ZRP Std intake valves with black nitrided finish for Audi VW Volkswagen 3.0L Turbo RS4 RS5 EA839

ZRP standard intake valves with black nitride coating for Audi/VW 3.0L Turbo RS4/RS5 (EA839) (Set of 12)

ZRP standard black nitride-coated intake valves are designed for Audi RS4 and RS5 EA839 biturbo engines. Engineered for high-performance and high-boost applications, these valves offer exceptional durability, dimensional stability, and long-term reliability under demanding thermal and mechanical conditions.

Manufactured from high-quality, one-piece forged stainless steel (EV8/21-4N), each valve undergoes a specialized black nitriding process. This advanced surface-hardening treatment diffuses nitrogen into the outer layer of the valve, significantly increasing wear and fatigue resistance while reducing friction between the stem and guide due to the hardened, smoother surface.

Unlike localized chrome coatings, the entire valve—both the stem and the head—receives the black nitriding treatment, ensuring uniform surface protection and an extended service life. Each valve is precision-forged, CNC-machined, polished, and tip-hardened to meet strict dimensional tolerances. This ensures precise valve seating, stable operation at high RPM, and consistent sealing in turbocharged EA839 engines.

Technical Specifications

Base Material: High-quality stainless steel (EV8 / 21-4N)

Surface Hardness: Nitrided layer up to approx. 800 HV

Manufacturing Process: Precision forged, CNC machined, polished, and tip-hardened

Treatment: Full black nitriding of valve stem and head

Dimensional Accuracy: Strict tolerances for concentricity, straightness, and sealing surface finish

Advantages

Reduced friction between stem and guide for less wear

Increased stability at high RPM

Longer service life compared to untreated stainless steel valves

Reliable sealing in high-performance turbocharged engines

Suitable for street, track, and endurance racing applications

Additional Information

Set Quantity: 12 valves

Valve Size: 33.85 mm / 5.98 mm / 104.00 mm

Engine: Audi RS4 / RS5 EA839 Twin-Turbo Quattro

Material: Black nitride