The ignition maps control the timing of the ignition spark, the values in these maps are typically degrees before top dead centre (BTDC).
The values in the ignition map tables are usually degrees of advance i.e. degrees before the piston is at the very top of its travel.
Ignition timing is very important because it will affect how efficiently the combustion of the air-fuel mixture translates into power output.
- If ignition timing is set too early, the expansion of gas will try and push the piston downwards while it is trying to move upwards towards the top of its stroke. This can also cause pre-detonation which can increase engine temperatures, and cause severe damage to the engine, particularly under high loads.
- If the ignition timing is set too late, the output will not be used effectively as the expansion of gas will be trying to catch up to the piston while it is already moving downwards. This can also cause backfire to occur from the exhaust.
If you are going to advance the ignition, make sure to make a small change and test the bike before advancing it further.
One method for tuning ignition maps is as follows:
- Tune Fuel Maps for correct AFR
- Establish base torque curve with stock Ignition maps
- Add small amount of advance (e.g. 1 or 2 degrees) to ignition maps
- Tune fuel maps to correct for any changes to fuelling due to additional ignition advance
- Test on dyno to determine if additional ignition advance has improved torque curve
- If torque has improved go to step 3 above and repeat.
- When torque stops increasing after adding additional ignition advance, reduce ignition advance by 2 degrees to be on the safe side
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