Grow room temp/vent problem/question.

Just finished setting up my tent. Carbon filter at the end, then short duct to reflector, out other side of the reflector out the tent to fan, then duct to outside. Pretty short run. Fan is 6" 430 CFM, 6" Blockbuster reflector. I went to test it today and my temps went up to 88 degrees. I'm pretty sure i'm getting good air movement. If I close the test up and then close the intake the whole tent sucks in like a foot. Why are my temps so high still. Damn it. One thing is this, the only thing is the tent is a box in the middle with the thermometer baking right under the light. Seems like a valid test to me, but am I getting accurate readings with this sitting right under the light?

Yep, that's what your plants are going to feel... Do you only have passive intakes open? If so a small duct booster fan will help bring in the much needed cool air, just make sure it is about half of the cfm's of your scrubbing fan. Also you might consider having a separate fan to cool the light and exhausting that air into another room so it doesn't add to the ambient air temps outside the tent.

Do you have tempered glass on your reflector? Is the reflector sealed?

What are your ambient temps (temps in the room you are taking the air from)? What is your exhaust temperature? When you say it vents outside, do you mean outside outside, or just back into the room around the cab?
What is the brand and model of the fan you are using? What size carbon filter are you using? Is the 6" duct completely stretched out? What light are you using? What dimensions is your cab?
BTW, depending on the fan, a passive intake is fine, but it should be 25% larger in diameter then the exhaust duct.
Kind