Originally posted by Jon [in CT]
I guess the results of your test will depend heavily on how Subaru has initialized the two ignition tables. Recall that, according to my research, the ECU will never retard timing below the values represented in the low octane ignition table and will never advance timing beyond the values represented in the high octane ignition table. I think the question comes down to: What octane fuel did Subaru use when it developed the high-octane ignition table? One possibility is that Subaru set up the the high octane ignition table based on the recommended fuel octane, 91. In that case you probably won't see a difference when doing a Vishnu reset while running 91 octane or 112 octane. But what if Subaru had observed that 94 octane was available in many parts of the country and chose to construct the high octane ignition table based on that? Or what if Subaru, because it was easy to do, simply inserted its JDM 100 RON table as the high octane ignition table? In these cases, I expect you would see a difference.
Great thread. What I suggest as to why the IGADV reset works is simple. You take a stock car, you slap on a boost controler and up the boost. This causes the ECU to default down to the low advance map and you loose power. In a sense you have exceeded the knock threashold of the octane you are using based on the conditions (more boost). Now you add in some higher octane fuel and perform the reset as described. Now you have the best of both worlds. High advance and high boost. As long as you add in the required octane you stay this way. But, in the end on sunday when you fill up for the weekly commute and add in 91 your ecu responds with the low advance map and or the ECU trims back troubled areas. You end up with reduced power.
I agree, It would be interesting to see some posts or better yet some graphs of the low and MTB ignition maps and some examples of the fine tune ignition retard map(dont know what to call this). This way we can see the effects of slight knock and the coresponding RPM points. It is also going to be interesting find out what these tuners are going to use as solutions to gaining more power and consistancy. In the end the ECUTEK is just a tool and it will all depend on what the tuner changes/adds. The idea of making the low map match the high map to me with my limited knowledge seems scary. I worry that tuners will end up blind folding the ECU which could cause major damage. In the scenario in the above paragraph would you end up running high advance and high boost with that 91 octane on the way to work monday morning? Is the suplimental retard map(the one based on knock) enough to handle the knock that could be present? Time will tell.
What I hope is that these tuners will take the time to learn how to make the ignition advance scheme faster with more advance for power, yet keep all safetys intact. Teach the ECU that its goal is to run the most advance that it can within reason and if knock happens that it might not happen again.. Something along the lines of the remarkable ME5 or ME7 bosch ignition scheme. Reset the ECU and you start out with a fairly agressive advance map. Run WOT a few times and trims are made per the 4-6 sensitive knock sensors. If knock occurs reduce advance in that area to stop the knock. Then on the next cycle give it right back. In effect, these systems "ride" the knock sensors. Maximum advance and consistant performance is the result along with higher effeciency and better fuel mileage. Maybe the Subie engines cant take slight knock like an Audi engine. Maybe the Subies knock sensors and related systems cant support that kind of sensitivity. Maybe I am dreaming... Its a good dream though.