Heres where it gets tricky. Yes and no, the Ozzirt design is more efficient around 300-500 degrees but that is really it. Above that the oil seems to vaporize too quickly and burn too short to fully burn and thats with either design. I am going to modify our heater at some point and properly seal the bottom chamber and add more air holes to the secondary burn chamber. You need a hot lower chamber with little oxygen, and as much oxygen as you can get in the second chamber and if your design works out well I would say 600+ degrees should be no problem and produce very little soot.
My heater uses a 50 gallon water heater as the main body/heat exchanger, a piece of 10" cast iron plumbing pipe as a secondary burner and a cheap dutch oven as a primary. The exhaust is 8" stove pipe from Lowes and there is a lot of it in the shop (12 foot ceiling) so there is a lot of area for heat exchange.
Here is a pic of the heater please pardon the mess around it, its as bad as it looks lol
