427lsx
F1X procharger
Holley dominator ecu
C16 fuel
Magnafuel pro tune mp4303

Original dyno the car started starving for fuel over 6000 rpm so we shut her down making 1117hp/903tq. Tuner recommended a bigger fuel pump but after a call to magnafuel they felt the mp4303 was more than enough to feed that engine on c-16.What i did notice though was the fuel lines where all improper according to magnafuel.The original builder had -10 coming out of the tank that was looped way up then down to the pump.Then it had -8 up to the rails with no pre or aft filters.The pump also had no relays and was wired off the alternator post not directly to the battery.The return line was -6
I sent the mp4303 back to magnafuel for a rebuld.Now i have a -12 fitting out of the tank which threads directly onto the magnafuel pre filter mp-7009 which is 74 microns.Then -10 up to a Y behind the rails then -8 up to each rail.No aft filter.Now -8 return line vs the original -6
Then i wired the new mp-1050 dual 40 amp relay directly off the battery and have the pump mounted just under the sump of the fuel tank.
I had the bosch 160 all rebuilt and flowed by FIC. The only item not changed in the fuel system was the fuel pressure regulator.
I also sent the alternator back to powermaster and they rebuilt it because it appeared to be overheated.We increased the pulley diameter a touch to slow the alt rpm down a bit.

So today we go back on the dyno and battled some issues but got them all figured out.On a good pull the fuel psi is solid right till just about 5900 rpm going from 19 to 20lbs of boost the fuel pressure drops right off and pretty quickly.We shut her off there making 1078hp/930tq.so essentially nothing i had done changed the fuel flow.If i am not mistaken idle pressure was 45-48 and on the pull 66-67

We questioned battery voltage but it was solid 13.7 to 13.9 volts straight across the pull and i remember magnafuel telling me that pump is flowed with 12.5v so no way 13.9 is too low.
The only component left is the fuel pressure regulator which im going to change but i highly doubt its the problem
LOST!!

 

PS....at 5900 the fuel psi dropped from 67 down to 48...so a drop of almost 20psi

 

I have had similar issues with getting enough fuel to the engine. The way I started testing my system is the following, this will save the trips to the dyno for fuel issues. I am assuming you are running a boost referenced regulator. That implies you will need to supply about 80psi pressure at the fuel rail when boosting 20 psi (ref 58 boost 20 pressure 78). So what I do with the engine not running is disconnect the fuel return line and run it into a weighed empty gas can. Turn the fuel regulator up to 80 psi and then run the pump for exactly one minute, The amount of fuel in the gas can is what would be available to the engine under boost. I measure the fuel by weight and divide the pounds increase by 6.5 to get the gallons of fuel pumped in one minute. In your case 2 gallons would be safe, doing it this way makes it easy to measure flow restrictions of items like the 10 micron filter. Hint you will need a battery charger or power supply to get 13.7 volts to the pump. Note this is a lot of fuel to flow thru some pressure regulators, good luck with getting that info as some manufactures do not supply that info, you might need.

 

A forged 427 w/ dominator ECU - having some fuel delivery issues?

Two ways to deal with this, first is my recommendation if you brought the car to me this is what I would do to it w/ no expense spared:
First thing I would do is get rid of the C-16 and switch to E85 (E55+ is fine) This will exacerbate fuel delivery and necessitate re-vamp of the entire fuel feed.
Fuel filtration and check-valve is critical using alcohol fuel so these need to be looked at to keep atmospheric water content out of the tanks.
Several stages of fuel filter is needed. Something course and easy to clean, and something very fine near the engine also easy to clean. ID Makes a good looking easy to replace fuel filter block.
Change to 2000cc+ injectors from Injector dynamics
This will necessitate re-thinking of the fuel system.
I will remove all external pump and use only internal quality pumps. A surge tank and lift pump will help keep full fuel tank volume if desired (Street cars full tank of gas). We will use a fuel pump controller on a single staged pump to PWM the output for reduced fuel heating and reduce the base pressure of the system as low as possible to conserve energy, reduce heating, and allow max pump flow rate on the big end.
Lower pressure + PWM = happy fuel pumps and more fuel delivery.
Also,
I also prefer to reduce alternator output at WOT to approx 12.45 volts to allow battery provide capacitance to the electrical system, this will keep the injector delay and coil dwell steady, leads to spark consistency and injector spray consistency, helps to prevent sporadic episode of oscillations evident in dynojet curves. If the voltage fluctuates at WOT or if the alternator suddenly fails you need the fuel system to be able to handle whatever power the engine is currently making anyways, otherwise engine may be damaged. This is a critical overlooked aspect of high performance setups which many people still do not seem to understand, you cannot rely on an alternator with so much power output. It is negligent to the setup.

The result will be near stock heating of fuel system components, low noise fuel system which can easily supply 1200rwhp on E85. Using dominator ECU to trigger aux fuel pumps as needed. And if the alternator fails the system still runs normal and provides full fuel system support even with battery voltage and no alternator.

Now as to your current setup fuel pressure monitoring is your friend. I would be data-logging fuel pressure at various points to diagnose, before regulator, after regulator, before rail, etc... find some spots where you think the pressure is bottlenecked and test it. Or just guess and start replacing parts and lines and pumps. At least maybe check the pressure at the fuel pump outlet and compare with some other part of the fuel system, 60psi off the pump and 40psi at the rail is something wrong with a bottleneck obviously. Its really hard to guess over the internet where the bottleneck. A regulator is a good place to start though.
It depends what is more difficult: changing parts or installing and data-logging sensors. Sometimes its easier just to start changing parts than to collect data.
No matter what course you choose keep in mind the alternator voltage should not be critical to the setup, make sure the pump can still provide enough fuel at 12.5v so when the alt fails (not 'if' but when) the engine doesn't turn into toast.
Also make sure filtration is up to par. 80uM Is not nearly good enough. There should be a high quality low micro element near the engine and on a high power setup as 700+rwhp always keep changing it and perform cylinder injector balance tests by shutting off 1 injector at a time and making a note of the RPM drop and sound quality changes.

 

Couple things I forgot in my haste
-Sometimes the fuel can overheat and overheat the fuel pump if using 100% DC current to a huge fuel pump, this can kill fuel pump output or introduce cavitation.
-I recommend a fuel temperature sensor at 800+ tire.
-Data logs of the injector duty during your WOT runs are helpful diagnostics.
-Use the lowest fuel pressure possible to get the most flow from fuel pumps (all fuel pumps flow more at lower pressure)

Most commonly the issue with pumps overheating is fuel filters clogging. Therefore I should have said something like "before you start replacing parts, investigate the fuel filtering situations, fuel pump sock pickup, and fuel heating relationship with fuel flow". It could be simple as a filter causing the issue or fuel temperature.

 

I've seen the 4303 drop pressure at 900whp on E85 so while they might support 1200whp on gas its pushing it. I'm guessing you're aiming for 1200+whp with over 1000RPM still to go, kinda surprised they would say that pumps perfectly fine with it. Blower eats up a bit more pump than a turbo setup, as do auto transmissions (not sure what you are running?). I think Magnafuel rates that pump around 1300 crank HP @ 75PSI so you're knocking on the door. Most guys leaning on those pumps run them at 16v so you could try a boost a pump but I would just get a pump with more capacity. I also doubt the regulator is the concern, I ran the 4703 pump with a 6AN return and it was fine.

 

Cant comment on the pump, but have run 427/F1x on C-16. Used -10 feed, -8 return, Fore triple pump with -10 filter. Zero issues at 45psi base psi, over 1500hp.

 

The only areas I deviated from as far as the magnafuel instructions is using the stock tanks I have the factory vents at the top of each tank with a vented cap...magnafuel wants a -8 vent on the top..and I have the return on the side of the tank maybe an inch or so above the -12 feed which i have seen done on several c6...magnafuel wants the return at the top of the tank.
so are these items the culprit or do I need a bigger pump and im just not facing the facts?

 

When I used magnafuel pumps I ran them with a fuel cell with 10AN vent, that didn't change anything related to fuel flow. If anything dumping the fuel in the top of the tank will cause more aeration, having the return below the fuel level works perfectly fine, that's how a lot of big power cars are setup.

 

Thanks for that info!!
I talked to a great tech at magnafuel.he worked with me on flow numbers and voltages and he agreed to get the 4303 where i want to be will not happen unless i increase voltage to as much as 18v. So its coming out and im putting the mp4703 In her.I really dont like driving it on the street anyways but if i do i can always swap back and forth with the mp4303 and keep it under 6k
Our state is after everyone who has loud exhausT,tinted windows,dot approved slicks and parachutes bolted to the back Not worth it!!!

 

Glad you finally got ahold of someone there that knew what they were talking about. I used the 4703 on the street and took it on highway trips, but I had it mounted under the rear deck where it got some airflow.

 

Thats amazing!! They sayin 30 to 45 minutes max which would easily get me to a car show in the neighborhood lol

 

Weird, I've driven mine to Carlisle two hours away, Ocean City 3 hours away, and to the track 1.5 hours or so. Usually stop for a quick break on those trips but only a couple minutes for an energy drink and back on the road. If a fuel pump only worked for 30-45 minutes zero chance I would own it.

 

What did Magnafuel say that 4303 would hold on 12v on E85?

 

I am on c16 so we didnt even talk E85

 

You should really look into a brushless pump for your setup. Since you’re running gas you can probably get by with a 3-5gpm pump. They don’t heat up the fuel, pull minimal amps, and don’t drop pressure. I’m running a base of 60 psi and holding 80+ psi of pressure no problem. Use the Holley to trigger a relay to alternate between lo/hi fuel flow settings

 

I find it odd that some folks like myself have no issues making big power with the 4303 and a 450 in tank Walbro. Zero fuel pressure drop at similar power numbers. Did you correct the way your lines were in your last thread? Just curious. Fuel aeration was mentioned and yes... the return can be a problem if plumbed above the pickup. Mine is 1 inch above so I make sure to run around half a tank of fuel when I want to really lean on it. The weight is actually beneficial too on my setup with the LSX brick block and blower hanging off the front. Also, you were pulling fuel straight uphill vs having the pump gravity fed. ****- Doug from Motion makes 1500 with a 4303 at 16V too. Also- the 4703 is not a continuous duty pump so you will eat them up street driving them. Do you have a factory in tank for the street driving?

 

Thats what is so interesting about this site....massive amounts of conflicting information!!
This is why i stuck with the mp4303 so long because there are numerous cases of it working.but in my case with everything set up to maganafuel spec im still not there.there is nothing else for me to do except add more voltage and the magnafuel tech confirmed it.
magnafuel saying 30 to 40 minutes max on the bigger pump im installing but if you read up above skydan says he runs it all the time on the street over 2 hour trips!!

 

16v is a game changer for pumps, akin to running a boost a pump. Fuel pressure also makes a difference, base pressure of each setup, how much boost, etc. Almost all these pumps drop flow as pressure increases so if one setup is at 60psi in boost and the other is at 80 it makes sense why a pump supports more power on one setup vs another. Nothing is wrong with running a lower base pressure to get more out of your pump if you have big enough injectors. Lower fuel pressure = more pump flow with less injector flow, higher fuel pressure = more injector flow with less pump flow.

I think the pump ratings are more of a CYA for the manufacturer. The 4703 is basically just a belt drive head being run by an electric motor, so yes the electric side gets warm because fuel isn't flowing through it like a 4303 but if you mount it somewhere with airflow it certainly helps. Aeromotive and Weldon state similar things like "intermittent street use" or "needs controller for street use" on some of their pumps but I've seen them driven on for years without issue. I guess it depends if you care about having a warranty or support after the sale or not, in my case if it didn't work I would just move on to something else, which I did but not because of any issues with the pump. A bunch of brushless pumps hit the market that not only flow more, but are also great for big power street use as they have built in controllers that you can easily trigger with your ECM.

 

What I don't like about high voltage supply to fuel pumps is, if the pump flow rate insufficient at lower voltage then now you have a completely new source of potential catastrophic failure. You are risking the engine life over a $20 voltage booster circuit completely unnecessarily. Huge risk when it can be completely avoided by using the correct fuel pump in the first place.

Doing things right > pushing a system to the max effort using janky electronic supplements.

Its like steroids, eventually they wear off, you need more. One day the circuit will burn up or fail. Then bye bye engine??