Log file format
You have to post a single file per session. By default, rFactor is logging this way.
If not, you have to edit a configuration file :
Check/edit your Driver.PLR (<rFactor folder>\Driver\Driver.PLR) and find the line
Multi-session Results="0" // whether to store all sessions at a track in a single results file, new default is one session per file
Number of log files
By default, rFactor only kiiep the last 10 log file. To increase this number :
Check/edit your Driver.PLR (<rFactor folder>\Driver\Driver.PLR) and find the line
Number Race Results="100" // how many results files to store (using default naming convention only!)