I benchmarked AC8's render settings one at a time using a 3-minute in-flight replay at native 4K, with frame generation off so only real frames were counted. Almost all the commonly shared tweaks (shadows, fog, contact shadows, reflections, culling) made no measurable difference. The real cost is the game's cloud renderer, which is set higher than it needs to be. The game also ships with DLSS Frame Generation and Reflex built in but switched off. This file turns them on.

Test system: RTX 4090, Ryzen 9 7950X, 64 GB RAM, native 3840x2160, DLAA. I play on Linux/Proton, but this file works the same on Windows.

• Shipped settings: ~33 fps (~30.5 ms per frame)
  
• Cloud quality 2 -> 1: ~40 fps (-5.3 ms)
  
• + cloud trace resolution -25%: ~43 fps (another -2.2 ms)
  
• + DLSS Frame Generation x2 (RTX 40/50 only): roughly double the displayed fps, ~70-80 in flight here

• No RTX 40/50 card? Delete the whole [ConsoleVariables] block and keep only [SystemSettings].
  
• Want full-resolution clouds? Delete the ScreenFraction line. You lose about 2 ms per frame.
  
• Don't put comments at the end of a line. Unreal's ini parser treats them as part of the value.

Important: the game deletes Engine.ini every time it starts, so the file must be set to read-only or your changes are wiped.

Windows

1. Start the game once to the main menu, then quit.
   
2. Press Win+R and paste: %LOCALAPPDATA%\BANDAI NAMCO Entertainment\ACE COMBAT 8\Saved\Config\Windows
   
3. If Engine.ini is missing, create it: New > Text Document, rename it to Engine.ini. Turn on View > File name extensions first so it doesn't end up as Engine.ini.txt.
   
4. Paste the block above into it and save.
   
5. Right-click Engine.ini > Properties, tick Read-only, click OK.
   
6. Start the game.

Linux / Steam Deck (Proton)
Same folder, inside the Proton prefix:
steamapps/compatdata/[app id]/pfx/drive_c/users/steamuser/AppData/Local/BANDAI NAMCO Entertainment/ACE COMBAT 8/Saved/Config/Windows/Engine.ini
Create and paste as above, then run: chmod 444 Engine.ini

To undo: untick Read-only (Linux: chmod 644 Engine.ini), then delete the file.

• r.Cloudly.QualityLevel=1: the game's own volumetric cloud renderer (0-3, it ships at 2). Level 2 cost 5.3 ms per frame in flight, the biggest single cost I found. Judge level 1 yourself in a cloud-heavy mission.
  
• r.Cloudly.ScalabilityBias.ScreenFraction=-25: traces clouds at a lower internal resolution. Saves 2.2 ms. This one does soften fine cloud detail slightly, so it's optional.
  
• [ConsoleVariables] block: loads NVIDIA Streamline and turns on DLSS Frame Generation (x2) and Reflex. The game includes these but ships them disabled. They only load from [ConsoleVariables]; putting them in [SystemSettings] does nothing.

Each of these was within ±0.5 ms (benchmark noise) in flight:

• Virtual shadow map resolution bias / soft-shadow ray counts
  
• Volumetric fog off
  
• Contact shadows off
  
• Lumen reflections off
  
• Occlusion queries / HZB / scene culling
  
• Lumen GI quality reductions (they help ~3 ms in the hangar, nothing in flight)

Copy-pasted tweak lists that turn these down cost you image quality for no fps. Ray tracing off saved only ~1 ms (measured in the hangar), because the game's ray-tracing scene only includes objects within ~300 m of the camera.

With DLSS Frame Generation, HUD elements show slight ghosting during fast motion. The game draws its HUD into the scene before frame generation runs, so DLSS can't keep it separate. I haven't found a fix yet. If it bothers you, remove the [ConsoleVariables] block.

Bottom line: native 4K at 60 real fps isn't reachable through settings alone. The GPU is busy for ~23 ms per frame even after these changes. Cloud quality is the one setting that matters; frame generation covers the rest.