2byte load's
 

Hi Guys,

This is a bit more of a technical request for discussion.

The ECU (IX at least and probably others) uses different load variables for timing and fuel map lookups.

I have traced it back to the MAF_Scaling routine and they are all based on the same source.

Now the fuel map uses a pretty raw 2byte load that comes straight from MAF_SOURCE0 x MAF_SCALING.

The timing map(s) uses a slightly modified version of the above - which apparently brings some fuel_enrichment parameter into account.

Any ideas as to why this is like this?

I will be doing a log of both variables tonight - and will post the results tomorrow.

Cheers
David

Dave,

Here is a little input from Bez (the last post on the first page): https://www.evolutionm.net/forums/sh...highlight=load

I remember Bez talking about the different variables, too, and I think more info is on AktiveMatrix.

Nonetheless, I would be interested in seeing your results.

Edit: Actually, I have a question for you. Notice that Bez says you can log the air mass, trimmed, through MUT 28. Could you tell me how to log this 2-byte, if possible?


Eric

Also. Mrfred made a post about this.

https://www.evolutionm.net/forums/sh...d.php?t=288214

I did a log of the three load variables that are used in Fuel and Timing routines;

0xFFFF6B22 and 0xFFFF6B28 are used for Fuel, there doesn't seem to be any reasoning behind the choice of these 2, I have logged the variable that makes the decision as to which (22 or 28) load var to use and there doesn't seem to be any correlation to events in the car.

0XFFFF6B28 and 0xFFFF6B26 are used for Timing, it would appear that the ECU uses 26 when the air_temp's are above 65 which according to a log is basically all the time.

note - these variables are only good for 88580013/14 ROMS they wont mean anything in the other ROMS.

Cheers
David

Interesting results. Looks familiar...a lot like graphs that Bez posted in his SD research, if I am remembering correctly.

Have you read through that post on AktiveMatrix before? Maybe it will give you a bit more information that you are searching for. I have no skills in disassembly, so I can't help you with this. :)


Eric

hrmm well I am just trying to pick the best load variable to use - I dont really want to have to log all three :)

You should see the IGN routines, what a nightmare, I am logging 3 different timing outputs at the moment.. but thats a whole other discussion :(

Did no one look at the link to mrfreds post??

Yes - but his loads are different again, more around boost control :)

unless I am missing something?

edit - reread his posts, yes he has found the same thing as me.

I guess I am trying to find out what these loads represent, are some of them temp corrected etc etc?

Just going through this, 0xFFFF6B26 (and 28) seem to be barometric compensated load variables.

does that make sense to anyone that understands how a baro-reading affects AFR's/air density...?

Yes, that makes sense. Load should incorporate baro and intake temperatures to arrive at a mass airflow/rev.

I think I remember Bez saying that the 'main' load variables has all of this compensated already, but there are other variables if the temp sensor or some other sensors don't work.

Maybe the other load variable are estimated load without the baro or maybe temp sensor's data??


Eric

so far, basically:
0xFFFF6B22 = MAF_SOURCE_0 * maf_size (value is 0x9884 in my ROM)
0xFFFF6B26 = 0xFFFF6B22 * some baro thingy / 128

Ok this is interesting,

0xFFFF6B22 is the 2byte of MUT1C before the 160max gets applied.
0xFFFF6B26 is a baro compensated 6B22
0xFFFF6B28 is a baro AND temp compensated 6B22
0xFFFF6B24 is a temp compensated 6B22

Now 24,26 and 28 also have 160max MUT's just like 6b22 (...MUT1C)

so the obvious question is:

why doesn't the ECU use "Baro+Temp" compensated load for timing AND fuel map lookups?

So for the ignition timing routines, the ECU only uses the Temp+Baro compensated Load when intake_air_temp is less than or equal too 65 - all the other times it uses Baro only compensated.

Anyone have an explanation as too why the ECU only takes Temp into account when the intake temp's are below 65 (25C???)?

Is the temp compensated load result in a lower or higher load? I'm still trying to understand this.... iirc I remember someone say the IX ecu had VE compensating routines.