Quote:
Originally Posted by jad03060
While we can argue about why the PHEV have the pressure release button to enable unlocking the filler flap, or if it's required, we also have to note that BMW did not include a similar system for their ICE vehicles. I think we can also agree that it does not make much sense to add complexity for no reason. Whether BMW followed that rule or not, I would like to believe they have a valid reason for the expenditure of designing a special module, writing the software, and including the switch. The training guide does say this about the fuel system:
"2.3. Fuel supply
The G05 PHEV too has a stainless steel pressurized fuel tank. Unlike in the predecessor, the pressurized fuel tank is not secured to the
underbody, but is instead located underneath the luggage
compartment (like G12 PHEV and G30 PHEV)."
Regarding the tank vent, the user's manual says this:
"The vehicle is equipped with a special fuel tank.
The fuel tank is designed for special requirements
that arise from hybrid operation of the vehicle,
i.e., alternating drive with combustion engine
or electric motor."
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This is very interesting and possibly explains the phenomenon. Fuel tank pressure is the result of active fuel tank pressurization rather than passive vapor buildup. I'm guessing during hybrid electric mode operation, the fuel pumps shut down and fuel line pressure would be otherwise lost. Pressurizing the fuel tank and system allows for faster ICE startup not having to wait for the pumps to pressurize the system. Still it would seem a better design would be automatic de-pressurization when shutting off the vehicle for refueling. A pressure release button and an emergency fuel flap door release seem a rather primitive afterthought.