[glaser67]

Hey guys,

Making some upgrades to the 408w this winter in the 91' f-150. Reasonable expectations are ~500+ at the crank.

Currently (425-450 crank) running 30#/hr injectors at stock rail psi, forget off hand. Duel fuel tanks; trouble verifying flow rates, but results found range from 90-110 LPH.

Charts I've found indicate my flow requirement for 500 HP should be about 190-225 LPH.

So my question is; is it possible to run an inline booster pump to deliver more flow and/pressure? Or am I looking at upgrading both in tank pumps?

Side note: if whatever I go with can deliver more flow and more pressure at the same time, I anticipate increasing rail pressure and scaling the injectors.

Any advice or input would be greatly appreciated. I'm just looking to be pointed in the right direction.

Thanks,
-glaser67

[cgrey8]

Short answer, you will want to upgrade the pumps to higher flow pumps.

Now the long answer...

Most fuel pumps are positive displacement pumps which means their flow rate is fairly well fixed to the RPM they spin at (assuming they are moving non-compressible fluids).

They do have a max pressure that they will operate under, but this has more to do with the stoutness of the motor spinning them and the physical strength of the pump to handle that pressure while still supplying some acceptable amount of flow.

That said, yes the pump will have a flow curve that typically shows as pressure increases, the flow reduces. But what I believe is happening is the pressure is just slowing down the pump with the assumption the pump is being fed with a constant voltage. With stock N/A pressures, this is likely not a problem. But as soon as you start running boost, fuel pump flow rates become a concern. The pump is NOT going to deliver the same amount of fuel when it has to deliver the base 39-43PSI of fuel pressure on top of the booster's 15-25PSI. Fuel line pressure under these conditions gets into the 65-70PSI range so you need to make sure the pump can flow your fuel demand AT the pressure your application will require at that time.

So can you put a booster pump after it to increase it?
Yes. But you'll only get what the pump is physically capable of delivering. To get more flow from a positive displacement pump requires spinning the pump faster. And while reducing the pressure will get you a little more flow, it's not likely to get you the increase in flow you need. So if you need more flow, you need a higher flow-rate pump OR you need a secondary pump (not a booster pump) which will be plumbed parallel with your pump to give you a total flowrate equal to the sum of the 2 pump's flow at whatever pressure you are at. This setup does have its benefits in that you only need to run the second pump when under heavy loads. How you'd control the 2nd pump is going to be up to you to figure out...or just run them both all the time.

Now this just addresses the pump. It does not address the fuel lines and rails. Is your existing supply line (including the filter) capable of flowing this much fuel? It sounds like it can handle whatever you are laying down now, so it MIGHT? However I've always heard once you start flirting with 500hp, stock fuel lines can be a restriction even if a larger pump is installed. I have no clue how accurate that is or by how much of a resistance stock lines inflict. I'm sure there are better resources than my vague recollection of already 2nd hand info. But I can say ideally, the pressure at the pump should be VERY NEAR the pressure you get at the fuel rails on the engine, indicating you aren't getting significant resistance from the lines. However if your lines are a restriction, it's similar to an electrical resistance. The pressure at the pump will be significantly higher than the pressure at the rails. The higher the flow AT the injectors, the more differential you get since the lines can't supply the rails as fast as the injectors can dump from them. And of course this is only a problem when you need the fuel the most AND when not getting the right amount of fuel is the most destructive. And BTW, I'm ignoring the FPR. If you have ANY flow through the FPR, then you are maintaining enough pressure to supply the injectors. But most of us don't have flow meters in our return lines to hint to us when we've LOST return line flow indicating we've completely maxed out our supply.

Also don't forget that when you upgrade the supply, you'll also need to upgrade your return. When the engine isn't demanding fuel, the return line has to be able to get that fuel back to the tank just as fast as the supply line can supply it or you wind up with more pressure than you want on the rails.

Now all that said, I've been running a TREPerformance 255LPH pump now for quite some time on a bone-stock 89 Ranger fuel system. Granted my engine doesn't need anywhere near 255LHP. It was just cheaper than buying another Walbro 155LPH unit. The stock Ranger pump, I believe, is spec'd at 88LPH and that was perfectly acceptable for the stock 97 Explorer 5.0L I originally installed in the truck in 2005. But the 331??? I have no clue what it is actually producing for power, but I estimate it somewhere in the 250-270hp range based on MAF max flow rates and guessing at the BSFC. A stock 88LPH with a 20% margin can handle 250, but 270 eats into that margin. So I've kept an aftermarket pump in the truck just to be on the safe side. When the 155LPH Walbro I bought from Summit went bad, I replaced it with the TREPerformance one. They didn't offer anything less than 255LPH, so that's what I got and it has served me well all these years. One of the most notable features is it is SIGNIFICANTLY quieter than either the OE or the aftermarket Walbro.

What I don't know is if the pump is significantly slowed due to its higher flow capability pushing against my stock lines. If it were really a concern, I guess I could disconnect the return line and measure how quickly it filled a 1 gallon container with fuel then do the math. But it just hasn't been a concern. For all I know, it's been running 60+ PSI at the pump to give me stock fuel pressure at the rails.

Since you are running right at 500ish, I'd say just replace the pump(s) and see how it runs.

[glaser67]

Appreciate the detailed response, all makes sense.

Logical path forward would be to increase the flow via upgraded in tank pumps, and go up to at least 42# injectors. If I run into restriction after that in regards to flow, would have to re-plumb everything.

Either way bigger pumps would be required so I'll start there.

Prolly going to remove the bed in liu of dropping 2 tanks...

Have a great holiday

[cgrey8]

I dropped the tank once because I didn't realize how much easier pulling the bed is. Never again as long as I have someone that can help me lift it on and off. And if I have to do it myself, I'll figure out how to hang tow straps from the ceiling of my garage. Dropping the tank was SO annoying.

[lilboss82]

94 F150 Lightning, 408w, Novi SC. I'm running a Radium fuel surge tank upfront with stock in-tanks setup. Works perfect and keeps about a liter of fuel in reserve to mitigate the risk of in-tank pump cavitation/starving. I can swap the surge tank pump easily with other sizes if needed. I have a sketch on it.

[lilboss82]

sketch

[glaser67]

This looks like a more simple setup. With two tanks, I don't like having to change both pumps, and possibly adding larger conductors.

Also, (question here) I'm not sure if the truck in tank pumps even have an upgraded flow option: all I see at summit are OEM style replacements (large, white, plastic housings). Where the units rated for mustangs are the smaller metal cylindrical pumps.

Am i mistaken, or does the white plastic housing come apart and I just replace an inner pump unit?

I'm going to consider a setup like yours.

Thanks

[cgrey8]

If you never run different fuels in the tanks, then the 1st setup is certainly an option. What I don't see in the 1st example is how one tank doesn't get over-filled with return fuel. I'm assuming the same valve that activates/deactivates the supplys is also activating/deactivating the return. But that seems like there's the possibility to get some amount of cross-contamination between the two tanks on switch-over. With gasoline and E85, that's not likely to be enough to be of any importance or significance. But if this were a diesel setup with one tank containing taxed fuel and the other containing red-dye (non-taxed) fuel, getting red-dye in your taxed tank seems problematic.

However as the 2nd one shows, you can run different fuels in the tanks without cross-contamination since the system never "returns" after the pumps. It reminds me of the transition Ford did to the 98-01 Ford Explorers. The 96-97 Explorer 5.0Ls use a traditional Fuel Pressure Regulator and return line. However in 98, the regulator was located at the pump so the "return" fuel was dumped directly back into the fuel tank allowing for a single returnless-fuel system setup. Although it wasn't the same as the similar-year Mustang returnless systems that did it right by having a fuel pressure sensor and a multi-speed pump. I've never looked into exactly what their sending unit looks like to see how this pump/regulator setup is pulled off. However I wouldn't be surprised if they used the same cylindrical pumps the way the Ranger/Mustang sending units did. Point is, it sounds similar to what this 2nd setup would do. But as you stated, it would require updating BOTH pumps if you determined both were undersized for the task. The 1st setup would allow you to run a single-pump.

[lilboss82]

@glaser67 The only one i know of that has a intank upgrade is Quantum. The have 340 and 255 options. I'm skeptical that those big pumps would work right without sucking the canister dry. Also read posts by marc2000gt on nloc.net like the thread below. They have a flaw in the grommet design on the canister that needs to be addressed.

@cgrey8, you are right. I've had the shuttle/check valve fail before and cross contaminate. The sketch with the two FSTs eliminates the threat of cross contamination. Only thing to worry about is the check valves at the rail but it's so much pressure that i doubt they have a problem. Could always do double check valves in series if i needed to.

Quantum pumps:
https://www.highflowfuel.com/product-re ... 50~zp_5-8l

NLOC talk:
https://www.nloc.net/forum/index.php?th ... st-2212583

[cgrey8]

It's interesting you mention sucking the canister dry. Even with the aftermarket 155LPH Walbro I had, if my fuel level got near 1/4 tank, a sharp turn to the left while at hard acceleration would slosh all the fuel to the back of the tank. The tank was designed with a spiral raised lip around the sending unit to hold some around it under accel/braking, but it doesn't seem to hold enough. You can see what I mean in this picture:

Ignore the fuel leak. This isn't my picture, but it serves the purpose of showing what I'm talking about.

IIRC, my tank's design is much more circular where this tank has larger cavity due to the more-oval pattern. I also don't think my tank's walls are as tall either. Apparently Ford resigned the Ranger tank to be a bit more resistant to this problem...or my memory is off. It's been MANY years...

The point is, the higher flowrate of the pump just sucks the fuel down fast enough to cause the engine to fall right on its face the moment air gets pulled in. It doesn't take a lot of air to lose the "prime" on the pump and thus kill pressure ESPECIALLY when the engine is also pulling heavily from the fuel line. I don't know if it's literally running dry or if the higher flowrate is creating a vortex thus allowing air to make it into the pump. Regardless which is the case, the result is the same. Even after the fuel washes back over the sending unit, it takes the pump a good 2-3 seconds to reprime and restore pressure. It's QUITE annoying when this happens.

When I replaced the failed Walbro with the 255LPH pump, this only got worse and no, the higher flowrate pump does not recover any faster. So I've learned I simply can't rely on the engine to "be there" at heavy loads if the needle is much below the 1/2 mark. I'm SURE this could be fixed somehow, but it's never been a high enough priority with such an easy workaround.

All that to say if your tanks are long and thin the way my Ranger's tank is, you may experience a similar problem with upgraded pumps. Hopefully you have the better tank design.

[lilboss82]

You seem to have the same experience as me. And call me crazy, but i hate not being able to use the full capacity of the tanks and always needing 1/4 tank or more. I had even more problems with the sumped tank and fuel rushing out of the sump on braking and such. That why the FST looks so appealing. Always have a liter of reserve on the HP pump. little chance of starving and going lean. Especially being supercharged. It was either this or the Aeromotive Phatom hats.

[glaser67]

Great info here...still thinking this through;

Cheapest option would be to add a single in line pump.

2nd cheapest to add single inline with reservoir

Most expensive and most work would be to upgrade both in tank pumps

I like the in line with or without reservoir. What I'm getting hung up on, is if the boost pump could draw more fuel than the stock in tank pumps can push, would it not cavitate the line between the two? With a reservoir, would a stronger pump not just drain it dry constantly? I intend to up the rail pressure up as much as 10-20 psi as before my upgrades, my duty cycle with 30#'s is right at 90%. Maybe the increase pressure could mitigate the difference in flow between the pumps? Maybe a 155 or 190LPH could be more suitable as a booster?

Perhaps run the return line back into the boost pump inlet with a check valve?

Maybe I'm overthinking the first two options?

[lilboss82]

the FST and FSTr option would not drain it since the excess/return go back in to the reservior. only the overfill goes back to the main tank. I did the math on mine and if would take something like 30 seconds of full load/WOT for the reserve to starve where the intank pump wouldnt keep up with the high volume FST/FSTR pump.

[richadd]

Dreaming of fuel system upgrades with dual tanks, one might imagine extended range and enhanced touring capabilities. Enthusiasts may envision conquering longer journeys with ease, minimizing refueling stops, and unlocking new possibilities for exploration and adventure on the open road. gb whatsapp pro

[Primrose44]

Upgrading your fuel system is a crucial step when aiming for increased horsepower, and it's great that you're considering the necessary modifications for your 91' F-150 with a 408w engine. Here are some suggestions and considerations:

Inline Pump Addition: Consider adding a high-performance inline fuel pump to supplement your existing system.
Ensure it's compatible with your fuel system's requirements, providing both adequate flow rate and pressure.

In-Tank Pump Upgrade: Explore upgrading your in-tank pumps to higher-flow options designed for your vehicle. Choose pumps tailored for your application from reputable aftermarket brands.

Consult Professionals: Seek advice from professional tuners or mechanics experienced in high-performance builds.
Ensure proper calibration and compatibility of all fuel system components, including injectors and pressure regulators.

[harsel]

The FST and FSTr option wouldn't cause drainage issues because the excess/return fuel cycles back into the reservoir. Only the overfill returns to the main tank. Through calculations, it's evident that even under full load/WOT conditions, the reserve wouldn't starve as the intank pump matches the high volume FST/FSTR pump's output. fm whatsapp

[harrison]

Exploring fuel system upgrades with dual tanks, contemplating the benefits of increased range and versatility for long-distance travel or off-road adventures. Considering factors like installation complexity, cost, and compatibility with existing components to enhance vehicle performance and convenience. lic calculator

[harrison]

In a person's thinking, "Fuel system upgrades w/dual tanks suggests they are exploring enhancements for their vehicle's fuel efficiency, range, or capacity. They might be considering options like installing larger tanks, improving fuel management systems, or adding features for increased reliability and convenience during travel or work.