Ignition Timing Explained
Ignition timing controls when the spark fires, measured in degrees of crankshaft rotation before top dead centre (BTDC). Get it right and the cylinder pressure peaks just after the piston starts down; get it wrong and you leave power on the table — or damage the engine.
The timing map
Like a fuel map, an ignition map is a table indexed by RPM and load. Each cell is an advance figure in degrees. Higher numbers fire the spark earlier.
MBT and the knock limit
For every operating point there is an advance that produces maximum brake torque (MBT). Push beyond it, or run cheap fuel, and unburned mixture can auto-ignite — knock (detonation), which destroys pistons and rings quickly.
Practical tuning lives between these limits:
- Advance timing to gain torque
- Stop short of the knock threshold, with margin
- Account for fuel octane, air temperature and altitude
Fuel quality changes everything
More advance demands higher-octane fuel. A map that's safe on race fuel can knock badly on pump gas. If you change fuel, revisit timing.
When in doubt, pull timing. A few degrees of lost power is cheap; a holed piston is not.
In MotoEditor
Ignition tables edit exactly like fuel tables — grid, 2D and 3D views, and the stock comparison so you can see precisely how far you've advanced from the factory numbers before you export your BIN.