K-Tuned 8th Gen Honda Civic Si Header 06-11 Honda Civic Si - K20 409 Stainless Steel

Item SKU: KBH-CSI-409

K-Tuned 8th Gen Header for the 2006-2011 Honda Civic Si coupe and sedan with the K20Z3. This KBH-CSI-409 version uses 409-series steel and is built for race use only, not highway or street vehicles.

• Layout: 4-2-1 Tri-Y header with 44mm primaries stepping to 50mm secondaries, then a 2.5-inch outlet. The stepped tubing and smooth transitions are there to keep the exhaust path moving without abrupt changes in diameter.
• Construction: Mandrel-bent 409-series steel tubing, TIG-welded throughout, with CNC-cut 3/8-inch flanges that are double welded and ported at the entry and exit.
• Fitment: Direct replacement for the factory two-piece K20Z3 exhaust manifold arrangement on 2006-2011 Civic Si coupes and sedans. K-Tuned also offers this header for stock K20 and K24-swapped setups, so select the correct engine version when ordering.
• Connection: 2.5-inch outlet and a short 2.5-inch test pipe with a secondary O2 sensor defouler. The factory catalytic converter is eliminated.
• Service note: The donut gasket can be replaced with Honda part number 18229-PCX-003, but the metal ring must be reused.

This is the raw 409 steel version, not K-Tuned's polished 304 stainless variant. 409 keeps the material cost down, but the unfinished steel can be coated or painted if you want added rust resistance. K-Tuned recommends a Hasport rear engine mount to limit engine movement. That matters with a header routed past the subframe and sway bar, especially on a car that gets driven hard. No more factory catalytic converter or two-piece manifold, but it also means this setup is not emissions compliant and isn't legal for street use.