2017 REx Fuel Tank size

[Tacfoto]

OK I understand the 2014-2016 REx models had their fuel tank software limited to 1.9 gallons. There is actually 2.4 (or is it 2.5?) salons of fuel in there. But after using 1.9 gallons the computer stops the REx.

I have a 2017. Is my tank also software limited? I ran it out of fuel, and it took 2.1 gallons to fill it. Can I code it to 2.4?

 

[jadnashuanh]

Don't know for sure. But, at least some BMWs, to preserve the fuel pump, won't actually let you run the tank dry. The pumps they tend to use rely on lubrication and cooling based on the gasoline flowing through them, and with fuel injection, the pump feeds the injectors more than they use, so some of it is returning to the tank.

 

[alohart]

I have a 2017. Is my tank also software limited?

BMW didn't limit the usable fuel amount in i3's with the 94 Ah battery pack (most 2017 i3's and later).

 

[SSi3]

It's not limited like the 14-16 years, but as Jim said above, it won't run the tank dry, it leaves some in there otherwise the Rex won't start next time you need to use it if sucked the lines dry the last time you used it.

 

[Tacfoto]

It seems like it is limited just like the 14-16, just to a different number. 2.1 vs 1.9. About 10% more. This seems to jibe with the range predictions on REx that only jump from 78 to 83 with the 2017 model. (according to Wikipedia)

What is the most anyone has put into a tank on a modded REx?

And why wouldn't the REx start if you sucked the lines dry? Isn't that a pretty normal thing for any gasoline engine?

 

[alohart]

And why wouldn't the REx start if you sucked the lines dry? Isn't that a pretty normal thing for any gasoline engine?

A fuel pump is lubricated and cooled by gasoline, so running it dry isn't good for its longevity.

When air enters the pump, pumping could stop. Air in the fuel lines would cause the REx engine to stop running or fail to start.

I don't know whether most ICE cars allow their fuel pumps to pump air. I know that some owner's manuals warn that running out of fuel could damage the fuel pump.

 

[bwilson4web]

. . .
What is the most anyone has put into a tank on a modded REx?
. . .

I've only filled 2.3 gallons but this is going to the 'tippy top' of the filler tube. This is not a practice I encourage.

Bob Wilson

 

[jadnashuanh]

Fuel injected cars' fuel pumps tend to be able to provide way more volume than the injectors need, so some of it is bypassed and returns to the tank. This also filters the fuel more often and to cool things. Trying to get all of the air out of the lines can be problematic, and injectors are also lubricated by the fuel as well as being cooled. Running out of fuel is not a great idea on many of them, and the car will shut off before the tank is actually 'dry'. Then, because the tank is so small, if the car is not level when it is filled, any small angle can potentially prevent you from filling it. Some older diesels can't be restarted if you run out of fuel without a manual priming, but most more modern ones can.

 

[Tacfoto]

How much fuel can a coded 2014-2016 use?
How much fuel can a stock 2017 use?

 

[bwilson4web]

How much fuel can a coded 2014-2016 use?
. . .

I can get 2.3 gallons in if I go 'tippy top.' It usually clicks off at 2.1-2.2 gallons with slower going higher.

Bob Wilson

 

[jadnashuanh]

Filling any car much beyond where the pump's sensor turns it off is not a particularly good idea. Especially if you then leave it or do not run the engine...the cold fuel from the underground tank does expand as it warms up. Potentially faster than you might use it, which may be why some people have problems with sensors going bad.

 

[REvans2001]

I topped off my 2017 i3 REx ONE TIME. Check engine light then appeared and susequent trip to dealer for weekend 4-day repair. Never again!

 

[frictioncircle]

I topped off my 2017 i3 REx ONE TIME. Check engine light then appeared and susequent trip to dealer for weekend 4-day repair. Never again!

Not laughing at your dealer woes, REvans2001, am just enjoying your nicely worded re-telling of the experience!

 

[REvans2001]

 

[jfran2]

When I used Bimmercode to code the Hold State of Charge on my 2015 Rex, it also upped my gasoline volume from 1.9 US gallons to 2.1. I've read that the full 2.4 gallons can be accessed, but it takes coding in Expert mode on Bimmercode, and I've never delved into it.

 

[REvans2001]

 

[sharase]

It is unclear if the fuel tank in the 2017 BMW i3 REx is also software-limited. However, if you were able to fill the tank with 2.1 gallons of fuel after running out of gas, it suggests that the tank is not software-limited to 1.9 gallons.
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