45 Degree Transition Hose 3.5in I.D. to 4in

The 45 Degree Transition Hose 3.5in I.D. to 4in is an essential intake and exhaust routing component for performance automotive builds and engine modifications. Whether you're fabricating a custom air intake system, turbocharger piping, or intercooler ducting, this transition hose bridges the gap between mismatched diameter tubing with a precise 45-degree angle that minimizes turbulence and maintains volumetric efficiency. Mechanics and fabricators rely on stepped transition hoses to adapt between OEM and aftermarket components without costly custom bends or welding.

This hose features a 3.5-inch inner diameter inlet that tapers smoothly to a 4-inch outlet, engineered to reduce flow separation and pressure loss across the transition zone. The 45-degree angle geometry provides optimal flow dynamics for both positive-displacement and turbocharged applications, making it ideal for charge-air cooling systems, custom intake manifolds, and emission system rework. The flexible tubing construction allows for simple installation in tight engine bays without requiring rigid piping modifications, while the graduated bore maintains boost pressure stability and prevents compressor surge in forced-induction setups.

Fabricators, engine builders, and DIY enthusiasts benefit most from this transition hose when scaling up intake or exhaust piping diameters during turbo upgrades, supercharger installations, or large-displacement engine swaps. Its compact 14.17-inch length makes it suitable for tight underhood spaces while accommodating the angled routing common in modern engine bay layouts. Installation is straightforward—simply clamp or weld the inlet to your 3.5-inch tubing and the outlet to your 4-inch system component, ensuring proper alignment for smooth airflow and eliminating the need for expensive custom mandrel bends.