Did I Do This Right? Pics

[70bird]

My fuel system "deadheads" at fuel rails is this ok?
I see pics of other cars where the the 2 fuel rails are connected. (usualy at front of rails)
Is there a reason for this?

My system, 1999 LS1,stock cam and injectors, A-1000 in tank, #8 line to f/wall mounted reg., #6 return back to tank, #8 from reg. to "Y" block on f/wall, #8 to both fuel rails at rear and plugs at front of rails.

The motor runs great, no probs, just wondering if I am missing something here?

https://static1.pt-content.com/images/noimg.gif (http://img201.imageshack.us/my.php?image=lowresfirebird037ct3.jpg)

https://static1.pt-content.com/images/noimg.gif (http://img174.imageshack.us/my.php?image=lowresfirebird036bf9.jpg)

Thanks for looking, Mark

[aggressive male]

I can't see the harness for the electric fans. Is it there or are you just waiting til summer?

[aggressive male]

Let me ask you something, Is that a black wire going from the fuel pressure guage to another fuel pressure guage inside?

[70bird]

I can't see the harness for the electric fans. Is it there or are you just waiting til summer?
Fans are both wired and functioning.
Wiring harness & relays etc. are on pass. side core support

"Busy" little corner of the car

https://static1.pt-content.com/images/noimg.gif (http://img47.imageshack.us/my.php?image=lowresfirebird065su9.jpg)

[70bird]

Let me ask you something, Is that a black wire going from the fuel pressure guage to another fuel pressure guage inside?

That's not wire, it's a vac line to fuel reg.

[aggressive male]

That's not wire, it's a vac line to fuel reg.a vacuum line to the fuel pressure regulator? What's it for? And the other end goes into the manifold?

[megaladon6]

the factory runs it---fuel into one rail, through the rail and pipe to the other rail, to the pressure regulator, back to the tank. if you have the right type of regulator you should be fine. is there a test port on the rails to double check the pressure?

[RSX302]

a vacuum line to the fuel pressure regulator? What's it for? And the other end goes into the manifold?

Yes, At Idle or off load coasting (Under vacuum) the regulator will lower the fuel pressure to the rails. (~5 psi less) At WOT (0 psia manifold) it will be at full fuel pressure. (~45 or what ever factory sets it at)

[RSX302]

My fuel system "deadheads" at fuel rails is this ok?
I see pics of other cars where the the 2 fuel rails are connected. (usualy at front of rails)
Is there a reason for this?


Yes, typically you plumb through the rails back to the regulator. The only reason I would see it being an issue is for vapor lock. This is typical when gas is deadheaded and heat is induced. Since EFI pressures are higher then carb set-ups, it will have a higher boiling point. Don't know if this would be a factor or not? Maybe on a very hot day and everything is heat soaked.

[70bird]

the factory runs it---fuel into one rail, through the rail and pipe to the other rail, to the pressure regulator, back to the tank. if you have the right type of regulator you should be fine. is there a test port on the rails to double check the pressure?
Ok, I get it now, If fuel is being fed to just one rail, then it would need 2nd line to feed other rail, but if fuel is fed to both rails from reg. it is not necessary unless there is a press. diff. from one rail to the other. Right?

My set up has sperate feeds to each rail via Y block, so I'm probably ok here.

I do have ports on the rails, so I will check press. to see if it is even on both sides

Thanks for the help, Mark

[GetMore]

If the Y is open then the pressure will be equal on both sides. An increase in pressure on one side will "back up" into the other side.

As ronracer said, the way the factory runs the lines, as a big loop, helps eliminate the possibility of vapor lock, since the fuel and vapor has an exit at the fuel pressure regulator. Having the system deadhead means that if there is any vapor in the lines it only has one exit, through the injectors, and that will throw off the mixture and make it hard to start the car.

I'm not sure which system is better for fuel pressure regulators, having it before the rails or after. Having it after the rails means that you (typically) would have at least the set pressure, while having it before the rails means that you should not have more pressure.
Basically, one responds to an increase in pressure and bleeds off the excess fuel, while the other responds to a drop in pressure and allows more through to the rails.

Now, having said all that, OEMs are now using "returnless" fuel systems, where the regulator is near (in?) the tank, and only one line runs to the engine. So, whatever advantages there are to having the regulator after the rails don't seem to be a requirement, or have been outweighed.

IOW, don't worry about it, your system is working and you'll be fine.

[Hammered]

I'm pretty sure one major reason for the returnless systems is to prevent the fuel from heating up too much, especially on high HP applications. I just installed an Aeromotive controller to cut down on the fuel flow in low demand conditions to cut down on the amount of heat going back into the tank.

[70bird]

Tested press. at rails today at idle and both are even. Had to do one side at a time as I only have one gauge. Reg. is adjustable and set to 47 idle and 60 at WOT. No way to test under load at WOT yet till I make a (test) line to reach where I can see the gauge while driving.

Won't know about the vapor lock until I get it good and hot this summer.
Thanks for all the great info. Mark :twothumbs

[RSX302]

Tested press. at rails today at idle and both are even. Had to do one side at a time as I only have one gauge. Reg. is adjustable and set to 47 idle and 60 at WOT. No way to test under load at WOT yet till I make a (test) line to reach where I can see the gauge while driving.

Won't know about the vapor lock until I get it good and hot this summer.
Thanks for all the great info. Mark :twothumbs

With the engine off, turn the key to the on position (fuel pump only) this will be your WOT pressure. Once the engine starts, it will go down. If its a factory set-up, I would expect it to be about 47 psig. It will run lower with engine on at idle.

If your engine is making a little more power and the engine needs a little more fuel to get the A/F back in check, you can turn up the fuel pressure a little. I would start out at the lowest setting of 47psig first with the engine off. If you get to 60 psig to maintain proper A/F, its time to step up to a bigger injector.

[megaladon6]

actually the new returnless systems don't use a regulator. they're using a variable output pump.

[70bird]

With the engine off, turn the key to the on position (fuel pump only) this will be your WOT pressure. Once the engine starts, it will go down. If its a factory set-up, I would expect it to be about 47 psig. It will run lower with engine on at idle.

If your engine is making a little more power and the engine needs a little more fuel to get the A/F back in check, you can turn up the fuel pressure a little. I would start out at the lowest setting of 47psig first with the engine off. If you get to 60 psig to maintain proper A/F, its time to step up to a bigger injector.
Thanks for the great info, Will eventualy get wiide band O2 set up. Until then I will go with fact. spec 58.8 psi. as mine is stock cam & injectors. Thanks, Mark

[RSX302]

Thanks for the great info, Will eventualy get wiide band O2 set up. Until then I will go with fact. spec 58.8 psi. as mine is stock cam & injectors. Thanks, Mark

Didn't realize factory runs that high. Doesn't give you much room for adjustment. I would imagine on the new single line sytems that GM is using, this high pressure would eliminate vaporlock (not to mention cost) Good luck...

I got this off of PHR Project car-
"Although there are many ways to go about it, we went with the most cost-effective, reliable, and simple solution, and that was to use the C5 Corvette self-regulating filter. In case you weren't aware, all '99-and-newer Corvettes have only one fuel line to the fuel rail (instead of two). This is because the fuel-pressure regulator (set at 58 psi) is built into the filter, and on a production level, reduces the amount of fuel circulated to reduce harmful vapor emissions. As an additional benefit, it offers an easy and affordable solution that can handle 500 naturally-aspirated horsepower. With a few -6AN adapter fittings, we had a fuel system that was as quiet and reliable as a production car."

[70bird]

Didn't realize factory runs that high. Doesn't give you much room for adjustment. I would imagine on the new single line sytems that GM is using, this high pressure would eliminate vaporlock (not to mention cost) Good luck...

I got this off of PHR Project car-
"Although there are many ways to go about it, we went with the most cost-effective, reliable, and simple solution, and that was to use the C5 Corvette self-regulating filter. In case you weren't aware, all '99-and-newer Corvettes have only one fuel line to the fuel rail (instead of two). This is because the fuel-pressure regulator (set at 58 psi) is built into the filter, and on a production level, reduces the amount of fuel circulated to reduce harmful vapor emissions. As an additional benefit, it offers an easy and affordable solution that can handle 500 naturally-aspirated horsepower. With a few -6AN adapter fittings, we had a fuel system that was as quiet and reliable as a production car."
I thought that I would add to this for the benefit of others following this thread.

I too thought that 58+ psi seemed a bit high, so I did a bit of research in some LS1/6 material I have here: (paraphrased)

"Most injectors are rated @ 3-bar (43.51 psi), while LS1 operates @ 4-bar (58.02 psi)" (not 58.8 psi as I stated earlier).
"Convert the injector advertised flow rate to the LS1/6 4-bar operating pressure for proper sizing in LS1"
"GM changed ECM in 99-up LS1 and changed to smaller injector and longer pulse times for better computer control"
"97-98, 28.5 lbs./hr. @ 4-bar. 99-up 26.5 lbs./hr. @ 4-bar".
(Chevy LS1/LS6 performance by Christopher P. Endres)

This material was written in 2003, so I'm sure the specs. have changed for LS2/7 motors.

So, this opens up a new can of worms for me as I am running stock 99 motor with a 98 ecm. (required for Painless' fuel inj. wiring harness #60507) The 98 ecm is giving me shorter pulse times to 99 injectors rated at longer pulse times. Aaaargh! I really need a wide band O2 sensor now! And, I can see with future power mods: I am going to run out of injector pretty quickly to keep inj. duty cycle at or near 80%.

Fortunately, I have way more fuel system than I need (A1000 pump and adjustible reg: (30-70 psi). So, with stock injectors, I should be able to compensate for smaller injectors with "shorter" pulse times by running slightly higher pressure. (?).

Now I am more educated, AND confused at the same time!
Mark

[Fuelie Fan]

re the original question:

another important point and that is pressure waves within the fuel rail. Dead-headed rails need pressure dampers or standing waves will form, which can have adverse affects. If you can, loop them.

[70bird]

re the original question:

another important point and that is pressure waves within the fuel rail. Dead-headed rails need pressure dampers or standing waves will form, which can have adverse affects. If you can, loop them.
Fuelie fan, THANK YOU!! I knew someone here would chime in here with a direct answer to my question.

Not that I don't appreciate the education I have got from all of you, I have learned quite a bit here about efi in general. So,this discussion has been a great help to me as this is the first non carbed project I've done.

I have also learned, just today, about the pressure damper and It's purpose, but now I have some questions about where to locate it. I suspect for my application it should be plumbed into the "loop" at the rails, but this will cause it to sit pretty high above the motor, so any suggestions would be well received.

Man, every answer just seems to ask another question! :confused:
Thanks, Mark

[MonzaRacer]

Ok here is the straight skinny on the returnless systems.
It is to reduce the emissions coming from the hot fuel returning to the tank and vapors coming out of the tank.
so what they do is PWM (Pulse Width Modulate, take a volt meter and touch it to the battery and you see battery voltage, now if you sitthere an tap the probe to the battery you will see voltage, faster pulse more voltage.
The computer controls a fuel pump module which inturn runs the pump on most cars.
Also if the car sits the heated fuel will over saturate the newer smaller more compact vapor canisters and it just wastes fuel if over saturated as the computer has no control over the EVAP canister other than on or off to draw fumes out, and then it messes with emissions as the computer tries to work harder.
The thing about those that regulate back at the filter is its a stop gap to returnless as it returns before it has a chance to absorb heat in the engine compartment.
If you have a proper setup PWM fuel control is much better and power equirements for the system are lower too.
The big trick is the computer knowing enough to control things.
Figure most car radios now have 10 times the computing power of the first moon landings.

[70bird]

Thanks for all of the info. everyone. I'm gonna' loop my fuel rails.

I have some more Q's. I'll start a new thread, so they don't get "buried" here. https://www.pro-touring.com/forum/showthread.php?t=38604
Mark