Closed for me and I give it enough time to reach temperature and stabilize. I don't know how it figures out how much fuel to feed but it seems to me that opening the lid during the preheat messes that process up.
specially on the new units. The ignite and preheat is all one process.
can do lid closed on the older units as well. Just make sure it lights and does not fill the pot with pellets without lighting. The. You have a boom on your hands.
Agree, lid closed, not only does it speed preheat but the newer ones monitor the temp and look for the grill to be heating up within a certain time window or it will spit out an error. With WiFire it pushes an alert "ignition fail" message.
Even with all this my 850 has both failed to light within the window and failed, it has also over filled the firepot and had a decent flare up so they aren't perfect yet.
"With the door open, turn the switch ON (I) and the temperature dial to SMOKE. In about 2 minutes, the pellets will ignite and whitish-gray smoke will come out of the grill. After the pellets have ignited, close the door and turn the temperature dial to any cooking setting desired. Allow the grill to preheat for about 10 minutes with the door closed before placing food in the grill."
I'm new to Pellet smoking and to Traeger, but I figure the manufacturer must know what's best. And, it works for me.
I have a T850, ignite with lid down. I have had overtempt shutdown issues if I set the temp too high at ignition. Support says that they tend to overshoot temps when igniting so is best to set the temp below 300, after start up temp reached, then increase higher as needed. This seems to work solid for me now