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I know that the knock sensor could trigger the ECU to retard ignition timing. What else could cause the ECU to retard ignition timing, specifically under high load?

Basically I have noticed that the ECU would retard ignition timing when the engine is under high load. For example when I am accelerating quickly, going up a hill, or accelerating in a higher gear. Also the ignition would only retard timing up to 3000rpm. After 3000rpm the timing would advance as usual and the car will keep pulling with full power.

I have also noticed that when I am accelerating lightly or cruising around, the ECU would advance ignition as normal and everything drives fine.

There are no check engine light, and I am running 94octane fuel. The engine is not running lean and the long term and short term fuel trim is all normal close to zero.
AF is normal around 14.7 in closed loop.

There are also no knocking noise, at least not that I could hear it.

Also at IDLE and neutral the engine would rev fine and the ignition timing would advance as normal, usually around 30~40 degree. This lead me to believe that the ignition system itself is working fine.

Any one here have any suggestions on what could be the problem?
 

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Is this using data logging software? If so I would very much like to see your data. I have data logging software on the way and am going to be doing some parametric equations for fuel economy and perhaps eventually power.

There are several things but the biggest realistic thing I can think of would be high EGT which would certainly lead to retarded timing. How many miles on the engine - perhaps the EGR passageway is a little restricted.
 
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