1/4 Wave Tuning

[Donald Whisnant]

Hi guys...

Does anyone know the exact reason for the "1/4 wave tuning" modules (or that is
what GM shop manual calls them) on the intakes of a lot of vehicles??  It appears
to me that it is just an extra box or chamber in between the air filter and
the throttle body ... My Formula Firebird has one as well as most SFI and CMFI
injected pickups and vans) ...  My only guess is that it is a method of "tuning
the intake" kind of like length tuning of exhausts...  My next question is how is
it's volume calculated?  1/4 wave of what?  How much extra horses does it
produce (if any)?  Also, does the shape matter?  My Firebird has a round one
mounted vertically between the two cooling fans...  The vans and trucks that
I've seen with them have more of a square box mounted at the top (toward the
inside) of the radiator... ...  Can anyone answer these questions?? (or has
anyone even looked at or thought about it? -- as I never noticed until I
was hooking up a CMFI 4.3 engine that came out of a van into my '85 Grand
Prix and noticed it in several diagrams of the GM shop manual) ...

Thanks...
Donald Whisnant
dewhisna at ix.netcom.com