Currently I'm running my unleaded-converted x-flow on super unleaded petrol so that I can use the original leaded petrol ignition settings (or close to them anyway - I've got Megajolt now so have remapped).

Shortly I will be setting up a switch to allow dual-mapping, and will be using the 2nd map for standard unleaded, for times when I can't get the good stuff (or can't be bothered to pay the extra).

So the question is, what should I use as the base point for my ignition map? Originally it was 10 degrees BTDC for leaded petrol, and currently it's 12 BTDC for super unleaded. 7 or 8 degrees seems a reasonable starting point - any views?

I'll then take my current map and notch all the values down a bit to match, and then develop them later.

cheers,
David

I used to run my crossflow with a maximum advance of 36deg and idle of 15 deg and normally used lead replacement and octane booster additive.I did find that it ran ok with plain unleaded when I tried it with out octane booster apart from if allowed to labour up hill.
The base timing is not as important as the advance on full and medium load sites, remember that with a dizzy you had to retard the whole thing but with mappable ignition you just alter the parts of the map that are required.
Paul.