The Ticon 3.50 in titanium exhaust valve is specified as "closed with boost open," meaning the valve remains closed until boost pressure actuates it open. Sized for 3.5 in piping, this valve provides a compact way to alter exhaust flow based on boost conditions and uses titanium construction to minimize component mass in the valve assembly.
Ticon Industries 3.5in Titanium Exhaust Valve (Closed w/Boost Open)