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Author Topic: MAF transfer function at Siemens MS42/43, bigger MAF needed  (Read 5384 times)
Cloudforce
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« on: November 23, 2015, 03:09:48 AM »

Hello guys,

i know Siemens is not the most common here in this forum, but maybe someone  has a hint on how to modify the program section of that ecu.

Siemens ecu seems to have a function which translates maf voltage into airmass reading according to the following map.



The problem now is, the max the ecu can read is 1024kg/h (65535) which is fine for natural aspired engines, but with more people going FI, we need bigger maf to account for the bigger airmass.

Instead of fooling the ecu with changing the maf to a bigger one and simply changing the axis values to fractions of the stock value, i would like to tweak the maximum accepted value from 1024kg/h to ~2048kg/h.

Therefore i´ve disassembled the sub function which handles the id_maf_tab, which should correlate between 0-5v and 0-1024kg/h measurement range.
Unfortunally i´m not much into assembler programming so if someone more knowledgeable has a clue, i´d appreciate any help Smiley
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prj
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« Reply #1 on: November 23, 2015, 01:30:57 PM »

Unfortunally i´m not much into assembler programming
Then underscale.

No one is going to do it for you.
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Cloudforce
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« Reply #2 on: November 23, 2015, 02:18:09 PM »

Then underscale.

No one is going to do it for you.

Did i state anyone should do it for me?  Roll Eyes
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prj
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« Reply #3 on: November 24, 2015, 09:29:55 AM »

Did i state anyone should do it for me?  Roll Eyes

Yes:
Quote
Therefore i´ve disassembled the sub function which handles the id_maf_tab, which should correlate between 0-5v and 0-1024kg/h measurement range.
Unfortunally i´m not much into assembler programming so if someone more knowledgeable has a clue, i´d appreciate any help Smiley
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Cloudforce
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« Reply #4 on: November 24, 2015, 11:16:27 AM »

As you stated in a different thread, you currently have no time... Why are you waisting both our time?

If you try to read the quote you´ve taken without any intentionally misguiding, you could actually read that i´m NOT looking for someone to do it for me.

But again, thats only readable being unbiased...

So feel free to stay away from this thread if your only intention is collecting posts or whatever it might be.
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prj
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« Reply #5 on: November 24, 2015, 12:48:23 PM »

It's very simple, if you found the subroutine in the assembly code, then you should know what to do with it.
You need to determine why there is this limit, and how far it propagates.

Then you either add a division by 2 somewhere and there a mult by 2, or you rewrite the whole MAF code with a different scale.

If you are not very good at assembly, then FORGET IT, because as I said, no one is going to do this for you.
Just use the simple option and underscale the MAF somewhat. On this ECU it does not matter in the slightest if you do this.
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Cloudforce
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« Reply #6 on: January 03, 2016, 04:29:17 AM »

Well, in the end we found the correct solution  Tongue and its way easier as to underscale each map where maf measurement is used  Wink
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