That's true. Never thought of it that way.
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I believe I have experienced a bug in the IMA software that Honda's engineers probably didn't think to plan or test for:
With the IMA battery switched OFF, the "auto stop" feature is disabled, as it should be.
Under normal conditions (IMA working), "auto stop" kills the engine (once warmed up, etc.) when braking or coasting below 19 km/h, provided the driver shifts into neutral. When shifting back into gear, the ICE spins up again via the 144v motor.
Makes sense that this shouldn't happen with IMA disabled: because there's no juice to spin up the ICE via the motor/generator, or feed 144v to the DC-DC converter to power the 12v accessories.
BUT...
I've noticed under specific circumstances the computer
will kill the ICE despite the big hybrid switch being in the OFF position. If I manually key off when coming up to a stop or a turn, and then I clutch-start the engine before stopping, auto-stop will blink its dash light and cancel my clutch-start!
It's like that machine that guy built where you turn it on, and a hand comes out and turns itself off again.
I have to either shift into gear to prevent the "stall", or I have to key start (12v starter) to get the engine running again.
Note that this only happens if I'm doing a key-off coast, and then a clutch-start below 19 km/h. If I leave the ICE running after first key-starting it, IMA will
not auto-stop the engine.