Lethal Return FPR loosing psi.

[XXWildCoyoteXX]

Currently tuning my Mach 1 and my tuner has come to this issue and is wanting me to figure out the issue. He is thinking i may have a poor quality regulator, line restriction, or regulator isnt seeing correct vacuu/boost.
What he is seeing is a drop in Fuel Pressure at WOT, 5 psi to be exact.
It seems to him its falling off with rpm so it possibly could get worse over 3500rpms.

Setup:
Lethal Performance Budget Return fuelsystem
Stock Feed Line
Stock Fuel Rails
60lb injectors
Dual Walbro 465 pumps
-6 Return Line
Lethal FPR with FPS attached

All this is running with a Cobra Engineering GT500 swap kit, so my boost reference for the bypass and FPR/FPS comes from the back of the Cobra Engineering plate, right above the rear drivers intake runner.

Any useful info or help would be great. Thanks

 

[XXWildCoyoteXX]

Ive been reading that the 5psi drop is seemingly normal with the liquid filled Regulators.
Next thought would be upgrading to -8 feed line.

 

[Jon82387]

Dual 465s for only 60# injectors??? And your trying to push it through stock lines????

Honestly if all your running is 60# injectors 1 465 pump is plenty..... try turning the other one off and see if issues go away.

If so your lines/rails are restricting too much which i almost gaurantee and causing different issues.

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[XXWildCoyoteXX]

Dual 465s for only 60# injectors??? And your trying to push it through stock lines????

Honestly if all your running is 60# injectors 1 465 pump is plenty..... try turning the other one off and see if issues go away.

If so your lines/rails are restricting too much which i almost gaurantee and causing different issues.

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After looking back up the amount the 465s push, i came to the same thought. The stock lines are just way to small for all the pressure. Only reason I had the dual 465s was because i aimed to have a 76mm turbo setup, but changed my route midway through. So I just left the fuel system how it was.

-8 fuel line be a good upgrade or do most of yall just go straight to -10 like i see a lot of?
Injectors are just the 60s till I make the change to E85 or selling my kit to go turbo in the future.

 

[Jon82387]

Yea i figured you had planned on going bigger at some point. But yea for now just try disconnecting one of them and see what happens.

-8 is probably the bare minimum i would try and run dual 465s on.... i will be doing it here soon myself when i get a bigger supercharger.

-10 would be plenty and ensure no issues at all though.

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[XXWildCoyoteXX]

Yea i figured you had planned on going bigger at some point. But yea for now just try disconnecting one of them and see what happens.

-8 is probably the bare minimum i would try and run dual 465s on.... i will be doing it here soon myself when i get a bigger supercharger.

-10 would be plenty and ensure no issues at all though.

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Now if i went with the -10 wouldnt that be to much for the stock fuel rail. saidly have to stick with it unless i find some cheap used rails. Only reason for that is due to the GT500 supercharger swap makes for aftermarket rail fitment issues.(aka welcome grinder)

 

[Jon82387]

Honestly with the pumps and setup you plan to run at some point i would try and get some aftermarket rails. If not yea it may be difficult to adapt to the factory rails.

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[MG0h3]

Only reason your lines being too small would cause a pressure drop is they can't carry the volume and you're sucking them dry. I don't know how much power you're making but pretty sure the budget kit uses that setup and is rated for 800hp or something.

I doubt that is your issue.

Not sure what those fuel rails are like but guys go north of 700whp on factory cobra rails.

I would look at other things before reconfiguring your system.

Your fuel pressure should jump to base when you remove the line from the reg. You can then use a cheapo vacuum pump and air nozzle to apply pressure to the reg and see if it's operating correctly.


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[XXWildCoyoteXX]

Only reason your lines being too small would cause a pressure drop is they can't carry the volume and you're sucking them dry. I don't know how much power you're making but pretty sure the budget kit uses that setup and is rated for 800hp or something.

I doubt that is your issue.

Not sure what those fuel rails are like but guys go north of 700whp on factory cobra rails.

I would look at other things before reconfiguring your system.

Your fuel pressure should jump to base when you remove the line from the reg. You can then use a cheapo vacuum pump and air nozzle to apply pressure to the reg and see if it's operating correctly.


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I will possibly be around low 600s when all said and done. My main reason for using the budget system from lethal was that I wasnt going to be that high and have seen quite a few cobra guys with stock fuel systems, just pump area upgrades getting higher then my goal area. Thus believing my fuel system should be golden and able to handle later power.
My tuner thinks its something up with the regulator but everything is brand spanking new from lethal. I know theres always that possibility of getting the one bad egg in the bunch, but my regulator works pretty well visually. Just the odd 5psi lose at WOT is what my tuner was concernd about.
Could a pump thats just barely off the bottom of the tank cause a pressure drop at WOT and act perfectly normal during idle and normal driving?

 

[MG0h3]

You are correct. Factory lines and rails will handle 600rwhp. Bap and injectors will handle it.

Also correct on the pumps sitting too low in the tank. I guess some hats cause this and others have accidentally dented the bottom of the tank right below the pumps when using a jack to raise and lower it.


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[XXWildCoyoteXX]

You are correct. Factory lines and rails will handle 600rwhp. Bap and injectors will handle it.

Also correct on the pumps sitting too low in the tank. I guess some hats cause this and others have accidentally dented the bottom of the tank right below the pumps when using a jack to raise and lower it.


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Now my tuner has said my issue must be the regulator being faulty.
Have you any chance heard people having issues with the liquid filled regulators causing a Fuel Pressure issue from lethals kits or in general?
Ive noticed there are liquid filled and non liquid filled regulators so that brought up my question. Havent found a discussion anywhere about the pros and cons of either.

 

[MG0h3]

I dont have any info on the liquid filled regulators. Not sure how to do a volume test on our setups with aftermarket lines. Id call lethal and see what they have to say but it seems irregular to me.

Did you try and crank the reg up and see if itll hold the pumps at 75 or 80 psi?

 

[XXWildCoyoteXX]

Well I readjusted my pumps in the tank. seemed like they may have been sitting on the bottom of the tank. Had a few odd rub marks under the location of the pumps. Also removed that odd Metal Saucer device just before the fuel rail. (hardest thing to find online of what it is and if it is an issue with fulltime pumps)
Time to test and see if any difference

 

[MG0h3]

Cool man probably it. Not sure which hat/pump combo causes it but you wont be the first.

 

[JeremyH]

Jons advice is spot on. Even on "small" factory lines they will continue to flow fuel as pump outlet pressure goes up. When the pump cant put out any more pressure is when flow would drop and in return a drop at the rails. Dual 465 is 1200hp worth of fuel so its not a flow issue unless you have a physical pump issue which is doubtful on a new setup. In short, as long as you have enough pump you can push as much flow and power you want through a given line. There's just more restriction so pump outlet pressure is higher. I will agree that its not idea for that flow and it will definitely shorten pump life and an upgrade to a larger feed and return line to 8an would def be more efficient, that's a great idea as well.

With the proper baffled filter sock ( walbro 125-190 ) you can smash that sucker right on the bottom tank no problem as its internal structure prevents it from collapsing and it pulls fuel radially 360 degrees through the filter. I have a customer with a single 465 pump setup with a 67mm turbo and he made 625rwhp with the one pump flat on the bottom of the tank with that filter.

I will tell you not all regulators are created equal. And the demands on a basic pass through suitable regulator (where its meant to be post rails) are much higher when its pre rails. Its now acting more like a bypass valve and the fuel is dead ending in the rails. Ideally you want a quality 4 port regulator for this setup where feed line comes in and each rail has a dedicated line from the regulator and then return out the bottom.

I cringe a little every time I see "budget" return system so remember that's exactly what it is. I personally would never spec a system with that much pump for that kind of regulator rail setup, its a lack of understanding or care to get a product out the door or both it seems.

That said if your efforts bring you to swapping out the regulator I would highly recommend a Fore unit. Best regulators on the market from a company that specifically specializes in fuel systems. I use them exclusively for fuel systems and not once had an issue with their regulators on any setup. But as recommended a proper line/filter rail setup would be my first upgrade to that setup.

 

[XXWildCoyoteXX]

I understand totally what your saying JeremyH. It was suppose to be a Pre-rails regulator setup that fed the passenger side from rear, crossed infront and then returned back to the regulator from the driver side. Time and money aimed me towards the Lethal Budget kit that allowed use of the stock rails and feed lines. Researched to much about people making the stock system push out high numbers and wanted to see if I could take something from that also.
The regulator I have is a DivisionX product, still should be a reputable company. I havent heard anything lately about a drop in quality from them.

After inspecting the pump filters, I also saw the sock design and noticed its ability not to collapse. Made me happy to know I could factor that issue out.

Ill upgrade the feed to 8an along with a good filter. Then if i can find a good deal on some rails ill throw them on also. Hopefully that will all help me out in the end. Hell im getting close to the point at selling my whole swap setup and go back to my single 76mm setup I had planned XD.

 

[MG0h3]

plenty of people run the "budget" line setup. If your pump/sock issue isnt it then Id look at the boost ref/reg. I just cant see how you are draining the lines when I and tons of others make 600rwhp with nothing but a BAP.

Im not opposed to running better hoses but I don't think that is the issue. Cant see how it is actually.

 

[XXWildCoyoteXX]

plenty of people run the "budget" line setup. If your pump/sock issue isnt it then Id look at the boost ref/reg. I just cant see how you are draining the lines when I and tons of others make 600rwhp with nothing but a BAP.

Im not opposed to running better hoses but I don't think that is the issue. Cant see how it is actually.

yea same here, just weird to have this issue. But he says that there is a loose of 5psi at WOT and this is just 4th gear 1500-3500rpms. hes thinking it might increase the higher we go. and the vacuum line setup is exactly how everyone else runs it on the H122 swap kits. lower manifold port, T , Bypass from one, FPR/FPS on the other line. pretty damn simple.