Hi i have this config: Core 2 Duo E6550, Nvidia 8800GTS 640mb, 2 gig ram etc.... it produces more than 100 fps in lfs @ 1680x1050 resolution and full graphics. how can i turn off fps limit in lfs to see what is the exact fps? thx.

In options theres a frame limiter, go have a look.

options>misc>turn off FPS limitor

Keep in mind though that FPS above 100 is pointless since you'll effectively be rendering the same frames multiple times as the physics only run at 100Hz.