| Under certain cold-start conditions, the ECU switches to using a secondary ignition map instead of the regular maps. This secondary map forces the timing to between 15 and 20 degrees BTDC (dependent on RPM). This retarded timing causes the EGTs to spike and my understanding is that it is used to rapidly heat the catalytic converters up to their operating temperature. This is actually a common technique used in OEM engine management systems for reduced emissions on cold-starts. The exact conditions under which the ECU uses the catalyst heating map are as follows:
- Coolant temperature measured at engine start was between 15C and 35C
- Current operating coolant temperature is between 30C and 55C
- Engine RPM is less than 2600rpm
- Engine Load (TP) is less than 44 (for 370cc injectors) The easiest way to test for this is to see if timing immediately returns to normal once coolant temp hits 55C, or when RPM goes above 2600rpm.
Sam
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13:25:57 01/06/14
