Sniper EFI 3/8" lines and return vs returnless

[JJK]

I received my BPE347 (dyno'd at 426hp at the crank) with Sniper EFI and took the advice posted by many to download and read the full EFI instructions, not just the Quick Setup. Having this additional information has put me in a dilemma, but I am unsure if it is real enough to cause concern. Here is the crux of things, Holley recommends a minimum of 3/8" supply and return fuel lines, which I do not currently have. I ordered the EFI In-Tank System with my kit and am afraid I may regret that. That option came with a Walbro 255lph in-tank pump, which is fine. It also came with a fuel pump hanger that has a 5/16" supply side port and 1/4" return port. Additionally, it came with 6AN flexible fuel lines to connect from the fuel filter to a regulator, a 6AN line to connect the regulator to the Sniper, and a 4AN line to route from the bottom of the regulator back to the fuel hanger in the tank. Clearly, this setup has a restriction of 5/16" at the fuel pickup from the tank and a restriction of 1/4" on the return side.
Given that this does not meet the recommendations from Holley, should I upgrade to the Pro-M hanger (3/8" output and input) as well as 3/8" return lines? If doing this, should I bypass the regulator and route the return line directly from the Sniper? Is there any difference in performance or durability/reliability between the return vs returnless setups?
Or, should the components provided by the 'EFI In-Tank System' option be sufficient even though the lines are smaller than Holley recommends. What I don't want to do is jeopardize the reliability of the EFI due to poor plumbing choices or create a system that will cause undue stress on the fuel pump, since I have no desire to replace that in the near future if not necessary.
Thanks

[mladen]

I am/was in a similar boat as you except I have a BPE427. I ended up upgrading the lines to 3/8 in both directions and getting an in-tank pump and hangar from Breeze to match. I don't think I need a regulator, the way I understood the instructions, but I still have time to remedy that when I'm hooking up the lines to the engine. I have limited/no prior experience with this, so my main reasoning is that I'll go with what the manufacturer recommends and not risk anything. And as you mentioned, this isn't something you plan on replacing, nor is it really easy, especially with hard lines.

[CraigS]

Does Holly have any HP specs in their recommendations. I ask because, when I have seen recommendations for fuel line size, it is usually based on HP. If the Sniper is rated for up to (pulling a # out of the air here) 600 HP it could be they are giving fuel line sizes based on the possibility that someone may use it on a 600 HP engine. So your 426HP is well below and may not need the 3/8. I would do a search to try to find recommendations (from any efi manufacturer) based on HP and see how yours compares. Regarding return vs returnless systems, I believe most car manufacturers have gone to returnless. At one point I heard that the old return system ran the fuel up to the top of the engine and then back. The engine compartment gets pretty hot so the fuel was actually being slowly but surely warmed up. The problem was at it's worst in slow city traffic. Returnless fixes that problem. I also understand that w/ advances in computer control fuel pumps are now able to be run at infinitely variable speeds which helps regulate fuel pressure based on the engine need right now. That compares to older systems where the pump always ran at a set speed (enough for full throttle fuel usage).

[Namrups]

EdwardB has used the Walbro pump you mentioned along with the Pro-M hanger and 3/8" feed and return lines on a number of his builds. It has worked flawlessly for him for years. That alone was good enough for me to use it on my 500hp SBF in my coupe. That will be one system I won't worry about down the road. A few extra bucks for peace of mind works in my book.

[Papa]

1. Holley recommends 3/8" lines for the Sniper.
2. Returnless (deadheading) the Sniper can be done, but the preferred method is to use a return line. Most "returnless" options you'll see marketed are still actually return systems where the return is a short run from a regulator near the tank or actually in the tank as part of the pump assembly/pickup.

The Pro-M hanger is an excellent product regardless of whether you need 3/8" lines or not and will serve you well.

[GTBradley]

I would add that the return, whether using return lines or returnless (actually a short run return), causes some level of agitation in the tank. This can cause cavitation with some systems and the more fuel being returned the more likely that becomes. The 255 lph system was more than was needed for my 435 hp Coyote, so I’m using a 190 lph and dyno numbers prove it delivers maximum hp. The point of my story is that I learned all this from Mark at Breeze. He seems quite knowledgeable on this subject, so I would suggest asking what system he would recommend. BTW, I think he terms it a single line system, rather than returnless.

[rich grsc]

I would add that the return, whether using return lines or returnless (actually a short run return), causes some level of agitation in the tank. This can cause cavitation with some systems and the more fuel being returned the more likely that becomes. The 255 lph system was more than was needed for my 435 hp Coyote, so I’m using a 190 lph and dyno numbers prove it delivers maximum hp. The point of my story is that I learned all this from Mark at Breeze. He seems quite knowledgeable on this subject, so I would suggest asking what system he would recommend. BTW, I think he terms it a single line system, rather than returnless.
So true, too large of a pump will just endlessly pump fuel through the system. Two things happen, aeration of the fuel and warming the fuel. Best to size the pump to the intended use and HP.

[Namrups]

The PRO-M hanger has a longer return line that reaches the bottom of the tank. It eliminates aeration of the fuel as it's feeding the return fuel into the existing fuel.

[TMartinLVNV]

I voiced my frustrations with the F5 EFI kit and how it is undersized for the Holley Sniper setup. With my Sniper, I used the Pro-M pickup and 3/8" lines with a return. I used the EFI kit fuel pump but junked their filter and regulator. When you hook up the sniper, don't forget to get a fuel pressure gauge from Earl's.

[JohnK]

So true, too large of a pump will just endlessly pump fuel through the system. Two things happen, aeration of the fuel and warming the fuel. Best to size the pump to the intended use and HP.

This is a valid point, but one thing worth mentioning is that a primarily street-driven car will rarely be making max HP so even if your pump is properly sized for the max HP your engine can make you will be recirculating most of the fuel most of the time. Fuel warming is partly a result of restriction, so larger larger fuel lines will limit restriction and reduce fuel warming. As others have pointed out, the design of the Pro-M hanger helps reduce fuel aeration.

[rich grsc]

John, that's true and why I think 'intended use' is is something to consider. If all you do is just cruise and go to car shows, the stock Foxbody fuel pump and FFR fuel lines are good enough, but if you track the car, then anything over a short burst of full power and you will start running out of fuel with a small pump and lines. Even the Holley Sniper is fine with the small lines if you don't track it.
I installed the Pro-M hanger because of fuel aeration. I was sold a 255 lpm pump, I think a 190 may have been ok, but maybe not at 6000rpm's down the track.;)

[JohnK]

Rich - agreed. That's definitely one approach. However, to play devil's advocate, I'd have a hard time spending a bunch of money on an engine that can make, let's say, 500HP only to then install a fuel delivery system that's only capable of supporting 300HP. Why spend the money on a 500HP engine to begin with? This then also raises a bunch of problems in those instances when you do put your foot in it, only to fuel-starve the motor.

[Namrups]

For what it's worth, the Earls pressure gauge is a good unit and I used it to verify line pressure during first start. I removed it after verifying due to reports that they tend to leak if left in. I have no experience with that but after verifying didn't want to take the chance. The Sniper unit also has it's own internal fuel pressure regulator eliminating the need for an external one. Saves space in the engine bay and money in the pocket.

[Avalanche325]

So true, too large of a pump will just endlessly pump fuel through the system. Two things happen, aeration of the fuel and warming the fuel. Best to size the pump to the intended use and HP.

But, but, but MORE = BETTER.

[GTBradley]

But, but, but MORE = BETTER.
Let’s be specific here - more expensive = more better!

[Papa]

Logged in to post a question about my BP347.... Then I read this thread so now more confused. Installed a BP347 with Breeze supplied 190LPH in tank EFI pump and the single line kit, which basically is designed to not need a return line from the Sniper, it returns from the filter/regulator. So here's my issue. On the very first start, it started immediately, so fast in fact it startled me. Since then (and it only has 2 miles on it, engine has run for may 30 minutes) each start now takes 3-4 key turns of 3-5 seconds each before it coughs to life. Then on approaching a intersection, getting off the gas and it will stall, unless I bump the gas a couple of times, although that doesn't always work either, and finally, upon shifting down from 2-1, I got a backfire, only happened once. I was wondering about the "smartness" of installing the return line regulator/filter setup. The feed line is 3/8 so should be fine, but the "return" side is a bored out 1/4".. Breeze part 70734.
I also wondered if by some weird chance if the timing got knocked off. Tried to move the distributer, and it is tight, although it did "flex" maybe just a touch.
Any thoughts would be greatly appreciated!!!

First things first. What inlet port are you using on the Sniper? Have you verified you are getting 58 psi at the Sniper? Are you letting the Sniper boot up before trying to start the engine? You need to give it 3-5 seconds with the key in the on position before cranking.

[sittonb]

option 1, driver side "rear", yes, I can hear and let the fuel pump continue until it shuts off, usually 4-5 seconds. I've been re-reading the BP documentation and the Sniper documentation, and think I might just go back to step one, reconfirm/check all connections, wiring etc. Even re-run the wizard, walk through slowly. Just weird that first start, and probably 2-3 others hit so fast....

[Papa]

I'm not sure if it really matters, but Holley says to use either of the front inlet ports if you are using an external pressure regulator, so you may consider moving your connection. Again, you need to verify the pressure at the Sniper. The only way to do that is to put a gauge at the inlet. What is your idle set at? The Sniper likes to be at 850rpm or higher. If set too low, that could explain the stall condition you are describing.

If you want to PM me your e-mail address, I can send you the last good tune I had on my car when I was using the Sniper. I also have a BPE 347, so it may give you a good starting point.

[rich grsc]

But, but, but MORE = BETTER.

More, More = expensive :p

[Reddrig]

I’m looking at running the Holly internal fuel pump return-less or one line system as some call it. I’m going to run it with BP stage 2 427, has anyone run the return-less system yet? Is so any recommendations or thoughts. I like the clean look of one line and overall ease of install. Thoughts?

https://www.summitracing.com/parts/sne-19-360

[JMD]

I would recommend going with what Holley specifies. My reasoning is that 1) you don't want problems with the EFI, always wondering if it's due to your smaller than spec fuel system, 2) if you do have any problems everyone is going to tell you to fix this first before any other troubleshooting can take place, and 3) you really don't want to have to replace the lines and pump after the body is on. I had a similar dilemma but decided to scrap the FFR EFI setup and used all 3/8" fragola PTFE lines. I did use the 255lph pump in a Pro-M hanger. I've only got a ~360hp 302, but if I ever wanted more power the fuel system is already in place for it...and I will never have to wonder if my EFI is getting enough fuel.

I have heard from many sources that the Sniper is very sensitive to getting the right amount of volume and pressure to function properly. I wouldn't chance installing smaller lines and hoping it all works out since you've invested this much so far.

Oh, and I also used a return style system as that's also what they show in the Sniper setup, with the regulator on the return leg. I believe this does the best job of making sure the injectors are getting the most consistent supply and pressure possible compared to other configurations.

Good luck!

Edit: Just realized this was an old thread and my post was not really helpful to Reddrig, the most recent poster who resurrected it. Sorry I couldn't be of more help!

[PMD24]

From studying the literature that came with my BP347 that was delivered recently, my understanding is the Sniper 1 has an internal regulator, and the Sniper 2 requires an external regulator. Both show a return to the tank. For the Sniper 2 it says you can connect the pump supply to either port on the passenger side of the throttle body. The remaining port is connected to either inlet (upper ports) of the regulator. The remaining upper port on the regulator is plugged and the bottom port of the regulator goes to the tank return. In this configuration, the regulator maintains pressure at its inlet by relieving to the return. This results in essentially equal fuel pressure to both ports of the throttle body. Here's a diagram from the Holley info.

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Hope this is helpful.

Pat

[JJK]

Since I started this thread, I will chime in on a few things. After running some calculations based on my engine, I ended up keeping the FFR supplied EFI completion kit that included 6an lines to a regulator mounted on the engine side of the firewall, a single line to one side of the Sniper, and the 4an return line from the bottom of the regulator back to the tank. I ended up adding a fuel-rated extension tube to the return in the fuel tank to lower the point where the fuel re-enters the tank to minimize the splashing and aeration of returning fuel flowing at high volume back into the tank (watch the Pro-M video do better visualize this). All works fine for my application, which is a 426hp engine for street use only.
If I were to have a bigger engine, I would feel more comfortable with the Pro-M hanger (due to the inlet and outlet port sizes as well as extended return tube) and 6an lines throughout.
Regarding deadhead vs thru-flow fuel lines, both have been repeatedly used for these builds with good results. At the end of the day, the EFI wants sufficient pressure and volumetric flow rate for the fuel. If the lines are too small, then it will require a higher powered pump to ensure sufficient volume, which will result in higher velocity of the fuel running through the lines and back into the tank. For deadhead (returnless) systems, there is actually a return line, it is just plumbed a bit different. Corvette has used a combination fuel filter/regulator for many years that is positioned close to the fuel tank and returns the fuel. This involves a very short return line and a bit more distance between the regulator and the fuel injector. The system I have (as supplied by FFR) has the regulator close to the engine for decreased risk of pressure drop, but a longer return line. To my knowledge, all modern cars use a deadhead line into port injectors to minimize the heat added to the fuel returning to the tank. The fuel pump you referenced appears to return the fuel directly from the pump, such that it is all inside the tank. I am not familiar with this system, as most on the forum use a Walbro intank pump.
All that said, for your 427, I would recommend the Pro-M hanger, a tried and true Walbro pump, and 6an lines throughout. Whether you deadhead close to the tank or close to the engine into the EFI, or run the fuel through the EFI is a personal preference as all have been utilized successfully.

[Reddrig]

Since I started this thread, I will chime in on a few things. After running some calculations based on my engine, I ended up keeping the FFR supplied EFI completion kit that included 6an lines to a regulator mounted on the engine side of the firewall, a single line to one side of the Sniper, and the 4an return line from the bottom of the regulator back to the tank. I ended up adding a fuel-rated extension tube to the return in the fuel tank to lower the point where the fuel re-enters the tank to minimize the splashing and aeration of returning fuel flowing at high volume back into the tank (watch the Pro-M video do better visualize this). All works fine for my application, which is a 426hp engine for street use only.
If I were to have a bigger engine, I would feel more comfortable with the Pro-M hanger (due to the inlet and outlet port sizes as well as extended return tube) and 6an lines throughout.
Regarding deadhead vs thru-flow fuel lines, both have been repeatedly used for these builds with good results. At the end of the day, the EFI wants sufficient pressure and volumetric flow rate for the fuel. If the lines are too small, then it will require a higher powered pump to ensure sufficient volume, which will result in higher velocity of the fuel running through the lines and back into the tank. For deadhead (returnless) systems, there is actually a return line, it is just plumbed a bit different. Corvette has used a combination fuel filter/regulator for many years that is positioned close to the fuel tank and returns the fuel. This involves a very short return line and a bit more distance between the regulator and the fuel injector. The system I have (as supplied by FFR) has the regulator close to the engine for decreased risk of pressure drop, but a longer return line. To my knowledge, all modern cars use a deadhead line into port injectors to minimize the heat added to the fuel returning to the tank. The fuel pump you referenced appears to return the fuel directly from the pump, such that it is all inside the tank. I am not familiar with this system, as most on the forum use a Walbro intank pump.
All that said, for your 427, I would recommend the Pro-M hanger, a tried and true Walbro pump, and 6an lines throughout. Whether you deadhead close to the tank or close to the engine into the EFI, or run the fuel through the EFI is a personal preference as all have been utilized successfully.

Very nice answer in detail. Thank you.

From what I understand about the Holly, it has a built in regulator. Excess fuel is returned at the unit. I know most modern cars now run these type of returnless systems. I know I have some demands because I’m running a 500 + HP motor. They claim it meets fuel demands up to 700 HP for FI. Fits a minimum of 7.250 in. to a maximum of 12.000 in. tank depth. Must be used with a non-return style system. Supports up to 700 EFI or 900 carbureted hp.

I was just wondering if anyone had real world experience with this system from Holly? Thanks again for the reply’s.

[JMD]

As PMD said, Sniper 1 had an internal fuel pressure regulator (that always seemed to be a point of failure), whereas Sniper 2 requires a separate fuel pressure regulator. Sniper 2 has no ability to regulate fuel pressure and relies on external unit to do so. If you are using the Sniper 2 either fuel supply system will work as long as you have a fuel pressure regulator that results in 58psi supplied to the fuel inlet on the throttle body unit/injectors.

[Reddrig]

As PMD said, Sniper 1 had an internal fuel pressure regulator (that always seemed to be a point of failure), whereas Sniper 2 requires a separate fuel pressure regulator. Sniper 2 has no ability to regulate fuel pressure and relies on external unit to do so. If you are using the Sniper 2 either fuel supply system will work as long as you have a fuel pressure regulator that results in 58psi supplied to the fuel inlet on the throttle body unit/injectors.

So that’s what I figured, the regulator is built into the pump on the system I referenced in the post. I’ll need to see which direction I want to go.

[Mike.Bray]

215414

I've been playing with aftermarket EFI systems since the old DFI days. Here are some additional points of interest.

Maintaining fuel pressure is critical. The ECU can only command the injectors to open for a set amount of time in ms. If you have a known open time and a known pressure the ECU knows how much fuel it injected. Change the pressure and the amount of fuel injected changes, thus changing the A/F ratio.

You want to measure the actual fuel pressure with a good quality gauge and make sure the actual pressure and the ECU are in agreement. If you're aiming for 58 PSI and it's 54 PSI either adjust the regulator or the ECU.

If you look at the diagram above you see the regulator is on the return side. This is the only way to maintain constant pressure with the injectors opening and closing all of the time. Trying to regulate before the injectors, which seems logical, will not work.

Be careful when comparing aftermarket systems to new cars, most OEMs are now using PWM on the fuel pumps so they run quieter and don't require a return line. You can do this with aftermarket systems but it's expensive.

[gbranham]

If you look at the diagram above you see the regulator is on the return side. This is the only way to maintain constant pressure with the injectors opening and closing all of the time. Trying to regulate before the injectors, which seems logical, will not work.



This may be true on the Sniper setup, but interestingly, that's not how the ProFlo4 works. There is no return line connection from the ProFlo4 fuel rail. The return is from the regulator, which is before the fuel rail. Maybe it's because it's a fundamentally different design than the Sniper2.

Greg

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[JJK]

Greg,
Your plumbing sounds identical to mine with the Sniper (per FFR instructions https://www.factoryfive.com/wp-content/uploads/2021/10/EFI-fuel-system.pdf). With my bypass regulator, it is the return side that is actually regulated, which to Mike's point, is the preferred setup. Regulate the return side not the supply side, which I suspect is how yours is also setup.

[gbranham]

Greg,
Your plumbing sounds identical to mine with the Sniper (per FFR instructions https://www.factoryfive.com/wp-content/uploads/2021/10/EFI-fuel-system.pdf). With my bypass regulator, it is the return side that is actually regulated, which to Mike's point, is the preferred setup. Regulate the return side not the supply side, which I suspect is how yours is also setup.

Mine is regulated in the feed side, just as my picture from the ProFlo4 installation instructions show.

[Blitzboy54]

You can add your own return. You can drill a hole in the hanger and close off the 1/4 line. Use a bulkhead elbow. Thats what comes with the Sniper install kit. This is the easy button if you don’t want to re run your whole fuel system

[Mike.Bray]

Greg,
Your plumbing sounds identical to mine with the Sniper (per FFR instructions https://www.factoryfive.com/wp-content/uploads/2021/10/EFI-fuel-system.pdf). With my bypass regulator, it is the return side that is actually regulated, which to Mike's point, is the preferred setup. Regulate the return side not the supply side, which I suspect is how yours is also setup.

This is true and works well as it is still regulated on the return side with a return line. My early stack systems had the supply in one fuel rail, looped around into the second fuel rail, and a regulator on the outlet of the second fuel rail feeding the return line. These were simple straight shot regulators. What the Pro Flo and my Borla system use are regulators with a bypass port for the return so it accomplishes the same thing, constant pressure to the injectors.

This is an interesting regulator from Holley that has three ports: supply, feed, and return. It comes with two springs so it will work with low pressure for carbs and high pressure for EFI so if you currently have am ancient carburetor you can go ahead and setup the fuel system for EFI and upgrade from the carb later. https://www.summitracing.com/parts/hly-12-880

[Reddrig]

Just as a side not you can also add a pulse regulator/dampner to a return less system which cleans up any pulses caused by the injectors. These pulse regulators work very well, you just need to keep them as close to the rail as possible for best practice. They make one where you can add a pressure gauge to the regulator as extra security and monitoring. I know people that run these with a one line system and have great success.

https://www.summitracing.com/parts/rdm-20-0199-06

[BUDFIVE]

This is true and works well as it is still regulated on the return side with a return line. My early stack systems had the supply in one fuel rail, looped around into the second fuel rail, and a regulator on the outlet of the second fuel rail feeding the return line. These were simple straight shot regulators. What the Pro Flo and my Borla system use are regulators with a bypass port for the return so it accomplishes the same thing, constant pressure to the injectors.

This is an interesting regulator from Holley that has three ports: supply, feed, and return. It comes with two springs so it will work with low pressure for carbs and high pressure for EFI so if you currently have am ancient carburetor you can go ahead and setup the fuel system for EFI and upgrade from the carb later. https://www.summitracing.com/parts/hly-12-880
Mike, yes the Holley 12-88X 3 port regulators are useful. I’m using an in tank 255 lph pump and a 12-887 (4.5-9psi) reg since I’m using as you say an ancient carb:) It is footprint compatible with the 12-886 (15-60psi) so if I ever want to change to EFI it’s a simple regulator swap. They are <$100, 1/2 the money of the one with both springs. For completeness, both the supply and return lines are 3/8” (6AN) with the feed port going to the carb fuel log (rail). I designed my system this way so I had this upgrade path and since the cool fuel supply of a return system helps prevent vapor lock in the Texas heat.

[Mike.Bray]

My doctor keeps telling me to cut down on carbs:rolleyes:

[rich grsc]

Bad for your health & performance. ;)

[MakoGT350]

Working on a similar build - MK5 complete kit with BPE 347, sniper 2.
Using the FFR EFI kit and the BPE stuff.

One thing I can't seem to find is whether the regulator needs the manifold vacuum or not. I have read through several threads here and find no mention either.
Appreciate any input you can offer.

[Papa]

You don't need a vacuum reference unless you are boosting the engine.

[JJK]

Papa, I am not so sure about that. The Sniper 1 had an internal regulator, but with Sniper 2 an external regulator is required (not just belt and suspenders). Folks on the Holley forum have argued both ways. It appears it may be ok to run without vacuum, but it is preferred to maintain stable pressure throughout the range of RPM. But, the ECU needs to 'learn' with the plumbing in place, so it is not recommended to change from one to the other unless you have the ECU relearn things. I have a vacuum line running from my manifold to the regulator and things work fine.
Sniper 4150 external fuel press regulator. - Holley Performance Products Forums (https://forums.holley.com/forum/holley-efi/sniper-efi/391386-sniper-4150-external-fuel-press-regulator)

[Papa]

Papa, I am not so sure about that. The Sniper 1 had an internal regulator, but with Sniper 2 an external regulator is required (not just belt and suspenders). Folks on the Holley forum have argued both ways. It appears it may be ok to run without vacuum, but it is preferred to maintain stable pressure throughout the range of RPM. But, the ECU needs to 'learn' with the plumbing in place, so it is not recommended to change from one to the other unless you have the ECU relearn things. I have a vacuum line running from my manifold to the regulator and things work fine.
Sniper 4150 external fuel press regulator. - Holley Performance Products Forums (https://forums.holley.com/forum/holley-efi/sniper-efi/391386-sniper-4150-external-fuel-press-regulator)

It's my understanding that a vacuum reference on a throttle body injection is only needed if the injectors are located below the blades like on the Terminator throttle bodies. The Sniper 2 places the injectors above the blades. Look at posts 11 and 12 in this thread linked to the one you posted:

https://forums.holley.com/forum/holley-efi/terminator-efi/3397-holley-fuel-pressure-regulator-question#post68247

[bobl]

Running the vacuum line to the regulator in a N/A application does a couple of things I can think of and probably some I can’t. It lowers the fuel pressure by a few lbs. under high vacuum (idle and cruise) taking some load off the fuel pump as this is where street engines spend most of their lives. Secondly it causes the ecu to increase pulse width to compensate for the lower pressure. The larger the injector the harder it is to control at very short pulse widths. So this aids in achieving a bit more control of the A/F under these conditions. I personally don’t run it with aftermarket efi systems because it skews the fuel usage data when logging it, which I look at a lot when dynoing and tuning. In most cases you define the fuel pressure in a parameter and that is used for all calculations. If it fluctuates the data is not correct. This is also true with Sniper. Of course this doesn’t apply to the modern day PWM fuel systems.

Bob