Retrofitting/fixing EU gas tank into US model?

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Tomasz

Well-known member
Joined
Nov 18, 2014
Messages
175
So I've looked at the realoem's catalog and it lists the same part number for fuel tank for both EU and US (part number 16117391827).
It there a chance this is an error? Or maybe the tank is the same, but they put some kind of 0.5 gal filler part (piece of plastic) inside US version (can't find it on the diagrams though).

Does anybody know what the story is there? I'd love to increase my tank to european size.
 
Yes, the only differences seem to be in the charcoal filter and the piping pieces under Ventilation subsection, but I don't see how this will account for the difference in capacity. The US Technical training manual for the W20 engine (http://www.kneb.net/bmw/I01/12_W20 Engine.pdf) statets on page 41:
"The fuel tank capacity is 9 liters / 2.38 gallons with a 2 liter / .5 gallon fuel reserve." Could the difference be due to not accounting for the reserve in the US?
 
Sorry I can't help, but I would like to join the chorus of people who'd like to know exactly what BMW did to reduce the tank capacity. I've been on the lookout for any information of the subject for a few months now and haven't seen anything.
 
rtanov said:
Yes, the only differences seem to be in the charcoal filter and the piping pieces under Ventilation subsection, but I don't see how this will account for the difference in capacity. The US Technical training manual for the W20 engine (http://www.kneb.net/bmw/I01/12_W20 Engine.pdf) statets on page 41:
"The fuel tank capacity is 9 liters / 2.38 gallons with a 2 liter / .5 gallon fuel reserve." Could the difference be due to not accounting for the reserve in the US?

Not sure about the reserve. I've run the tank in my UK Rex down and had to put over 8.5 litres in to fill it back up.
 
PhilH said:
Not sure about the reserve. I've run the tank in my UK Rex down and had to put over 8.5 litres in to fill it back up.

I've run my tank dry and I was able to put 2.14 gal in (which is 8.1 l). I figured that it's 1.9 plus about in filler tube.

Anyway, if I were BMW I would use the same tank and simply use 0.5 gal filler somewhere. I silently hoped it would be a part listed somewhere around fuel sending/pump unit, but it's not listed on any parts diagram.

The only different part number I could find is filler tube, which is different for cars with S991A package installed. Maybe that additional 0.5 gal goes in the tube? If so it should be easy to replace just that part.
 
Can't believe this tank capacity is being brought up again?
Is it me being stupid? Do i3's in the US have 8 or 5 litre tanks?

The tank is 9 litres in Europe.

Equates to UK imperial gallon 1.98

Equates to US gallon 2.38
 
BoMW said:
Can't believe this tank capacity is being brought up again?
What do you mean by 'again?' I was under the impression that this is well known and established fact that US version has smaller fuel capacity. No matter which units you use (liters, UK gallons or US gallons) all sources I've checked say that this is the fact. Are you saying that EU version has exactly the same capacity just marketed differently?

I want bigger, because contrary to urban legends size do matter.
 
There are other topics about this subject on the forum.
I just want to know how many litres fit into a U.S. tank?

I have ran my i3 dry and I've never got to 9 litres of petrol, more like 8.5L
 
BoMW said:
There are other topics about this subject on the forum.
I just want to know how many litres fit into a U.S. tank?

I have ran my i3 dry and I've never got to 9 litres of petrol, more like 8.5L

#uk
We've filled our twice. First time it took 8.8 litres and second time it took 8.9 litres. Both times at Shell gas stations.
 
I'd hang on before going EU spec. I'm sure some clever so and so will bring out an after market 15-20 litre tank, assuming there is space. It would sell like hot cakes.

Probably need to do some coding though or the GOM and gauges won't be correct.
 
BoMW said:
SSi3 so when refilling at the gas station the pump clicks and stops at about 1.75 US gallons or 6.8 litres?

Normally I can put in about 1.9 US gallons in. Once when I run it dry on purpose and then filled up to the brim (I could see fuel after pulling out the nozzle) I managed to put 2.14 US gallons (8.1l) in.

Due to my commute I'd love to be able to put another 0.5 gal or so, that would allow me to go two trips without refilling, as a result I would be seeing gas station only once a week (I do my commuting trip twice a week). Now I'm coming slightly below 1/2 tank after one trip so I effectively have to fill up every time I drive to my HQ.
 
nowtta60 said:
I'd hang on before going EU spec. I'm sure some clever so and so will bring out an after market 15-20 litre tank, assuming there is space. It would sell like hot cakes.
I seriously doubt it. Seeing how portable gas tank manufacturers are being driven out of the market by liability insurance costs I simply can not see anybody having funds to certify (and then insure) new tank with that limited user base. Even if every REx out there bought one.

nowtta60 said:
Probably need to do some coding though or the GOM and gauges won't be correct.
Frankly I couldn't care less about GOM readings as long as zero reading is in the right place (as in: when there is zero fuel in the tank).
 
Well, let me speak from an experience I had with a REx that may explain your discrepancy.

I was out test driving a service loaner for a drivetrain malfunction after the REx ran for an extended period(this was before we knew about the moisture in the REx generators), and was coming back from a trip to the beach trying to get the fault to appear. I was about 2 miles from the dealer, and was running on the REx when I ran out of gas according to the gauge-which shuts down everything, no driving power available(even with battery power still showing as ~5%!!!). Being so close to the dealer, I really did not want to jog back for a gas can, so I tried a few things trying to eek a bit more juice out of it. One of my ideas was attempting the Emissions Inspection Mode, to recharge the vehicle just enough to let me drive it up the last hill. Popped the hatch and started the test mode, and the REx fired right back up and ran without a problem for almost 10 minutes before it began to stumble and then shut off from fuel starvation. This means there was enough gas left in the tank to support high speed running for 10 minutes, but the REx would not use it in normal operating modes.

I obviously cannot prove this accounts for all the discrepancy reported in tank capacity, but it does make a difference. I would be curious to see how close to being truly empty the UK REx system will run compared to my findings. Maybe the reserve BMW incorporated is not a physical reserve, but a software modification to shut off the REx a bit sooner than the UK counterparts?
 
has anybody looked around the fuel tank is there any room for a larger one or is it rammed in with no room for maneuver, i am an engineering/fabricator and do this for a living and ive only had my Rex for a week so not looked yet, but if its possible i might consider making them.
 
GodFollower said:
I obviously cannot prove this accounts for all the discrepancy reported in tank capacity, but it does make a difference. I would be curious to see how close to being truly empty the UK REx system will run compared to my findings. Maybe the reserve BMW incorporated is not a physical reserve, but a software modification to shut off the REx a bit sooner than the UK counterparts?
That would be exactly the way BMW does things. 10 minutes of high speed REx run is equivalent of about 4.5-5kWh which is about 16-20 miles. Which turns is awfully close to the magical 37mpg we are supposed to be getting on REx.

So the next step would be to runt he REx dry, then re run it to make it really dry, then go to the gas station and see if you can put 2.5gal in it. And if you could, start poking into coding settings to find out which one it is.
 
busaman said:
has anybody looked around the fuel tank is there any room for a larger one or is it rammed in with no room for maneuver, i am an engineering/fabricator and do this for a living and ive only had my Rex for a week so not looked yet, but if its possible i might consider making them.
I studied BMWs documentation and the problem I saw is that i3 is measuring pressure and temperature in the tank. Then it compares it to a map stored in the memory to detect leaks. Any artificial modification of original tank will throw things off and result in constant CEL illumination.

The only way I can come up with is to install an aux tank with transfer pump and shut of valve close enough to the original installation as to not affect volume of air in the original tank when the valve is closed too much. Then you could transfer fuel from one to another when it's getting close to empty.
 
ive just had a good look at the PDF as i see it there are two easy ways that shouldn't trigger any faults. 1 increase the size of the base of the tank (if there is room) that wont interfere with any sensors just give more volume (there is very little pressure in there anyway).
2 have a reservoir built into the filler neck pipework also shouldn't interfere with the electronics.

i would just love to get my hands on one so i can see exactly what im dealing with.
 
busaman said:
ive just had a good look at the PDF as i see it there are two easy ways that shouldn't trigger any faults. 1 increase the size of the base of the tank (if there is room) that wont interfere with any sensors just give more volume (there is very little pressure in there anyway).
2 have a reservoir built into the filler neck pipework also shouldn't interfere with the electronics.
It's not the physical interference that matters. It's the amount of air and it's pressure changes when the temperature changes. Any volume of air that you'll add to the tank will throw off pressure changes in correlation to temperature changes, and that's what the system is monitoring.
 
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