How to edit a Gran Turismo 2 DexDrive Save
Important! These instructions apply to (North American) NTSC Version 1.0 of Gran Turismo 2. Other versions (NTSC 1.1/NTSC 1.2/PAL/Europe/Japan) may have different addresses or block lengths. Use these programs and instructions at your own risk. Always make a backup of your game before modifying!
First, understand the purpose of this is generally to "Hybridize" cars. The best way to accomplish this is to start a game and collect one or more cars for modification. You might want to get some basics out of the way as well, such as passing your license tests and collecting a lot of cash - or you may be able to do these things while editing your save.
Second, make sure you have the necessary tools and programs. You'll need, of course, Gran Turismo 2 and a Playstation. You'll also need a DexDrive (a PC peripheral which allows the PC to read and write from/to Playstation memory cards), and PSX Game Edit, a program to read files from a memory card in a DexDrive, save them to PC files, read them from files, write them back to the DexDrive, and edit them in Hexadecimal form. See the link on the home page to get this program.
Third, understand that you will be using a hexadecimal editor to change the save data from Gran Turismo 2. Random changes will almost surely blow up in your face (not literally - just lock up the game or be totally unusable). Collect some necessary information in order to understand what those hexadecimal characters mean. http://www.rogs.dial.pipex.com/indexref.htm is a great place to start. You'll want at least carsb.htm, chartx.htm, and engine.htm from this site.
Finally, you'll need the fchop.exe and crc32.exe programs to extract a region from a save file on your PC and calculate its CRC-32 checksum. You need to do this or Gran Turismo will reject your modified save as soon as it tries to load it.
Now to get started.
1. Save your game to a PSX memory card, and put that card into your DexDrive.
2. Start PSXGameEdit and read the memory card. Use the full read, not the quick read - I've had no success with the quick loads and saves and GT2.
3. Use PSXGameEdit and the charts from www.rogs.dial.pipex.com to change the cars in your saved garage as desired. This can be a quite elaborate process, which I leave up to you to figure out. A very simple example for me was: edit the third block; go to address 264; change the value from C0 to C6. This changes one car's engine from a Mugen Integra to a Takata NSX.
4. Save your modified memory as a single game save file, named temp.mcs.
5. At a command prompt, where temp.mcs is, do this:
fchop temp.mcs temp.tmp 128 32412
crc32 temp.tmp
(you'll see something like:
File Bytes CRC-32 Filename
---- ----------- -------- --------------------
1 32412 39cd0024 temp.tmp)
del temp.tmp
del temp.mcs
6. Back in PSX Edit, go to the last block of your save and edit address 1E9C. Type in the CRC value from step 5, in reverse byte order. In this example, type 2400cd39.
7. Do a full save to update your memory card. Once again, I had problems when using the quick load and save, so do the full save.
8. Put the memory card back in the playstation and try out your modification(s).
Gran Turismo Web Site
DexDrive Hybriding Thread
PSX Game Edit Home Page
Gran Turismo 2 Settings Tables
GT Forum's GT2 Gameshark/Dex/Hybrid Information Central
