MBRP 4" Downpipe for Ford (2008-10) F-250/F-350/F-450/F-550, 6.4L Power Stroke, ARMOR Plus T-409 Stainless Steel

The MBRP FS9CA455 4" downpipe is an ARMOR Plus series upgrade built for 2008–2010 Ford F-250, F-350, F-450, and F-550 6.4L Power Stroke trucks. It replaces the factory turbo downpipe with a larger, mandrel-bent 4" T-409 stainless assembly designed to improve exhaust flow, reduce restriction, and support better performance and efficiency on stock or tuned 6.4L builds.

From the turbo outlet, the factory downpipe necks down and follows a tight path between the engine, firewall, and transmission, which can limit flow and contribute to higher exhaust gas temperatures when the truck is towing or operating under heavy load. By stepping up to a 4" mandrel-bent design, this MBRP downpipe helps the turbo evacuate exhaust more efficiently, which can translate into quicker spool characteristics, lower EGTs, and a more responsive feel during acceleration.

As part of the ARMOR Plus line, the FS9CA455 is constructed from T-409 stainless steel, which offers strong corrosion resistance and stands up well to the heat and moisture typical of diesel exhaust systems. This makes it a solid choice for daily driven work trucks, heavy towing rigs, and fleet vehicles that see year-round use in harsh climates and on treated roads, where basic aluminized pipes can show surface rust more quickly.

The downpipe uses a two-piece configuration to simplify installation in the confined space around the 6.4L’s turbo and transmission tunnel, and it is designed to bolt directly to the factory turbo outlet while aligning with OEM-style exhaust components downstream. It is also commonly used as the front section in full MBRP and compatible aftermarket exhaust systems, allowing owners to build a complete turbo-back setup over time.

For owners searching for a “4 inch 6.4 Power Stroke turbo downpipe,” “MBRP ARMOR Plus T-409 downpipe FS9CA455,” or “2008–2010 Super Duty 6.4L stainless downpipe upgrade,” this part delivers a durable, warranty-backed solution. When combined with quality tuning, intake, and exhaust components, it supports better flow, cooler running, and a more enjoyable driving experience from the 6.4L Power Stroke platform.