I’m going to say, from my understanding, even though I can’t find anything definitive about JLR MHEV (I did find a YouTube video on the disco):
The BISG doesn’t have a “bendix” or other disconnecting means. That’s part of why the engine start is so immediate. That’s how it does regen braking, it drags the engine. That’s how it provides torque assist to the engine.

I'm pretty sure the electric supercharger is separate from the BISG.


I do wish JLR would give a better explanation of the system.

 

The MHEV system is just to support the auto stop start of the vehicle and to assist the electric super charger in building pressure in the turbo at low rpm’s. That’s what my service manager told me and also this thread on an Evoque forum explains too.

https://www.pistonheads.com/gassing/...f=91&t=2015955

 

So, not related to the drivetrain, it seems some other electric power functions may be supported by the lithium battery associated with the MHEV system. E.g., when I turn on the heated seats, I can hear what sounds like the battery cooling system turn on coming from the rear of the car. Anyone else notice that?

 

Are you sure that's not just the fans for the seat heater turning on?

 

Likely the DC-DC charger helping the 12V system along. You don't have a 12V alternator, just a 48V alternator that charges the MHEV battery. The 12V battery that runs all the vehicle ancillaries is charged by a 48V DC to 12V DC charger. With seat heat and other systems that use a lot of power switched on, the DC-DC charger is likely being taxed somewhat.