Venting Fuel Cell

[Mike Jones]

I have a Lola T-342 and have gone from the side mount fuel bladders to a wedge fuel cell behind the seat. I originally vented it to the bottom. This will not work as it will not clear the trailer, the road, small animals, etc. Where should I go with this? What about the carburetor side of the engine compartment? Everything is AQP. Lost

Mike

[RussMcB]

I've been wondering lately if routing the fuel cell vent to the catch can would be a good or bad idea.

In the FB rules, it only says it needs to be a certain distance from the driver.

[kea]

Nothing better than venting fuel and its vapors to a can....Boom!
By routing the vent hose, first up, and than down to the lower frame rail (at least 12" away from the driver, not like the FSCCA car), if the vehicle were to ever end up, upside down, than the fuel would not siphon out.
Keith

[bob darcey]

In addition to Keith's good advice, you should try to route the vent line so as to avoid fuel spilling out the vent during cornering. If the vent connection is one side of the cell, run the line to the other side of the car before turning upwards.

[Charles Warner]

Or use a simple one-way valve and be done with it.

[CWilcox]

The crossle I'm driving has an inverted stop valve in it (ball in canister so if you go inverted the ball seals against the outlet and stops fuel leak). Otherwise it is just a piece of tubing routed 10" or 12" (whatever rulebook says plus some) behind the driver on the right hand side as far away from sparks or hot exhaust parts as possible.

[Eric Cruz]

Nothing better than venting fuel and its vapors to a can....Boom!
By routing the vent hose, first up, and than down to the lower frame rail (at least 12" away from the driver, not like the FSCCA car), if the vehicle were to ever end up, upside down, than the fuel would not siphon out.
Keith

On my FE I extended the vent line with AQP hose all the way back until it exits the bodywork by the bell housing, on the side of the car AWAY from the exhaust. It is fitted with a one way valve. The point of a fuel cell vent is to allow air to enter the cell to replace the lost volume of fuel as it is consumed, and prevent a negative pressure situation, not to vent anything out. But the one-way valve doesn't act instantaneously, so it's good to have the end of the vent line well away from you and hot things as Keith implies. And the siphon point is a good one as well - mine exits down by the lower frame rail, but that was more a matter of convenience than thinking ahead.

Best regards,
Eric

[Mike Jones]

Thanks for the info to keep me from going boom.

[Modo]

I vented to the bottom of the engine floor pan with a tire valve stem with the schrader valve removed and it was flush mounted....hose went to tire stem with clamp and up to one way valve and tank filler neck....was hoping to slightly pressurize the fuel cell....had filter material in it of course and up top the one way valve......they say not to pressurize cell but this would not amount to much. ( FT-3 design spec is aprx 450 psi...holy mother of G)
Anyway bottom vent didn't hit anything and cost 2 bucks

Mike O

[stonebridge20]

The Ex Peter Revson McLaren Mk1c Can-Am car we restored a couple of years ago used a Schrader valve (Tire valve stem) mounted directly in the fuel cells (two of them) filler plates. We wanted to keep the car "correct" so they stayed there and work fine!

[rickb99]

Could always install one of these close to the cell for that extra bit of security.
http://www.atlltd.com/ventvalves.htm

Have I lost it? I seem to remember these check valves used to be a required item. Maybe the fuel sample port took its place

[racer27]

That's what I use --- a check valve at the tank (Sourced from Pegasus). I've seen some people use a valve at the end of the vent line, but it makes no sense to me to have several feet of line filled with fuel in the engine bay of a car that could be on it's side or upside-down. I also routed the line as reccommned by Dave W, so even without a value, it should not leak,

[RussMcB]

Or use a simple one-way valve and be done with it.

First: Good topic. I'm learning some useful tips.

I think I may need to be educated. I'm feeling ignorant about the condition(s) that we'd want to eliminate.

I understand the obvious desire for fuel not to flow out of the car when it's upside down.

I understand (I think), that when fuel (or vapors) needs to be vented (for whatever reason - expansion, overfilling, etc.), that you would want the vented fuel or vapors to come out in a relatively save place - away from driver and hot parts.

I also understand that good routing will prevent fuel from sloshing out during lateral/longitudinal G forces.

But, regarding one way and/or pressurized valves - Don't you need to allow for the vent to work both ways? Out for expansion and in to replace lost volume as the fuel level goes down during a session?

Lastly, re: the tire schrader valves. Are they really valves? If so, what opens them and in which direction?

Thanks.

[Tom Sprecher]

...I'm feeling ignorant...

Most people who know you would say go with your gut on that one.

...I understand the obvious desire for fuel not to flow out of the car... when it's upside down...

Or in any position for that matter hence the use of a one way valve.

...you would want the vented fuel or vapors to come out in a relatively save place - away from driver and hot parts...

Yes, in the event that something should go terribly wrong with the one way valve.

...I also understand that good routing will prevent fuel from sloshing out during lateral/longitudinal G forces...

See last comment

...Don't you need to allow for the vent to work both ways?...

No. You need to prevent negative pressure building up as the fuel is consumed. Any positive pressure will be eliminated by pumping fuel out of the cell.

...Lastly, re: the tire schrader valves. Are they really valves? If so, what opens them and in which direction?

They are more like a screw-on quick disconnect vs. a snap-on style like air line fittings.

[RussMcB]

So, are you thinking the sole purpose of the fuel cell vent is to allow air in and never to allow anything out?

What about when your race car is sitting in the morning sun as the day warms up? No problem because your fuel cell and connected system should be able to handle it?

[Tom Sprecher]

On my fuel cell the one way vent valve is built into the AN fitting on the fill plate and allows air IN. Any pressure that builds up due to the thermal expansion you described is minimal compared to all the other forces acting on the system and will quickly be relieved once the fuel pump starts and fills the float bowls/fuel rail/surge tank/whatever.

If this is not the case than it is I who is ignorant of the situation. If there is not a rule stating that all cars with fuel cells must run a one way check valve venting in only then there should be.

On Edit: See page 246 of the 2007 GCR F.3.b as it pertains to GT cars. Apparently check valves are not required in any other class.

[Modo]

Russ the tire valve stems with the schrader valve removed is just a cheap way to make a pipette with a flange and nut to attach to a plate...you then can connect a vent hose to it..........to turn such a thing on a dirty chip throwing lathe would be time consuming and a pain, been turning some stuff this week, well used to think it was fun.........the vent cannot be 2 way because the gas would spill out....it only needs to let air in so a vacuum isn't formed when gas is used...that would slow or fight the fuel pump.......I agree when you remove the cap on a warm day there is a nice whoooosh or release of inside cell pressure but not much to worry about

about the above one way valve at the end of the hose deal....I agree that would be dangerous and possibly form a fuse into the cell if the vent hose was cut

[RussMcB]

I think I've got it now:

- Venting only needs to happen in one direction (into the fuel cell). If there is any pressure build up the system can take it and will go away when the engine starts using fuel.

- Preventing "the build up of negative pressure" = preventing vacuum.

- When people say "tire schrader valves", they don't really mean valves at all because the guts have been removed.

- Some people feel strongly that a one-way valve is absolutely necessary - otherwise why would it be a requirement for GT cars?

- For those that don't think a one way valve is necessary, it's important that any venting of vapors or fuel should be far away from the driver or hot parts.

- "screw-on quick disconnect vs. a snap-on style like air line fittings" means ..., Well I guess I still don't know what that means, but I can live with that. :-).

[Tom Sprecher]

Negative Pressure - see http://en.wikipedia.org/wiki/Negative_pressure

vs.

Vacuum - see http://en.wikipedia.org/wiki/Vacuum

Schrader Valve - see and purchase at the bottom of the page at http://www.rparts.com/Catalog/Major_...oid_valves.asp

I hope this helps.

[RussMcB]

Negative Pressure - see http://en.wikipedia.org/wiki/Negative_pressure

Okay. So next time I see one of your posts that I don't understand I'll go to Wikipedia to see what you were trying to say, and I'll get get something like this to clear it all up for me:


Absolute negative pressures occur in some theories in physics. See dark energy, equation of state (cosmology) and negative mass.
Pressure is defined in terms of a force applied over an area. In many physics problems we consider idealised situations; typically a single, positive ("pushing") force acting on a surface. For example, an ideal gas is modelled as particles (e.g., air molecules) that strike (and elastically bounce away from) the walls of its container. In many idealised contexts like this, pressure cannot be negative: the lowest pressure is zero (e.g., a vacuum where no gas molecules are present to strike the container walls).
However, the term "pressure" is used in a much wider variety of situations. It may be used to refer to the difference in forces on two sides of a surface, for example, or in a model where a surface is being "pulled" rather than "pushed." In cases like these, the pressure difference may be negative, or the system may behave in a way most simply described as having negative pressure.
In theoretical physics "pressure" may refer to more abstract ideas that emerge from the use of mathematical equations. If an equation for a particular system resembles that for an ideal gas, for example, then physicists may identify the term that takes the role of pressure in the ideal gas formula and refer to that term (and to whatever physical idea it represents) as "pressure". Doing this helps physicists use their intuitive understanding of everyday objects (like gas filled balloons) to help work with the complex mathematics involved in physical processes outside normal experience (like the evolution of the universe over billions of years). And, again, the term identified as "pressure" may take on negative values in these cases.
So while "negative pressure" makes little sense in idealised situations (common in both physics textbooks and as close approximations to many real life problems), it can be useful in many other contexts.

Schrader Valve - see and purchase at the bottom of the page at http://www.rparts.com/Catalog/Major_...oid_valves.asp

Where would you recommend putting that in a fuel system vent system? As the one way valve?

I hope this helps.

Not a lot, but thanks for trying.

[Tom Sprecher]

The Wikipedia page to where Negative Pressure is in bold and the text defines it. All that verbiage you quoted above is about pressure in general as applied in physics.

The following is what I was hoping you might have read and understood.

Negative pressure is a term used to describe a pressure less than that of a surrounding fluid (such as the air). The term comes from gauge pressure pressure gauges, which measured a pressure against air pressure. These were extensively used in steam engines because the pressure was relative to air pressure, which was the final pressure of the exhaust steam. The standard pressure gauge design (Bourdon tube) measures gauge pressure by default, making this an easy design choice. Negative pressure meant that the pipe or vessel being measured was below atmospheric pressure.
Negative pressure is the opposite of positive pressure.

Also from the same page...

In normal circumstances, the lowest possible pressure is a vacuum, which corresponds to 0 absolute pressure (or −1 atm gauge pressure measured relative to atmospheric pressure).

I typically do not use the term vacuum as it is a certain condition of negative pressure. In my line of work much consideration, discussion and design is spend making sure enclosures containing a source of ignition within an explosive atmosphere never see negative pressure. The condition is never described as "a vacuum". People outside of this field may not know or care for that matter.

As far as the schrader valve is concerned I would not recommend using it in the vent line. Since you asked I simply tried to explain it and show an example. You could use it as a fuel sample test port if you can get one that if it uses a rubber or polymer seal that seal is compatable with racing fuel.

Perhaps in the future I should either simplify my terminology or lower my expectations of others.

[rickb99]

So, that means a 'vacuum cleaner' really isn't?

I have very low expectations of myself. So, the lower you talk the closer I'll be to understanding.

The key point here is, with the roll over check valve, if you turn the car upside down, the little ball rolls into a seat and stops the gas from coming out. If the car is on its side with the breaher tube down, the check valve will stop 'much' if not all the fuel from coming out. All else is just 'interesting'. Check valve or not, route breather hose per K. Averill above.

In looking at our car today, I quickly concluded that having the fuel cell vent hose running up inside the roll hoop fairing was not good. If the car was inverted, fuel would pour out directly under the drivers (my sons) head. Actually I noticed this within the first 10 minutes of looking at the car when it arrived and knew it needed a fix to probably include a check valve. This thread just got me going on it again.

[Modo]

I mispoke above about the schrader valve on the floorboard....the schrader valve is removed and u r using basically the tire stem as a hose Thru-connector in this case thru floor board and the Can-Am case thru the top filler plate.....at least the can-am guy got the use.......tnx for the vacuum discussion sounds good

Horst Kroll my favorite Can-Am effort...big time on a low budget

[Tom Sprecher]

The comment of lowered expectations of others was meant to be an inside joke. Any other implication was not intended as I have a very high regard for most on this forum.

[Modo]

no problem with the comments, wasn't even paying attention.....more concerned about confusing folks with the "tire stem" with the schrader valve removed used as a thru connector......as for the vacuum, I like the fact that it is negative pressure and will use it, we are in a technical field....however most people would incorrectly say vacuum in a conversation or suction, saying negative pressure would require hand movements as you are talking to illustrate (Italian style!) or a keen raising of the eyebrows!

[rickb99]

Actually Tom, I was joking too. Should have put some smily's in there I used to build Klystron's and Traveling Wave Tubes. We considered 10 -10 Torr a good vacuum. But I don't expect to see that condition in our fuel cell no matter how pluged up the breather gets.

[Modo]

Funny stuff...my wife informed me of the smiley face and LOL web manners...that would have worked for the Italian Joke.......RickB....have fired up a few Klystron's and TWT's in my time.....it's amazing when the Klystron heats up and shuts off the TV station you are controlling in a top 10 market how your blood pressure goes up in square-law fashion.........Nice Drive at the Glen Tony...I think he passed thru F2000

[rickb99]

Wow Michael, You're bringing back memories. After building those Klystrons and stuff I made a change. Went to RCA and eventually became Business Line Manager for VHF & UHF transmitters/antenna systems. Hope it wasn't an RCA transmitter that went off line? But then I can always blame it on Varian I suppose you know, those giants were continuously out gassed to keep the real vacuum in them.

[4redno]

Does a check valve have to be mounted perpendicular to the ground (straight up and down) to work properly?

[Charles Warner]

Does a check valve have to be mounted perpendicular to the ground (straight up and down) to work properly?

No it doesn't.

[RussMcB]

I had an annual inspection this past weekend and they made a note in my logbook that I need to add a check valve. I have the "loop routing" method (mentioned in this thread and others), but they said that wasn't good enough. I didn't really feel like arguing with them since I had things to do, and they're hard working volunteers. Kinda rubs me wrong, though, since it's not required. Not a big deal. I'll do it before the next race.

[Dave Gomberg]

GCR 9.26.3 (9.3.27 in the updated GCR), second paragraph:

If the fuel filler cap is located directly on the fuel cell, a check valve is not required, provided the filler cap is a positive locking type and does not use an unchecked breather opening. If the filler cap is not located on the fuel cell, a check valve must be installed on the fuel cell to prevent fuel from escaping if the cap and filler neck are torn from the tank.

Most formula and sports racer caps are on the cell, but they usually do have an unchecked breather. If that description fits your car, you need the check valve.

Dave

[RussMcB]

Thanks, Dave.

My fuel cell has a filler neck inserted directly into the cell. The neck has a positive (screw on) cap. There is an unchecked nipple and that's where I have the long rubber hose connected. The hose is about 5' long, is routed up to just underneath the roll hoop, then down the other side, ending near the ground behind the engine.

[stephen wilson]

I would recommend using braided hose for the vent line. I was very lucky when my vent line was cut where it passes thru the bulkhead, and sprayed fuel down the header side of the bolck on my CF. I didn't even realize it until the competitor behind me that I sprayed with fuel told me.

[RussMcB]

I would recommend using braided hose for the vent line. I was very lucky when my vent line was cut where it passes thru the bulkhead, and sprayed fuel down the header side of the bolck on my CF. I didn't even realize it until the competitor behind me that I sprayed with fuel told me.

This sounds very odd. The only time the vent line might have gas in it is if the car gets inverted, or maybe a small bit gets in there when pouring gas into the cell. It almost sounds like you are describing the supply line, not the vent hose. The vent hose will be negative pressure (if any).

[DanW]

This sounds very odd. The only time the vent line might have gas in it is if the car gets inverted, or maybe a small bit gets in there when pouring gas into the cell. It almost sounds like you are describing the supply line, not the vent hose. The vent hose will be negative pressure (if any).

Hello Russ,

I work with Murphy every day and have experienced his laws in a CF first hand...
The vent on my cell is on the top of the cell, drivers right, just above my right shoulder. It has a check valve in the vent fitting. The -8 braided vent line went out and down to the bottom of the frame rail of the right side of the chassis. The cell has a filler and threaded cap mounted directly on the cell, drivers left.

The very first time I took my car out on a test day another driver remarked he could smell raw fuel and see liquid coming out on the bottom right of my car. Every time I went round a left hand turn, fuel sloshed up and out the vent.

I rerouted the vent line to the left side of the car, put a vertical loop in the hose behind the roll bar and back down to the right side bottom frame rail out the back. No more fuel going out the vent. There was an extensive thread about fuel cell venting and check valves several years ago with some really good information.

If the oil pressure line, fuel line or vent line is routed through the drivers bay it must be braided stainless line.

[Purple Frog]

Interesting discussion.

I've always vented the cell in the manner Keith describes (post #3 on this thread).

I'm guessing every pro car I looked at this season is the same. Every pro weekend as the cars go out, especially in practice sessions, the corner workers are calling in numerous cars for losing fluid on the first lap or so. It is caused by the driver leaning back onto a full cell and pushing fuel out the vent. I've seen it dozens of times this year. I've had it happen myself in the ol' Reynard.

We are so used to seeing it, that we casually ignore the phenomenon (tell the corner workers to call us back on lap 3 if it's still happening. . ) We watch it to know who's going out with full tanks and who isn't.

But, the more i think about it, check valves may be mandatory next year in the Series. Or, at least highly recommended.

Reading Gomberg's post:

GCR 9.26.3 (9.3.27 in the updated GCR), second paragraph:
If the fuel filler cap is located directly on the fuel cell, a check valve is not required, provided the filler cap is a positive locking type and does not use an unchecked breather opening.

we're all illegal! It appears we should have check valves on the breather hoses.

So, Russ let me know where you buy yours.


Just saw that this is in the "Vintage-Historic" Forum... maybe the rules don't apply to old cars. Or at least old cars that are not running in SCCA.

[rickb99]

[quote=Purple Frog;227158]Interesting discussion.

Reading Gomberg's post:

GCR 9.26.3 (9.3.27 in the updated GCR), second paragraph:
If the fuel filler cap is located directly on the fuel cell, a check valve is not required, provided the filler cap is a positive locking type and does not use an unchecked breather opening.

we're all illegal! It appears we should have check valves on the breather hoses. [quote]


WE ARE LEGAL!

Like I said in the post way above, when did the SCCA NOT require a check valve in the fuel tank or cell vent hose?? I recall this 'rule' from as far back as the late 60's and probably earlier. Seem to recall being 'checked' in tech for it.

Yes LEGAL with one of these in the vent hose:

http://www.pegasusautoracing.com/pro....asp?RecID=899

The vent hose is routed out of the vent and along the bottom frame rail all the way to the rear of the car and when positioned so the ball will remain open in 'normal' conditions and close if hit by fuel flow out.

After spending part of an afternoon trying to keep a fire suppressed as gas flowed into the cockpit from the UNCHECKED vent hose of an inverted car with an E-crew guy and the DRIVER still in it, I HIGHLY recommend check valves in the vent line. Actually, the ideal is to have the ball type valve right ON the cell and then the hose routed away from it.

If you're high dollar AN type guys, this one can be put in line closer to the cell:

http://www.pegasusautoracing.com/pro...p?Product=3606


Or if you want to get really serious:

http://www.pegasusautoracing.com/pro...asp?RecID=5284

There are other options look around.

[RussMcB]

So, Russ let me know where you buy yours.

After Googling, I'm leaning towards this one:

http://www.apexspeed.com/forums/sear...archid=1039449

It has no spring so venting can occur in both directions. It relies on gravity to close the valve (check ball) in a roll over. I think this valve, mounted close to the cell, and then still have the longish "up-down-and-back" rubber hose loop should be the best compromise. I don't ever anticipate filling the cell completely before a race, so not too worried about pushing gas out. I don't see a need for steel braided hose.

[stephen wilson]

You nailed it Mike! Long race, very full fuel cell, my chubby butt leaning on it.

One thing to consider, a "tip-over" valve does not function like a check valve. My car has the tip valve built into the cell vent, but it doesn't shut when fuel is pushed out as mentioned, only when inverted. I may add a check valve to mine, or just loop the vent up higher than is currently ( only a few inches ) .

Steve