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| E3 spark plugs |
Here I study the ignition timing @crank before TDC. A closed-wedge chamber is used. Gasoline is used where the air-fuel ratio is 12.5.
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| variable timing vs fixed timing |
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| Measurement data |
Advancing the ignition timing means that the spark plug fires the air-fuel mixture in the cylinder sooner and the timing is always measured in degrees before TDC. Increasing the timing advance raises the high-end power but the low-end power is reduced. In contrast, decreasing the timing advance raises low-end power but weakens the high-end performance. If the advance is too much, the engine will suffer from pre-ignition where the efficiency of burning air-fuel mixture is poor.
On the other hand, retarding the ignition timing minimizes the effect of detonation. However, if the retardation is too much, the engine will lose power.