FreeGameDev

Hello,
First let me tell you my story to this:
Today I started building my new gaming PC, for testing i downloaded one of my favourite games: SuperTuxKart.
I installed some other games and played for this time STK (quality 6, FullHD, 105FPS, 19 AI). After restarting my PC i tested again, and got only 65 FPS. After some testing i found out, that the "Epic Games Launcher",
known for "Fortnite" boosts the SuperTuxKart from 65 to 105 FPS. I don't know, that this is onley on my PC.
But why it is like this? Can you help my to figure out.
Note: It only worked with STK. And while testing it again, this effect was gone (back to 105FPS)

Thank you for your attention!

It's really hard to tell as there can be lots of different factors involved, and drivers inner workings can be pretty obscure. Maybe the launcher changed some setting for performance in your driver on your operating system, it's hard to tell since I don't know what the launcher does

Let me guess: An Nvidia card? My GTX 295 does this, sometimes the framerate is awful, sometimes partway through the race it gets decent, with no reason.