Q: Why should the OEM valve be replaced?  
A: The OEM valve is what is commonly known as a diaphragm valve.  This valve has been

since the mid 80's and has always been a very problematic part that typically wears out within
the first
6 months of operation.  An improperly working diverter valve will cause multiple problems.  First
of all,
a improperly working or defective valve will cause boost loss.  We have seen a 7-9 HP gain on
dyno on a small displacement motor just by replacing a worn out OEM valve with our Billet
Second, in between shifts when the valve is suppose to open to re-circulate the built up boost
pressure, if it is defective and cannot open, the built up manifold pressure will "stall" the
of the turbocharger causing it to rapidly slow down which can cause turbocharger failure. This
"stalling" of the turbocharger will also increase turbo lag in between shifts and reduce power.
Blow off valve

Small blow off valve, one inch inlet tube six 0.327 in outlet holes. Can be mount or weld on.

Blow off valve

Large blow off valve, one and half inch stainless inlet tube.


G type BOV with flange welded on 3 x 6 inch aluminum tube, the tube wall size 3.5 mm thick.


Stock fitting for

PORSCHE 951, 965, 993 TT 996 TT

For Porsche 930 to convert to 965 style intercooler.

Comes with 4 level of springs for different pressure setting.

G type BOV