What ultimately causes the PCM to switch between the high octane spark timing table and the low octane spark timing table? Does it initially try using the high octane table and switch based on the tendency to knock? If so, what makes it look back to the high octane table?

I am getting mixed opinions on other forums, so I opted to ask the experts.

By the way, the tried searching older threads but came up empty.

 

I uses a biased value between the two tables based on the knock learn factor. If it never sees any knock it would use the high table. The more knock it sees the more it migrates toward the low table. Sort of a blend between the 2 tables. The less it sees, it migrates back toward the high table. According to the HP Tuners people, they say it moves back up much slower than it moves down.

 

High/Low Octane Adaptive Spark Scaler, ASPARK in EFILive. Well explained in the above post. Also fully controlable in EFIlive.

 

Great info. I knew I could depend on you guys.

 

After re-flashing with EFILive will it default to the High Octane setting immediately or is it still a slow learn process?

 

Defaults to the High Octane table after flashing.