Found this while searching for a MAF..
Introduction
If you have just
reset your ECU or
reflashed it with a new map you may know that this also resets your ECU learning data. 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.
Background
There is something called Ignition Advance Multiplier (
IAM). 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 ECU reset or ECU swap defaults to 8 and usually creeps up to 16 (if well mapped) 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 (Newage WRX)
- With the car fully warmed up, reset the ECU.
- 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.
- 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 our reset or reflashed ECU, is worth an immediate 10–20 BHP.
Fast learning procedure (Newage STi)
The procedure is slightly different for STi’s.
- First you have to reset the ECU.
- Then let the car idle until it is fully warmed up in closed loop fuel control.
- Then hold approx 4–5psi (0.3 bar) of boost at 3500rpm for 3–4 seconds. Again left-foot braking will help you maintain a constant speed. This usually results in a increase of 20 BHP. This is something that you would probably see eventually over the course of a few days of driving. But this takes a few seconds and is great for those who are dyno testing/tuning or are just really impatient
Warning: This little trick artificially speeds up the learning process. This is only a good thing if the re-mapped ECU is mapped properly. If there are trouble-spots where knock is present, this trick will make it even more present. So be careful!