O.K Not sure why but I am going to try and help further more Think of the way ECU's work. Inputs tell it what is happening, ECU makes calculations and controls outputs to change the running conditions of the engine Inputs talk to the ECU Outputs are direction from the ECU The CAS is an Input, so tells the ECU what is happening When you set the base timing to 15 degrees, that is setting the BASEline for the timing, its point of reference. ECU shows input of 15 degrees ECU fires coil packs at 15 degrees BTDC using the data obtained from the CAS. The coil packs are an output As per above, unplugging the TPS on stock ECU is the best way to lock the timing, it is obvious when the ECU is altering the timing as you can see the timing jump around (a couple of degrees only) If you are getting roughly double the expected value, I believe this is due to setting the timing light using the wire loop and not the plug lead method Now think about this. Assuming your ECU is locked at 15 degrees output and is outputting signal to fire at 15 degrees, what should the input (reference) be? A bit like your knock sensor discussion, I feel like you are overthinking it.