the popular Tial 50mm valve. Uses the same weld flanges as the original.
The QR's are set up to accept two different types of return fittings - 1" for Bosch style BPV's
and 1.34" for DSM and Evo type valves. This is the 1.34" variant.
The spring pressure in the valve does not correlate with the amount of boost pressure you
want to run. The size spring you need is determined by your engine vacuum at idle. Please
refer to the charge below to select the right pressure for you.