I am going to modify my factory 1g awd fuel hanger for a dual intank pump setup, and cannot find any info about if both fuel pumps need to be the same size, flow wise. I have a walbro 255 and a jay 340 and want to use these two pumps if possible. Thanks

How do you intend to plumb them? Parallel or series?

I was going to use a y fitting in tank.

So, parallel.

2 pumps in parallel will deliver the combined flow of each pump, but only at each pump's rated pressure. Simply, you'll gain flow, but will still be limited to what each pump (in in this case, the 2 pumps together) can deliver at a specific pressure. To figure out those specific pressures, you'll need to refer to the flow chart for each pump.

To maintain flow at increased pressures, you would plumb 2 pumps in series. However, this is more difficult, as the pumps need to be somewhat closely matched to ensure the larger of the two pumps doesn't get starved.

In a turbocharged application, where pump pressure rises with boost pressure, you typically run out of flow because as pump operating pressures (also know as head pressure) increase, pump flow decreases. Meaning, as boost comes up and you need more fuel, your fuel pump flows less. The way to fix this is to run a pump that can sustain adequate fuel flow at high pressure. Or, run a series of pumps that together can sustain that flow.

In short, combining 2 pumps in parallel that currently do not produce adequate flow at high pressures will not solve your fuel problems (assuming you're trying to solve a fuel issue).

Thanks for reply and info. I currently am swapping in a forged short block and wanting to push about 60-65lb/min of air with new setup. Injectors will be 1650 hi z and wanted to make sure I have enough pump. It sounds like running an inline 044 may be a better solution? Fuel line pressure with boost will be about 80 psi. I wanted to use the walbro 255 and the jay 340 simply because I already own them.

I'm in a similar situation myself. I'm targeting about 30psi of boost pressure on top of 50psi BFP, which adds up to about 80psi total FP: http://www.dsmtuners.com/threads/gstwithpsis-galant-vr4-1837-2000.482807/page-10#post-153619762

You should first figure out approximately how much fuel flow your setup will require. You can use the calculator in the link I provided above to figure that out. Once you have that flow number, simply find the right pump, or pump combo, to get the job done. You'll need to dig up the flow charts for whatever pump you intend to use to make sure it will support.

I'm currently reworking my fuel setup to use an Aeromotive Stealth in-tank 340 in conjunction with an A1000 external pump plumbed in series. The idea being, the two pumps combined in series will maintain flow at higher working pressures.

I can't answer your question for sure on the 044. I know the Bosch 044 is one of the better pumps out there, but you'd need to dig up a flow chart for that pump, and ensure it will yield the proper flow at 80psi, while also supplying the required fuel to support your airflow/HP levels. Again, you'll need to figure that out by crunching the numbers.

http://www.ecmtuning.com/forums/showthread.php?t=20089

Here is an interesting read. Not exactly your question but something to think about

buddahboost said:

http://www.ecmtuning.com/forums/showthread.php?t=20089

Here is an interesting read. Not exactly your question but something to think about

Click to expand...

Thanks for the link. On page 7 of that thread it is said a 255 feeding an inline 044 is not enough for 600whp on e85, but I have read on this forum of people making well over 600+ whp on e85 using just a single 044 intank.

http://www.dsmtuners.com/threads/bosch-044-real-world-limits.368215/

Im going to punch the relief valve on the pumps I have and try them in parallel. Im just planning ahead, so it will be awhile before I can see what happens.

buddahboost said:

http://www.ecmtuning.com/forums/showthread.php?t=20089

Here is an interesting read. Not exactly your question but something to think about

Click to expand...

That's good information overall, but some of what's written is misinformation regarding pumps ran in parallel.

The first post shows exactly what it should; that 2 pumps put in parallel will increase flow at low/no pressure. What it doesn't show you is those 2 pumps performing under high pressure. If it did, you'd see the pressure fall off as pressure increases almost as badly as you would a single pump. Perhaps even more, as 2 pumps may draw more voltage/amperage, and therefore tax the charging system more heavily.

I'll just restate this in case anyone is confused by the ECMtuning thread: 2 pumps plumbed in parallel will not increase flow under pressure. Two pumps in parallel will be subject to nearly the same pressure losses at high pressure as a single pump would.

The only way to increase flow at high pressure is to run a superior single pump, or multiple pumps plumbed in series.

The issue with most pumps isn't that they can't supply enough fuel. The issue is that, for example, an Aeromotive 340lph pump doesn't deliver 340lph at let's say, 80psi. At 80psi, an Aeromotive 340lph pump delivers closer to 200lph. However, plumb another pump in series, and the fuel system's ability to deliver fuel at high pressure increases almost proportionally to each pump's rated working pressure (when you match different pumps, there will be variations). Each pump setup would need to be matched properly to ensure 1) the lift pump isn't starved and 2) the pumps combined will deliver adequate flow and the desired pressure.

This is a basic principal that can be found tons of places online. A well put example turned up in a Google search:

MGAguru.com said:

There is an issue (or discussion) that pops up occasionally related to fuel pumps plumbed in series or in parallel. In general, two pumps in parallel running at the same time can produce twice the volume at same pressure (if there is enough flow demand at the time). Two positive displacement pumps in series running at the same time would produce twice the pressure at the same volume.

Click to expand...

More good resources which outline various pieces of these principals here:
http://www.engineeringtoolbox.com/pumps-parallel-serial-d_636.html

http://mgaguru.com/mgtech/fuel/fp125.htm

https://www.aeromotiveinc.com/tech-help/faqs/faq-efi-fuel-pumps/




TLDR; forced induction applications typically benefit the most from a fuel system that performs best at high pressures. Parallel pumps won't achieve this if the pumps used don't flow enough on their own to begin with.

http://www.4gtuner.com/topic/6672-how-much-powerpsi-will-a-walbro-fuel-pump-support/

Good read here.

You have the pumps...go ahead and set them up in parallel. Keep your BFP at 43psi and go from there.

i ran dual wally 255's in parallel in both my 2g can and my current 1g (until one died) I had also ran a 255 feeding a 044 inline pump.. the 044 didn't last long on ethnol, (neother did the older wallys for that matter)

but although your theory holds true, I have to say at high boost, the two pumps in parallel delivered more fuel in a real worl scenario, because when one went bad I went lean, (and was running oean being out of pump before I setup the dual in tank setup) although it maynot be optimal, if pressures are kept decent (lower your base FP) two pumps in parallel will deliver more fuel than one pump alone ...like I said, the theory says it's doesn't but there's way too many oeople running parallel pumps for it not to be a functioning solution

not trying to start an argument, just saying based on my use and plenty of peoples setups on here it's proven to provide more fuel than one pump alone