Fuel Pressure Regulator Placement

[eLeSthree]

If you put the FPR before the fuel rails, what is stopping the rise in fuel pressure (1:1 rising rate when boost applied) to just get forced back through the return line?

I know the AGP kits are setup this way, and people have great success with them. However, I just built my own kit and I can't seem to get consistent 1:1 fuel pressure.

I've got 3 x 274 pumps, -10 feed -8 return, -8 rails, 1300cc injectors, a Holley adj fpr. I've tested the fpr with my air compressor at idle and I've seen 83psi. Even replaced the FPR with a new one from summit. Same deal.

I set static to 58 without the hose on. It drops to 55ish connected. Add 20 pounds of boost and should be at 78psi. But it levels out around 68-70psi. It's enough fuel for my needs, but I need a consistent fp reading to tune the afr.

Currently my -10 feed goes from pumps to the regulator in/out, then from the other reg in/out to my filter, then to the driver side rail. Then I'm using a -6 crossover hose (came with my fuel rails) to feed the passenger rail. The FF sensor is directly connected to the return port on the regulator and the -8 return line is plumbed into FF sensor, and back to the tank.


If I move the regulator after the rails, will this help me maintain steady FP??

[dreksnot]

Where is your fuel pressure sensor in your system? Are you sure all 3 of your pumps are kicking on when in boost?

[eLeSthree]

I've had the FP sensor in 3 locations. First it was in the stock location near the tank. I bought the necessary fittings to get it into my -8 return.... like an idiot. Theres no pressure in the return line.

So I moved it to the fuel rail, based off the lovely advice of the internet. (also bought more fittings) Which didnt work, because the signal looked like my EKG, from the freakin stress this shjit is causing me.

After listening to Ted, it is now installed right in the FPR gauge port. Reading smoothly. I also have a mechanical gauge on the rail, which reads within 1-2 psi of HPTuners (fp gauge).

So for trouble shooting purposes I am currently running 2 pumps as my primary, and the 3rd is boost activated at 2psi.

In my logs it is very evident when the 3rd pump kicks in. I see pressure rise. I also place my hand on the Hat while driving (wot mind you) down the street and feel the third pump come on.

And let me clarify, I dont have pressure DROP. It raises to 68-70 and stays there. It's just short of what I expect so see.

Does the FPR placement play a roll in accurate FP regulation?
(well obviously, it cant be placed on the shelf)

[Big Biscuits]

Originally Posted by eLeSthree

If you put the FPR before the fuel rails, what is stopping the rise in fuel pressure (1:1 rising rate when boost applied) to just get forced back through the return line?

I know the AGP kits are setup this way, and people have great success with them. However, I just built my own kit and I can't seem to get consistent 1:1 fuel pressure.

I've got 3 x 274 pumps, -10 feed -8 return, -8 rails, 1300cc injectors, a Holley adj fpr. I've tested the fpr with my air compressor at idle and I've seen 83psi. Even replaced the FPR with a new one from summit. Same deal.

I set static to 58 without the hose on. It drops to 55ish connected. Add 20 pounds of boost and should be at 78psi. But it levels out around 68-70psi. It's enough fuel for my needs, but I need a consistent fp reading to tune the afr.

Currently my -10 feed goes from pumps to the regulator in/out, then from the other reg in/out to my filter, then to the driver side rail. Then I'm using a -6 crossover hose (came with my fuel rails) to feed the passenger rail. The FF sensor is directly connected to the return port on the regulator and the -8 return line is plumbed into FF sensor, and back to the tank.


If I move the regulator after the rails, will this help me maintain steady FP??

I would move the FPR to after the rails. I plan on doing this when I get the Fore system going. I would also filter before the FPR. Dirt in a FPR is not a good thing. Text me if you want me to walk you through anything.

[eLeSthree]

Yea, that was Ted's suggestion also. The parts to re plumb are sitting on my front porch. Also ditching the -6 crossover. I'll post some pics once I'm finished.

I was just reading about how some regulators have a Regulation Slope and cant provide a true 1:1 at higher flow, since less fuel is going through the return. However after speaking with Holley, they don't have any technical data on this regulator having slope, especially at 20psi of boost.

[stevieturbo]

It's very simple.

The closer the FPR is to the fuel rails, the more stable FP will be at the rails.
Now whether it's before, after, upside down, sideways....really doesnt matter. But proximity to the rails does matter.

Also how you plumb the fuel to flow through the rails can make a difference...but in reality as long as you didnt do something really stupid, it wont make much difference.

As for slope....sounds like bullshit someone has made up.

The regs in general should see 1:1, but as other factors can influence this, it may not always be 1:1

One simple scenario. A little FPR, with a megawhopper pump. At idle you might have it adjusted right out to get some sort of sensible base pressure. However...that's just a symptom of a reg that cannot cope with the flow of that megawhopper.
So ramp on to 5000hp, and fuel consumption at the engine has massively increased....and now that wide open regulator is suddenly dropping pressure like mad, because the volume of fuel through it has dropped to a far lower level.
Basically that regulator was not designed for the flow rates required and has been incorrectly adjusted far too wide open. It's not that there is a problem with the regulator....just it was a bad choice for that application.

Or I've seen regs where some air leaks out the top chamber via the adjustment threads. No big deal ? Depends on the size of line supplying air to it. ( remember how we fool wastegates with air leaks...same thing, in reverse, so a leak there with inadequate supply to it, could cause pressure to drop vs MAP )

There are various factors to consider, but it is very simple. No air leaks, no fuel leaks lol...and a FPR close to the rails, and the FPR is capable of dealing with the flow levels involved.

[eLeSthree]

Originally Posted by stevieturbo

It's very simple.

The closer the FPR is to the fuel rails, the more stable FP will be at the rails.
Now whether it's before, after, upside down, sideways....really doesnt matter. But proximity to the rails does matter.

Also how you plumb the fuel to flow through the rails can make a difference...but in reality as long as you didnt do something really stupid, it wont make much difference.

As for slope....sounds like bullshit someone has made up.

The regs in general should see 1:1, but as other factors can influence this, it may not always be 1:1

One simple scenario. A little FPR, with a megawhopper pump. At idle you might have it adjusted right out to get some sort of sensible base pressure. However...that's just a symptom of a reg that cannot cope with the flow of that megawhopper.
So ramp on to 5000hp, and fuel consumption at the engine has massively increased....and now that wide open regulator is suddenly dropping pressure like mad, because the volume of fuel through it has dropped to a far lower level.
Basically that regulator was not designed for the flow rates required and has been incorrectly adjusted far too wide open. It's not that there is a problem with the regulator....just it was a bad choice for that application.

Or I've seen regs where some air leaks out the top chamber via the adjustment threads. No big deal ? Depends on the size of line supplying air to it. ( remember how we fool wastegates with air leaks...same thing, in reverse, so a leak there with inadequate supply to it, could cause pressure to drop vs MAP )

There are various factors to consider, but it is very simple. No air leaks, no fuel leaks lol...and a FPR close to the rails, and the FPR is capable of dealing with the flow levels involved.

Challenge accepted. Lol

[stevieturbo]

Only advice with hoses...is do teflon from the start.

By **** I've spent thousands on hoses and fittings over the years ! It really gets ridiculous when you make changes.

[eLeSthree]

Originally Posted by eLeSthree

Challenge accepted. Lol

Sometimes I amaze myself. I ordered all non-ptfe fittings. FML!

Report back next week...

[stevieturbo]

Haha !

I've been through all sorts. Started with the Earls Superstock push on...no issues, worked fine. Although externally, I wouldnt say the hoses lasted as well over time as they should. I doubt they'd ever have leaked....but a few did develop age type cracks, making them unsightly. The push fit stuff can be a bit of a pain to put together too, and have to be cut off if for any reason they need changed.
So after a years later I changed some to the compression style.

Ultimately later on with various other changes and a view to running ethanol at some point, I decided teflon just makes the most sense. It's any fuel compatible and for any given size, overall smaller OD so actually a little easier to package.
The rubber based hoses can be very large and bulky.

And some of the compression style fittings....well, whilst they do work, I was just never that happy with some.
With the teflon stuff, it's lighter, smaller, just as flexible ( perhaps more so because of the smaller overall diameter ), more heat resistant. So other than a little extra initial cost, there arent really any downsides. And you can get them with black or other outer coverings so you arent stuck with the shitty stainless overbraid of years gone by.

[eLeSthree]

Originally Posted by stevieturbo

Haha !

I've been through all sorts. Started with the Earls Superstock push on...no issues, worked fine. Although externally, I wouldnt say the hoses lasted as well over time as they should. I doubt they'd ever have leaked....but a few did develop age type cracks, making them unsightly. The push fit stuff can be a bit of a pain to put together too, and have to be cut off if for any reason they need changed.
So after a years later I changed some to the compression style.

Ultimately later on with various other changes and a view to running ethanol at some point, I decided teflon just makes the most sense. It's any fuel compatible and for any given size, overall smaller OD so actually a little easier to package.
The rubber based hoses can be very large and bulky.

And some of the compression style fittings....well, whilst they do work, I was just never that happy with some.
With the teflon stuff, it's lighter, smaller, just as flexible ( perhaps more so because of the smaller overall diameter ), more heat resistant. So other than a little extra initial cost, there arent really any downsides. And you can get them with black or other outer coverings so you arent stuck with the shitty stainless overbraid of years gone by.

This last order was from a different store, but I had good luck buying bundles from HotRodFuelHose.

Stevie, Do you think the regulator placement is causing my issue? Im starting to think maybe I should swap out the Holley Billet Efi regulator with an operating range of 25-65psi, to an Aeromotive A-1000. It runs between 40-75psi.

Is it a coincidence that my FP is maxing at 68ish psi, just over the cheaper Holleys limit???

After all, several agp users make 1000+ with regulators before the stock rails. I bet the plumbing is fine.

[eLeSthree]

Every log I have looks like this. Most I can get out of this thing is 68ish PSI, no matter what boost it sees. Granted, parked in the garage with the air compressor on it, it will go to 83psi, but not under real boost.

Aeromotive A1000 has been ordered.

[stevieturbo]

Again...the closer the FPR is to the rails, the better control you will have over pressure.

If it is far away from the rails, I would have little expectation for it to ramp 1:1. And that would likely get worse as boost AND fuel demand increases ( ie more into the engine, and less out the return, for reasons already mentioned )

Is a little pressure drop a problem ? Not really. As long as it is repeatable and consistent every time and not dropping to silly levels, then that's just normal behaviour for your install.

I would take any claimed pressure ranges for FPR's with a pinch of salt, as there are just too many variables. And they dont even stipulate if that range is with boost applied or without.
Much the same as rods rated to 800hp, a fuel rated to 20psi, an intercooler rated to 1000hp....and other such silliness.

[stevieturbo]

Originally Posted by eLeSthree

So for trouble shooting purposes I am currently running 2 pumps as my primary, and the 3rd is boost activated at 2psi.

In my logs it is very evident when the 3rd pump kicks in. I see pressure rise. I also place my hand on the Hat while driving (wot mind you) down the street and feel the third pump come on.

And let me clarify, I dont have pressure DROP. It raises to 68-70 and stays there. It's just short of what I expect so see.

Does the FPR placement play a roll in accurate FP regulation?
(well obviously, it cant be placed on the shelf)

It would probably make a good difference if you drove on a single pump, and then staged in the other two pumps at higher load.

It would mean the FPR is more "shut" at lower loads, as it's dealing with much lower flow....but then if anything it may then struggle to cope at the higher loads with all 3 pumps. Except in the direction you want it to forcing higher pressures.

I do dislike just turning pumps off/on like that, hence why I chose to PWM my pumps so flow is always variable, and never any big jumps. Although without an aftermarket ecu or controller, not sure how you'd achieve that.
I run 2 450's at present, but only PWM'd at 38% duty at low loads, ramping up to 100% duty at higher loads.
So really at low load and idle, the FPR and system doesnt even have to deal with 450's worth of fuel, maybe more like "400" or so.
And as fuel demand goes up....the FPR is probably still only dealing with that same volume overall in terms of the return as the engine is then consuming a lot of the fuel.