Check that you don't have vertical synchronization on in the Launcher. Use your GPU options instead to lock the maximum FPS to your screen's maximum frequency. Of course you have to have a screen that is capable of that kind of refresh rate, and you have to have that mode selected from GPU options.
That way the FS_Open will run faster (up to 120 FPS actually as far as I know, if your machine is up to it), but the graphics processing unit will select only the frames that are 1/85 second from each other to be displayed, showing maximum of 85 frames per second.
Should work fine.