After a couple of my first cooks on my large BGE, I keep seem a behavior with the temperature I don't quite understanding and nothing I've searched in forums makes any mention of the behavior I see.
The rule of thumb seems to be to close down the vents to where you think it should be when within 25-50 degrees of target temp. Lets say I'm targeting a dome of 250 and I close the vents at 225. Based on everything I've read, after closing the vents I would expect the temperate increase rate to decrease and climb slowly toward my target temp. However what I see is that my temperature drops 100+ degrees first and then climbs back up but at a gradual pace. I've see the same thing happen on a 375 target cook today where I closed down the vents to the approximate final location (and this time leaving the top open) and the temp still dropped from 325 down to under 200.
Is this the behavior others see or am I doing something the wrong way? If this is normal, why wouldn't I just close the vents down at a higher temperature (25 degrees over target temp) to reduce the ramp up / stabilization time?