inline vs. double pumper

[Mysterio]

There has been a lot of debate locally over this subject for awhile now. What do you guys think is the best option. What are the pros and cons of each set up?

[Sharkbite2000]

Inline ? at least I think that's what ams uses 2 in tank 1 inline :)

[logic]

(Apologies in advance; I didn't mean to write a thesis here, but it's a pretty vague/broad question.)

It depends on your needs. Luckily, the fuel system is one of those few places on the car where you can actually work out ahead of time what it is you need, as long as you have some airflow targets in mind, and enough data about the operating characteristics of the equipment you're using.

In general, two pumps in series will flow quite a bit less fuel volume at a given pressure than the same two pumps in parallel; a pair of pumps in parallel will come in just shy of double their individual total flow at a given pressure. However, flow drop-off at higher pressures will mirror that of a single pump, which can be more or less of a problem, depending on the pump. So, if you run a Bosch -044, it'll push just shy of 310lph at idle, but only about 290lph at 30psi of boost. Double those numbers (roughly; lop about a percent off) if you run two in parallel.

The interesting thing about running in series is that, while ultimate flow is only moderately improved, that flow rate tends to not drop off much as pressure increases. In some situations, this might be more desirable, giving more consistent fuel volume delivery at differing operating pressures. (This makes sense when you consider the pressures each pump is operating at; you can run a relatively low-operating-pressure pump in-tank, as long as its ultimate flow keeps up with the larger inline pump, which will be responsible for maintaining pressure.)

A side note: in any dual-pump configuration, but more-so in a parallel setup, you should take care to prevent cavitation damage; if your pumps lack an integral check valve, you might consider adding one to the system.

Another thing to watch for with pump selection is whether the pump has a pressure relief of some kind. Anyone with a stock Evo VIII pump will have seen what happens to their IDCs when you turn the boost up to about 23-25psi; the relief opens at around 65psi, and that's all she wrote.

Some good starter reading would probably be AMS' fuel pump testing (http://forums.nasioc.com/forums/showthread.php?t=1238595) from a couple of years ago (Martin did an excellent job with that), which will give you an idea of the flow vs. pressure characteristics of a few common pumps, and get you started on asking smart questions about your fuel system. It'll also give you something to compare to the technical literature from aftermarket vendors, so you can see where your money might be better spent. (For example, Aeromotive has always been good about providing flow data, although you almost always have to convert to measurements we're more used to dealing with on sport compacts.)

I guess my question to you after all that is: what specifically are you wondering about?

[DIDYSIS]

Whats the best way to hook up a second inline fuel pump?? How would I wire one? Etc, prob asking to much but a write up would be great to see.

[David Buschur]

I have run/tested both ways of doing it and the double pumper (parallel)definetely supplies more fuel than one pump running into another pump (series).

We have gone as fast as 9.0 at 159 mph with our double pumper, that is on stock fuel lines, stock fuel pressure regulator and only 1200 cc injectors.

I am currently working on possibly doubling the HP potential of the system we currently have while still not having to touch the stock lines. I just have to finish the project on the new build I am doing.

The kit we sell uses a simple pressure switch that activates the secondary pump directly from the battery. You can also do it from a relay if you like through a stand alone.

Good luck.

[itzwolf]

I am currently working on possibly doubling the HP potential of the system we currently have while still not having to touch the stock lines. I just have to finish the project on the new build I am doing.


I'm eager to see what this option is!

Any update on the stock power source/harness upgrade for the primary fuel pump? I remember you mentioning you had something in the works as far as bumping the voltage to the primary pump for more stable and better fuel flow.

[logic]

For some reason, that sounds like a boost-a-pump (http://www.kennebell.net/accessories/boostapump/boostapump.htm) to me.

[kcevo]

I'll be trying out a Bosch 044 in the tank, stock FPR with a B&M Adjustable regulator hat, and Bosch 1000cc saturated injectors or PTE 1200's. Plans are to run around 80-90 psi of base pressure.

I'm doing this as an alternative to 2 pumps, as with E85 setups and a 255lph pump (with the pressure relief still intact) are done at 450whp. Plus they don't flow for shit after 70-80 psi, whereas the Bosch is good for about 120-130psi.

[logic]

In theory, that should actually be a really good match; at 70-80psi base (yes, I know that's lower than you were targeting; I'll get to that in a second :)), the pump should be able to sustain well over 1100 cc/min/injector of fuel up to moderate boost levels. I've said it for a long time: these pumps are very impressive, especially since they're an OEM application.

Something you might want to keep in mind, however, is that the 044 starts drawing a lot of power after 7 bar or so (about 100psi), and performance drops off very quickly after 8 bar (115psi or so). JayRacing has a good chart (http://www.jayracing.com/images/products/BFP-044_flow_chart.jpg) that demonstrates the behavior pretty clearly. That spike in amperage draw suggests to me that you're starting to get well outside the safe operating pressure of the pump. I've never actually seen a detailed operating spec sheet for these pumps other than the basics (max 15.5A draw (http://hardparts.com.au/catalog/banga/genuine-bosch-044-external-fuel-pump-0580254044.html) my ass); if anyone has a link to one, I'd be very interested in reading it.

But, because of that I'd be very hesitant to run one of these pumps much beyond 100psi. If you really want to operate it at that range, plan for a bit of manufacturing variation, and definitely make sure your wiring will accommodate your worst-case expected load plus some headroom. Definitely let us know how it works out for you!

[logic]

I should probably note too, that at those pressures, AMS' testing (http://amsteam.net/files/8/fuelpumpgraph-3.JPG) and Jay's chart (http://www.jayracing.com/images/products/BFP-044_flow_chart.jpg) seem to disagree a bit; Jay suggests somewhat lower ultimate volumes at 7-8 bar (somewhere in the 800-850cc/min/injector range). That's not a small discrepancy, and something you should strongly consider when testing.

[Aaron@English]

Not sure if this one has been mentioned, but Stealth 316 (http://www.stealth316.com/2-fuelpumpguide.htm) has had some charts for a bit.

[evodan2004]

is there a way to have both pumps running at the same time weather it is on the double pumper or a fuel blown setup rather then using a switch or relay??? i know 2 pumps running at idle or around town driving is not needed. im just asking if it can be done as its less that can go wrong IMO.

[David Buschur]

Yes, that is possible and easy to do evodan. I see no reason for it though.

[evodan2004]

Yes, that is possible and easy to do evodan. I see no reason for it though.


ok cool. also can your double pumpers be setup to run bigger lines then stock or if bought to use with stock be able to be upgraded in the future.

[Fathouse]

is there a way to have both pumps running at the same time weather it is on the double pumper or a fuel blown setup rather then using a switch or relay??? i know 2 pumps running at idle or around town driving is not needed. im just asking if it can be done as its less that can go wrong IMO.

I assume you would need a aftermarket FPR to bypass enough fuel at idle.

Fathouse

[David Buschur]

Our double pumper uses the stock feed line. So far it is adequate to over 700 whp on my own car, actually, if I dyno'd my car in 4th gear like I do most customers, I'd say 750'ish on our dyno. That's a lot of power evodan, not saying you will or won't make that much but it's a lot and upgrading the fuel line is probably something you won't need to do. The single stock line should flow enough for almost 1,000 flywheel HP according to Weldon.

Fathouse is correct, you would need an aftermarket regulator or modify the siphon tube on the pump assembly to run both pumps at idle. Personally, I say don't do it but it's up to you.

My new project white is going to be the first car I try out my new double pumper ideas on. I am planning a trip to Kinsler in the next week or so. I have a bunch of ideas on our double pumper and need to have them tested on their flow bench.