@User265 Me with my work with piston engine also can only reach around 925 RPM without load. I've also tried your engine with the mod and it reach around 900+ RPM. I'm kind of incline to believe it's limitation of the physics engine.
The rotator's spin limit with limitlessspinn mod is around 2700 RPM. But I'd believe with reciprocating design I'll believe it can do only 1000.
Maybe someone better than me can do better tho.

@User265 ok,maybe a manuel

@Halcyon215 you mean Continuously Variable Transmission? That probably too difficult for this game😢

@Johnnyynf thx for advicing. Yes this car currently runs very slow and I don't know how to improve. The engine's speed now is 800°+/s, I don't think this will reach speed limitation, but anyway I'll try this mod

@Pleco123 sure ok

Can i update it?

please consider further development with LimitlessSpin mod in mind
This has some potential

Now make a cvt version of it

@Graingy it does, infact, work. I tested it.

Love it

There's no way that engine works...
The wheels definitely don't, though.