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Discussion Starter · #1 ·
I just received an email from a member of the Corral asking about my fuel system. So, instead of answering his question via email, which makes using pictures as a reference difficult, I thought we could turn this into an interesting discussion on the inter-web. (It actually started as a thread over at www.stangsofsouthflorida.com. They're an up and coming site.)

So let's get started. :)

First, we'll start with the test mule, my 98 Cobra.

Here's a picture of the car from when I first bought it in 2003. In fact, when I bought it, it had roughly 42000 miles on it, a BBK CAI, PRO-M mass air meter, Superior 31 spline axles, and a PowerTrax locking differential that destroyed itself in less than 3000 miles. :DI

The car now has 52000 miles on it, believe it or not.



Now, because the car is a 98, it's got some challenges that make a fuel system different for the 98 than both the 97 and older cars, as well as different than that of the 99+ cars.

In 1998 Ford went to the "basket in a tub" system which, at least on paper, was a good idea. The technology behind it was pretty sound: put the fuel pump in a "basket" that was fed fuel and "always" kept full.

The way it was designed to work, in a stock car, was pure genius. Suck fuel from a low point in the tank and make it so the fuel pump was always submerged in fuel, even if the tank was low.

The problems started showing up when people wen to bigger than stock fuel pumps and lines. Suddenly, the basket became a limitation, since now you had a fuel pump that was capable of emptying the basket MUCH faster than the stock lines in the tank could refill it.

As you can imagine, that's bad.

So, being the creative souls we are, people (including myself) started hacking up the fuel baskets. This was a band-aid fix that uncovered an issue that caused a LOT of trouble for Walbro.

What people didn't realize was the fuel system in the 98's are a "hybrid" system. What that means to you cats and dogs out there is it's got a variable voltage fuel pump like the soon to be released in 1999 RETURNLESS fuel system.

This increases and/or decreases the voltage to the pump, thereby controlling both fuel pressure and fuel flow in the tank.

It's a great idea, except for the fact that very few people realized this was going on. We all assumed it was the same as every other mustang out there, and when you put a fuel pump in the tank that wasn't designed to be run with variable voltage, like 99% of the Walbro line, it killed the pumps with surprising quickness.

Personally, I killed a pump in less than 50 miles in a full tank. (crazy, I know.)

So, this leaves you three possible fixes:

  1. Switch to a 97 tank and direct wire the fuel pump
  2. Find the right fuel pump (Aviator, Focus, etc...)
  3. Run a sumped and baffled tank and external fuel pumps

For me, I took the high road and picked up a www.glennsperformance.com sumped and baffled fuel tank and I'm running two external fuel pumps.(More on that later.)

One side benefit of this tank is it eliminates the need for a drop in style fuel pick up. You suck fuel directly out of the sump, which is always the lowest point in the tank.

This tank is designed with the driver in mind. I have been told you can run this tank to basically empty and not have fuel issues. While I don't recommend letting the fuel supply get that low in a boosted application, things happen. This design also means you don't have to worry as much about around town driving related fuel starvation like SOME tanks (older Aeromotive, for example) where the fuel can be as high as 1/4 of a tank remaining, but if you make a hard turn the fuel sloshes away from the pickup, causing a lean condition.

Now, the only real issue with that tank is that it's designed to be used with a 97 and older car. So, as you'll see in the photo below, the plug design is different from a 98 to a 97. This means you'll have to get our hands on the proper harness out of an older car and splice it into your 98+ harness to make the fuel level gauge work.

< 97 tank connection:



> 97 tank connection:



So, as you can see; this is a completely different setup. (It's an easy swap.)

One last thing: if you want to cause trouble for yourself in a modular powered SN95, go ahead and simply weld on a sump. They're cheap to buy and have welded on, but since there are no internal fuel controls (baffles, basically) inside the tank, you're going to have low fuel level starvation issues on not only hard turns, but I've seen it rear its ugly head even under hard braking and launch conditions. I've seen dozens, and they're hard to diagnose if you don't know what you're looking for.

So now you've got your fuel tank sorted out, what do we do about lines, rails, regulators, and the all important fuel pump?

Well, here's what I did, but please keep in mind that this is a fuel system for a twin 60mm turbo car with a built motor and ported heads. Your individual needs may vary, but this system will support upwards of 1000 RWHP. :)

Now, in addition to the tanks, you need to look at fuel pumps. For most people, it's pretty simple to go is with some sort of Ford pump. As I mentioned earlier, the Focus, Aviator, and Ford GT pumps have worked pretty well for quite a few people. The issue is once you climb past a certain point, even two of those pumps reach their limits.

I went straight to the top with this and I'm running two Bosch 984 fuel pumps. (they were SUPPOSED to be 044 pumps, which flow a little more, but my parts guy grabbed the wrong ones. No worries, as these should work just fine.)

Here's the part number:



Here's a link to Bosch fuel pump flow, sizes, and amperage requirements.

http://www.lucasinjection.com/_borders/fuelpumps.pdf .

So, in that document you'll see that the 984 flows 165 LPH (liters per hour), whereas the 044 is 200LPH. If I have any fuel issues at all, which I don't anticipate, I'll pick up the 044 pumps. They'll be a 3 minute swap given my current setup.

I digress. :p

Now, to give you an idea of how big these pumps are, here's a picture of my 984 pump next to the stock pump that came out of my Cobra.



Now, to really drive home the point, here's a picture that should put these pumps into prospective.



Yes. I'm running two of these pumps. :)

When it comes to wiring the actual pumps themselves, I recommend (and use personally) them being wired through individual 30 amp Relays from Painless. (Summitt sells them for 30 bucks.)

The reason you want to run them to individual relays is to decrease the likelihood of both pumps failing at once. By running them on a single relay and single power source you kill both pumps by tripping a single relay.

I'd like to have at least one pump to get me home, if possible.

Anyway, you can find them here:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=PRF-50102&N=700+1003+115&autoview=sku

And here are installation instructions:

http://www.painlessperformance.com/webcatalog/plarge/50102.jpgwiring When it comes to filters, I recommend an Aeromotive 100 micron and 10 micron.

Remember: 10 micron filter AFTER the pump and the 100 micron filter BEFORE the pump, otherwise you will starve the pump for fuel.

Aeromotive said:
Noting the appropriate flow directions, install the provided fuel filter, Aeromotive p/n 12301, on the fuel pump outlet
and the other fuel filter, Aeromotive p/n 12304, on the fuel pump inlet.
p/n 12301 = 10 micron
p/n 12304 = 100 micron

1-8: http://www.aeromotiveinc.com/pdf/17141.pdf

So, once you have the pumps, lines, tank, and filters sorted out, here's what you end up with as a finished product:

No tank in the car:



Tank installed with pumps, filters, and lines:




Close up:





Here's what the car looks like from behind, on the ground.





Now that you've got your pumps and filters figured out, you need to focus on the lines. I've got stainless braided hoses with A/N (which stands for Army/Navy) fittings from front to back.

Continued in next post because I exceeded the maximum 10000 characters. :hb
 

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Discussion Starter · #2 ·
...On with the show... :)

Anyway, from the tank to the pumps I believe it's a -20 fitting (I'll double check that for accuracy) from the tank to an Aeromotive fuel filter, to the pumps, to another filter.

From the filters/pump assembly I'm running a -8 stainless line to the rails.

It's another -8 line to a pair of 5/8" UPR rails, which cross over at the front of the motor, and then down to the Aeromotive fuel pressure regulator. (FPR)

These rails feed high impedance 83# injectors. These are controlled by the stock computer. They are NOT controlled by some sort of injector driver. (they always fail.)

Here's a rail and the line:



Pics of the rails and lines installed:







Here's the regulator:



From the FPR I'm running a -6 "return" line that takes fuel BACK to the fuel tank.

While we're talking about fuel making a circuit from the tank all the way back to the tank, let's talk about temperature. I'm sure a bunch of you have heard that Aeromotive fuel pumps have been problematic. While this is typically true, most people don't know WHY they're problematic.

I'm going to be redundant here for a second, but here's the short answer: Aeromotive, and other big single pumps, flow all out, all the time. This never gives the fuel a chance to cool as it makes its trip from tank back to tank.

Additionally, some people confuse the pressure increase with the fuel boiling. They think because the fuel is flowing so quickly that it hits the regulator, gets backed up, and THAT causes the fuel temperature to to increase , but that's not the whole story.

Things to consider:

  1. When it hits the regulator it's immediately dumped into the return line. What we're describing above would cause the fuel to "dead head" at the regulator and that would cause a whole other series of problems unrelated to temperature.
  2. Increasing the pressure of liquid raises the boiling point.

Think of it this way; removing a hot radiator cap forces the coolant out violently because the system is pressurized, not because it's suddenly boiling. When you provide pressurized ANYTHING with a sudden escape point it's going to try to do so as quickly as it can. That's why you only have that initial spray of coolant upon removal of the cap. Once the pressure has been released the coolant goes back to business as usual.

Without any other contributing factors, fuel temperature typically stays 10-15 degrees above room temperature.

Some people suggest some fuel pumps (Aeromotive in particular) cause problems because they're "too efficient." It's not the pump being "too efficient", but more of the pump working harder than necessary. (Anyone can make a pump that'll flow high volumes of liquid.) It's heat related vapor lock caused by the high recirculation rate at cruise.

What really causes it is heat the fuel absorbs from the supporting fuel system hardware. (The rails are the big culprit.) Fuel absorbs heat from the rails and is returned to the tank, then almost immediately sucked back into the lines by the pump.

Since the fuel has little time to cool it eventually gets hot enough to boil in the inlet to the pump. The pump doesn't quit, it simply stops drawing liquid fuel. (I can't imagine the car runs well on foam/vapor.)

The vapor lock is caused by the high inlet vacuum generated by their roller vane pump. (as opposed to gerotor, sliding vane, etc...) Vacuum, by definition, lowers the pressure of the fuel on the inlet side. This lower pressure causes the fuel to flash sooner. (the opposite effect of what we discussed a second ago.)

When you shut off the car the fuel cools and stops boiling. (this is made worse when you have anything other than a full tank.)

A "returnless"s system typcally uses a variable voltage pump, which is the same thing as the new Aeromotive pump controller. Great idea, just like the "basket in a bucket" idea, but only if you can get either of them to work.

Anyway, now that we're done talking thermodynamic properties of liquids in a pressure elevated environment... ;)

So, as I said before, this setup will support 1000+ RWHP with relative ease.

I think that's pretty much everything we need to talk about, but if I'm leaving anything out please let me know.

I hope this helps someone. I know it's an expensive and nerve-racking (is that spelled correctly?) decision-making process.

Later peeps,
Alan
 

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Big Top, That is a very nice set up. If you find your self running out of fuel anytime soon you might want to consider running from the pumps to the filter and putting 2 separate filters there and having each line separate all the way up to the rails and feeding each rail then each line to the regulator. Other then that, that is a very nice setup.
 

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Discussion Starter · #5 ·
Thanks BlkGT. You wouldn't believe how long I've been working on building this POS. It's been a battle every single step of the way. :dumb:

Big Top, That is a very nice set up. If you find your self running out of fuel anytime soon you might want to consider running from the pumps to the filter and putting 2 separate filters there and having each line separate all the way up to the rails and feeding each rail then each line to the regulator. Other then that, that is a very nice setup.
It's funny that you say that, because another member and I were having that same conversation this morning.

That'll be the exact thing I do if fuel becomes an issue.

I'll individually feed the rails, then Y block them back down to the regulator.

Some of my buddy's concern with the way I have it now (in series) is the potential for pressure differences across some of the injectors.

He's concerned that a big hit on the throttle will cause a significant difference for injectors further down the rail at the moment you flatten the gas pedal.

I don't know that anyone has had that problem, but the idea of it is enough to make me wonder if I need another fuel line. :D
 

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You wont need to y block it into the regulator. Aeromotive makes a reg that allows you to run 2 lines in and one out. I believe its 2 8s which each one comes from each rail and then the return line is a 6. I believe the part number is 1310. I'm not positive on the part number but I can check for you if you want. its the same one I had on my car.
 

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Discussion Starter · #7 ·
Actually,I'm pretty sure the regulator I have on the car has two ports to run from the rails.

I'll look at the car when I have a chance and start pricing out splitting the lines to feed them in parallel.

:)
 

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OK so I am putting together a similar set up to Alan, except instead of using a sumped tank I am using a drop in pick-up to feed my 044 pump. Obviously mine will be in front of the tank instead of behind it. Anyone have a reason why the 10 micron filter could not be mounted further upstream? Every in-line set up I see have 100 micron, pump, 10 micron, lines. In an effort to save space and possibly make the element changes easier, i'm thinking about putting the second filter further forward on the car. Hell, maybe even in the engine compartment. Comments?
 

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pritch you can move it were ever you want. It really isn't that big of a deal. I think some people like myself connect the filters to the pump to save on buying that extra fitting a cutting and stuff like that. But to answer your question about filter location, it doesn't reallymatter as long as it's there before the rails.
 

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Nice set-up and write-up on your fuel system.

I took a different approach. When I was in the planning phases of the car, I wanted the fuel system to be adequate so I could grow the HP. Good thing I did because since the car has been down so long, I've already grown it and it isn't even done yet, lol. At any rate, here's how it evolved.

My tuner suggested keeping my stock tank and pump set-up and welding on a sump. The large Weldon fed by the sump would come on under boost with a Hobb's switch. I didn't like the appearance from behind the car with a sump. I wanted more of a sleeper/OEM look. And, as BigTopGT pointed out, modifying the stock system just wasn't going to work for me for large power. So, I got a used '04 Cobra tank and had the tophat modified with another line coming out. I installed two FordGT pumps and used the Gates submersible fuel hose to plumb them up. I got a special adapter/grommet from Motion Dynamics to double as one of the stock vacuum hoses and the fuel return line. The tophat has 4 wires coming out. So, I used one hot wire for each pump, one hot wire for the fuel sending unit, and the other to ground all three. One pump runs all the time, the other comes on under boost. I used Aeroquip Socketless 8AN fuel hose feeding 120 lb/hr injectors. I opted for the large low impedance injectors because I may be running E85 as an alternative and also because they respond and perform better under high HP/boost conditions.

The main reasons I went with this set-up were:

1. I needed enough fuel to support over 900rwhp with E85. These pumps flow about 760 liters/hour at 60 PSI at 13V combined so I can reach my goal easily. They will support well over 1000rwhp on gas.

2. They are quiet being in the tank.

3. Wanted an OEM look.

4. Pumps stay cool in the tank.

5. Pumps are cheap ~$65/each

6. They could be safer vs. the sump if ever rear-ended.

Anyway, I know everybody has their preferences but this is what I did.
 

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Discussion Starter · #11 ·
Yeah, but please don't run a fuel line into the passenger compartment. ;)

Turbo98: I think that's a pretty solid setup. My only recommendation is to try to avoid simply slapping a sump onto a stock tank. They don't have the necessary baffles to control the fuel in the tank. Under hard acceleration, braking, or cornering, fuel can start doing all kinds of crazy things. The worst of which is go someplace other than the pickup.

I'm always pimping Glenn's Performance's name, so I'll do it again. :)

They make a great looking sleeper tank that lets you mount the pump to the front of the tank. I hear it's a pretty great setup.

I don't mind the sump out back, But I'm going to paint it black so it's at least a little less obvious. :D
 

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Yeah, I didn't go the route of sumping any stock tank. I went with the '03/'04 tank with the stock baffles unmodified. It has a pretty nice baffle set-up in it. I'm going to do one more thing and return the fuel to the baffled area which it isn't right now. The welding on of the sump to the stock tank would have been with my '98 tank. I thought at the time that with the stock basket (with an Aviator pump in it) still in place supplying fuel too, it would supply enough fuel to supplement if the sump ran dry momentarily. But, I didn't go that route.

I was set on a Glen's "Street Sleeper" tank (I believe that's the one I was looking at). It is a very nice design for sure. I was disapointed when we discussed it and he determined it wouldn't support the amount of fuel I was looking for.
 

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OK so I am putting together a similar set up to Alan, except instead of using a sumped tank I am using a drop in pick-up to feed my 044 pump. Obviously mine will be in front of the tank instead of behind it. Anyone have a reason why the 10 micron filter could not be mounted further upstream? Every in-line set up I see have 100 micron, pump, 10 micron, lines. In an effort to save space and possibly make the element changes easier, i'm thinking about putting the second filter further forward on the car. Hell, maybe even in the engine compartment. Comments?
I don't have a sumped tank in my car, instead I purchased a "fuel hat" (same as a drop in pick-up I assume?) from MMR that replaced my factory fuel hat. It has a -10 feed and a -6 return line on it. Currently I have only one in-line Walbro 255 pump on my car, but I just purchased a second in-line Walbro 255, because I am planning on selling my KB and picking up a centri blower and turning up the boost.

Right now my pump/filter is in front of my tank, just like your's, but what about when I install the second pump? There is no way there is any room up there for the lines/fittings/filters/pumps/etc., so the only way I see to mount everything would be to mount it just like Big Top GT mounted his, which is on the back side of the fuel tank itself, not the front side like I have mine now.

So Big Top GT, or anyone else, do you see a problem plumbing a line out of my fuel hat (which the hat has both the -10 and -6 lines pointing forward, kind of toward the passenger side) and wraping it around the drivers side of the tank to the back so I can plumb/install everything just like Big Top GT's pictures show of his set up? In his pictures, it shows that there is approx. a foot of braided line between the sump and the pumps, but if I plumb everything like I said, the pumps will be approx. 3-4 feet away from my fuel hat (by the time the fuel line comes out of the hat and wraps all the way around to the back of the tank to where the pumps will be mounted). Will this extended distance cause any problems for the pumps to be pulling fuel out of the tank?

Sorry for all the questions, it's just that I have my fuel system set up exactly like Big Top GT's system (except for the sumped tank/twin pumps) including the inline pump/filter, -8 feed, -6 return, Y block feeding each UPR fuel rail, Aeromotive regulator, etc., I'm just not too sure how to (more importaintly where to) install this second pump. Thanks for any and all advice.
 

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Discussion Starter · #15 ·
I'm still not convinced that running a smaller feeder pump is a good idea.

I can't help but feel that it limits the volume you can push through the bigger pumps. There's simply no way one smaller pump can sufficiently feed two bigger pumps.

You can't power a garden house by pushing the water through a straw first.

I'd think you're okay running the pump a foot or two away from the hat, but you've got to make sure you can feed that line. either the pickup has to be completely submerged at all times, or you'll run lean when the pump runs dry.
 

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which wire did you use for your switch power for the relays? should i use the same power wire i had used with my KB BAP by the inertia switch?
 

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Discussion Starter · #17 ·
You know, I'm not sure... how sad am I? :D

I'll snap some pictures for you this week and post them up. LOL
 

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i went with the inertia switch wire because i followed the other side of that wire and it went to the stock pump.
 

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I have an 044 pump in line and then have a 100 micron Aeromotive filter AFTER the pump. The only filtration I have before the 044 pump is the strainer on the end of the Walbro 255lph that's still in the tank. What's wrong with having the 100 micron filter after the pump?
 

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Discussion Starter · #20 ·
It's my understanding that having the wrong filter in line before the pump causes an issue with having to suck the fuel through the smaller filter, vs. pushing it through.

If you go to Aeromotive's site, they're very clear as to how they recommend you run the filters and what size.
 
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