Applications: 
06-11 Civic SI Coupe and Sedan
Features:
* Fits Civic Si with K20Z3 engine.
* 4-2-1 Tri-Y Design - 409 Series Steel
* CNC cut 3/8" thick flanges
* 2.5" Outlet
Note:
*It is highly recommended to upgrade your rear engine mount to a Hasport rear mount to limit movement.
*Donut gasket can be replaced by OEM Honda part (18229-PCX-003), you will have to reuse the metal ring.

K-Tuned Stainless Steel Header Civic SI 06-11 FA5 FG2 409 Series specifically designed to optimize the performance and power output of the K20Z3 engine that is found in all 2 and 4 door SI models. The header was developed using a proven 4-2-1 Tri-Y design that delivers power gains almost everywhere in the power band, not just the higher rpm range. Additional performance is accomplished by using large diameter piping to speed up the flow of exiting exhaust gases. We also use stepped piping and smooth transitions that minimize restriction. Fitment past the subframe and sway bar is perfect with extra clearance available for engine movement.

We start with 44mm primaries that smoothly step into 50mm secondaries and finish with a 64mm or 2.5î exit. Our 409 Series 8th Gen Civic SI Header is assembled using mandrel bent, 409 series steel tubing and is fully tig welded. We also use a slightly thicker gauge tubing that allows for better weld penetration and additional strength. The CNC cut 3/8" thick flanges are also double welded and then ported for optimum flow at entry and exit. This header directly replaces the OEM 2 piece design and eliminates the catalytic converter so we included a short 2.5" test-pipe with defouler for the secondary O2 sensor.
 
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