Evolution 8/9 Supertech Black Nitride Exhaust Valves
Evo 8/9 Supertech Black Nitride Exhaust Valves
Production of our racing valves begins with a one piece forging, where the head of the valve is forged under a slow two-step process to keep a good material grain flow. The forging is then CNC machined in several steps to ensure the precision of the final dimensions. We then do another heat treatment for stress relieving followed by a nitride hardening treatment (or coating process depending on the application). Lastly, we do one more grinding, followed by our patented Superfinishing of the surface to ensure that each valve is free of any imperfections and the dimensions are precise.
This is a hardening treatment that even though it is not widely used as the chrome coating, it has several benefits and is becoming very popular, mainly for European and Japanese applications.
The microhardness is higher than the stainless steel base material, keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum).
Surface finish is smoother than with chromed stems, having less friction between stem and guide.
Valve seat surface is harder with the nitrided layer, lasting longer with lead free fuels, alcohols, nitro or other "explosive" mixes. Matches any kind of seats (nodular iron seats, steel powder metal seats, hard aluminum-copper seats or beryllium copper seats).
Higher rpm's engines take full advantage of all previous features. The higher the engine speed the bigger the power loss due to internal engine friction! The black nitride layer reduces this power loss due to less valve-guide friction.
The nitrided layer is adhered to the base material at a microscopic level, so does not "flake" or break when the valves bend due to impacts with the pistons.
The Black Nitride applies to the whole valve while the chrome coating is only applied to the stem.
All valves are swirl polished, have stem undercut and a hardened tip.