Nightmotorsport EJ25 Oil Control Valve Cover Kit 2006-2014 WRX / 2004-2021 STI / 2006-2013 Forester XT / 2006-2009 Legacy GT
Subarus like all flat engines, blow a lot of oil out of the crankcase in their blow by gasses. This is always a problem with performance flat engines like Porsche or Subaru. The fact that the WRX and STI are turbocharged just makes the issue worse because turbo engines produce more blow by. When oil is ingested into the engine via the crank vents and PCV system, it contributes to detonation which will damage your engine, especially if is turbocharged. Oil can accumulate in your intercooler, reducing its effectiveness. Subarus blow so much oil that they can run the crankcase dry in one track session which obviously causes engine damage. Because of this, there is a big market for Subaru air oil separators. Nightmotorsport has another solution to help remove the oil from blow by gases internally by incorporating an improved air-oil separator into their billet valve covers.
The Nightmotorsport valve cover is CNC machined from 6061 aluminum billet. When looking inside the valve cover, you can see the big hump of the new air-oil separator inside the valve cover right in the middle. You can easily tell that the Nightmotorsport part has way more interior volume than the stock part and is much longer internally.
If you have changed plugs in your Subaru you know what a pain it is! Nightmotorsport has made the plug change much easier by relieving and adding this radius to the valve cover to make more room when getting the coil packs out to get to the plugs. This makes a big difference and makes it worthwhile to get these valve covers just for this feature alone. The Nightmotorsport valve covers have cooling fins machined into them on the bottom where hot oil tends to accumulate.