Bob Jones wrote:OK, my first post, I hope I'm doing this correctly. I have also, been searching for an answer to this question for a long time. I don't think anyone really knows. They all just use the size/dimensions that someone else posted. I too am looking for the CSA/Burn Tube/Feed Tube/Riser ratios. I assume it must be volume related, not length. I'm thinking the same as you. I want combustion that roars like a "rocket" and flame that just reaches the top, then I can cover it and the gases are now done burning at the top and starting to cool going down. I can't seem to get the ratio right to achieve the "rocket" sound. Hopefully, someone with experience in the ratios will see this post. There has to be a "perfect" ratio to achieve complete combustion and the "rocket" effect. Have you had any more luck with yours? I have started playing with a bunch of varied lengths of pipe to try to find a ratio that works. I'll let you know.