...
It will only make adjustments to the running octane total when its is within the knock study area and the temperatures etc are all satisfied.
HI / Low Octane Mode switching and its Relationship to Dynamic Ddvance
If the ECU calculates that the octane is low, because the knock retard is high (octane level drops), it will swap into low octane running mode, in this mode timing can be added through the knock control system (i.e. dynamic advance) running the engine on the knock threshold of the current low octane fuel. This is likely done to keep driving performance at an acceptable level with low octane fuels.
When the ECU swaps to low octane mode it would normally change to a low octane base timing map and reset the knock retard value, after which it would try to start of advancing the timing (dynamic advance) until it finds the octane limit of the fuel. If tuning the OEM timing this would be acceptable however using RaceROM simplified ignition means that it does not change into low octane mode even though the knock retard and change to dynamic advance mode is still performed.
This means that if no further knock is determined it will add timing using the dynamic advance to the RaceROM base map value until knock is detected again. this may not be a desired attribute and can be prevented, please skip to controlling dynaic advance section for advice on this.
Octane to timing Conversion
The calibrated value for octane to ignition is approximately 1.4deg per octane number. when a change in octane is detected an amount of ignition retard is applied, see the flow chart and map values for how much this is. If no knock is detected it will increment at the rate set by the octane increase.
...
The simplest way to show how the systems integrate is using the below flow chart.
...
Controlling the Dynamic advance
...
The ability for the system to add timing above the tuned set point is sometimes not desired for example if the car is tuned on a known high octane fuel then usually used and further ignition advance is not desired even if it is possible.
To prevent the dynamic advance adding timing above the base ignition maps is to set the octane maximum maps at a point where on a full pull with the current fuel no additional timing is added, this is resetting the maximum octane that can be calculated and how much freedom the ECU has to add timing.Alternatively set the octane maximum maps to be the same as the 1D value for maximum octane, when the two are equal it should not calculate a difference to the target octane timing try add timing.map setpoint you can try the following methods,
Prevent it from swapping to low octane mode by setting the low octane judgment threshold very low.
Set the high and low octane 1D’s to the same value so when it swaps into low octane mode and calculates the drop in octane (octane estimate – octane setpoint) it doesn’t have a positive offset to octane drop/difference calculation.
Use the Dynamic Advance Limit (octane max) to prevent the ECU trying to add timing above an octane amount