|While the debate over the merits of blow off valves (BOVs)
is sure to continue, what remains is (as was so eloquently said by someone),
those that have them, love them; those that don't, simply don't understand.
Check out the FAQ section for a detailed explanation of the theory behind
blow offs. They essentially replace the existing recirc valves and in the
process add a very cool 'pssshhhh' sound when shifting. BOVs
are made by several of the big manufacturers such as HKS, Greddy and Blitz.
This install covers the installation of the APEXi BOVs (1.). I chose
them due to both the low price, and the distinct look. They may not be
as loud, or as high pitched as some of the others, but they work well for
Socket wrench and 8, 10 & 12mm sockets
10 mm box wrench
5mm hex wrench
Long screwdriver (optional)
1. Remove the factory re circulation valves. Use steps 1-7 of the TwinPOP
Installation TECH to remove them, it covers the passenger side recirc
valve. The procedure is the same for both sides. This does not cover the
(unlikely) possibility of having the stock air box in place. If this is
the case, reference K&N TECH for details
on removing the stock air box.
2. Plug the holes in the intake piping with the rubber stoppers included
in the kit. The hole is where the other end of the hose coming out of the
stock recirc valve is going to (red dot in 2.).
3. Start assembling the BOVs. First attach the small hose (green dots
in 3.) between the two fittings on the BOV. Remember to put the
hose clamps on the tube before pushing them on the fittings. Put a little
WD40 on the fitting, it makes it MUCH easier to put the rubber hose on.
Bolt the chrome tube to the BOV (4.). Remember to put in the gaskets
supplied in the kit. Note: while the diagram included in the kit shows
the bolts going in one direction, they must go in the other (the nuts simply
won't fit on the BOV side). Now put a copper connector in the end of one
of the long hoses (don't forget the hose clamp) and the other end of the
connector to the small vacuum line pulled out of the top of the recirc
valve (removed in the second part of step 7. in the TwinPOP
Installation TECH) to extend the lines.
4. Push the end of the chrome tube into the lower tube that looks like
it's coming from the engine and tighten the clamp. Connect the mounting
bar on the chrome tube to the recirc valve mounting hole closest to the
front of the car. On the passenger side, take care not to gouge the A/C
lines. The lines rubbed against the brace on my car, so I *carefully* bent
the brace where they didn't rub anymore. The A/C tubing is soft aluminum,
so the brace would probably gouge a hole in the line. Not good! Other cars/BOVs
might fit differently. Finally, push the end of the long small vacuum line
onto the front end of the BOV (blue dot in 3.). Don't forget the
hose clamp! Repeat on the other side.
5. The installed valves should now look like this (5.). Turn
the red dials to adjust the sound (yellow dot in 3.). Supposedly,
the smaller hole is louder.
6. Adjust the pressure release spring tension by using a hex key to
twist in the screw (5 mm hex wrench, red dot in 3.) on the end of
the BOV, there is a 12 mm lock nut to loosen first. I was able to hit full
boost without any adjustment, but according to APEXi, the screw should
only protrude 2-4mm. Experiment with it, just keep in mind the further
the screw goes in, the higher the boost required before the BOV releases
pressure. Too little spring tension will cause erratic boost response.
WARNING: A tight valve results in better boost response between shifts,
but may cause some excess boost pressure to flow back to the turbos. Tightening
the valve too much could potentially damage the turbos through compressor
surge (see Z32FAQ on merits of BOVs).
7. Reinstall the filter & panel and it's done! (6.).