@_ArkAngel_

I adjusted my microcontroller to output the ON to the starters with very quick pulses, but some additional info I've posted elsewhere:

Keep its crankshaft between 0.1 and 1.3RPS (preferably below 1RPS entirely)
Pulse them on and off very rapidly, and steadily
Keep them all in sync, preferably all of the starters that are on a single crankshaft are on at the same tick, if they get desynchronized and start pulsing on different ticks then the sound will start playing fully rather than being interrupted.
You will still get one last sfx if a crankshaft's starters are all turned off(to stop the motor)

Doing all this, the motor is barely audible under a diesel engine, but still not as quiet as the regular electric motor


You can peep my microcontroller for controlling this in this vehicle here https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3143234098

I started only using starter motors for boost sparingly when it became impossible to mute the noise at some point around industrial DLC time. Have you ever found a way to mute them again?