Changes HEX file, Motronic 1.7 BMW M43

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Changes HEX file, Motronic 1.7 BMW M43

Post by HansV »

I have a BMW 316 1996 with a M43 motor. Thas has a Motronic 1.7, Bosch 0 261 203 660.
Can anyone help me getting a XDF difinitions file for this ECU?
How similar is this to the M42 (282 og 990 dme)?
Where is the rev limiter located in this EPROM?

I have read out the .bin file from my car and will order a updated code for this chip with correct immobilizer data. But it would be nice to know that I have the possibility to change some parameters myself also.
Anyone interested in this .bin file? Where do I send it for uploading in the BMW section on this page?

I would also like to know if anyone can confirm what type of EPROM is used here. 27C256 or 27C512?
Last edited by HansV on Sat May 22, 2010 10:55 am, edited 1 time in total.
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Post by tom »

EPROM 27C512
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Post by HansV »

Thanks for conferming this! Then I have to read it again with the correct settings for the PROM.
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Post by HansV »

I have compared the .bin files from my car with the E36 316/318 XDF files, and they do not match at all. So I would need a new XDF file to do any serious changes.

When I compared the original HEX file from my car and the modified file a have got, there was 16 places the code was changed.
HEX file changes:

1: 42A6-42A9, 4 bytes
2: 42E7-42EA, 4 bytes
3: 5A3A-5A49, 16 bytes
4: 5A5C-5A6B, 16 bytes
5: 5B0E-5B1D, 16 bytes
6: 5B30-5B3F, 16 bytes
7: 5B9A-5BF9, 96 bytes
8: 5C46-5CA5, 96 bytes
9: 5CF2-5D51, 96 bytes
10: 5D74-5E53, 224 bytes
11: 5E76-5F55, 224 bytes
12: 5F78-6057, 224 bytes
13: 607A-6159, 224 bytes
14: 617C-625B, 224 bytes
15: 627E-635D, 224 bytes
16: 9900-9941, 66 bytes

Does this look like a proper remap. Seller claims this will give me +10HP, but I am waiting for a new PROM so I have not tested it yet.
Using WinOLS I detect 29 possible maps in the HEX file, so about half of the maps are changed. Is this normal prosedure?
I am new to this. so any comments are welcome.
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Post by HansV »

I have done some more work with comparing the files and finding out what is changed.
The first two changes is only 4 bytes each, and is propaply to rise the rev limiter.
The next four changes is 16 bytes and contains a table with a curve where all the values are incresed and the curve form changed
The 12x12 maps where 96 bytes are changed have 12 curve "peeks" each. All the values for the last 8 "peeks" have been increeced by 10(decimal)
The 14x16 maps have all values increesed by 10, keeping the curve form identical.
There are also two 14x16 maps and some smaller maps that have not been changed.
This seems to me like a simple tuning, but it would be nice to know what have been tuned.
How can I find the info I would need to make a XDF file for this PROM? I would of cause need to know what the different maps are, and how they are arranged. All help are welcomed!
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Post by HansV »

Here is some updates:
- The first two 4 byte changes seems to be the rev limiter
- The 16 byte chages are the WOT tables
- The 12x12 are probably fuel maps
- The 14x16 are probably ignition maps

This ECU should be a Motronic 1.7.3. But is this using the WOT tables or not? Some says not, but I would like to get this confirmed.
I would also like to know how the rev limiter values are calculated, how to update the checksum and how the fuel and ingnition maps are arranged.

Is remapping fuel and ignition by adding a constant to all values normal procedure, or just a hack by someone that doesn't know what he is doing?
I am trying to figure all this out to verify if the changes done to my HEX files are OK or not, and how I possibly could tune it better myselfe.
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Post by HansV »

Checksum calculation:
I found this post on ECUconnections on how to fix the chechsum manualy: ... f=2&t=1440
I downloaded the HEX file editor HxD and used it to calculate the 8-bit checksum for the original and modified HEX file. I found that the checksum was the same for both files, and this confirms the what is written in the post.
The changes in the modified file at 9900 where a lot of FF is replaced by 00 is done to get the checksum to match, simply by removing unused values until the checksum comes out the same as before. Then there is no need to locate and change the checksum byte(s) in the file.
Smart workaround that seems to work:)
This ECU does not have checksums for each map, it goes directly to the header on the next map after the end of a map. The motronic header format is expalained here: ... ?f=2&t=183

Still working on what the different maps do and how then should be changed for optimal performance. It would also be nice if someone would help me making a XDF file for this ECU.
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Re: Changes HEX file, Motronic 1.7 BMW M43

Post by E36alpina »

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