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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?

Illustration 1 (fuel map found by qoncept):
FUEL_RPM_START = 0x20C74;
FUEL_RPM_STOP = 0x20C93;
FUEL_LOAD_START = 0x20C95;
FUEL_LOAD_STOP = 0x20CB4;
FUEL_START = 0x20CB7;
FUEL_STOP = 0x20DB6;



Illustration 2 (other fuel? map):

FUEL_RPM_START = 0x20DB7;
FUEL_RPM_STOP = 0x20DD6;
FUEL_LOAD_START = 0x20DD8;
FUEL_LOAD_STOP = 0x20DF7;
FUEL_START = 0x20DFA;
FUEL_STOP = 0x20EF9;



Thanks in advance for any advice,
-Steve.

I'm guessing one of the maps is a low det fuel map and the other is a high det fuel map.

I've found in some of the JDM ECUs, there are 4 fuel maps. I don't know what they all do. Oddly, they are all the same.

Mike

crazymikie wrote:I'm guessing one of the maps is a low det fuel map and the other is a high det fuel map.

I've found in some of the JDM ECUs, there are 4 fuel maps. I don't know what they all do. Oddly, they are all the same.

Mike

Thanks for your reply Mike. What to you think is the low det and the high det map in the above illustration?
-Steve.

I would guess the second one is the high det map- if you look at the last column, you can see how it's richer than the top one.

With the USDM car, after your advance multiplier drops to a certain point, it will trigger the car to switch to that map. I guess the EU models work the same way, although I've never really had the opportunity to work with one.

Please let me know if you have any questions.

Thanks,
Mike

Thats correct.

You can really tell that w/ newer models.

Thye pre 00 done seems to that the function,and if it does, not fully setup like the 00+, especially the 02+.

I know the pre 00+ pulls some timing, but the fuel consumption is not to bad.

Well I guest when colby and others are successful in pulling the Unisia JECS Corp roms, we will see then.

crazymikie wrote:With the USDM car, after your advance multiplier drops to a certain point, it will trigger the car to switch to that map. I guess the EU models work the same way, although I've never really had the opportunity to work with one.

Maybe my thinking is wrong, but I assumed the transition between hi det and low det timing and fueling was some sort of interpolation based on IAM. That is, if IAM is maxed, you run pretty much completely on the low det map. If IAM is somewhere in the middle, it interpolates the hi and low det map.

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?

Freon wrote:

crazymikie wrote:With the USDM car, after your advance multiplier drops to a certain point, it will trigger the car to switch to that map. I guess the EU models work the same way, although I've never really had the opportunity to work with one.

Maybe my thinking is wrong, but I assumed the transition between hi det and low det timing and fueling was some sort of interpolation based on IAM. That is, if IAM is maxed, you run pretty much completely on the low det map. If IAM is somewhere in the middle, it interpolates the hi and low det map.

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?

This is turning out to be a very interesting thread, raising more questions here than answers. Freon's theory here for IAM being used as a variance between these two maps sounds extremely plausible. I feel is this something we need to fully understand before playing with maps.

Can anyone else shed any light on how these two maps are used?
-Steve.

When the IAM drops below a certain threshold, it just switches maps completely.

The IAM will affect your ignition timing in steps- as the IAM drops, the overall amount of knock correction that the car can run will be limited (if you have an 8 in your knock correction table and your IAM drops from 16 to 8, you will only have a maximum of 4 degrees for that site), however, fueling seems to be one map or the other.

Mike

Please don't take this as the bible truth but I think there is a value in the ECU below which the ecu changes from low det to high det. On the cars around these parts(Singapore-Euro version ecu), the threshold value is 4. Thus if your IAM drops below 4 then more trips to the gas station, I guess.

Also, knock correction timing is pulled with lower IAM, not sure by what factor though.

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.

qoncept wrote: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.

that's my understanding as well.