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Fuel What PSI from an in tank 255 or other high volume pump

  • Thread starter Thread starter DAVE94LIGHTNING
  • Start date Start date Apr 20, 2021
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DAVE94LIGHTNING

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#1
  • Apr 20, 2021
  • #1
What is the unregulated (before FPR) pressure that the typical high volume pump produces? Anybody know? I'm tapping into the fuel system before the regulator and would like to know what kind of pressure I'll be seeing.

Thank you.
 

Noobz347

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#2
  • Apr 20, 2021
  • #2
DAVE94LIGHTNING said:
What is the unregulated (before FPR) pressure that the typical high volume pump produces? Anybody know? I'm tapping into the fuel system before the regulator and would like to know what kind of pressure I'll be seeing.

Thank you.
Click to expand...
Even the stock 88 lph fuel pump will reach well over 100 psi if you close off the return.

It's your [regulator] that makes that determination, not your fuel pump. Your regulator doesn't step the fuel supply down. It restricts it until the desired pressure is achieved and returns the excess to the tank.
 
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DAVE94LIGHTNING

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#3
  • Apr 20, 2021
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Noobz347 said:
Even the stock 88 lph fuel pump will reach well over 100 psi if you close off the return.

It's your [regulator] that makes that determination, not your fuel pump. Your regulator doesn't step the fuel supply down. It restricts it until the desired pressure is achieved and returns the excess to the tank.
Click to expand...
I won't be closed off but it won't be regulated by the FPR directly. If a 4an line is "T" off the main feedline before the FPR what pressure would it see when flowing? Lets say the FPR is at 45 psi.
 

Noobz347

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#4
  • Apr 20, 2021
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DAVE94LIGHTNING said:
I won't be closed off but it won't be regulated by the FPR directly. If a 4an line is "T" off the main feedline before the FPR what pressure would it see when flowing? Lets say the FPR is at 45 psi.
Click to expand...
If the FPR is set to 45 psi then it will see 45 psi. Any volume of fuel that causes the pressure to exceed 45 psi will be returned to the tank by the regulator.

If for instance, you should put in this [T] and leave that line open then the regulator won't do anything because the fuel volume is escaping and the system will never build to 45 psi. If you close this off, the regulator will begin bypassing fuel once it reaches 45 psi.
 
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DAVE94LIGHTNING

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#5
  • Apr 20, 2021
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Noobz347 said:
If the FPR is set to 45 psi then it will see 45 psi. Any volume of fuel that causes the pressure to exceed 45 psi will be returned to the tank by the regulator.

If for instance, you should put in this [T] and leave that line open then the regulator won't do anything because the fuel volume is escaping and the system will never build to 45 psi. If you close this off, the regulator will begin bypassing fuel once it reaches 45 psi.
Click to expand...
Thank you. So even the psi in the lines before the fuel rail is maintained at the same pressure as the overall system. Exactly what I needed to confirm. Thanks.
 

Noobz347

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#6
  • Apr 20, 2021
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With the regulator set to 45 psi in a closed system, the entire system will run at 45 psi until you begin to exceed the pump volume.
 

Noobz347

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This is a good read if you're going to be working with fuel system components:

https://www.stangnet.com/mustang-forums/resources/fuel-flow-forensics.55/download
 
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DAVE94LIGHTNING

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#8
  • Apr 20, 2021
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Noobz347 said:
This is a good read if you're going to be working with fuel system components:

https://www.stangnet.com/mustang-forums/resources/fuel-flow-forensics.55/download
Click to expand...
I'm just jetting my nitrous systems so I needed to know the jet sizing and it is based on psi. I wasn't sure if the rails/injectors alone were pressurized to the set psi on the regulator such as using the schrader valve to pull fuel of if the feed line pre regulator was also at the same psi. Thanks.
 

Noobz347

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#9
  • Apr 20, 2021
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DAVE94LIGHTNING said:
I'm just jetting my nitrous systems so I needed to know the jet sizing and it is based on psi. I wasn't sure if the rails/injectors alone were pressurized to the set psi on the regulator such as using the schrader valve to pull fuel of if the feed line pre regulator was also at the same psi. Thanks.
Click to expand...

Yeppers. So long as you have enough fuel pump you should be golden.

Do happen to have a method of measuring your air/fuel ratio once it's installed?
 
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DAVE94LIGHTNING

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#10
  • Apr 20, 2021
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Noobz347 said:
Yeppers. So long as you have enough fuel pump you should be golden.

Do happen to have a method of measuring your air/fuel ratio once it's installed?
Click to expand...
I measure the tune by reading plugs after each pass.
 
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7991LXnSHO

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#11
  • Apr 20, 2021
  • #11
An added in wide band O2 sensor sounds like a useful item here.
 
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