Below is a little trick I found on a Subaru forum that has been shown to accelerate the factory ECU’s ignition timing learning process. This procedure is commonly known as the Vishnu Reset after the company, Vishnu Performance, that wrote this on a Subaru forum (it works!).

Background

There is something called Ignition Advance Multiplier (IAM) as part of the OEM ECU software. It represents, by some complicated algorithm, the average learned positive knock correction applied to the ignition maps. It’s represented in 1/8th degrees increments. 1 being the lowest and 16 being the highest (1/8 to 2 degrees in absolute terms).

The “happier” (knock free) the car is, the higher the number will be. Conversely, the lower it is, the more knock prone it is.
This number, after an ECU reset or ECU swap defaults to 8 and usually creeps up to 16 (if well mapped, over a week to re-learn) through normal driving. Depending on driving characteristics, this can happen within a few hours or a few weeks. Well, here’s a way to make it happen in about 5 seconds ….

Fast learning procedure (GC8 WRX)

1. With the car fully warmed up, reset the ECU.
2. Drive to a nice open road without traffic. Don’t go on boost until you get there. Put the car into gear (3rd gear works the best) bring the revs up to 2600rpm.
3. Push the accelerator pedal down slightly so boost stays around 2–4psi (~0.2 bar). You will need to MAINTAIN 2500rpm and 2–5psi for approx 5 seconds (You can do this by left-foot braking gently as to prevent acceleration).

During these few seconds, the advance multiplier (which you can’t see, so you’ll have to trust me) will go from 8, to 12 and then to 16. Works like a charm. And on your reset ECU, it is worth an immediate 10–20 BHP.


**The information above has been pulled from another Subaru site, but it works quite nicely and may add the pep back to your stock ECU if it's been feeling flat to drive**

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