BuildCraft version: 7.99.14
Forge version: 1.12.2- 14.23.3.2655
Link to crash report or log: -
Singleplayer or multiplayer: Singleplayer
Steps to reproduce:
Additional information:

I think it is more like a idea from older versions.
In older versions the speed off the engines grows with the time, whereever it is pumping items and so on, just were looking to the time, but in your version it consists on the items it transports.
Also the engine animation laggs sometimes, because of this.