Fuel system vent

[98blackbell]

We finished our updated fuel system and new t3/t4 hybrid turbo install. Wow what a difference. It woke up the beast. Ran SCCA Sunday at Hutchinson Island. 6 runs ended up 3rd behind 2 modified FRS Scions. Beat out other modified mustangs, brz,frs,Subaru.

 

New fuel cell, New a1000 aeromotive fuel pump, -8 fuel lines front to pack, new pallnet fuel rail with -8 fittings.

 

The problem:

 

We ran the 2 vent lines "Y'd" into one line -10. Coiled it 3 turns beside the fuel cell, then back up the fill neck to a filter that is sticking out the old gas cap hole. The fuel cell is flush with floor in hatch.

 

We are getting fuel out the vent/ gas cap then down the quarter panel during each run. What can we do to fix this?

[seattlejester]

That should work, but I guess under autocross and hard braking you can push fuel up through the line.

 

I would say drain the lines completely and try lifting the vent line before heading down would help the fuel from sloshing straight into the line. Mine goes up to where the stock filler is in the car using one of the vent lines in the filler, then goes down through the filler, coils, then terminates. 

Edited January 31, 2017 by seattlejester

[98blackbell]

Yes hard running gets the fuel there.

 

https://www.instagram.com/p/BP6cGQBgodg/

[98blackbell]

So the 2 turns with 3 coils has fuel in it. It may be that with the coils are almost 1/2 the distance of the depth of tank.

 

I will try to make the coils smaller and higher. Maybe as it comes off the Y elevate there.

[seattlejester]

Mine are fairly large lazy loops.

 

I think the problem is gravity. Looks like your system goes straight down to loop then comes up, when you smash on the brakes the fuel probably sloshes up there and down the line and sits in a coil, keep doing that and eventually you fill up the line and it pushes out the fuel. In theory if you have the line head up a bit first to a point where the fuel can't over come the height then it shouldn't fill with fuel so often, think of like a stock fuel system and how high the filler is compared to where the tank sits, granted they have a flapper valve. 

 

Kind of the downfall of a fuel cell, you could run with a bit less fuel, but looks like that is a fairly small fuel cell.

[NewZed]

You could use one of these things.  

[ZHoob2004]

I have no idea about regulations, but I would think you want the entirety of the vent line, including loops, above the top of the cell so it can drain back down. Right now the lines are just gradually filling with fuel and acting like a pump rather than a vent.

[beermanpete]

I don't get the use of the loops in the vent line. It seems that will cause problem by blocking the line with liquid fuel that collects in the low points. We ran a line from the tank to a tee at the fuel filler and then from the tee up above the filler and back down to the outside of the car. I have seem evidence it drips a little when coming off the track if the tank was full at beginning of the session. Other than this it works great.

[seattlejester]

Cheap roll over protection, and can act as a water trap to keep the smell of gas to a minimum. That's the reason I did it.

[98blackbell]

I agree about the loops. Definitely did not work. Here is picture from top.

[seattlejester]

Yea, you need to come up quite a bit. As someone else said your  setup is basically a pump right as the fuel sloshes it pushes fuel in the vent and just flows straight down, each subsequent pulse acts like a pump and keeps pushing fuel Through the loops and eventually out the vent. Where the tee is you need to come up like a foot or so before going down, give some of the gas that flows in a chance to flow back into the tank.