HELP!!! Intake/Exhaust Questions

I'm a first time grower...so please forgive my lack of knowledge.

Well I finally got a 400w HPS Grow Light System for my closet....but now I'm having big problems. My avg temperature is up to 87 degrees!!!

My closet space is roughly 2.5 x 6 x 6.

I currently have a 4" intake system from my AC unit into the closet. It works pretty well...but now I need something to control the hot air from my HPS light.

Currently, my only exhaust system is a small fan that's pushing air out at a very small rate...it's just not working well enough.

It really looks like I need a proper Exhaust system. My reflector is a Sun System Yieldmaster with 6" air cooling fittings on each side. It also has a glass lense.

Now here is my question....

Should I install a duct that runs from the 6" reflector fitting to the outside of my closet? If so, what type of inline fan will I need to suck the hot air away from the light? Does my exhaust need to be bigger than my intake? The same? Or does the intake need to be bigger?

Thanks for the Help!!!! I really appreciate it.

90 cubic feet can feel like a pretty tight space using a 400 without some efficient cooling. You're probably gonna want to look into getting a blower, one that'll move at least 3 times the volume of the area(<270cfm). Have it pulling directly out of the hood and possibly into a wall will assure that hot exausted air isn't being sucked right back into the grow.

Thanks for the advice.

Now when you say "blower"....that's just the same as an inline fan? Right?

I saw one for sale at my local hydro store for $50 bucks and its 188 cfm....is that a good deal? Will that work?

Thanks.

Inline means it sits in the line of the movement of the air, if that makes any sense. A centrifugal blower will do exactly the same thing when it comes to air movement, it just isn't as space efficient because it doesnt sit inside or inline of the ducting. Don't quote me on this but I think most inlines are a little more expensive too, depending on how much air you're tryin' to move...

Again, because of how tight your space is, your going to want something that'll move at least 270CFM. Just so your not constantly fighting your temps. 50 bucks sounds like nice price though, for how much air that thing will push.