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mrn2obelvedere
12-07-2009, 05:41 PM
Hello all,

I've been putting together pieces for my fuel injection project for awhile now and I have a mallory return style regulator (http://www.malloryperformance.com/ProductDetails.aspx?MajID=220&MinID=2206&productID=2599&txtSearch=4307). The instructions that come with the regulator (http://www.malloryperformance.com/pdf/4305M.pdf) indicate two outlets to run to the fuel rails and one outlet as a return. My question is would it be a problem for me to run the regulator close to the tank and just run a single line to the front of the car? I can think of no real reason why this would pose any significant difference (engine bay mounting vs. mounting adjacent to the tank).

Jim Nilsen
12-07-2009, 06:48 PM
You have the right idea with just one line going to the front. There is plenty of info in some threads about how to do it.

Have fun

mrn2obelvedere
12-07-2009, 07:30 PM
I've been trying to search for those threads...would you or anyone else be kind enough to point me to the right threads?

7t2vette
12-08-2009, 01:47 PM
Are you going to run the vacuum line to the back? I guess you have to, as that is the only way the regulator will know when you are WOT. I read on another forum about someone trying this, and he had driveability issues; he figured it was caused by too much signal lag from vacuum drop over the long length. He was using his existing stock 1/4" hardline for the vacuum signal.

:cheers:

camcojb
12-08-2009, 04:59 PM
Are you going to run the vacuum line to the back? I guess you have to, as that is the only way the regulator will know when you are WOT. I read on another forum about someone trying this, and he had driveability issues; he figured it was caused by too much signal lag from vacuum drop over the long length. He was using his existing stock 1/4" hardline for the vacuum signal.

:cheers:
I've run the rear regulator without a vacuum line, no issues, but I added some fuel pressure to the static setting. I've also run a line to the rear for boost reference on my turbo setup, again no problems at all.

Jody

mrn2obelvedere
12-08-2009, 06:56 PM
From what I have read on msefi forums (I'm going to be running a megasquirt) the length of the vacuum reference lines have little effect; the vacuum signal travels much faster than the engine actually responds.

I think I'll give this a go and hope that it works well.

jjump59
12-09-2009, 07:37 AM
here's a good thread on it

https://www.pro-touring.com/forum/showthread.php?t=22935&highlight=regulator

Jim Nilsen
12-09-2009, 04:54 PM
I didn't hook up the vacuum line on mine and have had no problems keeping right on the 45 psi the regulator is set at.

gkring
12-09-2009, 07:03 PM
You can do it if your computer setup is for a returnless style Fuel injection. Most aftermarket systems won't be. Search for returnless fuel injection for more in depth explanations.

mrn2obelvedere
12-09-2009, 07:51 PM
My system will have a return line. The regulator will be close to the tank and the return will go directly back into the tank.

My understanding of the vacuum reference on regulators is that it is mostly there to keep the pressure differential between the air in the ports and the fuel system relatively constant. This is mostly for forced induction engines, so not hooking it up on a NA engine probably won't have too much effect.

camcojb
12-09-2009, 08:53 PM
You can do it if your computer setup is for a returnless style Fuel injection. Most aftermarket systems won't be. Search for returnless fuel injection for more in depth explanations.
huh?????????????

Jody

gkring
12-10-2009, 12:19 PM
If the fuel pressure at the injectors will always be one fixed pressure then the fuel calculations will be different than if the fuel pressure is referenced to manifold vaccum and/or boost. Fuel systems that remain one constant pressure are considered returnless as far as aftermarket computers are concerned. Factory LS2/LS3, etc systems are returnless. Older LS1, LT1, and anything GM made before that were return style with pressure referenced regulators.

If you run the regulator in the back then the fuel line ahead of it just acts like a massive fuel rail, which is fine. Depending on if he references the manifold vacuumn/pressure to the fuel pressure regulator will affect what computer he can run.

There are ways to trick either system to run fine on the "wrong" computer setup, but it is way easier to start with the correct setup.


45 psi fixed pressure
idle = 45psi x duty cycle
WOT=45psi x duty cycle
10 PSi of boost = 45 psi x duty cycle

45 psi referenced fuel pressure
idle = 35 psi x duty cycle
WOT=45 psi x duty cycle
10 PSi of boost = 55 PSI x duty cycle

you can see where referencing the fuel regulator to change pressure based on what the motor is doing can greatly affect fuel delivery, as long as the compter knows the setup you can do it either way. All things being equal a fixed pressure system will have a longer duty cycle than the referenced system.

I think the confusion comes from me worrying more about the manifold reference affecting the fuel pressure than about the placement of the regulator (which was the original question).
Sorry, I think I just muddied up the waters more.

camcojb
12-10-2009, 12:54 PM
If the fuel pressure at the injectors will always be one fixed pressure then the fuel calculations will be different than if the fuel pressure is referenced to manifold vaccum and/or boost. Fuel systems that remain one constant pressure are considered returnless as far as aftermarket computers are concerned. Factory LS2/LS3, etc systems are returnless. Older LS1, LT1, and anything GM made before that were return style with pressure referenced regulators.

If you run the regulator in the back then the fuel line ahead of it just acts like a massive fuel rail, which is fine. Depending on if he references the manifold vacuumn/pressure to the fuel pressure regulator will affect what computer he can run.

There are ways to trick either system to run fine on the "wrong" computer setup, but it is way easier to start with the correct setup.


45 psi fixed pressure
idle = 45psi x duty cycle
WOT=45psi x duty cycle
10 PSi of boost = 45 psi x duty cycle

45 psi referenced fuel pressure
idle = 35 psi x duty cycle
WOT=45 psi x duty cycle
10 PSi of boost = 55 PSI x duty cycle

you can see where referencing the fuel regulator to change pressure based on what the motor is doing can greatly affect fuel delivery, as long as the compter knows the setup you can do it either way. All things being equal a fixed pressure system will have a longer duty cycle than the referenced system.

I think the confusion comes from me worrying more about the manifold reference affecting the fuel pressure than about the placement of the regulator (which was the original question).
Sorry, I think I just muddied up the waters more.my response was to the comment of

"You can do it if your computer setup is for a returnless style Fuel injection. Most aftermarket systems won't be."

Any computer can be tuned to run the regulator without a vacuum reference, at least any that can be tuned by the end user or professional tuner. All aftermarket definitely can be tuned that way. The factory computers can also be tuned to run it this way. You are correct, if your tune is set with the vacuum reference then removing it would require you to re-tune to compensate for the loss of additional fuel pressure under load areas. But they can all be re-tuned to work just fine without the reference line.

With a n/a setup I usually don't run the line, keep the fuel pressure at one setting and tune it that way, no problems. With a boosted setup I like to run it to compensate and add fuel pressure under boost, to help with the boost in the intake runner trying to "lessen" the injector spray, and to help with fueling at high hp numbers.

Jody

gkring
12-10-2009, 02:12 PM
Yep, I see the confusion. I am used to tuning on 25+ PSI turbo cars and that mandates a referenced regulator to be able to feed a motor without running out of duty cycle. On a typical hot cammed naturally aspirated motor the swing in manifold vacuumn is not much to affect the fuel pressure especially on 40 pound and smaller injectors. Older systems that just use duty cycle in the fuel maps don't care either way. It is only systems based off of volumetric efficiancy tables that have to be tweaked differently. Thanks for putting me back on the road the question was about.

mrn2obelvedere
12-10-2009, 07:05 PM
Quick question. For initial startup with the type of system I am planning, is there some method of bleeding the system that I have to employ to remove the air?

bigblockcamino
12-10-2009, 11:31 PM
Quick question. For initial startup with the type of system I am planning, is there some method of bleeding the system that I have to employ to remove the air?

Good question.. i'm almost to this phase too. :) My method was going to be hook the pump to 12v and start pumping to purge the lines.

camcojb
12-11-2009, 07:39 AM
you can crack a line open on the back side of the fuel rail and cycle the pump to remove air. I generally just start it up............. :) Might take an extra couple of seconds if that.

Jody

mrn2obelvedere
12-12-2009, 10:59 AM
Good question.. i'm almost to this phase too. :) My method was going to be hook the pump to 12v and start pumping to purge the lines.

I'd doubt this will work very effectively, there will still be a lot of air in the system, just like with your braking system. I was trying to think of a way to incorporate some kind of bleeder into the system for initial setup. If I just loosen up one of the pipe plugs on the end of the fuel rail I am afraid that I will get high pressure fuel spraying everywhere. Especially with a charged electrical system this could be very dangerous.

gkring
12-12-2009, 01:28 PM
Don't worry about it. Couple of key cycles will prime it enough for the initial firing. There won't be any air bubbles giving you trouble like you can get in a cooling system or braking system if that is what you are worried about. Those are closed systems that can't really bleed themselves. At worst the very very first time the systems sees gas it could take 4 seconds of cranking to get fuel presure to start the car instead of 1.5 seconds. No worse than running the car out of gas or starving it on a low tank during aggressive handling manuevers. You can always unhook it at the fuel rail and turn the pump on to fill up the filter and lines while pumping it into a gas can. Then when you plug it back up what little air there is left is only what was in the fuel rail itself.

camcojb
12-12-2009, 01:41 PM
I'd doubt this will work very effectively, there will still be a lot of air in the system, just like with your braking system. I was trying to think of a way to incorporate some kind of bleeder into the system for initial setup. If I just loosen up one of the pipe plugs on the end of the fuel rail I am afraid that I will get high pressure fuel spraying everywhere. Especially with a charged electrical system this could be very dangerous.
like I said, it will fire without bleeding, may just take a couple extra seconds to do so.

Jody

mrn2obelvedere
12-12-2009, 07:08 PM
Something has to happen to the air...does this get pumped through the injectors? Just curious.

camcojb
12-12-2009, 07:11 PM
Something has to happen to the air...does this get pumped through the injectors? Just curious.
I would imagine. I have plumbed several cars this way, never had a problem getting them to start, never tried to purge the air....................

Jody

mrn2obelvedere
12-12-2009, 09:01 PM
Cool...I'll take your word on it. Thanks for the info, this will certainly make things easier.