Dual walbro setup

AMS sells a kit with a 255 in tank and one in line as their 1000hp fuel system...

 

Bosch 044 Pump is 700whp pump without any questions.

 

[Gordian79]

i dont understand how having another pump inline would increase flow.If the inline pump gets fed by tank pump your fuel system will be as good as how fast the inline pump can move the fuel.unless the way it works is each pump has its own line and one line goes to the side of fuel rail and the other to the middle of fuel rail.

 

[curtis]

From the engineering stand point.

Don't run two pumps unless you run one pump to 2 injectors and the other to the other 2. Reason being pumps are like injectors they don't match perfect together. So if you have one that is stronger it will fight against the other and will kill it easily. Then what will happen is that one will die and lean out your engine. The only real way to do it is to have a dual system and run a dual hobbs switches so if one losses pressure the other will shut down. By the time you did all the work and payed the price for two separate systems you could have bought one large pump and sumped the tank.

My .02 cents for the day hope it makes since. I learned the hard way because I had the same thing except 2 155's in my mustang in 94. It lasted 3 monthes and died on the side of the road.

 

One pump does not keep up with the fuel demand of large injectors (runs out of steam). The second inline pump helps to maintain the flow and the pressure up at high rpm/boost to keep the injectors wet.
Parallel pumps work against each other which only puts more stress on them causing premature failure.

 

Very easy way to look at it...

Tug of war - What's better for one side? Two guys on one rope or two guys on two seperate ropes?

 

[Gordian79]

Ive run 2 weldon pumps.the pumps had -10 fittings on them so i ran a Y that had two -10 ends and one -12 and ran -12 line all the way to the front.return line was -6.

 

Think of each pump having a low pressure side (inlet) and a high pressure side (outlet). The low pressure side of the in-tank pump is at about zero psi, the high pressure side will only be at a few psi since the Bosch 044 pump is not providing any real restriction. Then, the Bosch 044 pump with the inlet, at a few psi, can push more fuel at higher pressures than it would be able to otherwise. Basically, the "boost" from the in-tank pump shifts the Bosch fuel pump's entire output curve up, especially critical at the higher pressures.

Basically a positive displacement fuel pump creates flow and the fuel pressure regulator causes a "restriction" after the fuel injectors to create pressure. Fuel flow (volume per time) is independant of fuel pressure (force per area).

The in-tank pump is creating low pressure and high volume. Then the Bosch 044 pump would create higher pressure and have to work less to make higher volume. This gives the Bosch 044 pump the capability to create higher flow than it normally would.

Anymore questions?

 

[PJGross]

Quote:
Very easy way to look at it...

Tug of war - What's better for one side? Two guys on one rope or two guys on two seperate ropes?



My question is how the hell does this have anything to do with pumps?

The ONLY reason the above would have a difference is two guys on separate ropes have a hard time pulling in the exact same plane so you have a slight loss vector for each of their forces. If they stood one in front of another, then there would be zero loss vector and the ONLY difference would be the added weight of the second rope.

With pumps, you need to consider volumetric flowrate vs pressure. Searching I'm sure could get some good studies, but two pumps in parallel, given adequate cross-sectional area after they are "y'd" together, will give terrific volumetric flow at "fairly" low pressure. This is good since there is an efficiency curve for pressure range of injector operation.
Two pumps in series, as pointed out, also can be a good way to go, too. One drives the other to just make the other work more efficiently, as pointed out.

The answer to which is best is really, "it depends". For tons of apps, I'm sure series works just fine. However, on a NA application with a 250 or higher 1 or multi shot nitrous setup, I would want a separate pump (in parallel) feeding the nitrous side.

Additionally, if one pump fails on a series setup, it might be difficult to run home on a street car vs if one pump fails on a parallel setup. With a parallel setup, you may not achieve WOT pressure to keep up with high load, but you'll certainly pump enough fuel to drive home safely with moderate throttle input.

-PJ

 

Id rather be stranded then think both of my pumps are working and lay into it, run lean, and kaboom

 

[CO VR4]

Let me make some corrections and observations.

Most people don't need a dual pump system, because they're not running enough air mass through their turbos to warrant that much fuel. For 95% of people, a TT Supra pump is more than enough. For the rest, see below.

The AMS dual fuel pump "1000HP" kit for the EVO runs in PARALLEL. One Walbro 255HP in the tank, the other is an in-line pump, but is run outside the tank due to space limitations in the fuel pump assembly, but still in parallel. The outputs from both pumps are connected together with a "Y" NOS fitting and run in a single -8AN line to the rail, using the factory feed line for a return. I have that system about 10 feet from me as I type. /ubbthreads/images/graemlins/smile.gif

The Buschur "HO" pump does not supply enough to feed 500 HP using one pump. Buschur just posted that his car had falling fuel pressures using his "HO" pump, which required him to add a second pump to his setup. He put that pump in the tank somehow, and runs them in PARALLEL. When he added the second pump, with no other changes to the fuel system, he gained 50HP! Of course, he had to readjust all of his ECM fuel map to pull out fuel (because he had added injector pulse width to compensate for the falling A/F ratios due to the loss of pressure in the single pump system). The second pump is switched through his ECM to come on at a certain boost level, which roughly approximates to an 80% injector duty cycle using the first pump. That requires a specific ECU flash, or adjustment of maps in the standalone ECU (for example, an AEM).

The Buschur "HO" pump is a Walbro with the numbers ground off. The important characteristic is that it is the correct (same as stock) diameter, so that it slips into the molded location of the Evo fuel pump/sender assembly. One person who had one in his hands said that he thought it was built for another car, like a Cobra etc. It is NOT a Bosch 044, which is much larger in diameter and could not physically fit in the plastic molded cylinderical hole in the Evo fuel pump/sending assembly.

There are many fuel systems that are designed to run multiple pumps in parallel. Others are designed to use one pump to feed the other. In the parallel system, if you lose one pump, the other has no flow impediment, the nonworking pump simply does not contribute to the ultimate volume capacity of the system. In series, if the nonworking pump is the closest to the fuel (in the tank) the other pump has to pull fuel through the nonworking pump, with greatly increased resistance to getting the fuel out of the tank. If the pump further from the fuel fails, the in tank pump has to pump fuel through the nonworking pump, with major resistance that resembles much higher line pressure resisting the pumping flow. Neither is a good alternative, but at least in parallel you have one good pump flowing without any higher than "stock" resistance...

If you want a single pump system, a Bosch 044 is a strong pump, and Bosch pumps have a characteristic of continuing to provide higher flows AT HIGHER PRESSURE levels than the Denso or Walbro pumps. This is a critical aspect of pumps, because your fuel pressure must rise at 1:1 with your boost to keep the actual flow through your injectors constant (the pressure in your manifold must be overcome by the pressure through your injectors in order for fuel to flow through the injector). Single pumps can die and allow your motor to run lean before it dies, but have the advantage of not providing any fuel after the pump dies, so you can't go very far in a lean condition. Large mechanical pumps are also available, but require priming in some cases. Some people have used the stock factory pump to prime the mechanical pump, although the systems are complex from a plumbing standpoint.