Question Why frame generator cause games slowdown?

[djsolidsnake86]

i have a 4080 super, using frame generator cause the game go slow, without frame generator games plays perfect
i found that disabling gsync let me know to use fg without slowdown, so i can't use g sync with frame generator?
these are my settings

 

[rgd1101]

if it plays perfect why did you turn on frame generator?