I'm getting ready to put in my 3574 and plan on running dual walbros in tank. I currently have the aeromotive FPR #8 feed #6 return...yadda yadda yadda.

I was curious how other dual pump users control them. I plan on using the output on my LT12 to trigger on the 2nd pump at 0 psi to insure no funkiness during the transition. Any other suggestions?

 

Dont do that.
Run 2 relays and run them all the time.
I actually wouldnt even recommend that setup. You will have surge problems.

Get a surge tank and 2 044 external pumps.
do things right the first time.

 

i think he wants to keep it intank, wouldn't this work the same way as staged injection??

i think you would be concerned about the surge because of fuel pressure, but if your run one pump to the pri's and one pump to the sec's why would you have a problem?

 

Look.
Running staged pumps is asking for trouble. It plays with fuel pressure and a whole lot of other things.

Why the hell would you want to run it staged?
What would hurt running them all the time. Consistency is the key to reliability and running them staged is asking for trouble.

I know he wants to keep intank, by why do a half assed job. Do it properly. Ive played with the above setups, blown up engines, wasted my time and money. I just try to pass on the experience, and save people the heart ache and money.

 

just run a surge tank. plain as that.

 

The staged pumps would keep the flow down unless it was needed, pressure *should* not change with a good fuel pressure regulator. Perhaps a small spike when pump 2 comes on but should settle back to the set pressure should the return be big enough to handle the additional flow. Cooler fuel temperatures would be the benefit as would available amps at idle and low rpm cruise conditions. FCs pretty much did this from the factory.

No fuel running into the pass compartment like with a surge tank...unless you guys have come up with slick ways to mount it. This is in addition to having that thing sitting in my mint interior. Lastly, I'm not sure what the IHRA/NHRA/SCCA techs would think about a tank in the hatch with no firewall. Again...street car, but would like to option to run what I brung should the desire arise.

I would be waaaay more worried about separate pumps to the primaries and secondaries. Secondary pumps fails, primary runs no idea that fuel isn't getting the injectors...booooooom.

Certainly I can test the effects on fuel pressure by turning pump 1 on (car off) and then bring in pump 2, record any difference. I have a electric fuel pressure gauge so it would be easy enough to record. Has anyone actually tried this and seen pressure spikes and or engine failure or tuning issues? Again my setup is #8 to a dual #6 with a #6 return using an aeromotive regulator and no additional puslation dampers.

 

i saw you mentioned you have seen failures. What was the root cause? Computer glitched and didn't turn the pump on? Pump came on during boost and had a funky spike that was hard to tune out? Ideally I would have it set so that at idle vacuum and highway cruising vacuum the pump would be off...anything above and beyond the pump would be on...part throttle vac, full throttle transition into positive pressure. A bit more feed back then don't do it would be appreciated.

 

Look mate.
If you are having trouble reading my posts. Id like to know.
I do not run fuel pumps in stages. It is stupid. And no matter what reg you have. When you activate the second pump after initially setting your fuel pressure, the fuel pressure will go up. I find that im wasting my time alittle with some people, i have tried this on a dyno and this is what it does. If you would like to believe it well then good for you, free information, but if you think youve worked out the theory or what ever you may be thinking, your just gona find out the hardway.

I have been in cars that have been low on fuel, and after initially setting fuel mixtures to for e.g 11.4:1, once the fuel got low, fuel mixtures at 20psi going to as lean as 14:1. and guess what, engine dosnt start no more.

I will say it again and again and again, it is stupid to run the pumps staged, let alone running high flow intank pumps, the only benefit of running a hiflow intank pump would be to fill your surge tank faster, their are no other benefits of doing this at all. Run your pumps together and run them outside.

As for external pumps, failing etc and one of your fuel rails not getting enough fuel etc. This is incorrect.

Running 2 external pumps will be joined together and fed into one line, which feed the fuel rails in serial, as per factory setup. If a fuel pump fails in this instance, it will cause the fuel mixture to go lean as well, because when one pump stops working, the fuel pressure will drop so you will get less fuel in your motor.

One more thing. Do you know how a fuel regulator works?
In simple terms, it restricts fuel flow to get pressure up. So when you set it at 2 bar for example with 5l/mino fuel from one pump. When you add another pump, the flow doubles. So the restriction has not changed, but the flow has doubled, in turn this will make the fuel pressure go up as the pumps need to push harder to get the required flow through.

I get worked up abit about this issue, as i have blown up alot of engines trying different intank combos, it has cost me alot of money, and then i see people trying to do the same thing, and being very thick about it.

If anything in my post dosnt make sense, high light it and point it out and ill try to explain further.


With fuel smell etc in cabin.
If you use the right Fuel line and fittings(Earls) you wont have any fuel smell in your cabin. If you use normal fuel line then you will have smell.

Put your fuel system in a aluminium box which is vented to the outside, that way if anything was to leak, it dosnt leak in the cabin.

 

I'm trying to get a knowledge backed answer and thats why I asked you to elaborate on your findings. Too many posts of people saying to not do this or that but for no real reason.

BTW: Here is a sweet reference to the output of the walbro pumps.

http://www.autoperformanceengineerin...l/fpspecs.html

Assuming a target of 500 crank hp, a BSFC of .8 (Pretty high) and 60psi max (20psi boost on a 40psi base) the car would need 4400 cc/min of fuel injector or .000073333 m^3/s at 100% .00064141 m^3/s at 85%.

The walbro HO outputs at 13.5volts:

40psi .000073605 m^3/s
60psi .00064141 m^3/s

So one pump is what I would consider borderline.

Now a single 044 pump with an intake sock kit from some 4G63 guys might workout as it can flow

I'm with you on the the regulator being a restrictor. Fuel flow doubles, assuming 100% efficient...pressure should go up. How much, I don't know yet as I have not run Bernoulli's equation on my setup.

From aeromotive's site:

After installing a larger (or secondary) fuel pump for my EFI engine, the fuel rail pressure went up and my regulator won’t adjust it back down, what’s wrong?

To understand this problem, it’s necessary to know that a fuel pump does not “put out” fuel pressure, it “puts out” fuel flow. A bypass regulator, correctly matched for a given flow volume, sets up a controlled restriction of this flow, thereby creating and then managing fuel pressure. If the regulator won’t adjust pressure down, verify it is large enough for the pump in use. Also, check the return line for kinks or obstructions and make sure the line size is adequate for it’s length and the flow it must handle going back to the tank. Remember, at low load (idle and cruise), the regulator and return line together must flow over 99% of the pumps volume. If the return line or the regulator, or both, are too small for the pump, the resulting fuel pressure is considered false-high. This means pressure is out of the regulator’s control and will drop to the actual regulator set point as the engine goes under load (WOT). A test for correct regulator and return line selection and function is to confirm pressure will adjust at least 5 psi lower than the desired base pressure, vacuum line disconnected.

 

I'm still not with you on the need for the surge tank. Are you recommending that just to prevent starvation issues?

 

I'll wade into this. I am using two Nippo Supra TT pumps that are run off of one high amp relay. The best way to improve on this setup IMO is to add a voltage regulator that is run off a PWM channel rather than switch the pumps individually. The regulator would allow you reduce the strain on the pumps at low power levels by varying the voltage without compromising the max output capacity, or causing any abrupt changes. However my setup is meeting all my needs at this point, so I don't have much motive to do it other than the potential benefit of extending the lifespan of the pumps.

 

That is all its for.
I never said your pumps wont flow the required HP. They will.

The surgetank is simply to stop starvation issues.
If you cant turn down your fuel pressure after adding a second pump, your fuel regulator or return line are a restriction.
Although with the regs i use never run into this problem.

Yes you are right, pumps dont create fuel pressure lol.
Your pump isnt going to get wrecked earlier by running at a higher fuel pressure.
You will actually find at a lower voltage the pump is going to get wrecked faster, run hotter. They are designed to run at 13-14V. I have seen pumps get damaged from low voltage. they get loud, hot, and crap them selves.

If you want your pumps to last. Make sure they have 1 relay wired to EACH fuel pump, good earths. They will flow the most, run quiet, and be reliable. Starve your pumps from power and they will **** them selves.