How it Works:
The OAR starts life at a value of 0.0 and is allowed to learn in both directions. When fuel and sensor feedback are optimal the OAR will adjust towards -1.0. When the feedback is less than optimal the OAR will trend towards +1.0. It's likely that you're now wondering why it is that the multiplier is negative when it's happy and positive when it isn't, the reasoning is that the value is not a multiplier and not an offset, thus the ECU code can be simplified and use just a single table comprised entirely of negative values to cover the entire spectrum of operating conditions. With an entire table of negative values it will be multiplied against, the negative multiplier from the optimal correction get's cancelled out into a positive timing correction, whereas the positive OAR value which is asking for things to get dialed back becomes negative and lowers the agression of timing.
OAR however does not just impact the timing. In the event that fuel quality is less than optimal other strategies step in to remove stress and prevent damage to the engine automatically. LSPI (low speed preignition) uses the OAR multiplier in order to blend several different load limit references in order to reduce the possibility of pre-ignition (detonation or knock). Part-throttle combustion stability strategy uses the OAR to allow for casual driving at moderate load and allow for leaner fuel ratios to increase MPG but at the expense of heat. Since this heat is generated much more rapidly on lower octane fuels which are already prone to detonation, the OAR steps in and makes adjustments in order to stave off the potential for disaster, while allowing your high horsepower machine the benefit of some decent MPG.
We here at COBB make an effort to utilize as many of the OEM tuning strategies as possible in order to offer the most advanced, powerful, and safest driving experience for you. The majority of our calibrations utilize the OAR multiplier in the same fashion as the factory tunes do, however on our higher power tunes we want to be able to maximize performance for the specified octane, as a result in the event of even minor knock being sensed by the ECU we aggressively shift the OAR towards positive which lowers the agression of all values affected by the OAR. Since we designed the OAR to be utilized in our tunes in order to maximize the potential of the available fuel type, it's very important to run the proper calibration for the fuel octane you are running. When you initially install the Accessport the OAR will be reset. Since OAR is a KAM (keep alive memory) stored value it may take a few days of driving in order to fully settle, however once learned the value will persist through start-up including when you change the map on your vehicle by using your Accessport. The value may change from time to time based on knock sensor feedback and is completely normal and expected.