Key Features
4-2-1 Tri-Y equal-length design
44mm primaries → 50mm secondaries → 2.5" outlet with smooth stepped transitions for power gains across the entire RPM range
TIG welding
All joints TIG welded for smooth, strong seams
CNC-machined flanges
3/8" thick CNC-cut flanges, double-welded and ported for optimum flow at entry and exit
Plug-and-play fitment
Direct replacement for OEM 2-piece design with O2 sensor bung and metal gasket included. No modifications required for quick installation
Compatible Models
Honda Civic Si Coupe (FG2) – 2006–2011
Honda Civic Si Sedan (FA5) – 2006–2011
Honda Civic Si (FD3 / FD4) – corresponding years
Why Choose This Header?
Unleash the K20Z3's high-RPM potential – The factory 2-piece catted manifold is the biggest bottleneck for high-RPM breathing. The 4-2-1 Tri-Y design lets this high-rev engine breathe freely where it matters most.
Gains across the entire RPM range – Unlike 4-1 designs that only benefit top-end power, the 4-2-1 Tri-Y delivers improvements in both low-end torque and high-RPM horsepower – noticeable in daily driving and on track.
Premium materials & workmanship – stainless + TIG welding + CNC flanges – several layers of quality for leak-free, rust-free, crack-free performance.
True bolt-on installation – Direct OEM replacement with O2 sensor bung and metal gasket included – no cutting or welding required.
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