[eelnoraa]

Originally Posted by streborx

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.

OMG. This is how misinformation started. People read the user manual, which is really a marketing document with lack of technical detail, then use imagination to fill in the gap. In this case god-fying bmw, make it sound like bmw did something magical.

Do you know what fuel pressure is needed at injector output? Look it up. Tank will explode with that kind pressure. Fuel pump main pump that supply the pressure to inject is driven by cam. It take a few rotation of cranking to get the pressure. PHEV use tow start meaning the rpm the engine get cranked is much higher than typical ice starter. No problem of getting fuel pressure. Q

[streborx]

Originally Posted by eelnoraa

OMG. This is how misinformation started. People read the user manual, which is really a marketing document with lack of technical detail, then use imagination to fill in the gap. In this case god-fying bmw, make it sound like bmw did something magical.

Do you know what fuel pressure is needed at injector output? Look it up. Tank will explode with that kind pressure. Fuel pump main pump that supply the pressure to inject is driven by cam. It take a few rotation of cranking to get the pressure. PHEV use tow start meaning the rpm the engine get cranked is much higher than typical ice starter. No problem of getting fuel pressure. Q

Fuel pressure required at the injector at 85mph is a bit more than what's required to start the engine. Besides, why a stainless steel tank when many non-hybrids get by nicely with polymer tanks, and manufacturers plasticize everything to minimize weight?

Waiting to hear what you think about the why for pressurization.

[eelnoraa]

Originally Posted by streborx

Fuel pressure required at the injector at 85mph is a bit more than what's required to start the engine. Besides, why a stainless steel tank when many non-hybrids get by nicely with polymer tanks, and manufacturers plasticize everything to minimize weight?

Waiting to hear what you think about the why for pressurization.

So pressure at injector isn’t a function of mph. It is more a function of engine load, or maybe rpm of the engine. VVT engine, compression ratio change a bit depend on load on engine, not necessarily car speed. Now you didn’t look up the actual psi needed, if you look at that number, you will know no amount of pre-pressurize at tank will make a difference. My take, no active pressurization at tank. No where ever mention in any manual. I haven’t seen one in any car. Active tank pressurization is an imagination. One more practical observation, the connection between the fill port to the actual gas tank, it is a piece of rubber hose clamp to ports from tank and fill port. I attached a photo. How much pressure can this thing take?? But I am open to learn new things

Steel tank is because the location is the tank. It is right at the crumple zone of the car, simple as that. It is a safety requirement. BMW cannot put this in user manual saying "yes, we relocated the tank to the crumple zone. To mitigate fuel leak in rear end accident, we use a steel tank", right? The fact is, even with steel tank a small rear end collision can still damage tank cause a leak. This happened to a friend's 23 330e. It is being repair through PeterPan BMW in our area. We had a lot of discussion about the condition of the car with BMW inspector and auto body repair shop.

Maybe a bit more information from me putting friend's car on quik jack for tire rotation. Rav4 prime has normal plastic tank, it is also at the conventional location, under 2nd row seat. Per Toyota user manual, it has "pressurized tank" too, one simple pull string mechanism to open gas flap like any other Japanese ICE car, no complicated depressurized procedure.

[jad03060]

Well, we may never know why BMW chose to design their PHEVs this way, but they do have a unique electronics module to monitor the pressure and control when the deadbolt can be disengaged, a unique pressure sensor for the tank, and the button to activate the monitoring system to perform its intended operation.

Yes, vapor pressure, as in the partial pressure laws of gasses will somewhat pressurize the tank (especially with temperature increases), but that's true of any gasoline fueled vehicle...something is different about the PHEVs that elucidated the changes. While with the right software, you might be able to view the pressure (BimmerLink? maybe) we don't know what that is, or if it's higher than with a more typical vehicle...all we know is that BMW chose to add this hardware to their PHEVs. If they have figured out a way to add more pressure to the tank, that would seem to help limit some of the more volatile components from evaporating. It wouldn't take much. Unlike a typical ICE, with a PHEV, the fuel could be sitting in the tank for a very long time, so trying to mitigate the degradation may have been the impetus of the whole system.

[-HR-]

I understood this to mean that the tank therefore remains pressurized and in particular has no ventilation, that the gasoline quality remains constant, because it is assumed that the PHEV often does not get fresh gasoline for a long period of time.

[jad03060]

While the 50e has a carbon canister to help absorb fumes and not vent them to the atmosphere as does a typical ICE, it's not clear how the rest of the venting works in the 50e versus their ICE vehicles. But, yes, part of the design parameters appears to be to help preserve the fuel quality over time and to help ensure proper activation of the ICE, even when its use could be quite intermittent with lengthy intervals between uses.

[Guy Fleegman]

I can go 8-10 months without filling up (45e). I wonder if there's any reason to depressurize the tank every now and then.

[Gene Horr]

Originally Posted by Guy Fleegman

I can go 8-10 months without filling up (45e). I wonder if there's any reason to depressurize the tank every now and then.

In general the answer is no. There are usually multiple safety points to avoid overpressure.

A more important worry for sitting for so long is that you are adding fuel stabilizer. Also, while in general it is best to store fuel in a full tank to minimize air exposure, I wonder whether in this case it should be stored half full to allow mixture with fresh fuel when needed.

[eelnoraa]

Originally Posted by Gene Horr

In general the answer is no. There are usually multiple safety points to avoid overpressure.

A more important worry for sitting for so long is that you are adding fuel stabilizer. Also, while in general it is best to store fuel in a full tank to minimize air exposure, I wonder whether in this case it should be stored half full to allow mixture with fresh fuel when needed.

I agree as well. We can look up what is the equilibrium pressure at normal human livable temperature. I am not sure it is high enough to be a concern. Personally, I have own cars without any mean of venting in the past. When I opened cap for gas fill, it was just a short hiss.

As to handling of gasoline in long term storage of car, I have been taking a different approach than yours, I make sure I have 1/4 or less tank left. When I use the car again, first thing is to fill it up with new gas. Not sure which way is better tho. this is just the way I have been doing. The longest I have gone without gas stabilizer is about 6 months.

[JMD]

Try moving the Flap slightly Vertical up and down when attempting to open!

[jad03060]

Just a thought...when I had my i3, the charging door was locked, similar to the X5's two filler doors when the vehicle was locked. Sometimes, the charging door would not unlock. What BMW found was that the bolt hole was slightly too small in some temperature conditions, and it provided too much friction for the solenoid to retract the pin. The hole was a plastic part...their solution was to use a particular sized drill bit, and enlarge it slightly.

There might be a similar issue with the X5's filler door. Also, a slight spritz of lithium grease in the hole might help long-term as well.

Also, one time when I was trying to get the door open, when I pulled the emergency cord, it broke. When BMW replaced it, they found that it was not clipped into the proper guides, and had become pinched when pulled. With a BEV, not being able to recharge can be as bad or worse than not being able to fill your PHEV. Usually, though, if you locked and unlocked the vehicle, it would eventually open, but not always...I'm not sure of the logic on the gas filler on the PHEV release...my guess is it just does one cycle to the deadbolt, but maybe multiple presses might help.

[ScaldedDog]

Originally Posted by jad03060

Just a thought...when I had my i3, the charging door was locked, similar to the X5's two filler doors when the vehicle was locked. Sometimes, the charging door would not unlock. What BMW found was that the bolt hole was slightly too small in some temperature conditions, and it provided too much friction for the solenoid to retract the pin. The hole was a plastic part...their solution was to use a particular sized drill bit, and enlarge it slightly.

There might be a similar issue with the X5's filler door. Also, a slight spritz of lithium grease in the hole might help long-term as well.

I think you're right about this, and that's why just hitting it a few times often works. I was thinking I'd spray some graphite on the pin - the kind of stuff you use in locks - to see if that would make it more reliable.

Mark