Tacfoto
Posts: 51
Joined: Sun Mar 11, 2018 11:48 pm

2017 REx Fuel Tank size

Sun May 13, 2018 9:01 pm

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
Posts: 4103
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: 2017 REx Fuel Tank size

Sun May 13, 2018 10:01 pm

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.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

alohart
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Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 2017 REx Fuel Tank size

Mon May 14, 2018 12:27 am

Tacfoto wrote: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).
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

SSi3
Posts: 229
Joined: Mon Sep 15, 2014 7:55 am
Location: Ontario, Canada

Re: 2017 REx Fuel Tank size

Tue May 15, 2018 6:32 am

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.
2015 i3 REx - born electric 4/25/15

Tacfoto
Posts: 51
Joined: Sun Mar 11, 2018 11:48 pm

Re: 2017 REx Fuel Tank size

Tue May 15, 2018 9:23 am

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
Posts: 1388
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: 2017 REx Fuel Tank size

Tue May 15, 2018 2:02 pm

Tacfoto wrote: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.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

bwilson4web
Forum Supporter
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Location: Huntsville, AL

Re: 2017 REx Fuel Tank size

Tue May 15, 2018 11:19 pm

Tacfoto wrote:. . .
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
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

jadnashuanh
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Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: 2017 REx Fuel Tank size

Wed May 16, 2018 8:21 am

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.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

Tacfoto
Posts: 51
Joined: Sun Mar 11, 2018 11:48 pm

Re: 2017 REx Fuel Tank size

Sun May 27, 2018 11:36 am

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

bwilson4web
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Location: Huntsville, AL

Re: 2017 REx Fuel Tank size

Sun May 27, 2018 4:38 pm

Tacfoto wrote: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
20k/27k mi 2014 BMW i3-REx
10k/10k mi 2017 Prius Prime

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