Not sure sure about that, mine started at 2 turns out, and really sucked it down, but i've been leaning it out a few clicks each weekend running around 1.25 turns now and getting a few more minutes out if it, (almost 10 now) the temperature is stil quite low, 150-160 degrees on a hot day, so it seems there is room for more improvement. Someone wrote that he is using a tuned pipe and got a big boost in power and efficency. i hope to try that out in a few weeks to see for myself i don't remember what the claimed time was but it think it was around 15 minutes, not too shabby i think.