How to Tune an OBD1 BMW (1990-1995)

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

EEPROM burner or Emulator
(optional) Wideband O2 Sensor, logging software
Some guts, an M5x/S5x based BMW motor
And the desire to learn!

Step 1

Familiarize yourself with the DME, and the community effort (granted it peaked four years ago) behind unlocking this DME and tuning with it!
1990-1992 M50nv = Non vanos.
1992-1995 M50tu = Vanos.
This DME can also run other M5x or S5x variant motors, but it will be trickier, and you will have to do more research.

To view some of these documents or to use many of these files you will need the free software "acrobat viewer" and "winrar", found through google. If any of the files are missing or copyrighted, please contact me so I can remove or reupload them.

Non Vanos ETM = http://www.greystonesagainst3g.co.uk/e34_91_etm.pdf
Vanos ETM = http://www.greystonesagainst3g.co.uk/e34_92_etm.pdf

Long, very informative thread started by one of the current top tuners in the BMW community : http://74.125.47.132/search?q=cache:1xUuDYTpnHYJ:forums.bimmerforums.com/forum/archive/index.php/t-431228.html+%22413+dme%22+8096&hl=en&ct=clnk&cd=1&gl=us

Here is a GREAT collection of threads and documentation AND a FANTASTIC corrected MAF table .xls... you NEED to get this.
http://uploading.com/files/NXCBDDKT/Docs.rar.html
Step 2

A screen shot from Mark Mansur of Tunerpro

Next you will need to download a few programs. The primary program used is tunerpro, great free software from : http://tunerpro.markmansur.com/downloadApp.htm

You will also need definition files which are used with tunerpro to read the information from your bmw :http://uploading.com/files/EZQWCWQH/XDF.rar.html

Stock ".bin" files which are found in the chip where the BMW's tune is stored on the DME : Non Vanos - http://uploading.com/files/ZL18SYXD/403Bins.rar.html
and Vanos - http://uploading.com/files/9WR8MW76/413Bins.rar.html

I also used a program called Analyze: http://uploading.com/files/0ZULJ06X/Analyze.zip.html

and Maphunter: http://uploading.com/files/MZCRZZWJ/MapHunter.zip.html

Depending on how capable you are, you will also want a hex editor of your choice and a disassembler as mentioned in the articles above.
Step 3

Burn2 image, courtesy of xenocron.com

Now make sure you have the necessary hardware. You will need to get access to your DME located in the top corner of the passenger side of the engine bay. You will also need an EEPROM burner like the "burn2" or an ostrich EEPROM emulator, I purchased both from xenocron.com. You will also need at least one rewritable chip, I recommend purchasing several SST 27SF512 chips from the same website. They are cheap and if you are not careful you might bend a pin.

You can also purchase a wideband oxygen sensor used for tuning your car, I would reccomend the LC-1, and logging the files directly to a laptop.
Step 4

Now you have the bare essentials to tune your BMW. There is a lot more development to be done, and I welcome all comments, developments and additions. Please email me! In order to develop this project further you will have to load the bin files from your BMW, and the stock bins included in this writeup in hex editors, map analyzers, etc, use what you see already and what is available on the forums to try and find more! There are still many key components missing, and some ill defined, like the oft discussed injector latency constant.
Step 5

To get started with what you have now, I am going to give you some steps... these are all optional, not guaranteed to work, do at your own risk, feel free to change it up, etc.

Open up tunerpro and load up an XDF and a BIN. Make sure that they match, you should be able to tell when the tables have logical values, for example 6450 for a rev limiter, 1.0 for an injector constant. Some tables may be off, you can use the hex viewer to find where the table starts, sometimes they are offset by as little as two bits.
Step 6

Now that you have the proper xdf and bin file for your car loaded up and some tables out, adjust the necessary values. For example if you are installing a 540HFM as a bigger MAF in your 325i/525i find the table for a 540 MAF and copy it in. If you are installing injectors that flow twice as much, you will need to drop the injector constant to .5 from 1.0... fuel and ign adjustments as necessary.
Step 7

When you are ready to try the bin, at your own risk of course, attach your EEPROM burner. Burn the bin file either using the function in tunerpro or your own burner. Take the chip out of your DME and MAKE SURE you install the chip facing the same way, with the mooncut on the chip facing the same direction. CRITICAL.
Step 8

With the chip installed in the DME I recommend unplugging it for a few minutes to clear out the fuel trims. When you fire up the car it may stumble or have a rough idle. It will either take about a minute to catch itself and smooth out, or you will need to adjust your tune. Hopefully at this point you have a wideband oxygen sensor installed and you can monitor your AFR's and try to keep them around 12:1 or richer at WOT and ~14.7 at part throttle. Your tune will be unique and you will need to watch out for stumbling, detonation, lean or rich operation and more.
Step 9

For actual tuning and more, there are tons of articles on the internet to read and years of experience to suffer through! Good luck in your endeavors and may the roundel be with you.