Prompt should contain any of the following;

"Engine, Mechanical, Big block, small block, engine components, vr00m, cylinders, gearbox, shafts, etc." use them like "made of engine components consisting of gears" etc etc.

trained on high resolution images of big block, small block and various engine components. I'll update later with best configs but it plays well at 0.6 to 0.8 with 3.5 guidance. Mixed with other loras back it off to 0.5 or lower and raise guidance to 4+