Originally Posted by cdelong
my point is that you can't just say..... richen the engine when it's hotter out.
that does not work except if you are just tuning for temperature and not performance. An aspirated engine- be it two or four stroke is designed to run at a narrow range of air fuel mixture for optimal performance. Tell me how richening your engine when it's hot accomplishes this? It doesn't
For example: a normally aspirated engine (which we have here) needs around 12 or 14:1 air(oxygen)/fuel mixture. If there is less air (oxygen) when it's hot, the engine needs less fuel to run optimally (performance wise). I'm not saying it won't run.... it just won't run optimally.
On an average race day you run rich in the morning when it's cold and leaner in the afternoon when it's hotter. By the time the mains roll around it's time to richen them up again as the sun is setting.
If you don't understand that I can't help you any farther.... it's simple physics
you make it too damn hard...it's simple my way and works. Use a good baseline and go from there. It's alot easier to have some base settings to start from, leaning out from there until the desired performance is reached.
It's not rocket science at all, as much as people like to make it seem. It's quite simple and doesn't require a complicated formula to figure it out.
What you'll have if you simply tell ppl to run leaner when it's hot is people closing off their carb then complaining about pitiful performance or an overheating engine. It is ALWAYS safer to go more toward the rich side rather than the lean. When in doubt go a bit richer and work from there. The only reason I lean a bit on cold days is because I find my engine to run poorly when not up to temp so I induce higher temps with a slightly leaner mixture. 1hour is very very small adjustments, almost hardle turning the needle. I'm not telling people to do full turns.
If you don't like the way I or anyone does it, don't use it. He was asking for temp info and I was still correct, 90c is pretty cold but if performance was good it's ok as each engine is different and temps are a pretty hard way to tune a small engine.