Lb7 fuel rail info

[sweetdiesel]

iirc a couple guys from ohio ported out there lb7 fuel rails....They said it threw CRAAZY fuel to the stock injectors with dual cp3's....They also had a custom gt42. Well they ended up throwing a stock rod threw the block in less then a mile On edit i dont know the rail pressure or pulse width they were running but they said that it smoked like a Train even when the 42 was fully lit

Thanks Eric
but where does the fuel line come in on the lb7?( duel Cp3 ) I assume that it comes in where the plug is? the same as the LLY? meaning the second CP3 doesnt have a orfice anyways

I mean i would rather have crazy fuel and turn it down, than not have enough fuel

 

[Diesel Pilot]

iirc a couple guys from ohio ported out there lb7 fuel rails....They said it threw CRAAZY fuel to the stock injectors with dual cp3's....They also had a custom gt42. Well they ended up throwing a stock rod threw the block in less then a mile On edit i dont know the rail pressure or pulse width they were running but they said that it smoked like a Train even when the 42 was fully lit

When are we going to port your's out?

 

[bullfrogjohnson]

This is interesting stuff Simon,

Is that orifice on the inlet or return side?

 

[sweetdiesel]

Inlet to the fuel rail

 

[sweetdiesel]

Scew drilling it! Im going to try with out the orfice

Whats the worst that can happen? No or low rail pressure but more volume?

 

[bullfrogjohnson]

Few Questions?

What is the point of having an orifice that small at the inlet side of the fuel rails?

Why why would it not be at the outlet side to hold more pressure in the rails so it would not have a slow recovery time under high fuel demands?

 

[sweetdiesel]

Perhaps im wrong Travis ....it's happened before( once )

When i get home ill have a look though the GM manual and see what i find and ill take apart the other rail and see what or if it is the same way.

 

[SmokeShow]

this is so interesting...

 

[mvnvltn]

Both rails have the same orifice. Passenger front, drivers rear. I may take mine out too for experimental purposes. Mine are already drilled to a 1/16

 

[mvnvltn]

Does the pump require back a certain amount of back pressure to stay efficient?

 

[sweetdiesel]

This is interesting stuff Simon,

Is that orifice on the inlet or return side?

As far as i can tell on a LB7 the fuel goes in and out the same hole and is controlled by the valve on the fuel junction block,not like the LLY
Atleast that is what it looks like to me as there is 2 inlets/outlets at each end and then 4 injector lines per side

Both rails have the same orifice. Passenger front, drivers rear. I may take mine out too for experimental purposes. Mine are already drilled to a 1/16

Thanks Deejay, i just checked before you said that too

Does the pump require back a certain amount of back pressure to stay efficient?

Not sure but the injector tips seem to be the back pressure now

 

[LBZ]

Few Questions?

What is the point of having an orifice that small at the inlet side of the fuel rails?

Why why would it not be at the outlet side to hold more pressure in the rails so it would not have a slow recovery time under high fuel demands?

Maybe so quick pressure changes by the cp3 don't surge into the fuel rails??

A fixed orfice metering system which allows more than enough mm3 through at max press that is within max amount of fuel required by a stock tune.??

I think I just confused myself here with what I am trying to say.

I think it may be related to streetability of the LB7 in the area of the fuel. The only way to find out is remove it and drive it and see what happens.

 

[sweetdiesel]

Maybe so quick pressure changes by the cp3 don't surge into the fuel rails??

A fixed orfice metering system which allows more than enough mm3 through at max press that is within max amount of fuel required by a stock tune.??

I think I just confused myself here with what I am trying to say.

I think it may be related to streetability of the LB7 in the area of the fuel. The only way to find out is remove it and drive it and see what happens.

whats a stock tune Dale Dont forget that the lb7 and lly both have a restriction just one is in the fitting and the other is inside the rail

i wonder what the lbz and lmm have? if you look at the fuel rails they have a sticker on them that states the amount of mm3 that the rail is rated for
atleast mine do

 

[bullfrogjohnson]

Maybe so quick pressure changes by the cp3 don't surge into the fuel rails??

A fixed orfice metering system which allows more than enough mm3 through at max press that is within max amount of fuel required by a stock tune.??

QUOTE]

Dale,

Wouldnt a fixed orifice at the inlet cause the pressure to back up in the CP3? If it was at the outlet port on the fuel rail, the fuel would be backed up enough to keep the rails full and not be effected by rpm. I have always been told that its not the pump that causes pressure its the restrictions. So as long as the pump is pushing full the rails will have fuel and if the injectors are not opening it will just return to the tank, but still slow enough to keep positive pressure at the injectors?

Maybe I am off base here?

 

[LBZ]

Maybe so quick pressure changes by the cp3 don't surge into the fuel rails??

A fixed orfice metering system which allows more than enough mm3 through at max press that is within max amount of fuel required by a stock tune.??

QUOTE]

Dale,

Wouldnt a fixed orifice at the inlet cause the pressure to back up in the CP3? Yes it Would If it was at the outlet port on the fuel rail, the fuel would be backed up enough to keep the rails full and not be effected by rpm. I have always been told that its not the pump that causes pressure its the restrictions. Correct So as long as the pump is pushing full the rails will have fuel and if the injectors are not opening it will just return to the tank, but still slow enough to keep positive pressure at the injectors?

Maybe I am off base here?

I hear what you are saying. I think that maybe the max your injectors can flow at WOT is still less than the max that the orfice in the fuel rail will allow-meaning you always get an ample supply of fuel to the rail to supply the injectors, just that as stated earlier, it won't "surge" into the rail but flow in at a sort of controlled rate.

 

[bullfrogjohnson]

Its hard looking at that orifice and believing that it would flow very much fuel at all.

Thanks for the clarification Dale

 

[JOHNBOY]

sorry very hard to see the hole here

the piece on the left is a orfice that sits inside 25000th of a inch orfice
very friken small!

Mine stock orfices checked .027. The fitting that holds it in has .118 hole thru it. My stock orfices ar drill to .093. The plug in the other end of the passenger side fuel rail is drilled to .125. That is where the Second CP3 line connects.:baby:

 

[JOHNBOY]

For those of you that dont know this is part of the FPRV on a lb7 the fuel lines are just low pressure line....I will remove these and run a T and plug off the place the the FPRV is

That is the Distribution Block is it not. The CP3 feeds into it than it splits the fuel to the rails. The Banjo fitting on the end is the return. Correct?

 

[mvnvltn]

Yes that is the block. The line in that pic is the return

 

[sweetdiesel]

Mine stock orfices checked .027. The fitting that holds it in has .118 hole thru it. My stock orfices ar drill to .093. The plug in the other end of the passenger side fuel rail is drilled to .125. That is where the Second CP3 line connects.:baby:

0.027 is possible all i had was .025 and 0.030 to measure with John
both lines as you have shown in the pic go to the rail from the distribution block
the return is also from that block but does not as far as i can tell come from the block, And as far as i can tell it comes from the return from the cp3 unless over pressured on a lb7( this will be removed on my truck)

That is the Distribution Block is it not. The CP3 feeds into it than it splits the fuel to the rails. The Banjo fitting on the end is the return. Correct?

yes its the D block but the FRPRV is inbetween the banjo and D block
the return line from the cp3 is inline with the banjo and from what i can tell AND comes from the CP3 NOT the rail.....I might be wrong? but im pretty sure