Originally Posted by Chip

Dojj, there is not really much to explain in terms of what the numbers mean:


For example

6990rpm:
26.75° at 0.24 bar


So it will fire the spark plug 26.75 degrees before the piston gets to the top of the bore at 6990rpm at 0.24 bar of boost.


As boost rises, you expect ignition timing to fall, in order to prevent there being too much cylinder pressure.

Too much cylinder pressure will cause the fuel/air mix to explode (detonate) rather than burn, this can damage pistons as it puts massive loads on them when it happens.