I know if you go higher you get HP.
Christian Ulberg
Hi Christian,
with your different fuel,
you need to try higher AND lower
to see which A/F your particular engine needs.
For example I would not hesitate to try as rich as 11:1
to see which direction to head.
The reason for this,
is some induction systems do not have the good atomisation needed
to support leaner mixtures,
or as I found with my own engine,
inadequate exhaust scavenging needed a richer setting to avoid power loss.
But for safety,
I would not go leaner than 12.5 personally,
but as discussed above,
some sensors may be used only as a "tool"
to detemine what YOUR combination NEEDS.
You also must try less ignition timing, particularly at higher RPMs.
Out of interest, is your quoted HP an "at the wheel" figure that you have converted to flywheel HP?