Inline fuel pump run in series with in tank pump

[rider384]

Say you have an inline fuel pump rated at 255lph @ 60psi. In tank pump is rated at 190lph @ 60psi.

Would the inline pump up the amount of fuel delivered? My thinking is that with the inline pump doing the work of keeping pressure at the rail the in-tank pump will have to work at a much lower pressure, instead flowing something like 300lph@10psi. Numbers are made up.

Thoughts?

[Zachariah]

Leave it be. How much more do you want your mileage to dip? With FTs - I'd say a 300LPH Deatschworks in-tank pump would keep up.

[rider384]

Dip? Why would mileage dip? It would be unaffected. It's not like the car would be using more fuel, just capable of having more fuel delivered if need be.

[Castor Troy]

yes, this would increase the volume of fuel delivered. in tank pump would act like a lift pump, flowing high volume and low pressure, and the second pump would be high pressure.

and it is possible that the rest of your fuel system wont be able to keep up with the additional volume, and you'll get increased pressure due to that, which would lower your mileage. i dont know enough about the 2.7t fuel system to know where the limits of that would be, though.

[eejimm]

I'd be concerned about too much pressure in the fuel system - remember, the only thing that regulates the fuel pressure is the FPR on the fuel rail. The pump(s) will actually stack the pressure(s) on top of each other - 60 + 60 = 120 psi (or at least they will try) but the flow rate will be the smallest/weakest link which is still the stock pump (which kinda defeats your purpose). If the FPR is furiously dumping fuel from the rail, and it can't keep up, the rail pressure will rise, the engine will run rich (at least until the ECM cuts the injectors back) and the FPR or a hose could blow. Don't think you want an engine fire...

If you really need more flow, do it right by replacing the stock pump.
Jim

[rider384]

Why would the pressure be compounding? The stock pump wouldn't still be pushing 60psi (or at least I assume) since the inline would be supplying the pressure to the rail. All the in tank pump would be doing is providing a low-pressure supply of fuel for the inline. At least that's my thought.

Does a dead inline pump cause too much of a restriction on the stock pump to run out of boost? I'm thinking of having the inline on a boost-triggered circuit.

[Scotty@Advanced]

yes, this would increase the volume of fuel delivered. in tank pump would act like a lift pump, flowing high volume and low pressure, and the second pump would be high pressure.

Only if the low pressure pump flowed enough volume at the supply pressure to keep up with the high pressure pump. If they are grossly mismatched then the low pressure pump will become a restriction and the supply pressure of the 2nd stage pump can drop, which is where surge tanks come into play.

Instead of using the stock pump I'd look at a low pressure high volume pump.

Why would the pressure be compounding? The stock pump wouldn't still be pushing 60psi (or at least I assume) since the inline would be supplying the pressure to the rail. All the in tank pump would be doing is providing a low-pressure supply of fuel for the inline. At least that's my thought.

Does a dead inline pump cause too much of a restriction on the stock pump to run out of boost? I'm thinking of having the inline on a boost-triggered circuit.

The pressure won't be compounding, the fuel rail will only ever see the pressure that the FPR it is set at, unless the pumps can outflow the FPR then you would have fuel pressure spikes at low injector duty cycles. If the secondary pump had an internal FPR that was referencing supply pressure then you would see a compounding of fuel pressures as eejimm says.

Fuel pumps are positive displacement devices, so a non working pump would create a large restriction, unless it has a relieve valve in it which most only have a pressure limiting valve.

[Scotty@Advanced]

This begs the question are you running out of fuel? There are also fuel pump boosters which convert chassis voltage to 16 or 18V.. Which increases your fuel pump volume by spinning the armature faster.

[Vinchenzo51]

What pump are you running?

Our tanks can fit the bosch 040 pump amongst other better pumps. Why not just replace your in tank pump? You're only running F21's on what appears to be an unbuilt engine. You don't run out of fuel.

[rider384]

I'm not running out of fuel (yet), still on a stock tune and the tune in the mail is a stage 3-. I ask because I received a free inline fuel pump from Frankenturbo and I'm looking at different ways of installing it and getting the most out of it. Also to retain the ability to easily revert to stock if the FT pump takes a shit. I've heard people saying they suck, but I have yet to see a documented case of one actually failing. I'm still wary.

[julex]

I run stock pump with stage 3 k04s at 22psi and it was fine but eventually swapped to something else (walbro 255 at the time). I believe I was running the pump at its flow max or close to it. If you don't plan exceeding that, don't monkey around with external pump.

If you really itch to change pumps, get internal turbine Deatsch/Aeromotive pump or 044 (if you manage to squeeze it inside the tank, not that easy!) and call it a day. Any of these will flow far more than you will ever need with frankens. Running external pump is asking for trouble imho and involves running power to the pump which needs to be professionally done. Just another point of failure imho.

[rider384]

Is the stocker really good for stage 3? VAST fed me so much shit when I was talking to them about getting a tune that I don't know what I really need and don't need. I want to put this pump in because, well, it was free. And I want to help Franken develop it and get some feedback; I like seeing cheaper alternatives on the market. Why would running power need to be professionally done?

Side rant about vast:
Talked to them to get a tune, said I needed x hardware and y configuration. Did that, just didn't do it through them (I could get the stuff for half the price elsewhere). Came back to ask them to tune it and they said I NEEDED to buy their package and hardware or they wouldn't touch it. Which they said nothing about before. I'm glad they closed down, with how much shit they fed me.
/rant

[034Motorsport]

Running two inline pumps will only increase your rails ability to maintain flow at higher pressures, and very marginally so. It will not simply increase the flow at the same given pressure by putting then together. They must be in parallel if you want to increase the actual flow capability.

Take an 044 in the tank, and add another 044 inline. You are still limited by the first 044, the only difference being that you can create more pressure. You'll notice that pump flow falls off dramatically as pressure rises. Adding a pump in line helps you produce a higher pressure at the same flow. Think about it... the second pump can only pump so much fuel as the first one allows. The first pump will be working against the second pump, etc. Unless you run the pumps at different voltages, which could make things even worse. If you use a less superior pump to supply the 044, you are going to be limited to the less superior pump output. At high levels the 044 will be able to flow more then a cheaper pump, which means the 044 will be trying to suck fuel through the fuel pump. This is not efficient.

You are much better off running a stock or cheap aftermarket pump in your tank, and running an in-line surge tank. The surge tank allows the pump to work at full efficiency, rather then fighting the tank supply pump. This will ensure that you can't starve the first pump as well. A single Bosch 044 in a surge tank can support nearly 600whp with a proper feed line. Your stock fuel pump will be running at under 1BAR pressure to supply the surge so it will flow more then enough to supply the 044.