hacked89
Full Access Member
On episode 1 of how it works and as author of the facet beat down meme, I thought I'd share some insight, math and pictures I took when putting together the fuel system for my T04Z.
#### Too Long / I didn't read the post #####
1. If your injection pump/engine builder informs you that your build requires more than 30gph then delete the FSV, it's internal supply port is 1/4" and you will encounter fueling instantability.
2. If you require up to 70gph (66 to be exact but we are rounding up) you can stay 3/8" supply with a pump whose fueling curve supports it at the documented pressure. If you require 100gph or more (92 to be exact same rounding up to numbers which correspond to pumps) then you should move to 1/2" supply line because otherwise you will be stacking multiple pumps, require higher end pumps to maintain the pressure to fuel flow curve, and have more pressure to flow instability.
#################################
Let's start with repeated statement on the forum #1:
"if you run the electric fuel pump with the FSV inline I heard/saw/read someone else say on the forum, that inside the FSV it will bottleneck depending on your GPH requirements.
True or False?.. Let's take a look
Here in the vice is our friend the FSV, about to meet its maker
Crack it open to see how it works.
Now we have two halves here.
The first half is an electric motor that turns a rotor which is attached to the plungers. The plunger rotor assembly rides on electric contacts for position, and then either cuts off the fuel from the front tank or rear tank.
A number of opportunities of failure here.
Stuck on the contact pads, motor goes bad, spring goes bad, orings crack and fuel is now mixing between tanks etc
Now in the one picture you can see the primary supply and return ports to the factory lift pump, which look very small.
Next we will half that again in a cutaway and measure the ports.
FSV Supply: 1/4"
FSV Return: 1/5"
Factory supply hard-line: 3/8"
Factory Return hard-line: 5/16"
what's the factory lift pump specs?
At cranking:
4-7psi to the IP @1/3 pint per 10 seconds
Or 15GPH cranking to the IP and
Maximum Free Flow Rate (gph): 30
Maximum Pressure Range (psi): 5.75
30gph is the target here.
I also cross calculated the fuel flow requirements and got 30gph for a 7.3NA
Now the length of the truck @3/8" line and 5psi pressure, what do you think the fluid flow is?
-> 28gph
Then you may say, uh oh the FSV is 1/4" supply.
Well, guess what 1/4" tube flows at 15ft to the end point?
-> 30gph
This isn't all by chance of course that all these numbers line up.
But now let's throw in modifying the IDI, adding a big turbo, what are the requirements?
My specific builds injectors, ip, and turbo will require 70gph max.
Here's my hungry Db2.
The injection pump takes 5psi at the inlet, creates pressures of up to 5-6k psi and the injectors open at 1700-1900k psi.
That's not going to happen through 1/4" line.
Also remember you can increase pressure to increase flow with a high pressure electric pump, but you are going to want to regulate it down right before the IP to 5-10psi depending on your ip specs.
Looping back to our original forum lore testing part 1.
"is the FSV going to be a constraint in a performance build?"
Answer: Yes - it's designed to meet factory specs at max, not exceed maximum factory components of the wholistic fuel system. Sometimes you get lucky and certain components on a vehicle may exceed certain individual component constraints, not this one.
Part 2: In reply post.
Sent from my SM-G955U using Tapatalk
You must be registered for see images attach
#### Too Long / I didn't read the post #####
1. If your injection pump/engine builder informs you that your build requires more than 30gph then delete the FSV, it's internal supply port is 1/4" and you will encounter fueling instantability.
2. If you require up to 70gph (66 to be exact but we are rounding up) you can stay 3/8" supply with a pump whose fueling curve supports it at the documented pressure. If you require 100gph or more (92 to be exact same rounding up to numbers which correspond to pumps) then you should move to 1/2" supply line because otherwise you will be stacking multiple pumps, require higher end pumps to maintain the pressure to fuel flow curve, and have more pressure to flow instability.
#################################
Let's start with repeated statement on the forum #1:
"if you run the electric fuel pump with the FSV inline I heard/saw/read someone else say on the forum, that inside the FSV it will bottleneck depending on your GPH requirements.
True or False?.. Let's take a look
Here in the vice is our friend the FSV, about to meet its maker
You must be registered for see images attach
Crack it open to see how it works.
Now we have two halves here.
The first half is an electric motor that turns a rotor which is attached to the plungers. The plunger rotor assembly rides on electric contacts for position, and then either cuts off the fuel from the front tank or rear tank.
You must be registered for see images attach
You must be registered for see images attach
A number of opportunities of failure here.
Stuck on the contact pads, motor goes bad, spring goes bad, orings crack and fuel is now mixing between tanks etc
You must be registered for see images attach
You must be registered for see images attach
Now in the one picture you can see the primary supply and return ports to the factory lift pump, which look very small.
Next we will half that again in a cutaway and measure the ports.
You must be registered for see images attach
You must be registered for see images attach
FSV Supply: 1/4"
FSV Return: 1/5"
Factory supply hard-line: 3/8"
Factory Return hard-line: 5/16"
what's the factory lift pump specs?
At cranking:
4-7psi to the IP @1/3 pint per 10 seconds
Or 15GPH cranking to the IP and
Maximum Free Flow Rate (gph): 30
Maximum Pressure Range (psi): 5.75
30gph is the target here.
I also cross calculated the fuel flow requirements and got 30gph for a 7.3NA
Now the length of the truck @3/8" line and 5psi pressure, what do you think the fluid flow is?
-> 28gph
Then you may say, uh oh the FSV is 1/4" supply.
Well, guess what 1/4" tube flows at 15ft to the end point?
-> 30gph
This isn't all by chance of course that all these numbers line up.
But now let's throw in modifying the IDI, adding a big turbo, what are the requirements?
My specific builds injectors, ip, and turbo will require 70gph max.
Here's my hungry Db2.
You must be registered for see images attach
The injection pump takes 5psi at the inlet, creates pressures of up to 5-6k psi and the injectors open at 1700-1900k psi.
That's not going to happen through 1/4" line.
Also remember you can increase pressure to increase flow with a high pressure electric pump, but you are going to want to regulate it down right before the IP to 5-10psi depending on your ip specs.
Looping back to our original forum lore testing part 1.
"is the FSV going to be a constraint in a performance build?"
Answer: Yes - it's designed to meet factory specs at max, not exceed maximum factory components of the wholistic fuel system. Sometimes you get lucky and certain components on a vehicle may exceed certain individual component constraints, not this one.
Part 2: In reply post.
Sent from my SM-G955U using Tapatalk
Last edited: