Ok im sure a few will have some interest in this, and some will already know (probably more than me). Please feel free to chime in if you have extra info.
Im making this thread to provide info on eprom tuning for nissan 240sx/D21 ka24e. This is basically same as uberdata/hondata tuning for honda ecus that most are familiar with. With nissan ecus, we use the program called Rom Editor available free from http://www.925style.com/
. This is a very handy editor, that with the correct address file, allows us to easily tune our ecus like JWT or others. With the ka24e ecu (240sx Jecs, D21 Hitachi) we are dealing with a single 27c256 eprom that is currently located on the ecu board. All we need to do is change values on this chip (just like uberdata, except the eprom is already there). This obviously requires de-soldering the 28 pin eprom from the ecu pcb, which can be done a few different ways. Once it is removed, soldering a socket in place makes for easy changes.
I have the correct address files for both ka24e 240sx, and ka24e D21, as well as stock eprom files (or .bin) for both. This is all the files that you will need to begin tuning.
Before i go any further, here is some screen shots from my stock 1990 240sx 5spd ecu.
Fuel Map 3D
Ignition Map 3D
Now, this may appear candy-glossed, you should research heavily before you go trying your tunes. A wideband o2 sensor is highly recommended. I am by no means an expert with tuning these yet, I want everyone to know this info so we can get some info/file swapping goin on.
An eprom burner is required to make your own chips, i bought mine on ebay for about 70 bucks (willem enhanced eprom programmer). Anyone that knows a uberdata tuner, or is an uberdata tuner, you can use same equipment. The factory ecu's use a 27c256 UV-erase 28 pin eprom. These require a high intensity UV light to erase and are rather difficult to work with unless you have one. You can buy Flash replacement chips (erase with click of a button) , such as atmel at29c256 (most popular), or sf27c type.
You should keep your stock eprom chip intact so it can be swapped back in and/or copied.
27c256 are cheap eproms, you can buy them used at about $10 for 30, or even less. Atmel at29c256 are under $10 a piece new, these are what i use. Check out http://www.moates.net
for sockets, chips, and even programmer/burners. I use the blue socket you see on that site, works nicely and has plenty of clearance on both hitachi and jecs ka24e ecus.
Ok i forgot anything else, maybe some questions would revive my memory. Anyone interested in the necessary files i have, i can email them to you.
BTW: Many older pc video cards used 27c256 UV eproms. You can re-use them if you have a high intensity UV light to erase.