When it comes to getting the most power out of your engine, the devil
is in the details. Paying close attention to how air flows into and
out of your engine is an obvious place to start making modifications
for optimal performance. A well-designed cold air intake and high-flow
cone filter are great ways to let your engine breath better, but a
filter on the end of a pipe has its limitations. If you've ever looked
inside an intake manifold, you've noticed a curved "bellmouth" profile
at the inlet of each intake runner. This bellmouth is added because it
increases the efficiency of air moving through the pipe by as much as
70% in the right situations. That said, the same sort of benefits can
be seen by adding a similar bellmouth (in this case a velocity stack)
to the end of your cold air intake.
Included in each kit is a velocity stack, filter, and a hose clamp to
connect the two together. The velocity stack has a 6" inlet and a 3"
outlet. All you need to connect it to your 3" cold air intake is a 3"
silicone coupler and (2) hose clamps. The velocity stack has a 2.25"
overall height. Fully assembled, the filter and velocity stack has a
6.25" overall height and 7.5" diameter.
Hybrid Racing recommends always running the filter on the cold air
intake. While slight gains can be seen by pointing the velocity stack
into oncoming air without the filter, this puts the engine at risk as
unfiltered air can cause unwanted debris to enter your engine.