Newb with grow cab question

Okay so I need to step it up a bit looks like my first grow is so far working out. I have almost finish constructing my cab. I would be done but due to lack of $$$... Anyways I'm on a budget so I have a can filter 9000 ready. My room is a tent I built out of black and white poly.

Here comes the math.

My cab is 5.5' x 5.5' x 7'tall = 215 cubic feet +/- 5 c3

I want to buy a 4" inline duct booster @ 90cfm. My run of duck work will be no more then 20' and a stright line.

Will I need to step up to a 6" booster fan?


Also I hear I could put my fan on a dimmer switch will this work?

Thanks a lot guys/gals.

You are going to need a real inline fan not one of those crappy duct booster fans. They won't be able to pull through a carbon filter. Check this link to a good inline fan for pretty cheap: http://htgsupply.com/viewproduct.asp?productID=52583

Thats alot of CFM isn't it... I should only need like 55cfm outtake correct. I will be buying a proper inline fan someday soon but for now the $25 booster will have to do. I wish I had the $$$

You only need 55 CFM to take out all the air once a minute... You want to take out all the air two or three times a minute so that it doesn't get hot