YOU pick which fan, goes where (PIC)

You are trying to air cool a 400w sealed lens in a Homebox.

You have an 80 CFM and 265 CFM fan to work with.

The fan with odor can also doubles as passive intake (flaps rolled up) for fresh air.

Which do you put where? I'm thinking 265 does the can/intake work.

It it were me, I'd put the larger fan on the exaust. You want a negative pressure in the box for cooling.

This is how you set it up properly...

Unfortunately, if you are using AXIAL in duct fans, I am afraid they will not do the job...

AXIAL fans loose too much cfm too easily...

You need CENTRIFUGAL fans, which can hold cfm under pressure much better than the AXIAL fans...

I say you use a 4" centrifugal fan rated around 170cfm, but remember, it will hold cfm much better, the duct isn't smooth, there are bends...

Better to save up and do it right the first time than waste time and money to get frustrated with less than ideal yields...

My 2 cents...

go with what you know...

Nice setup and thanks guys, but sigh, I knew this would happen.

The question is not what's the ideal cooling setup, but rather what would you do given these two size fans.

I know it's not ideal, but it's what I have and I want to keep everything INSIDE the homebox.

I would then try to make it work like this...

I would use the bigger fan for the light... put the fan on the cold side, pushing air for better results...

and use the smaller fan as an exhaust...

If this doesn't work, try the reverse...

But you will really need a better fan...

Regardless of which fan you use, the way illustrated will be the easiest way to control your temps... shortcuts will only hurt you...

Best of Luck...