Just received holly efi fuel pump

[81cutlass]

If you need that much pump and power for 10's something isn't right...

I thought the same thing!!

But 450's are rated for 450lph at like ~30psi with 14ish volts at the pump.

With 1 to 1.5 volts of drop from the battery to the pump and them supplying fuel at 70psi they turn into like 200ish lph. In a NA app with a battery mounted in the trunk I agree a 450 is superman but boost and realistic voltage drop is kroptonite to Wallys.

 

[Streetbu]

You shouldn't have that much voltage drop, that's a huge issue

 

[Northernregal]

Jake's right, a single 450 is very difficult to get a 3500+lb vehicle into the 10's with more than 10 psi of boost. NA it could be done, but the boost deal requires more pump. At least imho. One thing that is often overlooked in these calculations is the additional fuel pressure needed to maintain the same amount of fuel delivery as an NA vehicle requires to make the same BSHP. The pumps become less efficient as the pressure increases.

This is a quite common situation that's well documented as illustrated above. It is the main reason to not run a stock GM regulator at 58 psi if you have an engine management system that tune for a lower base pressure.

Absolutely agree. Larger injectors and 40psi base pressure is going to get you 25% more pump in some cases.

I thought the same thing!!

But 450's are rated for 450lph at like ~30psi with 14ish volts at the pump.

With 1 to 1.5 volts of drop from the battery to the pump and them supplying fuel at 70psi they turn into like 200ish lph. In a NA app with a battery mounted in the trunk I agree a 450 is superman but boost and realistic voltage drop is kroptonite to Wallys.

Time for a hellcat 525 pump. Or get the good 450 that works at 5 bar

 

[Streetbu]

Still seems off you need that much pump for 10's. 750hp should easily get you into the 10's. Per Racetronix calculator, and Walbro's flow chart, a single should do it.

Calculators - Fuel Pump Calculator - Raceworks

 

[64nailhead]

No way does a Walbro 450 pump 384lph at 18 psi of boost and 60 psi of fuel pressure let alone 76. I’d be amazed if it carried 284.

Shawn, that calculator is not to be trusted imo. Happel couldn’t hit 900 whp on 2 450’s despite trying and blowing stuff up multiple times before he went to the fuel squid 3 pump setup.

I do agree with you about Jake’s voltage drop. He needs bigger wires and the power source closer to the pumps to maximize the efficiency of the pumps (battery in the trunk). But the battery in the trunk creates other problems as well. You need a man size charge wire off the alternator right to the battery #4 minimum and #2 really isn’t too large. And then look at the grounds - they need to be better. Ask me how I know.

Lastly, if you want to throw real monkey wrench in the voltage drop equation, then throw in a weak battery. ‘Weak’ being defined as it can’t carry 120-150 amps of draw for 15 seconds without dropping a couple of volts. Man did I learn that the hard way a while back. Just because the battery will start the car doesn’t mean it’s good - it only means it’s good enough to start the car.


If any skimping is to be done on a boosted build, the last place to run on the thin side is with fuel if you have any love for the motor. I’m on my phone presently, later I’m going to look for that calculator on the computer and see if I can figure out how it’s working (damn old man can’t live on a phone.). 😉

 

[81cutlass]

I pounded my face against a wall this spring trying to find why my single 450 was not keeping up. The short version of what I found
-The single 450 was flowing 17% under the published amount (experimentally validated)
-Best case scenario (the pump flowed the published rate and zero voltage drop) a single 450 was only able to fuel 92lb injectors to (80's at 4 bar base) 80% duty cycle


I overcomplicate things with math and HATE overkill so I use my math to 'skimp' as much as I can while maintaining function. No matter how I crunched it and validated with tests, I couldn't get one pump to pencil out. I saw consistent voltage drop and underflowing pumps. 2 pumps was the best solution (plus if one pump dies on the street I can just flip the second race pump on with a toggle switch). Already saved me once.


Probably should clarify a tad-

(WARNING POORLY PRESENTED DATA OVERLOAD)

I used to have 12 gauge from the alternator to the single 450, with 12.3V at the battery (engine off wall charger on) I had 11.5V at the plug where the harness goes into the tank. I didn't like that and put 8 gauge in and it reduced the voltage loss to 0.3V instead of the 0.8V with 12 gauge, but not enough to get me the flow I needed.

I plugged my info into a voltage loss calculator and it predicted exactly what I observed.

I now have 8 gauge from the alternator to the battery and a junction block about 2 ft off the alternator where my injectors and fuel pumps pull power off (it helped). The voltage coming off the alternator gets the 'choice' of sending voltage to the fuel pumps OR battery at that junction block. I pull the fan power off the battery so they don't pull the system down as bad when they turn on.


In order to max 80lb injectors out on E85 you need ~110 GPH (418 lph)

At 70 psi and 12V (worst case) the pump flows 75GPH (285lph) and draws 18 amps.

I physically measured the flow of a single pump and observed 66.5GPH of flow at 64 PSI at 12V which is 17% under the catalog flow.


And since I am cheap (and had 8 gauge on hand so I used it) if I have 13.5 at the alt and am drawing 32 amps at top pressure I am only going to see ~13V at the pump figuring in my poor pump efficiency, I am probably only seeing 140GPH with twin 450's, which is like 128% injector duty cycle. Twin 340's didn't get me there either.

2 450's draw 25 amps (12.5A each) at 56 psi. The chart claims 15 each.

Did i confuse you, the reader? I know I confuse myself most of the time too.

 

[olds307 and 403]

Yeah, for most of us, who are happy with 500 NA hp max, these are a great option. They are also available for for my 70S as well and it will eventually get one. I would never run an inline pump, this is a much better option.

 

[Zippymac]

I went to rockauto and bought the 4.3 fuel tank and sending unit and modified it to hold a walbro fuel pump. Not sure you can still get the 4.3 fuel tanks it has the sump built in

 

[64nailhead]

Yeah, for most of us, who are happy with 500 NA hp max, these are a great option. They are also available for for my 70S as well and it will eventually get one. I would never run an inline pump, this is a much better option.

If you're well practiced at dropping a full fuel tank whenever an issue arises or want to cut a hole in your trunk floor.

It a good option depending on the application, no argument, but not the best in all circumstances imho.

 

[olds307 and 403]

If you're well practiced at dropping a full fuel tank whenever an issue arises or want to cut a hole in your trunk floor.

It a good option depending on the application, no argument, but not the best in all circumstances imho.

Yeah, I have done it enough, dropping a tank can be miserable if strap bolts snap off etc. I would definitely cut a hole in the trunk when I go EFI.