Big increase in heat out put. Changes made include Insulating the burn chamber and adding Secondary air inlet to the low pressure area of the burn chimney. Burn time 10 hrs. on one broken up pallet with a little left over. Right after this was recorded I cut down the burn chimney by 4in. and hung the mortar back over it. In 2 hrs. the 1 ton cast iron mortar was so hot you could not touch it with your bare hand it took more than 5hrs. Last time to accomplish this without the Vortex Generator and Secondary Air.