tscompusa

iTrader: (31)

most of those guys are on stock ID lines though. you have to keep that in mind. the stock lines with 2 modded walbros are capable of 800whp on e85.

so bigger ID lines are definitely going to benefit. get AFPR and drop your base pressure another 10psi and open even more fuel pump potential up as well.

look at this. this is a buschur double pumper, which consists of 2 modded walbro 255 and hes using the stock feed/return lines. made well over 800whp.

https://www.evolutionm.net/forums/ev...3-3794-ts.html

in my opinion a lot of people over complicate or over think their fuel system setups and end up opening up more error then good. (you'll notice buschur racing is very intelligent when it comes to simplifying the fuel system)

but i 100% agree relying on the switch to kick the 2nd pump on is not pleasing. i wish there was something i could get that has a below 1% failure rate and triggers the pump with no issues. (like your AEM)

but the thing is, anything can happen with cars or electronic parts, so in the end you're still relying on something from failing.

but you made a good point. when one pump fails on a dual walbro setup you will still have enough fuel to melt parts. where as one big single pump will just shut the car off potentially saving you from a catastrophic failure.

the scary thing is, even when my switch was failing and the car was hitting 15-16 AFR WOT, it just pulled right through it with no misfire or anything. the only difference is the car felt dead / flat / like a honda trying to pull a house. it still sounded like a high HP car, but felt dead. very scary feeling, and you know in your head its extremely bad for the car.

Wheatley

iTrader: (20)

I'm not chancing it by running a $200 fuel setup on an engine setup capable of making 1k hp. Its a potential for an easy failure on a very expensive engine. You're more than welcome to, but I'm switching to 1 pump for piece of mind.

I agree with what you're saying but to me the solution is to rid myself of two pumps. I know there are a LOT of cars not just evos making 1k plus hp on 2,3,4,6 whatever combo of walbros. For the money they are great pumps. Its the relying on them in numbers that bothers me lol.

tscompusa

iTrader: (31)

what single pump are you thinking of going with?

Wheatley

iTrader: (20)

magna 4303. Its no weldon, but I'm no baller.

tscompusa

iTrader: (31)

as long as its reliable that's all that matters.

Wheatley

iTrader: (20)

Id love to see the data of lph from x pump via y size line over z distance. I'm sure there are formulas out there for it all, I'm just not to that point yet of needing it.

tscompusa

iTrader: (31)

same here. i think with the Y fitting right after the pumps has some effect on the flow of the pumps. they fight to go through the Y portion.

I wonder what a dual line ran from each pump with lets say for example a bosch 044 external or similar inline on each pump would support.

i bet a lot!

evoredy

iTrader: (7)

tscompusa,

There is no externally visible or pressable valve on the exterior of an E85 Walbro 400. The non-E85 Walbro 400 does have one though!

mrfred

iTrader: (50)

nice testing, especially showing the effect that punching the relief valve shows. the similar flow between the punched walbro and the aeromotive matches up perfectly with my testing.

i would like to clarify about the relationship between boost pressure and pressure at the pump. flow-induced back pressure from the fuel supply line needs to be included, especially for the stock supply line. i measured a whopping 16 psi of back pressure in the stock lines at ~500 whp of e85 flow. back pressure increases as something like the square of fuel flow, so 600 whp of e85 thru the stock supply line increases the back pressure to around 25 psi. if anyone wants to tinker, there are some pretty good calculators out there for estimating back pressure in flowing pipes.

for my setup where i was hitting 27 psi of boost at peak fuel flow, the measured pressure at the outlet of the pump carrier housing was 84 psi with pressure across the injectors at ~42 psi. i'm sure its safe to add another 2 psi due to pack pressure between the pump outlet and the pump carrier outlet.

in summary, fuel line back pressure matters a lot, and 25 psi of boost at peak fuel requirements (peak power) with the stock supply line is more like 85 psi at the pump for e85.

https://www.evolutionm.net/forums/ev...l#post10114095

Svendiesel

iTrader: (25)

So youre saying keep them and do a larger send line and a regulator to turn the pressure up a bit?

tkklemann

iTrader: (6)

Keep in mind that two separate lines would eventually Y together, hence, your single fuel rail.

An interesting idea would be a split fuel rail. One pump for only two injectors, that way if one pump dies, you lose two cylinders (no fuel at all), and the other two will still run as expected. You will feel it right away from losing two cylinders, but the engine would (should) survive because the other two cylinders continue to go because of the working pump. Running two pumps into a single fuel rail that connects all injectors is where you get the lean AFR's across all 4 cylinders and blow motors when one pump dies..

tscompusa

iTrader: (31)

good info Mychailo. 25psi is around 85psi you say as a whole in the system? that is pretty crazy.. no wonder theres such a big difference after the walbro is modded with cars. it is riding that 150lph line forever, and not modded you lose half the capacity of the pump.

you know when i was researching up, i noticed AMS did not bother with the dual in tank pumps, instead they run 1 in the tank and another external inline but parallel and claim it outflow'ed two dual in tanks.

I also read there is cons and pros to both parallel and in series though.

It would be nice if all we had to do was put another pump inline on the existing feed so it would assist in flow and gain more fuel pump power that way, but it seems it isnt exactly that easy.

Well since the pumps work better with less pressure, from what i understand you will gain more fuel flow if you lower the pressure on the regulator. so for example instead of 43-45psi you drop it down 5psi or so and get more room to grow in the fuel system.

but yes id like to know what size line it takes to get to the point you actually start underperforming. with full blowns test, you can see the larger line makes a pretty significant increase in fuel flow. his flow numbers are inflated, but his overall testing shows more flow with the larger ID line of course.

https://www.evolutionm.net/forums/ev...ow-tested.html

Ya. you would still end up Y splitting it at the end which i guess could defeat the whole purpose of the dual lines being ran, but i imagine there is some gain there.. but the Y is definitely going to be a major restriction.

ya it would be interesting to split the rails up in 2 inj and run independent feed lines to the rails. im surprised it hasn't been done, there must be a con to it.

I imagine the con would be, if both pumps arent flowing the same amount you risk having to drastic of AFR swing between 2 cyl vs the other 2. then again v8 guys do it so i dunno.

mrfred

iTrader: (50)

Yep, at 500 whp worth of E85 flow at 27 psi of boost, my pump was seeing 85 psi. So many people claim a simple Walbro 255HP swap with no other changes is good to 500 whp on E85, but the truth is that its nowhere close to good enough at least for the intended pressure across the injectors of 43.5 psi. Of course the pump doesn't stall out, but instead the flow rate drops off and causes the pressure across the injectors drop below 43.5 psi. The fuel system becomes "returnless" under these conditions. Many people unknowingly tune around this by richening up the AFR in the fuel map. If the injectors are large enough and the WHP level is not too far beyond the capacity of the pump at the target rail pressure, what will happen is that the pressure at the pump will fall off to the point where it can flow enough fuel to support the needed AFR at the expense of a huge IDC.

Running two pumps in-series is a step up from a single Walbro 255, but its not a huge step up. The way to make this work effectively is to put the external pump as close to the fuel rail as possible so there is no fuel line back pressure for the external pump. The job of the in-tank pump is then to just deal with the back pressure of the stock line, at 500 whp worth of E85 flow, its seeing only 16 psi of pressure. Judging from the info in the Full Blown test where they measured about 340 lph (5.7 lpm) at 0 psi, I'd bet a Walbro 255HP at 15 psi is good for a solid 300 lph (5 lpm). This is about the amount of fuel needed to support about 575 whp on E85. The external pump then has to be able to supply that same amount of fuel at whatever pressure its seeing (43.5 psi + boost). The ultimate flow capacity this setup comes down to which pump can flows the least at their given conditions. English Racing uses this as their mid-level fuel system upgrade, and they say its good for 550 whp which lines up well with my estimate.

If you and svendiesel are talking about supply line size, moving up to -6 AN hose will substantially reduce the flow restriction and allow the pumps to run at lower pressure. Moving to -6 AN at 500 whp of E85 decreased the fuel line back pressure from 16 psi down to 3 psi on my setup. At 700 whp of E85 where the stock fuel line would have a back pressure of 30+ psi, the reduction would be even bigger. So -6 AN will get the job done pretty well. Moving one step larger to -8 AN would completely eliminate any fuel line back pressure.

Finally, one item I'd like to clarify is that the Full Blown test can easily be misconstrued as indicating that the stock fuel supply line is 5/16" inside diameter. It is in fact about 1/4" ID. Its dinky.

tscompusa

iTrader: (31)

Ya i just did a car with a modded single walbro 255. hes running out of fuel at 500whp pretty quickly. AFR just goes up at redline. i had to richen the map up at redline, which we both know is a temporary patch job just to force it to go alittle richer.

I had a -6, i am doing a -8 now because the line ID is only .405 in this brand -8 due to carbon inner layer on the teflon/ptfe.

it definitely makes sense that the closer to the in line external pump is to the rail, the more it will help. i know the bosch 044 can even suck through a dead walbro. some guy on another forum had his walbro die, and he had another bosch044 down the line and the bosch 044 kept the car from going lean, so it sucked fuel right through the walbro like it was no big deal lol.

seems like you can only safely get maybe about 850WHP from a double pumper with -8 feed line and proper injectors and rail. even then the safety part of it is questionable, because you're relying on a pressure switch to kick that 2nd pump on.

i underlined the word safely, because it may do a lot more then that, but as you just explained the pressure makes it not an efficient setup.

Wheatley

iTrader: (20)

You say double bumper but don't specify which pumps. I assume you mean twin modded walbro 255 but figured I'd post so other ppl know.