passive intake/exhaust question

I have a 5x5x7.5 grow tent with a 600watt light/air cooled hood, with a 175cfm 4 inch fan. i want to set up a passive intake. Basically, what I want to know is if the 4 inch fan is enough, I think it is, based on the math.

Does the intake need 6 inch ducting if the exhaust is 4 inch? will this create a passive intake?
Can I hook the 6 inch ducting up to a 4 inch wall vent, will it be just as effective?
I will attach my grow room diagram/setup.

Thanks again!

I'm having trouble deciphering your reply, lol... What's not ok? go with 6 inch for both intake and outtake? how does this make more room...?

I think he is saying that the volume your air circulation moves is as important as the main room where your plants will be growing. For that grow space I would use a 6 inch inline to exhaust and 2 6 inch ducting passive intakes. By less noise he means you can get a fan speed controller to turn the 6 inch blower down which will be more powerful and quieter than a 4 inch blowing full force.

If you're stuck with the 4 inch fan just exhaust it like you would and use the rest of your ducting to make two light traps as passive intake. The idea is little resistance for incoming air making it easier on the fan to pull air through.

If you had 6 inch ducting you could also jerry rig two 6 inch clip on fans to the intake ducts for even more efficiency, Not quite forced intake, more like assisted