crispyduck wrote:I've been validating qoncept's reverse engineered
hex addresses of my
Euro MY03 WRX. In doing this I came across what appears to be two fuel maps. They are only slightly different. The above ROM image is stock (no 'external mods'). Does anyone know what this is all about (see illustrations below)? Are they both used? If so, under what conditions?
In all of the ECUs spiider has posted offsets for, the low det map comes before the high det in the image. I assume that this was probably a pretty consistant practice, and so far it seems to hold up.
Freon wrote:I wouldn't see the point of IAM being more than 1 bit flag if the map switching was one or the other.
Maybe this is just for timing, but not fuel?
I'd never really thought about it and I certainly don't know for sure, but I did assume there was just a point at which the ECU switched from the high to low det fuel map. And yes, that the IAM was basically for timing, and anything else that depended on the IAM (fuel, boost, etc) was incidental and done because using the IAM worked rather than having to create a new variable. I think if it were variable or interpolated, it'd be called a "high det fuel correction" map or something.
Basically, this is my assumption: the ECU monitors the knock sensor and driving tendencies. If conditions are right, it'll raise to 16. If you're knocking, it'll reduce to whatever the car can run safely at, which in turn reduces timing advance. If it reduces past a certain point (4?), the ECU will run in a "limp mode" -- no boost control, high det fuel map, whatever -- because something is obviously wrong.