How to improve FPS in Borderlands 1, 2 (normal and VR) and Pre-Sequel on a high resolution 4K monitor on PC?

I got myself a 4K monitor and at its native resolution the Borderlands games give me low FPS:

• Borderlands GOTY Enhanced (remaster with all DLCs and support for high resolutions built-in)
• Borderlands 2
  • with Borderlands 2 Ultra HD Texture Pack DLC
• Borderlands 2 VR (played with Valve Index at its native high resolution)
• Borderlands: The Pre-Sequel
  • with Borderlands: The Pre-Sequel Ultra HD Texture Pack DLC
    

In all 3 games at 3840x2160 resolution and all max graphics settings I get around 30-45 FPS. Just lowering the resolution to 2560x1440 gives me around 55 FPS, and going down to 1920x1080 gives >60 FPS.

Turning down all the graphics setting to low/off still gives me below 60 FPS on 3840x2160 resolution in all 3 games. Even without the HD texture packs.

Process Explorer is saying that the GPU is basically idle at 5-10% usage, while the CPU is working at around 20% total (6-core Intel i5-8400, for which 16% is 100% of a single core utilization, making it around 1.5 full core utilization). It seems like both games are bottlenecked by single-core CPU performance. What can I do to get better FPS?

You can disable the cel-shading post-processing effect if you don't mind losing that signature thick black outline on all 3D models. This improves framerate dramatically. For me, it jumped up to 80-120 in all 3 of these games.

There is already a Q&A about doing this but the asker specifically wanted to get rid of this effect not knowing it can actually boost FPS significantly, and that it works in all 3 games. Check it out here. The answer there also shows how it looks before and after.

Here's how to do it in all 3 games (assuming you're playing on PC via Steam):

Borderlands GOTY Enhanced

• Go to: %userprofile%\Documents\My Games\Borderlands Game of the Year\WillowGame\Config\
  • (you can copy-paste this into your Windows Explorer window address bar)
• Find and make a backup copy of WillowEngine.ini. If you don't see it there, launch the game at least once after installing, it should appear.
• Find this text in it (mine was at line number 95):
  • DefaultPostProcessName=WillowEngineMaterials.WillowScenePostProcess
• Replace the value at the end with whatever:
  • DefaultPostProcessName=WillowEngineMaterials.WHATEVER

In my case it jumped from ~45 to ~90 FPS.

Borderlands 2 and Borderlands 2 VR

• Go to %userprofile%\Documents\My Games\Borderlands 2\WillowGame\Config\
• Find and make a backup copy of WillowEngine.ini.
• Find this text (mine was at line number 133):
  • DefaultPostProcessName=WillowEngineMaterials.WillowScenePostProcess
• Replace with:
  • DefaultPostProcessName=WillowEngineMaterials.WHATEVER

For me the increase was from 30-45 to 75-100 FPS.

In VR with Valve Index the increase was about 40% extra FPS across different resolution percentage settings.

Borderlands: The Pre-Sequel

• Go to %userprofile%\Documents\My Games\Borderlands The Pre-Sequel\WillowGame\Config\
• Find and make a backup copy of WillowEngine.ini.
• Find this text (mine was at line number 133 - wow, same as BL2!):
  • DefaultPostProcessName=WillowEngineMaterials.WillowScenePostProcess
• Replace with:
  • DefaultPostProcessName=WillowEngineMaterials.WHATEVER

For me it went up from 35-45 to 80-90 FPS.

I haven't had the chance to play the new Borderlands 3 but I assume they're reusing a lot of the same engine inner workings and configs as the 2 and Pre-Sequel, so in theory, it should also work for 3. I'll update this in about 5 months when it releases on Steam.