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Hot engine, rich idle

Practical Standalone Tuning

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Hi Andre,

This is in regards to Step 7: Steady State Fuel Tuning of the Megasquirt tuning series.

At around 20 minutes, after you had finished steady state tuning, when you came back down to idle the CLT was around 98 degrees C. The measured lambda was sitting at 0.90, which is richer than the target of 0.95. As the CLT came down to normal operating temperature, the measured lambda went leaner and reached 0.95.

Would you be able to explain the theory behind why this happened please? Also, is it necessary and is there a method to correcting this?

Thank you,


There was probably a coolant based enrichment to protect the engine.