Prius Bladder System-Tip to Restore Tank Capacity

hb06 · 10-24-2006, 01:40 PM

--Wikipedia

Prius-Fuel Tank/Gauge

"The North American Prius uses a rubber bladder system besides a charcoal filter for gas vapor emissions control. However, the rubber is temperature sensitive and will shrink/stiffen in cooler weather lowering the tank capacity from the default 11.9 gallons, and contributing to a wildly inconsistent fuel gauge. This is similar to the "memory" in NiCad batteries.

"Slow filling of the tank with careful "burping" of the fuel inlet past the first "click-off", without spilling, will stretch the bladder back out and restore the original tank capacity."

Page 206; The tank is 45L (11.9 gal., 9.9 Imp.gal) and decreases by 5L (1.3 gal., 1.1 Imp.gal) @ -10°C/14°F."

Beryl Octet · 10-24-2006, 01:54 PM

[quote=HBO6 @ Oct 24 2006, 01:40 PM) [snapback]337411[/snapback]</div>

Quote:

--Wikipedia

Prius-Fuel Tank/Gauge

"The North American Prius uses a rubber bladder system besides a charcoal filter for gas vapor emissions control. However, the rubber is temperature sensitive and will shrink/stiffen in cooler weather lowering the tank capacity from the default 11.9 gallons, and contributing to a wildly inconsistent fuel gauge. This is similar to the "memory" in NiCad batteries.

"Slow filling of the tank with careful "burping" of the fuel inlet past the first "click-off", without spilling, will stretch the bladder back out and restore the original tank capacity."

Page 206; The tank is 45L (11.9 gal., 9.9 Imp.gal) and decreases by 5L (1.3 gal., 1.1 Imp.gal)] -10°C/14°F."
[/b]

I think I tried this one time, and the car burped on me. It took a few days to get the gasoline smell out of my shoes, too.

Cheap! · 10-24-2006, 02:00 PM

If we put our heads together, we should be able to figure out how to install a small hose that sits just behind the gas cap and runs to the top of the bladder. A burp hose so to speak that would let air run from top of the bladder to the top of the fill hose, then on to the gas station recovery vents on the nozzle.

Is anyone working on this?

Charles Suitt · 10-24-2006, 02:19 PM

Quote: " a small hose that sits just behind the gas cap and runs to the top of the bladder "

One of the super low pollution features *IS* the bladder system to prevent gasoline fumes from escaping into the atomsphere when fueling the Prius. Sounds like such a 'hose' would defeat that feature if actually connected to the bladder itself. Can't see a practical way to connect such a hose to the station's vapor recovery system.

Perhaps you are thinking of a hose to the top of the 'tank' structure in which the bladder is contained to relieve any back-pressure in the tank. Anyone here know whether there is a back-pressure relief valve or system to allow bladder expansion within the tank?

eagle33199 · 10-24-2006, 02:21 PM

The only real problem with that is: what happens when the tank is full? with the hose there, it seems to me that the excess would just travel up the hose and into the gas stations recovery system... with no pressure infront of the pump, the auto shutoff wouldnt work, and we would end up giving them tons of extra money... all for a few extra miles of driving between pumps...

Cheap! · 10-24-2006, 02:50 PM

<div class='quotetop'>QUOTE(Charles Suitt @ Oct 24 2006, 01:19 PM) [snapback]337439[/snapback]</div>

Quote:

Quote: " a small hose that sits just behind the gas cap and runs to the top of the bladder "

One of the super low pollution features *IS* the bladder system to prevent gasoline fumes from escaping into the atomsphere when fueling the Prius. Sounds like such a 'hose' would defeat that feature if actually connected to the bladder itself. Can't see a practical way to connect such a hose to the station's vapor recovery system.

Perhaps you are thinking of a hose to the top of the 'tank' structure in which the bladder is contained to relieve any back-pressure in the tank. Anyone here know whether there is a back-pressure relief valve or system to allow bladder expansion within the tank?
[/b]

Sorry this is so crude, I just don't have time to draw this right now.

[attachmentid=5461]

<div class='quotetop'>QUOTE(eagle33199 @ Oct 24 2006, 01:21 PM) [snapback]337444[/snapback]</div>

Quote:

The only real problem with that is: what happens when the tank is full? With the hose there, it seems to me that the excess would just travel up the hose and into the gas stations recovery system... with no pressure in front of the pump, the auto shutoff wouldn’t work, and we would end up giving them tons of extra money... all for a few extra miles of driving between pumps...
[/b]

The hose would be very small since it only needs to let air bleed off into the closed system. It could be in the main fill line below the vapor recovery, but above the burp problem. If any gas station recovery system would fail, I would hope anyone driving would have an IQ big enough to know that the Prius won't hold 987 gallons, or even 12 gallons.

I understand your concern for the environment since I have it too. I think this would prevent a lot of fuel belching on the ground as it does now from time to time with new owners.

FarmGeek · 10-24-2006, 03:14 PM

I have never had a burp and I get consist readings and fill ups. Doesn't matter what station or pump.

I fill the first 4-5 gallons at full speed and then hold the pump handle at the slowest speed for the rest of the fill up. I'm able to pump 5-7 more shut offs after the first shut off. Usually getting another .5 - .75 gallons in the bladder/tank.

I have had the pump shutoff a couple of times on full speed and had to take the nozzle out enough to get the back pressure released.

With close to 28000 miles in ten months, I'm real happy with the Prius.

ScottY · 10-24-2006, 03:47 PM

Cheap! I think your diagram is pretty neat and should solve this problem without causing extra environmental damage.

Let me suggest an easier solution. Fill up, stop at first click, fill up again when "guess" guage down to 1 or 2 bars.

eagle33199 · 10-24-2006, 04:02 PM

I'm not really sure i (or any of us, really) am qualified to tell how such a proposed system would handle in terms of gas pumps and vapor emissions.

Regardless, i'll say it's an interesting idea. However, i think you would need several things to be able to pull it off: first, someone who's out of warrenty (you'd have to be crazy to invalidate much of the warrenty with something like this). Second, a mechanic willing to take the plunge. and third, a fluid flow expert (i have one in mind, actually), to model the situation properly and determine if it would actually work. oh, and maybe fourth, an expert on vapor emissions and gas pump design.

needless to say, i think all it will ever really be is a diagram on a website.

Leo · 10-24-2006, 04:14 PM

I had thought the solution would be a one-way trap on the filler pipe, that would permit fuel to go into the bladder, but prevent it from coming out.
As I understand it, the filler pipe has a rubber gasket that fits snuggly around the pump nozzle, and this gasket prevents displaced air or gas from flowing back up past the nozzle. So as the bladder becomes full, adding additional fuel causes the bladder to stretch somewhat (especially if there is any air in the bladder, which would compress). When you pull out the nozzle, the pressure forces some of the fuel back out the filler pipe.
Because the bladder collapses around the fuel, the engineers probably did not feel that a pipe to vent displaced air was necessary.
However, the problem with my suggestion of a one-way trap is that it might cause the fuel in the bladder to be under some pressure, which would then force the fuel into the fuel injectors if it couldn't escape through the nozzle.

10-24-2006, 02:19 PM	#4
Charles Suitt Senior Member Join Date: Oct 2004 Location: Dallas TX Posts: 1,624 My Car: 2007 Prius Model: Package: #6 Touring Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	Quote: " a small hose that sits just behind the gas cap and runs to the top of the bladder " One of the super low pollution features IS the bladder system to prevent gasoline fumes from escaping into the atomsphere when fueling the Prius. Sounds like such a 'hose' would defeat that feature if actually connected to the bladder itself. Can't see a practical way to connect such a hose to the station's vapor recovery system. Perhaps you are thinking of a hose to the top of the 'tank' structure in which the bladder is contained to relieve any back-pressure in the tank. Anyone here know whether there is a back-pressure relief valve or system to allow bladder expansion within the tank? __________________ Charles Suitt Dallas Texas 2007 Touring Edition (Former Prius: 2004)

10-24-2006, 04:02 PM	#9
eagle33199 Platinum Member Join Date: Mar 2006 Location: Minnesota Posts: 4,283 My Car: 2006 Prius Model: Package: #7 Thanks: 35 Thanked 70 Times in 40 Posts Friends: 3	I'm not really sure i (or any of us, really) am qualified to tell how such a proposed system would handle in terms of gas pumps and vapor emissions. Regardless, i'll say it's an interesting idea. However, i think you would need several things to be able to pull it off: first, someone who's out of warrenty (you'd have to be crazy to invalidate much of the warrenty with something like this). Second, a mechanic willing to take the plunge. and third, a fluid flow expert (i have one in mind, actually), to model the situation properly and determine if it would actually work. oh, and maybe fourth, an expert on vapor emissions and gas pump design. needless to say, i think all it will ever really be is a diagram on a website. __________________

LinkBacks (?) LinkBack to this Thread: http://priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/24964-prius-bladder-system-tip-restore-tank-capacity.html
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Tipped Bladder on RightHealth	This thread	Refback	07-22-2009 05:17 AM
Tipped Bladder on RightHealth	This thread	Refback	06-24-2009 10:15 PM
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10-24-2006, 01:40 PM	#1
hb06 Senior Member Join Date: Aug 2006 Posts: 486 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	--Wikipedia Prius-Fuel Tank/Gauge "The North American Prius uses a rubber bladder system besides a charcoal filter for gas vapor emissions control. However, the rubber is temperature sensitive and will shrink/stiffen in cooler weather lowering the tank capacity from the default 11.9 gallons, and contributing to a wildly inconsistent fuel gauge. This is similar to the "memory" in NiCad batteries. "Slow filling of the tank with careful "burping" of the fuel inlet past the first "click-off", without spilling, will stretch the bladder back out and restore the original tank capacity." Page 206; The tank is 45L (11.9 gal., 9.9 Imp.gal) and decreases by 5L (1.3 gal., 1.1 Imp.gal) @ -10°C/14°F."

10-24-2006, 02:00 PM	#3
Cheap! Senior Member Join Date: Apr 2006 Posts: 1,157 My Car: Model: Package: Thanks: 0 Thanked 1 Time in 1 Post Friends: 4	If we put our heads together, we should be able to figure out how to install a small hose that sits just behind the gas cap and runs to the top of the bladder. A burp hose so to speak that would let air run from top of the bladder to the top of the fill hose, then on to the gas station recovery vents on the nozzle. Is anyone working on this?

10-24-2006, 02:21 PM	#5
eagle33199 Platinum Member Join Date: Mar 2006 Location: Minnesota Posts: 4,283 My Car: 2006 Prius Model: Package: #7 Thanks: 35 Thanked 70 Times in 40 Posts Friends: 3	The only real problem with that is: what happens when the tank is full? with the hose there, it seems to me that the excess would just travel up the hose and into the gas stations recovery system... with no pressure infront of the pump, the auto shutoff wouldnt work, and we would end up giving them tons of extra money... all for a few extra miles of driving between pumps...

10-24-2006, 03:14 PM	#7
FarmGeek Join Date: Sep 2006 Posts: 15 My Car: Model: Package: Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I have never had a burp and I get consist readings and fill ups. Doesn't matter what station or pump. I fill the first 4-5 gallons at full speed and then hold the pump handle at the slowest speed for the rest of the fill up. I'm able to pump 5-7 more shut offs after the first shut off. Usually getting another .5 - .75 gallons in the bladder/tank. I have had the pump shutoff a couple of times on full speed and had to take the nozzle out enough to get the back pressure released. With close to 28000 miles in ten months, I'm real happy with the Prius.

10-24-2006, 03:47 PM	#8
ScottY Senior Member Join Date: May 2005 Location: Long Island, NY Posts: 1,249 My Car: 2005 Prius Model: Package: #3 Thanks: 0 Thanked 2 Times in 2 Posts Friends: 1	Cheap! I think your diagram is pretty neat and should solve this problem without causing extra environmental damage. Let me suggest an easier solution. Fill up, stop at first click, fill up again when "guess" guage down to 1 or 2 bars.

10-24-2006, 04:14 PM	#10
Leo Leo Join Date: Jul 2005 Location: Ottawa, Canada Posts: 55 My Car: 2005 Prius Model: Package: B Thanks: 0 Thanked 0 Times in 0 Posts Friends: 0	I had thought the solution would be a one-way trap on the filler pipe, that would permit fuel to go into the bladder, but prevent it from coming out. As I understand it, the filler pipe has a rubber gasket that fits snuggly around the pump nozzle, and this gasket prevents displaced air or gas from flowing back up past the nozzle. So as the bladder becomes full, adding additional fuel causes the bladder to stretch somewhat (especially if there is any air in the bladder, which would compress). When you pull out the nozzle, the pressure forces some of the fuel back out the filler pipe. Because the bladder collapses around the fuel, the engineers probably did not feel that a pipe to vent displaced air was necessary. However, the problem with my suggestion of a one-way trap is that it might cause the fuel in the bladder to be under some pressure, which would then force the fuel into the fuel injectors if it couldn't escape through the nozzle.