ha! just kiddin. yeah the Cv rating is like a ratio you can use it to plug in some pressure and the Cv value and get a flow volume for a specific time.
I can't for the life of me remember where I saw the downloads available.
what is your application? what size cylinder are you going to control with it?
alot of valves used in paintball are 4-ways, direct acting and a few air-piloted models. most are from .11 Cv to .06 Cv.
SMC valves are great and they are used on racegun, e-blade, angels and some matrix models, but they are really proud of their stuff.
humphrey makes great valves and they are now used in excaliburs, some matrix models. but they are a bit hard to find
I use the 44 series MAC valves because they are cheap and easy to get. they are a bit bigger than the others, but they are very fast direct acting, and high flow.
some info can be found here: http://airsoldier.com/~haveblue/tech/
this guys website is a great source of info.
if I find that Cv equation download, I'll let you know in this thread.