What is the benefit of loging Octane scaler ?

[wesam]

What is the benefit of loging Octane scaler ?

[joecar]

It shows you how quickly the adaptive spark mechanism is reacting to knock and how quickly it recovers... on some vehicles the recovery is way too slow.

[wesam]

when i log it how could i know from the loged number that its recovered

[joecar]

E38:
E38.OCTSCL_DMA
octane scaler is incremented towards 100% when knock is detected;
100% = running from LO spark table
0% = running from HO spark table
(so if it reads 0% then it has fully recovered)

LS1:
GM.ASPARK
goes in the opposite direction to the E38 octane scaler
octane scaler is decremented towards 0% when knock is detected;
0% = running from LO spark table
100% = running from HO spark table

High/Low Octane Adaptive Spark Scaler { E38.OCTSCL_DMA }

Units: multiplier
Range: 0 - 100%

The high/low octane adaptive spark scaler is an indicator used to determine the percentage of correction used from the high octane spark table values to the low octane spark table values.
The scaler is incremented towards100% whenever knock occurs, when knock is not occurring under the right 'learn' conditions the scaler will be decremented towards 0%.
For those used to monitoring this PID on an LS1 engine, it works the opposite to the LS1, where the LS1 at 100% meant the high octane table, not the low octane table like the E38 does.

As an example.
If the high octane table has a value of 20degrees and the low octane table has a value of 10degrees at the same RPM and load point and the octane spark scaler is at 0%, then the timing figure from those two tables would be 20degrees. (Use 100% of the high octane table value).
If the octane spark scaler was at 50%, then the timing figure from those two tables would be 15 degrees, which is half way between the high and low octane table values.
If the octane spark scaler was at 100%, then the timing figure from those two tables would be 10 degrees, the high octane table values are not used at all.
The PCM will set the octane scaler to 100% whenever a MAF or Knock Sensor DTC is set.

[wesam]

Is the octane scaler been reset after the ECM flash ?

[joecar]

I don't know.

[GMPX]

On LS1 from memory yes, but not E38's.