If the player who set the actual fastest lap (the one displayed in the finished list (1:41.10)) leaves the session (e.g. pits, spectates or leaves server) the fastest lap of the session will be reset to the fastest lap of the people who are still in the session. If someone does a faster lap than that it will be displayed by LFS as the fastest of the session.
edit: Here's an example as an explanation.
There are 3 drivers in a 2 lap race. The laptimes are as shown below:
Player Lap 1 Lap 2 1 1:50.00 1:40.00 2 1:51.00 1:41.00 3 1:52.00 1:42.00
At the moment the fastest lap in the session is a 1:40.00 (Player 1's second lap), so a driver will have to do a 1:39.99 or faster to get fastest lap. However, if player 1 disconnects from the server the fastest lap now becomes the 1:41.00 done by player 2 on lap 2, so a player only has to do a 1:40.99 or faster to get fastest lap.
Thats it, if a player who had the fastest lap leaves the server then the time will no longer count and it will go back to the next fastest persons lap.
Yeah, sorry amp, i was tired of seeing that noobs thread that was titled 'stupid ****1ng program' that bob closed, sat there iwhile looking at the main board index, so i bumped this so it wasnt there anymore.