On my server I have limited the base Create rotation speed to 128 RPM (to prevent lag and machine glitches). Because of this, when I try to use the Huge Diesel Engine, it always outputs 224 RPM by default, which immediately causes shafts to pop off or networks to desync.

To fix this, I tried to lower the Huge Diesel Engine’s base speed via datapack.

According to the wiki, fuels can be customized through datapacks at
data//createdieselgenerators/fuel_type/.json.

The mod’s JAR includes
data/createdieselgenerators/createdieselgenerators/fuel_type/diesel.json
with "huge": { "speed": 224.0, ... }.

I created a datapack with the exact same path and schema (including sound_pitch and burner_multiplier), and changed only the Huge engine speed to 128.0.

The datapack is loaded (/datapack enable ...), and I tested with full server restarts.

However, the Huge Diesel Engine always runs at ~224 RPM, regardless of the datapack value.

Expected behavior:
The datapack value for huge.speed should override the default 224.0.

Actual behavior:
The Huge Diesel Engine ignores the datapack override and keeps using the built-in default speed.

Notes:

Server configs (createdieselgenerators-server.toml) don’t provide base speed options.
Because of my 128 RPM cap on Create, this makes the Huge Diesel Engine unusable unless its speed can be lowered via datapack.

Pack structure:
dieselgeneratorsspeed/
 ├─ pack.mcmeta
 └─ data/
    └─ createdieselgenerators/
       └─ createdieselgenerators/
          └─ fuel_type/
             └─ diesel.json

{
  "fluid": "#forge:diesel",
  "normal": {
    "speed": 96.0,
    "strength": 6144.0,
    "burn_rate": 0.05
  },
  "modular": {
    "speed": 96.0,
    "strength": 8192.0,
    "burn_rate": 0.05
  },
  "huge": {
    "speed": 128.0,
    "strength": 16384.0,
    "burn_rate": 0.05
  },
  "sound_pitch": 0.9,
  "burner_multiplier": 0.6
}

Minecraft 1.20.1
Forge 47.4.0
Create Diesel Generators 1.3.4 and 1.3.5

Sorry, after another reboot, the datapack works fine