i’ve gone back on the engine ice, as while it has a far higher boil point as someone pointed out it doesn’t transfer heat as well as water. Axel the reason I am going along the hotspots is that all engines have them, ask TB, and some worse than others they have flow “deadzones” and bypass areas, sandcasting the barrels has engineering limitations and as well know everything is made to a market driven pricing system. Now usually if you run stock jetting/carburettion systems they run phat on the mixture which will help hide these issues, lean out the mixture to around the correct stoichometric ratio ato rerelease some ponies and they start to rear their ugly little heads. Mine runs about 4 pilot sizes beneath factory setup and the needle has a completely different taper (tri-tapered JD) which gives it unbelieveable boogie of idle, but also because it is burning more efficently and I run a very close tolerance skirt/bore ratio there is far more heat to be carried away, and any (notice I didn’t say “if”) deadspots in the cooling systems will be overtaxed and localised “steam pockets” can result, steam doesn’t do anything for heat transfer in this situation and so that area expands exponentially until something gets hurt.
This is why some of the old 24hr le-mans rotaries (which they outlawed in that race) had liquid cooled exhausts, to help get heat away from the exhaust ports where there were problems at high speed running.
Now a well tuned 2T has a fresh charge running back into and back from the pipe so the upper/large section of the port should be getting some incoming charge cooling, but the auxilary ports- (like the katos screw type) two sub-ports maynot benefit from this backwash of fresh mixture and it becomes superheated….easy fix= richer jetting, downside poorer performance.
These are some of the problems as i understand them, the fix is what rat and Bull have been working on, and from memory the GM silver and gold series screamers had similar issues back in the day.
BC
