Death Race should be like all other Color Dreams/Bunch Games/Wisdom Tree releases and be assigned mapper 11.  However it doesn't work with that mapper in emulators.  Any emulator that allows it to work uses a custom mapper.  Kevtris's says that the only difference bewteen the board used for this game and the board used for all other Color Dreams/Bunch Games/Wisdom Tree games has to do with bus conflicts.  Is this significant of an unimplemented mapper feature?
 
Mapper 11 seems to be a really wierd one.
I got a NES ROM image that is mapper 11, and works in all emulators.  But no matter what donor board I use (that is a mapper 11) the game is all messed up.
 
http://www.tripoint.org/kevtris/mappers ... /agci.html
Describes the slightly unique board that Death Race uses.
  
Yeah, Death Race relies on the 'feature' that dataline 0 on the ROM always wins when writing to the mapper. It boots fine here after implementing that just now (thanks for the link)... something like: written_data|=(read_rom(address)&1);