RedlineMan

Hey all;

There is periodic talk about fuel cells on the forum. They seem like a great idea, but as always there is a lot more involved than just dropping in the cell. Among many things, what you generally find is that the factory does a pretty good job of designing a system that scavenges all the fuel out without sputtering. No matter what you do to a cell, it is not baffled enough to scavenge like a factory tank. Here's my version of one accepted solution.

Two fuel pumps. Two cells, one big, one small. The fuel is pumped by the first pump to the small cell that will not cavitate. From there, the Bosch pump sends it to the filter and the engine.

Here is the system layout.



Large cell with Holley Red electric high volume low pressure pump just behind. This is a nice pump in that it draws only 2 amps to push 97gph at 7psi and is wired right into the exisiting electrical pump circuit. It out-does the Bosch pump at idle.



From there, the Holley pump fills the 2g surge cell at the top. If this cell fills, the overflow exits at the front right and goes back to the main cell. This overflow line Ts into the return line from the fuel injection system at the front of the main cell.





The surge cell is contained in a fabricated aluminum "can" to protect the lower portions from flying debris. The rear panel traps it in place, but it is all pretty easily removeable.



An OE Bosch pump takes fuel from the bottom of the surge cell and feeds the fuel filter. All the lines up until now have been Earl's Super Stock items. What I call Plug & Play. Simple barbed push on fittings. However, these simple fittings withstand up to 250psi of pressure, and in reality the only way to get the hose off is to cut it! Exiting the Bosch pump, fuel is carried by high pressure Earl's SS braided teflon lined hose and their top line Swivel Seal fittings.



The OE Bosch pump is mounted on an aluminum replica of the factory sheetmetal bracket. I couldn't resist the opportunity to fabricate, and my original steel bracket is welded on the back of the main cell anyway. Incidentally, you won't find a better backflow valve than the original. Ask me how I know.



For those of you thinking you need one of these systems, I'd implore you to think again. It's a pain, even if it does look totally trick! Oh... sharp eyed viewers will note that the muffler is missing. The exhaust exits from under the passenger door now. That's another ongoing trial!

Lemming

After seeing the complexity of the system, I believe that I'll stick with the stocker for quite some time. Having said that, it's a fantastic piece of work that you've done.

What is the cooler on the rear of the car, an external oil cooler for your tranny/diff?

Alan C.

John,
Keep a close eye on that plastic surge tank. A friend tried one of those and it leaked at the top seal after a couple of months. He went to a custom fab aluminum tank.

Chris Prack

That's a lot of work. Nice job!

M758

John,
I wonder if you agree, but this fuel cell in 944 seems like real pain.

I wonder if even the good old stock tank is safer given all the fuel line runnign around back there. I suspect the risk of the stock tank would be in a hard rear impact. The concern would be a tank rupture and fuel leak.

Now the fuel cell should be better protected more able to withstand a strong impact. However what about all those fuel lines. I wonder if those become the weak link in rear impact and possible more so than a stock tank with far fewer lines.

What are your thoughts?

BTW... there are always a couple people in 944 spec that come up with crazy ideas. One of them are fuel cells in 944 spec. When they ask I am always reminded by you pain in the rear expereince and quickly tell them no.

kurt M

Someones been busy swinging the neat work stick.

Can a surge tank be incorporated into the main tank? I was looking into just this type of thing for a project coming up. Already have the fuel cell in hand that has a large opening I could fit stuff into. My half baked idea is one pump pumps into a small but tall surge tank and the second pump pumps out if it to the motor. Surge tank just overflows out a hole in top back into main tank. Surge tank could/would also have a flap valve in the bottom in case of a secondary pump failure event. The gas would flow in on its own. Carbed motor so no return line or return line could go right back into surge tank. little external system exposed. I am missing something...

fatbillybob

Wow what a project. It looks very trick. John you are such a safety advocate how do you feel about all those lines? Plastic tacks do not make be feel warm and fuzzy. I thought fuel cell technology was way beyond your starvation problem already. I thought the big makers ATL and Fuel safe have integral surge tanks and baffles and duck feet as minimums. They have enven done this type of series specific work : http://www.circletrack.com/techartic...0_race_engine/

John Veninger

I installed a 22 gallon ATL fuel cell with their "black box" in the tank surge fuel pump setup. I can draw it down to ~2 gallons before I get a sputter on a high G turn.

MJR911

I always liked the design of the "fuel safe" brand b/c they pickup from the bottom. John, did you look into them? Maybe they don't even do a 944 design b/c of what you ran into?

RedlineMan

Let's see...

Tim; yes, that is a generic replacement for the stupidest factory cooler ever designed. That is a Turbo LSD pumper box.

Alan; The main cell is poly as well. Everything is sealed with Hylomar because none of the ports would seal otherwise. No leaks when it is done that way.

Chris; You know it's a lot of work, brother!

Joe; Good intuitions. I'm not sure why, but it did not occur to me till after I had started. The Plug & Play stuff saved me at least a couple hundred bucks I'd wager. As it is, I have about $260 in lines and fittings alone, even with the "cheap" ones! I also did have the thought that the lines run to the rear were more vulnerable, be they rubber or braided. I figure that if I were racing, I would not do it that way. since I am DEing, I have never even spun (yet), and it is not a 911, the chances of wadding the rear are somewhat more remote.

Feel free to refer your "thinkers" to me if the want to know about cells in 944s!

FBB, John, MJR; Of course I went there. For the cost of an ATL/Fuel Safe cell and surge, I could buy EVERYTHING you see in this fuel system, INCLUDING the dry break and discriminator fueling system you can't see. I just don't have that kind of cash.

So too are the rubberized bladders a maintenance item. They need to be replaced every few years. I just didn't want the hassle.

John; the main cell is only 12g. There is no room for anything bigger in that space. It would begin to sputter at about the 35 minute mark. I have a trap door surge tank that I made inside the main cell now, and it would still only get to about 3-4 gallons before it started to sputter. If there was a combined end-of-day run session, I would run out. Even if you had the fuel pump inside the cell, it still would cavitate.

M758

John, I will do that.

35 minutues = 12 gallons?
In a 35 min 944 spec race, which is common distance I typically put in 5 gallons of fuel and finish close to empty. For our purposes sputtining at 35 min is just not acceptable. Yet again another reason fuel cells in 944's are pain.

Thanks for sharing. Hey with all the nice work you do I'd be you could start selling these fuel cell jobs if taked about how "great" they are. Nice to see that you put praticality infront of $$$$$$$$$.

RedlineMan

Well...

The deal is that my cell is 12" deep, and the gauge sender only reaches 10." As I said, it starts to sputter at a 1/4 tank registered, which is what I figure to be about 3-4 gallons. With the surge collector in the left side of the cell (most turns are rights, after all), this begins to occur only in long hard left turns like NASCAR & South Bend at VIR, Turn 10 at WGI, etc. Unfortunately, it is a bit difficult to maintain necessary maintenance throttle through a turn when the engine cuts out.

The job was a hemroidal PITA. How's that for truth in advertising? Me speak'm truth! I would do a LOT of things differently if I had it to do again. If there is a next time, it will be a lot easier & cheaper. Any takers?

spazegun2213

wow, very nice setup!! While i would love to run something like that i simply do not have that type of budget I also agree that the stock system does a great job keeping starvation at bay.

surge tanks are something any subaru driver is fimilar with, If you race them in anything over T2, you NEED one. turbo car + fuel startation = kaboom

kurt M

Workmanship aside I still don’t understand why you would not want contain all this stuff inside the tank. You now have pumps and lines that encompass the entire rear ¼ of your car and near hot and rotating things like ½ shafts, tail pipes and rotors. A good hit in the back will get to some of it some how. Adding a cell is to decrease the likelihood of a fuel spill during impact. Fittings, hoses, pumps, tanks, all increase the likelihood of a spill IMO. You have now added many and have 2 tanks to protect. The small plastic one will be under pressure too. Its return has to work against the main pump return via the one shared tank mounted T connector.

A very small in tank pump that only has to move fuel into an internal surge tank with a correct sized protected external pump taking fuel to the motor and a line returning from the motor. This just seems to me like you are wearing all your flammable organs on the outside. The only + I can see is the external surge tank means you have more fuel cap to work with.


Internal surge system in a cell that is mounted to isolate impact distortion with the external fuel pump also mounted in a protected location all powered via an impact cutoff switch. I coment only as you posted this as "This is what it takes" My point is why should this not be an internal system? Total fuel cap?

RedlineMan

Spazegun;

Neither do I.

Kurt;

This is an addition to what I already had, which did not work well in some instances. If I were starting over from scratch again I would do things differently, I'm quite sure. This was relatively expedient and will do just fine for now. Some of your points are well taken (placement), some are not relavent (exhaust), some don't suit me (internal pumps), and some are incorrect (returns).

If this works, I might redo the whole thing. Call it a test.

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