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Learn me on Fuel Vent Valves Plz


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Building car 2's fuel vent system.  Car 1 takes fuel slow, want to make improvements by shortening the fuel vent hose distance from looping around the car.  Safety is %100 though, so no shortcuts.

 

Attachment method is a 5/8 hose or larger.  Most I see are AN fittings?

 

What I want is for it to let air out rapidly when filling fuel, let air in slowly when driving fast, and not let fuel out in any condition, but specifically turning left rapidly and in a bad case when upside down.

 

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Chris

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Still an e30? Only mod I've done or seen is removed charcoal canister and then cut the line just forward of the tank that runs all the way up to engine bay. Both teams can empty Hunsaker in about 20-25 sec. 

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Bump :)

 

Haven't personally messed around with vents on a stock tank system, but might need to soon, so I'm curious to see what the right way to do it is...

 

I'd probably make/buy a surge tank, set it up to have a little bit of air space in the top and put a fuel cell style rollover/vent valve there. Then route all the vents to it.

 

image.png.a293608e753d6550bc0a6bcf9afd055b.png

 

The tank itself I'd go for something like the below. Clump the vents/out towards the center of it on the top lid and return pipe would be a stand pipe up the center (center sees the least level change from G loading and less likely to slosh fuel into any of the vent lines)

 

image.png.273a3e7f3f5fc213089412d3fda44769.png

 

Like I said, I haven't personally done it, but it's what I would try first....

 

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16 hours ago, jakks said:

Still an e30? Only mod I've done or seen is removed charcoal canister and then cut the line just forward of the tank that runs all the way up to engine bay. Both teams can empty Hunsaker in about 20-25 sec. 

 

Hmm,  Id be interested to know how that is possible.

 

The issue is the large fuel vent (for pushing air out during fueling) is attached to the filler neck near the gas cap.  With the cap on and sealed, there is no way for fuel to escape (this is good) but with the hunsaker jug hose inserted into the filler neck, there is also too good of a seal for the air to go out (this is bad).  That negates that being a valid method of venting, unless the teams in question are using a funnel and open jugs (YMMV, but I do not like this method) which brings the question as to why they spent money on hunsakers.

image.png.4de8a0af999dfceaee4081f27abd93f7.png

 

The fuel vent line going to the charcoal canister is much too small to allow venting, especially if it must run all the way up to the passenger side, then back down and across to the driver side, then forward to the charcoal canister (flow is restricted by pipe length causing resistance).

 

 

The question is what to do with the large vent line once it is removed from the filler neck port. 

 

I want to run it to a safe place, install a race-specific type vent valve, and be done with it.  

I was hoping some other teams (of any car preference) had experience with these type of valves and could make a suggestion.  

 

The secondary questions are: How to mount/affix this device to the car?  Do certain types of these valves require perfectly vertical orientation to function?  Is there a required vertical height needed to be acquired over the maximum fuel level to prevent fuel slosh causing issues?  Is there any rated CFM of flow to determine what size I need to vent air fast enough to not impede filling activities?

 

Thanks

Chris

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We did quite a bit of brainstorming when re-doing our filler neck and vent system and came up with this...

 

Welded on a J1114 filler neck to use a modern gas cap (thanks to GWR for the idea!). This seems to have solved our "puking 2 gallons of fuel out in left hand turns" issue which was caused by the stock bayonet cap.

This neck and cap:

http://www.capsnecks.com/neckdetails/nj-1089-d-fuel-neck-with-diesel-insert

http://www.capsnecks.com/capdetails/cj-5299-tethered-gas-cap

 

We deleted all of the other fuel system components (stock vents, carbon canister, expansion tank, etc) and used the large (5/8"?) vent line on the top of the tank. The vent line runs up to the top of the trunk (above the filler neck) to the bottom of a small metal cylinder. Inside the cylinder is this roll-over valve.

https://www.summitracing.com/parts/sum-g3114

Then the top of the cylinder goes to a cheap breather filter which is sitting outside at the base of the rear windshield.

 

I tried to find an inline roll-over valve, but they don't seem to exist. We have every other line and vent plugged, so as long as the roll-over valve and gas cap work it shouldn't leak in a roll-over. We have only run this setup for 1 event, but no issues so far.

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8 minutes ago, mender said:

NASCAR check valve in 1.25" (could neck that down):

 

 

Would that work as a vent valve? My assumption with the check valves I found was it would allow vapor out, but wouldn't let air back in when the fuel level dropped (or vice-versa depending on direction). Maybe I'm overthinking it?

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Our old car had the same problem. I was considering using a Ford capless filler assembly for the vent on our car. But we installed a fuel cell before I got around to it. The plan was to make an overflow can to insert into it. Then there's no cap to mess with. The old charcoal canister line would have let in air while it was running.

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Euro cars don’t have the charcoal canister, so you can model that vent hose that runs from the plastic part that is in the fender well to the engine bay off of it. When we were replacing the tank, we cut the hose just forward of the tank and routed it to vent right near the driveshaft. You can choose to put a filter on it if you wish. We did not. As far as the pipe you’re talking about in the neck, you want to leave that covered so only drill out enough for the 1.25” hose off the Hunsaker and enough for air to escape as well. The whole thing shouldn’t need cut out. 

Refer to the post by AndrewK for the euro venting. http://spece30.com/t/charcoal-canister-removal/5229

 

One other thing, make sure that large hose in the passenger rear fender well is not collapsed. Take cover off and remove all the dirt behind it and reshape it. Seen that on 2 cars. 

 

Confident you don’t need to re-engineer that system. 

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1 hour ago, CabotTeg118 said:

 

Would that work as a vent valve? My assumption with the check valves I found was it would allow vapor out, but wouldn't let air back in when the fuel level dropped (or vice-versa depending on direction). Maybe I'm overthinking it?

 

Those aren't hermetically sealed so the cell can still vent to atmosphere preventing any pressure/vacuum build up.

Edited by Bremsen
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2 hours ago, Huggy said:

 

Hmm,  Id be interested to know how that is possible.

 

The issue is the large fuel vent (for pushing air out during fueling) is attached to the filler neck near the gas cap.  With the cap on and sealed, there is no way for fuel to escape (this is good) but with the hunsaker jug hose inserted into the filler neck, there is also too good of a seal for the air to go out (this is bad).  That negates that being a valid method of venting, unless the teams in question are using a funnel and open jugs (YMMV, but I do not like this method) which brings the question as to why they spent money on hunsakers.

image.png.4de8a0af999dfceaee4081f27abd93f7.png

 

The fuel vent line going to the charcoal canister is much too small to allow venting, especially if it must run all the way up to the passenger side, then back down and across to the driver side, then forward to the charcoal canister (flow is restricted by pipe length causing resistance).

 

 

The question is what to do with the large vent line once it is removed from the filler neck port. 

 

I want to run it to a safe place, install a race-specific type vent valve, and be done with it.  

I was hoping some other teams (of any car preference) had experience with these type of valves and could make a suggestion.  

 

The secondary questions are: How to mount/affix this device to the car?  Do certain types of these valves require perfectly vertical orientation to function?  Is there a required vertical height needed to be acquired over the maximum fuel level to prevent fuel slosh causing issues?  Is there any rated CFM of flow to determine what size I need to vent air fast enough to not impede filling activities?

 

Thanks

Chris

 

There is an acura in central region that just used a large diameter air-tool fitting...   so they routed that tube as a vent and an overflow tube out the back of the car....   when they fuel they have an old fuel jug with the round / open fitting on it, they snap that into the back of the car, and fill away, till fuel comes out into that "catch can"...

 

My understanding is this whole section of the rules was to make that setup legal... (apparently tech liked it because it prevents spilling fuel)  (although you are still required to run a catch pan under the filler neck)...

 

In this way, you can evacuate the air from your tank until fuel comes out into the tube, jug in the back...  when you disconnect that tube / jug the air fitting seals itself...  

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For the vent side of the system, you sir need a discriminator valve. Can keep the vent line short but keep fuel from pouring out VIA g-force when the tank is full.

 

We did have someone report some fuel slosh coming out of our car @ Daytona, need to pull mine apart and make sure the check ball didn't deteriorate from the eth gas. Up until Daytona we've had zero known issues of fuel vent spillover with a full tank since adding the discriminator valve (that was about 2 years ago...). 

 

https://www.summitracing.com/parts/abt-re185?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-atl-fuel-cells&gclid=CjwKCAjwlcXXBRBhEiwApfHGTYnRf8EQyvGLcFmjPqXT63PoziYg0TUvv6MA29AyggTo9xo5Omz1hBoCD_oQAvD_BwE

 

 

Edit: ATL's is nicer than mine (go figure), I am using a single ball, whereas this one uses 2, thus it seals off with the fuel at a lower point in the body of the valve.

 

 

Edited by pintodave
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2 hours ago, CabotTeg118 said:

 

Would that work as a vent valve? My assumption with the check valves I found was it would allow vapor out, but wouldn't let air back in when the fuel level dropped (or vice-versa depending on direction). Maybe I'm overthinking it?

Other way around: it's spring loaded to seal in the outward direction (upside down car) but will allow air to come in with fuel usage.

 

The usual is to have the valve mounted at the rear of the car and a crew member places a catch can on the end of the vent line. The catch can has a probe that opens the valve manually during fueling and the catch can is for the excess fuel that comes up the vent.

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4 minutes ago, mender said:

Other way around: it's spring loaded to seal in the outward direction (upside down car) but will allow air to come in with fuel usage.

 

The usual is to have the valve mounted at the rear of the car and a crew member places a catch can on the end of the vent line. The catch can has a probe that opens the valve manually during fueling and the catch can is for the excess fuel that comes up the vent.

 

Is the spring pressure that light that it allows air to be drawn in as needed? Or am I thinking of the construction incorrectly?

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2 minutes ago, pintodave said:

 

Is the spring pressure that light that it allows air to be drawn in as needed? Or am I thinking of the construction incorrectly?

It's an aluminum plate that provides the seal so it isn't perfect. It'll drip but not gush if upside down and will allow air in as the fuel load decreases.

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We use an inline rollover valve like the following link. Very simple mounted "inside" small fuel hose. Loop the hose and mount it in a vertical section (so it closes when upside down). Connect the hose via T to you main vent and this simply acts to vent the tank to television be negative pressure as you use fuel. The one we have is really sensitive and I suspect any sort of velocity on fuel trying to get out will close it trigger the check valve. It would also check up/close under pressure during fueling so it's just for when racing. 

 

https://www.racerpartswholesale.com/product/629/Valves

 

we tried a quick connect air hose (like for air tools in a shop) as the primary method. Click the male end in when fueling with a hose running to an empty fuel jug. 1) it wasn't enough air venting out to dump a hunsaker so we needed to add a second vent and 2) we could never get it to puke fuel to give warning of when the tank is. Early full. The fuel would just overflow at the filler neck at the same time. 

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SO whats the difference in a discriminator and a rollover vent valve?  Just the fact that the discriminator will stop fuel even with the car rightway up?

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Yes. Generally speaking, the in-line roll over valve is a steel ball, thus it is only activated by gravity. The Discriminator valve will engage whenever fluid is coming into contact with it since the "ping pong" balls float. I still have the steel ball rollover valve at the in-tank exit, then the discriminator valve mounted externally of that in-line with the vent line. 

 

We use this for the tank fitting: https://www.pegasusautoracing.com/productdetails.asp?RecID=696

 

Edited by pintodave
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1 hour ago, pintodave said:

Yes. Generally speaking, the in-line roll over valve is a steel ball, thus it is only activated by gravity. The Discriminator valve will engage whenever fluid is coming into contact with it since the "ping pong" balls float. I still have the steel ball rollover valve at the in-tank exit, then the discriminator valve mounted externally of that in-line with the vent line. 

 

We use this for the tank fitting: https://www.pegasusautoracing.com/productdetails.asp?RecID=696

 

Since pingpong balls float, will the discriminator valve stop fuel when the car is upside down?

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NO   With the car and valve upside down the weight of the fuel will override the float of the ping pong ball when inverted the steel check ball will fall seal and stop the fuel  .. 

Edited by okkustom
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Yup what he said to both points. I hope to never test it out but the weight of the fuel should overcome the ping-pong balls.

 

That coupled with the steel ball roll over valve I think is a good package to help prevent a fuel spill/leak in an accident. I don't mind a little redundancy there. 

 

I thought about how both could fail:

 

- Partial roll over concerns me with the steel ball not sealing

- In a serious roll over, thrashy type of crash, parts could start separating from the car, so the discriminator vavle doesn't work very well if it gets damaged or ripped off.

 

 

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Here's a question that's slightly on topic.

 

In the rules, surge tanks are limited to .5 gallons.

 

What if you have pumps in your surge tank?  Is it .5 gallons useable?  or .5 gallons overall dimensions?

 

Asking for a friend.....

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2 hours ago, SonsOfIrony said:

Here's a question that's slightly on topic.

 

In the rules, surge tanks are limited to .5 gallons.

 

What if you have pumps in your surge tank?  Is it .5 gallons useable?  or .5 gallons overall dimensions?

 

Asking for a friend.....

Wrong thread, please take this to it’s own thread.  

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5 hours ago, pintodave said:

Yup what he said to both points. I hope to never test it out but the weight of the fuel should overcome the ping-pong balls.

 

That coupled with the steel ball roll over valve I think is a good package to help prevent a fuel spill/leak in an accident. I don't mind a little redundancy there. 

 

I thought about how both could fail:

 

- Partial roll over concerns me with the steel ball not sealing

- In a serious roll over, thrashy type of crash, parts could start separating from the car, so the discriminator vavle doesn't work very well if it gets damaged or ripped off.

 

 

 

17 hours ago, okkustom said:

NO   With the car and valve upside down the weight of the fuel will override the float of the ping pong ball when inverted the steel check ball will fall seal and stop the fuel  .. 

 

 

Im not sure I understand.  The idea of the pingpong ball or whatever is in there as a “float” is that it is buoyant.  The weight of the gas doesn’t come into play?  

 

Im gonna order the ATL valve and play around with it before installing on the car.  I can always add another device, but I am limited on my vertical space to mount these things, and for each additional device the flow will be reduced.

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