Today I ran some more experiments in getting my particular 28cm/11" bore furnace hot enough to melt iron. The plan was to have 50 PSI diesel feed my small brass pressure sprayer nozzles which gives a spray fine enough for a cold start on the diesel and then once it was warm enough withdraw the nozzles so that they sprayed the conical sheet stainless air nozzle on the inside: it should be red hot as it would be inside the furnace chamber and hopefully the diesel hitting the metal would vaporize it directly into flammable gas... or so the theory ran. At any rate withdrawing the nozzles made the temperature plummet each time it was tried. Even with the narrower 38mm/1.5" air cone the furnace seemed sluggish compared to normal and was slow to reach 1000 degrees C, where with the old larger air cone it could reach barely 1305 degrees C. I did notice that running it really rich, like on the verge of black smoke rich while at any fuel flow setting seemed to keep the temperature rising. Once I set the fuel flow to it's normal rate of just under 20 litres an hour and throttled down the air flow, I had the temperature rapidly rising and the furnace looking like a video of those Pakistani foundry furnaces with 60cm/2' yellow flames out the top. By now the furnace had been running for over an hour, and burned 20 litres and I switched over to the reserve tank and the furnace hit 1363 degrees C / 2495 deg F and the temp display went blank after that as the K type thermocouple melted at 1365 and climbing. I shut it all down and poured a 150mm/6" long iron ingot into a preheated steel mould with lots of solid iron oxide dross from the brake rotors in the crucible too. The ingot was cut in half with a grinder and seems sound inside, I'll have to drill it and see how hard it is.