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Discussion Starter #1
I'm in the process of modifying my oem hanger for a Walbro 525 pump and running a -8AN feed and -6AN return line. I planned all this out and have all the fittings including a 90* bulkhead -8AN fitting for the feed to come out from the hanger. Seen many pics of this and did a lot of research, watched vids, etc. Now that I have it all apart, I'm having a little trouble understanding the theory of this. The outlet of the pump is only 5/16 inside diameter. So how is it that the entire feed line couldn't be 5/16? As far as I know, the rule of flow/restrictions means you can have an indefinite length of any kind of line, be it for fuel, an exhaust system, intake, etc. and the flow will be determined by the smallest restriction or biggest choke point right? So what makes the fuel system flow so well out of such a tiny pump orifice?
 

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Same reason your outside water faucet will fill a bucket in 1 min with no hose attached. Attach 300 feet of garden hose and fill the same bucket. It will take way longer because the length of the hose. Even though the garden hose is bigger inside than the narrow parts inside the water tap, all the distance factors in.
 

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I think it should be a 3/8" hose which works out to like a -6AN feed inside diameter which is more like the size of the stock feed.
If you use a 6an feed line you really aren't upgrading over stock, and you can ran a walboro on the stock feed line and do 400hp all day.

You are right in that you don't technically need that extra inside diameter of the 8AN hose, but it is more common to overbuild the feed line cause the cost of -8 is marginally more than a -6, but you can add an extra pump down the line on a -8 and have more options in the future, otherwise you would just use the stock feed line unless you are going for the AN line look but a 6AN even looks small. Seen dual 6ANs and I would rather just have one reasonable 8AN line than that unless I needed the flow of like a 10AN etc.. lots of ways to do it.
 

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Discussion Starter #4
I will definitely be using the -8AN line I have. Just wanted to better understand the system I'm setting up. I'm making sure that all lines are larger coming off the pump and as restriction free as possible. Using the good old PTFE flex hose you see in tanks from the pump to the top of the hanger. It clearly has as a bigger inside diameter and is a tight fit on the pump/adapter fitting I'm using. And the -8AN bulkhead fitting is a "high-flow" design without such a sharp 90* turn.

I was in the mindset of running dual pumps. But they are making some pretty impressive ones now days. The 525lph should be more than enough for my 800whp max goals. I was looking at the expensive hangers and reading on so many things. Just decided to save big money on one pump and some fittings to modify my hanger.
 

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8an feed and 6an return is a good setup, I think you are right on point don't throw in a second pump till you need it.
 

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Wow, the 525 is rated for 1000 crank HP at 13.5 volts! I think I may have found a new fuel pump, and won't have to pay an additional $592 for a triple hanger.

OP: do you have any links of how to adapt a the A/N bulkheads to the existing hanger?

That is one good thing about those pricey aftermarket hangers - the outlets are huge and already modified to A/N.

Al
 

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Discussion Starter #7
There are a few write ups and videos. I'll try to take good photos when I do the process and explain what to do. Haven't done the drilling and epoxying yet.
 

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Sounds good. I currently have a Weldon external pump (soon to be for sale), and am looking to go with something quieter, and not so race oriented.

Will you be running the stock fuel pump ECU with 12v mod?

Trying to get a handle on what I have on the car as I bought it with the fuel system installed. I would like to have a way to pump the fuel out to change to race gas if needed. May have to get creative on the return line with a provision to run a drain line into a gas can.

Al
 

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Discussion Starter #9
Yes it will be ran off the factory setup. I will do a hotwire mod as it's called to run battery voltage straight to the pump. Then it will get full alternator volts as it runs. I relocated my battery to the trunk, so this should be easy. I haven't got to that part yet or how I'm going to do it. But I will do the research for it soon. I did it on my C5 Vette when I upgraded it's fuel pump and that kit had it run right off the alternator positive post using a 10ish gauge wire.
 

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I was in the mindset of running dual pumps. But they are making some pretty impressive ones now days. The 525lph should be more than enough for my 800whp max goals.
The more I read up on this, the more confused I am about how much HP the pumps really support, lol!

Plus, all the good numbers are made with the pump running 13.5v. How will you get it above ~12v? The Kenne Bell boost-a-pump was one thought, but unfortunately, they only have two steps - 17.5v and 21v.

Just thinking out loud. I would love to run one in-tank pump, and was working towards that. I am just not so sure now. I am in the 700 HP range.

The tests below (by DeatcheWerks, lol!), they are claiming the DW400 is more powerful that the Walbro 525. Who knows. One downside is it doesn't have an internal check valve, so starting the car might take holding the key on for 2 sec before cranking unless you add a check valve inline. DW400 – DW’s Highest Flowing In-Tank Fuel Pump Available | DeatschWerks, LLC
Walbro 525 VS DW400:

Al
 

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Discussion Starter #11
Well when you do the Hotwire mod as it’s called, you are running full alternator power to the pump. So it runs at that voltage or higher. I’m sure the 525 is going to work great with that. I have DeaschWerks Hotwire kit that I’ll be installing.
 

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The hotwire mod diagram I have shows the battery wire running to a relay, which the fuel pump ECU 12v wire also runs to. Presumably, using the FP ECU makes everything behave more like factory - with the pump shutting off with the key on once pressure has built up, and also I assume it has an inertia switch?

I currently have a fused wire running right from the battery to my external pump. Sure, the battery reads 14v while the car is running, but I've never seen more than 12v at the accessories. I guess using a 10ga wire makes all the difference?

Al
 

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Discussion Starter #13
The gauge of wire helps, but really it's having it wired up so when the relay energizes it sends full running alternator volts to the pump. This is it's own added wire in parallel basically with the factory system. That's how I ran it on my C5. I left all factory wiring alone, just added the hotwire kit and ran the wires as necessary. The pump will still be controlled by the factory controller, but the added wire from the battery or alternator will send the electrical juice when the relay is activated. The added relay will be signaled by the controller too. That's the idea anyway.
 

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Discussion Starter #14
It's really a simple setup. You have a 4 wire relay. One is battery power going in, one is grounded, one leads to the pump, and the other to whatever control device activates the oem system. It just runs direct higher current to the pump. The system doesn't know it's there. It runs the same, just with the added relay grabbing the same signal to run the piggyback wire.
 

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Fuel Line Sizing — What Size Do I Need?
by Admin on November 16, 2012 in General, Technical Articles
Lots of strange information out on the internet regarding fuel line sizing and it seems like most of the time people run way more diameter fuel line than they need. This is an interesting article that I came across that seems to be pretty relevant.
Quick reference for AN to Inch line conversion:
-6AN = 3/8″
-8AN = 1/2″
-10AN = 5/8″
-12AN = 3/4″
Fuel Line Sizing
A question that is often asked of me when dealing with high horsepower applications is: “My fuel line is nominal 3/8” id. Don’t I need to increase the size of the fuel line to at least ½” id (from a #6 to a #8 or #10) to support say 600 HP”?
The answer is “NO”! A 3/8”id fuel line can easily support 600 HP given sufficient “pump head”! Given a big enough pump a 3/8” steel line could support 1000 HP.
The simple way to know is to install an electronic fuel pressure gage. If the pressure falls as the engine RPM’s go up you need more pump head. More pump head can be achieved with a bigger pump, higher pump voltage and/or increasing the line size. But before you do check out the following (and remember a dirty fuel filter is often the culprit of falling fuel pressures!).
The reason most people do not understand why is because “back in the day” when carburetors ruled and everybody ran a Holly electric fuel pump running at 14 psig then into a rail mounted PRV set to 6 psig the “pump head” was insufficient to overcome the pressure drop thru the 3/8” line: particularly if the pump was at the front of the vehicle.
Let’s see why today this is what I call a “wives’ tale”. For this example I will use gasoline. If we use alcohol we need about double the flow or with E85 we need to increase the flow numbers by around 30 % .
At WOT (Wide Open Throttle) a BSFC (Brake Specific Fuel Consumption) of ½ pound of fuel per horsepower is quite safe: resulting in A/F ratios of 11:1 or richer. Remember that maximum HP occurs at an A/F ratio of 13:1. We won’t go into why one chooses such rich air fuel ratios; suffice to say that using a BSFC of .5 is generous. Since gasoline has a weight of 5.994 lbs/gallon (@ a SG of .7201 typical) then in round numbers we need 1 gallon of gasoline per 12 HP (5.994/.5). The reason I am making all these conversions for you is because typical fuel pump measurements are made in volume versus mass although mass is more accurate.
OK stay with me now as we calculate how much gasoline fuel we need to support say 1000 HP. 1000 divided by 12 = 83.3 Gallons Per Hour or 315 Liters Per Hour.
Now we are going to calculate the pressure drop thru a 3/8” steel line for a typical vehicle at a flow of 83.3 gph or 1000 HP. Most of you know that the pressure drop thru a straight pipe is less than an elbow or a 45 (same principle as your air ducting from your blower thru the piping and on into the engine). Lets assume we have about 10 feet of 3/8” fuel line. Let’s double that to say 20 feet to take care of the bends in the steel pipe from the gasoline tank up to the engine fuel rail. Ingersoll-Rand publishes an engineers’ handbook called “Cameron Hydraulic Data”. In there they list the “Friction Of Water” thru various types of pipe. Using the pressure drop thru a new steel pipe of .364” id at 1.388 gpm (83.3 gph) we get a head loss of 35 feet per 100 feet of pipe with water as the medium. 2.31 feet of water = 1 psi therefore 35/2.31 = 15 psi per 100 feet. If I use 20 feet of steel pipe then that is 1/5 of 15 or 3 psi using water (gasoline is less viscous and flows more freely). A Fuelab Model 41401 can deliver 90 gph @ 70 psig. Can I tolerate a 3 psig drop if I need the fuel delivered at 60 psig? Yes. Will increasing the line size to ½” help? Yes the pressure drop thru a ½” line is a nominal 5 feet versus 35 feet for the 3/8” id fuel line. The ½” line will result in a ½ pound drop versus the 3 pound drop for the 3/8” line at the stated flow of 83.3 gph (enough to support 1000 HP at a BSFC of .5). The pressure drop at 1320 HP thru a 3/8” steel line might be around 5 psi.
The key to sufficient fuel supply is pumping power. As another example let’s look at a flow of 1 gallon per minute at a required fuel rail pressure of 70 psig. That is enough fuel to support 720 HP. The pressure drop thru a 3/8”id line at 60 GPH is less than 1 psig! Switching to a ½” id line would result in a pressure of about 1/10 of the 3/8” line. However, given sufficient pumping power, a one (1) pound drop versus a tenth (1/10) pound drop is insignificant. At 500 HP the pressure drop is even less.
VISCOSITY SG plays no role in friction loss. The key factors are viscosity and surface tension of the liquid being pumped. Gasoline has lower viscosity and much lower surface tension than water, which is why it flows more easily thru a pipe. Consider that most greases have a lower SG than water but much higher viscosity. Which do you think flows more easily thru a pipe? SG becomes a factor if there is vertical lift of the liquid involved or very long pipe runs (which represent a large physical mass of liquid.) SG simply determines the weight of the liquid per unit volume and it boils down to more weight requires more power (HP) to move it. Friction loss is the mechanical resistance exercised by the pipe wall on the liquid. Low surface tension and/or low viscosity liquids overcome that resistance more easily. Here is a little experiment you can try. Water has relatively high surface tension. Alcohol greatly reduces that tension. Place a small drop of water on a counter top. (The counter top is analogous to the pipe wall) The water lies on the counter as a small bubble. Don’t touch the water but let a very small drop of alcohol drip into the water. Watch the water immediately spread out on the counter top. The alcohol broke down the surface tension and the water molecules were free to move. If you put a drop of gasoline or alcohol (low surface tension liquids) on the counter top you see they immediately spread out. BTW, this is an area of misunderstanding with people.
Sourced from http://www.blowerworks.biz/docs/fuel-delivery-basics/fuel-line-sizing/
 

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Discussion Starter #16
Thanks for all that info. Helps to grasp how it works. I know 8AN is pretty big, but misconception or not, it seems like the safest route. My 525 pump came with paperwork stating that this pump requires a line size increase among an external FPR and the sort for most any factory vehicle. Considering the other restrictions in the system, it's likely better to go big. Running an in-line 10 micron filter for example, the corners in the bulkhead fittings and rail inlet/outlet. Furthermore, I was told once by a tuner that larger fuel rails/lines act as a sort of reserve. By keeping a greater amount of fuel over the injectors, if there ever was a moment of possible insufficient fuel delivery, there is more fuel there in "reserve" so to speak. Made sense the way he explained it. Not sure I believe it, either way, I'm sure my 525 pump running with a hot-wire kit through an 8AN feed and 6AN return system is going to work just fine. That's not to argue or disregard the info above whatsoever. I just happen to have this entire system's parts already and it's a tried and true system. I don't think anyone setting up a 600-700-800 hp + build should be going for just whats sufficient. You want to protect your investment by providing ample fuel. Because lean out once at high rpm, and it could be over. I'm a believer in overkill in certain areas, and this in one. In the real wold, too much can happen that calculations on paper don't account for. Other things I've read are the life of the pump is extended by a freer flowing system. I've even decided to keep a spare 525 on hand because I don't believe you can run such a pump and think it's going to last forever. I wanted a system that will support 1000hp for my planned 800ish hp. that is my idea of making sure the system is good to go. I know my selected injectors should be around 80% duty cycle at 800ish whp running in the 50ish area psi. Keeping things safe with low pressure, high flow, and easy injector pulse. Al least I'd like to think I have it planned put well lol.
 

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The gauge of wire helps, but really it's having it wired up so when the relay energizes it sends full running alternator volts to the pump. This is it's own added wire in parallel basically with the factory system. That's how I ran it on my C5. I left all factory wiring alone, just added the hotwire kit and ran the wires as necessary. The pump will still be controlled by the factory controller, but the added wire from the battery or alternator will send the electrical juice when the relay is activated. The added relay will be signaled by the controller too. That's the idea anyway.
I thought you were doing "standalone" power to the pump, bypassing all factory wiring, no? There is a factory connector on the fuel pump hanger, are you still using that?

I was looking at the DeatcheWerks hotwire kit, it only uses a 12ga wire. According to the wiring chart in Hot Rod magazine, you need a 10ga for 7-10 ft length and 20-25 amps. 15-20 amps only requires 12 ga. In those tests, they show the 525 and DW400 both hitting ~22 amps.

My external pump currently is wired 100% "standalone", if you will. It has a fused cable running from the battery, to a relay near the pump. I was looking to go more factory, with the added hotwire. I see a lot of people bypass the factory wiring entirely.

The factory controller does have an inertia switch, and does stop pumping a couple seconds after you turn the key on, correct?

Al
 

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Discussion Starter #18
Yes I'm still going to be using the factory connections. Just with a relay off the power wire so that when the pump is energized, it also energizes the relay to run direct battery power. I'm still devising a way to run the wire through the top of the hanger and seal up with no leaks. My battery is in the trunk, so the shorter distance will be fine with 12 gauge wire.
 

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Discussion Starter #19
Ok so according to the instructions in the DW kit, they want you to cut the power wire going into the pump connector and run it to the relay and out of the relay back to the pump. (Making it the only power source) which I am fine with either way. Whether in series or parallel, electricity will follow the path of least resistance meaning the hot-wire kit would be supplying the power even in parallel, just though it might be nice to run it in parallel so there is a fail safe if for some reason the relay didn't work. But if it's in parallel, that would mean battery voltage is being back-fed through the OEM system and might be bad for any modules and the small wires.. So I guess I'll just follow their instructions. They might know a thing or two lol.

So where the important wiring needs to happen is from the pump, up to the hanger connector (which I've already done) The 525 looks to be using a 14 gauge wire. This I used an OEM terminal and clipped directly into the connector, (not just wiring into the smaller old factory wiring like most do). So with the DW wire that goes to the pump I will do the same. Directly terminal it into the harness. This way there is the most direct "thick" wire possible the whole way. I'm sure the pump comes with a gauge of wire they know to be sufficient. But either way I'll do what I can to get it at least that size up to the hanger. I'm only looking at about 2.5' from my battery to my pump. So I think my wiring will be good.
 

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Discussion Starter #20
So I’m done mocking up my hanger setup. I had to use a flexible hose inside from the pump to the feed outlet. Same as the one you see coming from the return to the jet valve. Just snaked around inside. Do you think that will be ok for the big 525 pump? Turns to 8an at the bulkhead fitting. Wondering if it’s strong enough? It’s PTFE in tank plastic flex hose.
248118
 
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