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Teach me about fuel cell flappers...

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So I once had a fuel cell in my old malibu.  I couldn't get the car to take fuel quickly due to the fuel cell flapper.

 

I was thinking about doing a fuel cell for my new build (this is the easiest time to do it).

 

I'm scared that the fuel cell won't take fuel quickly.

 

What do y'all do with the flapper to make sure it doesn't restrict the fuel going in?

 

Any help is appreciated.   I am a bit of a newb with fuel cells, so dumb it down for me please.

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I never thought about the flapper being the restriction (now you have me rethinking that slightly), but I was able to speed ours up by increasing the vent breather size. The larger it is, the faster you can evacuate the air being displaced. 

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The modern Fuelsafe brand fill plates with rollover flappers have no such issue. I fueled a car with one of these last year and it took fuel as fast as I could pour it... close to 1/2 gallon per second.

Edited by enginerd

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Make sure the flapper is oriented so that the fuel's momentum opens the flapper and not just the weight.

 

In other words, the hinge needs to be closest to the side of the car that you're filling from.

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Cells only take fuel in as fast as the air in the celland  vent can evacuate. What size vent are you using! 

 

If you are using a small vent then sure has to escape through the filler while fuel is coming in which in turn slows the girl trying to get in. I use a 1.25" vent with discriminator valve. 

 

I use a Pyrotect 22 gallon fuel cell with a spring loaded flapper.. You also need to make sure flapper has a recess below the valve in the foam for it to open into. Never had an issue.

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So, I might be an idiot...

 

It seems like with the fuel cell I was using there is a flapper valve that is made for a remote fill and a standard fill.

 

The standard fill flapper is actually pushed out of the way by the fueling device.

 

The remote fill flapper is located on the remote fill port (where the gas cap is).

 

Anybody have experience with this?

 

As for the vent, I ruled that out by having just the hole in the top plate wide open.  Still didn't take fuel.

 

The fuel would literally fill up the hose and then just trickle in past the flapper.

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No. The cell should always have the flapper in case the remote fill hose is dislodged in an accident. Wouldn't want all/all the fuel to escape in an wreck. 

 

I've been racing in NASCAR/Grand Am/SCCA plus other venues for over 40 years. Never seen a fill cell have a device for a flapper/etc at the cap. Might be some jdm aftermarket or secondary fuel safety item. Might have to look into it.

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That is my thoughts as well.  Would want the flapper at the cell, not remote.

 

I guess the f lappers are not the same between the remote and standard fill.  I can tell you the standard fill one does NOT like to let fuel in.

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On 12/13/2019 at 10:02 AM, cagedruss said:

Cells only take fuel in as fast as the air in the celland  vent can evacuate. What size vent are you using! 

 

If you are using a small vent then sure has to escape through the filler while fuel is coming in which in turn slows the girl trying to get in. I use a 1.25" vent with discriminator valve. 

 

I use a Pyrotect 22 gallon fuel cell with a spring loaded flapper.. You also need to make sure flapper has a recess below the valve in the foam for it to open into. Never had an issue.

 

In ChampCar we are limited to 3/4" fuel vent sizes just as a FYI

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11 hours ago, E. Tyler Pedersen said:

In ChampCar we are limited to 3/4" fuel vent sizes just as a FYI

Actually there is no limit on the size of fuel cell vent hoses. There is a limit on overflow vents, but those are different than the typical vapor/air vent that all fuel cells will have. And those vapor/air vents do not have a rulebook-specified maximum size. 
 

A limit should be added. I have seen some very large vents which may on their own hold half a liter or more of fuel.

Edited by enginerd

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1 1/4" is typical for NASCAR and would have to be pretty long to hold any significant amount of fuel.

 

For example, a hose that size that is 36" long and full of fuel would hold about 0.2 gallons. A 3" dia filler hose would hold that much in less than 6 inches.

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7 hours ago, enginerd said:

Actually there is no limit on the size of fuel cell vent hoses. There is a limit on overflow vents, but those are different than the typical vapor/air vent that all fuel cells will have. And those vapor/air vents do not have a rulebook-specified maximum size. 
 

A limit should be added. I have seen some very large vents which may on their own hold half a liter or more of fuel.

 

You are correct. I misread and thought it was for all vents so I kept mine at 3/4" always. I learn something new every day :)

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On 12/15/2019 at 5:59 AM, E. Tyler Pedersen said:

 

You are correct. I misread and thought it was for all vents so I kept mine at 3/4" always. I learn something new every day :)

 

 

Glad i was told by tech no larger than 3/4" for vent when i did our conversion and gave you your information. Could have saved a lot of headaches. 

 

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