coating are all included in our comprehensive line of downpipes. We have the ideal downpipe for you whether you're competing in a time attack race or driving to and from work.
To find the differences between factory parts and make sure that our fitment is flawless everywhere, we 3D scan 10–15 OEM downpipes. Then, using those scans in 3D CAD, we build our downpipe keeping in mind the placements of flanges, transmission tabs, O2 bungs, firewall clearances, and materials. Using CFD (computational fluid dynamics) simulations in CAD, bend sites, tube lengths, and detached wastegate re-entry points are all verified for healthy flow. We employed a reduction procedure to seamlessly move from the 2.5" turbine outlet to our 3" downpipe material since even the largest stock position turbine outlets use factory exhaust gaskets. 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 choice is a crucial, but frequently disregarded, a component of an aftermarket exhaust system. Our meaty 1/2" flanges will resist warping and leaks in even the harshest environments. Stainless steel, particularly 300-series alloys, has terrific durability and corrosion resistance but is still quite cost-effective for fabrication of this type. The tubing we selected is a thick 3in, 16ga 304L Stainless Steel tubing. Higher quality alloys come at an excessive cost, while lower grade alloys (such as those in the 400 series) may be more susceptible to corrosion over time, lowering the life and attractiveness of your parts. A fully machined bolt pattern is used on all flanges to provide extremely tight tolerances and perfect fitting. Each tube is CNC mandrel bent and CNC laser cut for perfectly repetitive fitment and accuracy. The catalytic converter 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.
Where the rubber hits the road is here. Every single downpipe for the 02-07 model is welded in the same master fixture. One OEM downpipe serves as the foundation for the welding fixtures made by our rivals. Using the CAD data stated above, we averaged the locations of a variety of OEM downpipes and turbo/Catback flanges to create our fixtures. 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 our expert welders. Don't be fooled by shiny imitations where a robotic TIG pass has been made over a wire-feed MIG weld; real TIG welding takes the skilled hand of a true craftsman. We take the structural integrity and beauty of our work very seriously and when you handle your new GrimmSpeed downpipe, you'll know it.
We offer our "Limited" series of downpipes for individuals who want to push the performance of even the best downpipe to its absolute limit. Limited downpipes use the same 1/2" 304L Stainless steel for the flanges, but they are fully machined with recesses for each tube and a lovely 3D contour to elegantly transition the asymmetrical shape of your internal wastegate outlet into our detached tube for tighter boost control. Limited downpipes also come in a ceramic thermal coated version which is some of the best downpipes you can buy for your Subaru.
- Once you have added our downpipe to your vehicle, you must be tuned. Replacing your factory catalytic converter sometimes causes a ‘cat converter efficiency’ check engine light. You can either use tuning to delete this CEL or you can use a mechanical fix. GrimmSpeed aftermarket downpipes modify OEM emissions control devices and are intended only for off-road racing applications.
- The IWG in some TD04 Turbos is slightly different than others for which the downpipe divider tab may need to be adjusted. It's a very simple process, but please contact our customer service representatives if you have any questions.
- The gasket is sold separately!
- Subaru WRX/STi (2002, 2003, 2004, 2005, 2006, 2007)
- Subaru Forester XT (2004, 2005, 2006, 2007, 2008)
- Proudly made in the USA - Design, Materials, and Fabrication
- Innovative 3-D Contour Flange (Limited models only)
- FARO™ Arm Designed - We are at the leading edge of new product design hardware
- Flanges Fully CNC Machined (Limited models only)
- O2 Bungs for factory sensor and aftermarket wideband AFR
- Divorced Wastegate for Optimal flow
- High-flow, 300 cells, metallic substrate catalytic converter
In stock, non special order items can be returned within 30 days of the product arriving to your house or place of work.
Returns will NOT be accepted on final sales, special orders, opened, installed, incomplete, or otherwise used products. In order to initiate a return, an RMA number must be requested and approved via e-mail.
All returns will be subject to a 20% restocking fee minus complete shipping cost (roundtrip).
Any processed orders that have not shipped will incur a 6% cancelation refund fee unless the product was not available to ship within a timely manner. No fee will be incurred if used as store credit.
For complete details on our return policy, please see our Help and FAQ link under HELPFUL INFO.