Fuel Delivery on track

[drivemusicnow]

Well, since I've got some time (read: my car is in 400 pieces and I'm slowly putting it together) I figured I would address an issue that has been talked about for a while. Fuel delivery while racing.

If you look inside the stock tank you'll notice 2 things, 1, while the pump does rest at the "lowest" point in the tank, the lowest point is the entire bottom of the tank. Mitsu did baffle the tank, using some peices of sheetemetal that restrict fuel from leaving the fuel pump assembly area. Most notably is the large piece that is just to the passanger side of the fuel pump. This is hold fuel by the pump during hard left turns. The problem is, that during LONG sweepers, or lowish fuel conditions, the fuel pump can suck air, and this can mean anything from losing power halfway through a turn, to detonating by running lean.

I've thought of 3 seperate possible solutions and was wondering if we could discuss them as far as effectiveness, cost, and difficulty.


First option: Create a swirl tank inside the stock fuel tank. This would be a cylindrical tube essentially that the fuel pump is housed inside of. It would be equivelant to a 2 liter bottle or so in size, however not as tall, as the tank in our car is not that tall. This swirl tank would be fed by smaller, low pressure-high volume fuel pumps, such as the Facet models offered at www.aircraftspruce.com. GM uses a similar method in some of the F-Body models, as you can see here below


Second option. External surge tank. I could use the Stock fuel pump in the gas tank, with the addition of the facet pumps all pushing fuel into an external surge tank. I mount the Walbro in the surge tank, and run the lines like this:

Stock fuel pump+facet pumps into surge tank
Return line from surge tank to stock gas tank (for over flow)
Walbro 255hp from surge tank to fuel rail
Return line from rail into surge tank

This would mean that the surge tank is always "over filling" and that even in long turns you would still have 1-2 gallons of fuel for the Walbro pump to use.


Third option, go cheaper and just use the walbro fuel pickups that float in the tank, and automatically close when they are sucking air. http://www.autoperformanceengineering.com/html/ext_pump.html Use 2-3 of them and maybe even add some baffeling so that one stays on the left, on stays on the right, and the other stays in the middle. Supposedly they work very well.

Please discuss and add any thoughts on this issue.

EDIT: A fuel cell is a huge investment, and not one that I particularly want to make. This is why I would prefer to not go this direction.

 

[asian312]

Just signing on. I know on my 2G I encountered this just slightly below 1/2 tank of gas. I like the idea of an intank solution, but I foresee some major modification to the tank itself. External is another option, just don't know how comfortable I am with fuel lines being run into the car.

There is always that 4th option which is to run a full tank of gas or replace with a fuel cell (guess that makes 5).

 

[1LE]

I know on my 2G I encountered this just slightly below 1/2 tank of gas.

Interesting. I wonder if a previous owner of my 2g made some sort of modifications there. I can take it all the way down to just about nothing in the tank without encountering any issues. I was able to leave Toledo, drive all the way to Nelson Ledges and run in the morning without issue (and I had barely enough gas to make it to the gas station down the street during the lunch break). If I have the reason to do anything with the pump/tank, I'll check it out and post up...

 

[asian312]

Please do!

This fuel starvation occured in only one corner of the track. It was a fast short straight that lead to left sweeper that I felt the pause in the engine. It was unsettling the first time it happened, but pradictable after. If I paid more attention to the roll of the car I could avoid it, but as the laps continued my fuel dropped to just above a 1/4 tank and I had to slow down for that corner. I think it was specific to this sweeper because it was flat and one that could be taken near WOT.

 

[silvah_gsx]

Interesting. I wonder if a previous owner of my 2g made some sort of modifications there. I can take it all the way down to just about nothing in the tank without encountering any issues.

I don't think it was modified, I ran down to my fuel light at Willow with no problems. This is a stretch, but might it just be a tired fuel pump being more susceptible to poor pickup?

 

[eclipsegsx1736]

I know on my 2G I encountered this just slightly below 1/2 tank of gas.

Same here. This is pretty common with these cars and Evos as well. Several people at the track day I went to were running fuel cells or solutions in their Evos. RRE suggested to me to always have minimum 1/3 tank of gas before agressive cornering.

 

[asian312]

I've been throwing around the idea of placing a small surge tank under the hood with an external pump and regulator to help cure this problem. Does anyone have any reference material to how larget that surge tank should be?

 

[mavisky]

I ran into starvation at last year's Winged Warrior event. There was a slalom section followed by a quick left, then a long left sweeper and it nearly died in the sweeper. Interested to see where you go with this as I've been forced to autox with 1/2 tank or so at the start so I have enough that my last run doesn't stall out.

 

[asian312]

An idea I had was to relocate the battery and build a surge tank right there. It would eliminate me having to do much to the existing fuel system and allow me to keep any fuel outside the cabin. Big questions are:

- How big should the tank be?
- Will a stock pump without a regulator on it be sufficiant to feed the tank?

 

[4G63FLA]

This a very interesting topic and concern with people racing. I'm glad someone started this. Looking forward to see what everyone can come up with.

 

[mavisky]

I personally would not want a fuel swirl pot under the hood of my car.

 

[asian312]

I personally would not want a fuel swirl pot under the hood of my car.

Just curious as to your concerns.

 

[Evan K.]

All you GSX owners are lucky. I can get fuels starvation at as full as 3/4 tank on long sweepers. GST's have flat bottom tanks Turn 14 at Thunderhill kills me at anything less than 2/3 of a tank.

 

[eclipse2via]

Just curious as to your concerns.

Like fire probably. Seriously, any group you run with is going to unhappy about you running a fuel tank in a hot engine compartment.

 

[asian312]

And how is that any different that the fuel filter, rail, and regulator?

 

[eclipse2via]

And how is that any different that the fuel filter, rail, and regulator?

All those parts contain fuel by itself and under pressure. Not a tank with air and fuel sloshing around giving the fuel a good chance to atomize. If you try and pressurize a tank of any useful size you're going to run into fp failures quick even assuming you can find a cell that can be pressurized that much.

 

[mavisky]

Just curious as to your concerns.

1. Fire hazard - big time

2. Space constraints - A swirl pot will require a feed, return, and a outlet for the pump. This means you'll have at least 3 lines going into and out of that tank plus the fuel pump you'll have to mount in the engine bay along with the usual filter, lines, and fpr. In short no thanks. Not to mention the fact that the return will have to go all the way back underneath the car to the stock tank. You could mount it in the hatch easier and safer, or better yet mounted underneath the car by the rear bumper.

 

[drivemusicnow]

I made a few decisions for my own purposes on this issue.

A) Bringing weight up front isn't helpful, nor is there any benefit to running the swirl/surge tank up front.

B) The best way to do this would be with a dual pump, surge tank setup. I'm personally running a walbro 255HP pump in the tank installed normally. I'm building a tank with a conical bottem with the outlet at the bottom. (think 2 liter bottle turned upsidedown) This runs into another (inline) walbro 255hp pump that pushes fuel to the rail. Feed will be on the side to help de-airate the fuel. Return would be on the top, however would be restricted with a pressure relief valve set to about 5psi. This would allow you to run the second walbro pump more efficiently. This should support horsepower levels up through 500 at the wheels, and would not run into any fuel starvation issues.

A cheaper solution would be to open the stock tank up and add several more layers of baffeling, and a deeper sump area with an inline pump out of the bottom of the tank. This could be modified to work better for drag racers or road racers depending on your fuel pump location.

 

[asian312]

Looks like I'm just gonna have to get use to tracking with a full tank. I really dont like the idea of having fuel inside the cabin since I use this car daily on the streets.

 

[mavisky]

Mount the tank underneath the car like I mentioned. There's no reason that the swirl pot needs to be above the actual fuel tank.

 

[asian312]

Not that it has to be above the tank, but the tanks I've seen are vertical cylinders. I thought they were designed that way to minimize movement of liquid along the x and z coordinate. The tanks are tall in order to hold the desired volume and have varying circumferences to minimize the fuel from building up on one side.

 

[mavisky]

That's true, but there are plenty of places you could mount that, hell you could even isolate it with something like a modified battery box if it worries you that much.

 

[asian312]

That's not a bad idea mavisky. I guess I can't have it all my way if I'm planning on contining being serious about road racing. Just adverse to gutting holes in a prestine chassis.

 

[asian312]

Came across this in case anyone was interested:

http://www.more-japan.com/SARD-Fuel-Collector-Tank-Kit-S-For-1-Pump-p-16887.html

 

[eclipse2via]

What about these in the tank rather than a cell?

http://www.atlinc.com/US/download.php?file=pdfs/Racing/ScavengingDevices.pdf