Here's the situation:
I've got a brand new DBS4 which is in my shed vented to the outside, therefore wind & external temp shouldn't play too much of a roll with the oven temp.
Here's a pic of my set-up -

I've got 11 pounds of ribs spread across the 4 racks.
I admit I forgot to pre-heat the smoker to the required temp of 270 F, however I have the temp maxed @ 320 F and the door kept shut and having a hard time hitting achieving the required temp of 270, it's holding around 240 F.
Why do you think this would be? Too much meet in the smoker? or simply cause I didn't pre-heat it?
As I only ran the smoker for 80mins once that was done I closed the vent at the top hoping the temp would reach 270 but no.
Any thought or feedback is appreciated.
Here's the recipe I've got going right now for those who are interested -
http://allrecipes.com/Recipe/Sweet-Smoked-Pork-Ribs/Detail.aspxCheers,
G