[LKLusza]

Hi All,
NOTE: First, I want to acknowledge 63 bomb ohc and Danny Cabral, the forum moderator, over on the Holley Sniper forum for their help. I’m just sharing what I learned from them during my EFI install that may be of help to anyone else considering a dead head fuel setup for their EFI installation. I’ll include links to those conversations at the end of this post.

Most of the standard throttle body EFI setups out there operate at about 58psi. Mine happens to be a Holley Sniper Spread Bore unit. Fuel can be supplied to it in one of two ways. One is by using an electric pump with a regulator and a return line back to the tank just like the directions show. The second is called a “dead head” configuration. Given that my GTO came equipped with a brand new 3/8” factory replacement fuel line, I wanted to repurpose that in a dead-head configuration. It takes a bit more work, but will allow you to retain a more stock or stealthy look under the hood which is what I wanted.

To help make this happen, Holley produces an in-tank pump/regulator module. My GTO uses model 12-303. It replaces your stock fuel pickup and sending unit. The Hydramat pickup sock, fuel pump, regulator, and fuel return, are all on the pickup tube along with a new float and sending unit, inside the tank. So, no drilling holes in your stock fuel tank for return lines. This setup allows you to run a single rubber fuel line all the way up to the throttle body or, if yours is really clean like mine, re-use the stock steel line. However, using hard lines like I did is where you can potentially run into mischief, and it all has to do with maintaining consistent fuel pressure to the throttle body.

It seems that at 58 psi (or any pressure really) the injectors opening and closing at however many hundreds of times per second, produce pulses in the fuel flow. As these pulses race back and forth through your fuel lines they will collide and can inhibit the flow of fuel. It will show on a fuel pressure gauge as fluctuations by as much as +/- 20 psi. Imagine your EFIs CPU trying to deal with the changing pressure and you have an engine being nervous and jerky, and not happy at all. Running full length rubber fuel line will likely avoid this issue as the rubber hose can expand and contract like an artery, absorbing and attenuating the pulses, resulting in more consistent pressure and flow of fuel acceptable to your EFI.

On the other hand, steel lines behave like a megaphone. They transmit the pulses strongly without absorbing anything. It’s very much like the “water hammer” effect in your household plumbing. Run your faucet wide open and then slam it shut and you’ll hear the plumbing reverberate with the shockwaves from the water trying to stop its forward motion. Now imagine that at up to hundreds of times per second (Yikes!). To combat this phenomenon, you need to include a fuel pulse dampener in your fuel system if you're considering the use of large amounts of hard line.

Generally speaking, the pulse dampener should be mounted as close as possible to the injectors in your throttle body. It can be prior to the TBI so that fuel passes through it before going in. Alternatively, you could mount it to the TBI’s return port and put a cap on the unused end of the dampener. Either method will expose it to the pulses no matter what, and still be as close as possible to the injectors.

The dampener I chose was from Radium Engineering. My dead head plumbing install using the factory steel fuel line works perfectly with rock steady fuel pressure. With the air cleaner assembly on, no one is the wiser (except for the fuel pressure gauge peeking out from under the side of the air cleaner).
Links:
1) https://forums.holley.com/showthread...raJet-Question Post #7 shows pictures of my completed installation.
2) https://forums.holley.com/showthread...ight=quadrajet
3) Radium Engineering: Universal Fuel Pulse Dampers (radiumauto.com)

[Scott65]

Good info, thanks for sharing. Can the Holley sniper units make use of PWM pump control? Or if you use a separate controller, I guess it wouldn't know as long as it maintained 58 psi in all conditions? That's another method for non return fuel delivery.

[LKLusza]

Originally Posted by Scott65

Good info, thanks for sharing. Can the Holley sniper units make use of PWM pump control? Or if you use a separate controller, I guess it wouldn't know as long as it maintained 58 psi in all conditions? That's another method for non return fuel delivery.

Hi Scott64,

I'm pretty certain that the Holley Sniper Spreadbore does not use PWM. I do know that the FiTech units do. I had one on my last street rod. Unlike the Sniper Spreadbore, they have a built-in regulator on the throttle body, so the ECU uses that data to throttle the pump via PWM.

[67Fbird]

i was under the impression that dead head was a NEGATIVE system. Meaning less than desirable as the LAST injector in the system was shorted actual discharge volume. A CON to the return /regulator is the fuel "agitation" which has an effect on gasoline...?? but a PRO to the RETURN layout is the fresh "cool" fuel in the incoming line???? balance beam stuff with a multiport system maybe not so much with 4 injectos located with the confines of a carb body???? IDK

[Scott65]

I think the answer is "it depends". Usually a priming pulse will purge any air out. Dead head is not inherently bad, depending on how it's accomplished. PWM dead head is what I'd choose. (Haven't accomplished it yet on mine) When you talk about a return system supplying cool fuel, that's another it depends. It can in certain circumstances heat the fuel over longer periods.

[JLMounce]

Agree with Scott on this. There are positives and negatives to both.

As mentioned a true dead head system using a PWM controlled pump works pretty well in both ease of installation and pressure across the injectors. On the FiTech, the built in regulator is the last item in line, so dead heading this system will solve any "holes in a hose" issues with the dead head system. Having a PWM pump driver also means you can put the pump in the tank, wire it and run a single line as a true dead head.

The other option if you can't run this type of setup is to run what is commonly referred to as a "Corvette" setup. This is not a true dead head configuration as a return line still exists. In this configuration there is a fuel filter/regulator that is plumbed, typically right near the tank. The filter/regulator splits the fuel to an upstream dead head as well as a return. In this configuration because the regulator is passing fuel to the fuel rails and as a return you can maintain line pressure at the fuel rails be increasing or reducing the flow rate in the return line.

This is how you would want to run a dead head style system without use of a PWM pump driver, or with a pump like a walbro 255 which is not designed to be sped up and slowed down based on fuel need.

What you want to avoid with any type of dead head system is having a pressure regulator that exists before the fuel rail. That's when you get the "holes in a hose" effect working against you.

[LKLusza]

Originally Posted by 67Fbird

i was under the impression that dead head was a NEGATIVE system. Meaning less than desirable as the LAST injector in the system was shorted actual discharge volume. A CON to the return /regulator is the fuel "agitation" which has an effect on gasoline...?? but a PRO to the RETURN layout is the fresh "cool" fuel in the incoming line???? balance beam stuff with a multiport system maybe not so much with 4 injectos located with the confines of a carb body???? IDK

I think it would depend on your intended use. Agreed - a dead head setup like I have is absolutely worthless for racing or any other max power activities. Since my car is a cruiser with the occasional "back road blast", I was instead looking for a carb replacement that is infinitely adjustable and dependable; that can provide power on par or better than the original carb. As a bonus, a dead head configuration contributes to preserving the stock look as much as possible - something that is important to me.

Certainly, there is a benefit to cool fuel always coming through the throttle body. However, the unused fuel sent back will have absorbed heat from the engine bay, and slowly heat up the entire fuel supply in the tank.

I also agree that the balance issues experienced by some multiport systems would most likely not apply to a throttle body setup w/ 4 injectors. They are very close together, and the total volume of the internal passages between them is so small that I don't see even heat being an issue. The fuel would spend too little time in the passages to absorb enough heat to be problematic before hitting the injectors. The Holley kit includes a 1/4" thick heat spacer to help combat any under hood heat issues and, so far, seems to be working very well on my engine.

Also consider this: While a dead head setup may not be the "preferred" method, this setup was standard on C4 Vettes. The only difference was that they used a fuel filter w/ built-in regulator. With the filter/regulator mounted on the frame, close to the tank, the return was as short as possible yet still allowed for a single feed line forward to the engine compartment. Sort of dead head-ish. Those Vettes also used a multiport injector format and did, in fact, use a pulse damper too. Again, those cars were certainly not fire-breathing monsters, but they were reasonably powerful, reliable and efficient.

[Scott65]

Deadhead is standard on many in recent years.

[KS circutguy]

Great info,
However I would not recommend a long run of regular rubber fuel line.
NHRA and IHRA rules limit rubber fuel line to 3 ft. if memory serves.

Changed the tank to regulator on my old Bird from braided stainless (started seeping fuel fumes after 6 yrs.)to Aeroquip
910 PTFE Lined Aramid Braided Lightweight Racing Hose.
Goodridge G-Line XF 910 hose was developed with professional racing teams who needed a super-flexible, ultra-lightweight fuel hose with excellent flow that wouldn't collapse under vacuum.

The anti-static PTFE liner is compatible with all types of racing fluids (coolant, oil, brake fluid) and ALL types of fuel (gasoline, diesel, E85, alcohol, and nitromethane). It is also fully resistant to fuel vapor penetration. Unique semi-corrugated liner design is much more flexible than other types of hose, but the smooth bore retains optimum flow. The hose ends (sold separately) require no special tooling to assemble, so you can build hoses at the track. Black Aramid braid has a yellow strand for easy identification. 910 hose is specifically listed by the NHRA as an approved Woven hose type.

https://www.pegasusautoracing.com/pr...p?Product=3490

[krisr]

One thing to remember with OE "dead head" systems, there is still a fuel pressure regulator at play, it's just inside the fuel tank which helps drive the fuel syphon circuit to pickup fuel at the bottom of the tank.

With my fuel system in my car, it's "dead head" with 1 line going to the front of the car from the regulator and the return going through the ethanol sensor back into the tank. I just mounted the fuel regulator down the back next to the fuel cell. I set the regulator at 65psi but I use a PWM module to slow the primary pump down to 45psi and raise the pressure with RPM. The regulator is just a fail-safe if the PWM module fails and locks on.

Mine is also a dual pump setup, the second pump switches on when pressure goes under 50psi when over 3500rpm, mainly for e85 use.

[JLMounce]

Originally Posted by KS circutguy

Great info,
However I would not recommend a long run of regular rubber fuel line.
NHRA and IHRA rules limit rubber fuel line to 3 ft. if memory serves.

Changed the tank to regulator on my old Bird from braided stainless (started seeping fuel fumes after 6 yrs.)to Aeroquip
910 PTFE Lined Aramid Braided Lightweight Racing Hose.
Goodridge G-Line XF 910 hose was developed with professional racing teams who needed a super-flexible, ultra-lightweight fuel hose with excellent flow that wouldn't collapse under vacuum.




https://www.pegasusautoracing.com/pr...p?Product=3490

Just want to point out that you wouldn’t run standard hose for EFI anyhow. It won’t hold up to the pressures.

Pressure rated fuel line like an earls push-lock will pass tech, at least down to 11.59. I’ve had push like mine on my bird without issue since 2015.

You might have a run of regular fuel hose if you’re running a frame mount fuel pump near the tank. I’m not a fan of that type of deal.

[grivera]

OP - how accurate is the fuel pressure gauge and what brand?

Originally Posted by JLMounce

What you want to avoid with any type of dead head system is having a pressure regulator that exists before the fuel rail. That's when you get the "holes in a hose" effect working against you.

Can you elaborate on this? I had planned on reconfiguring my fuel lines on my Sniper. Currently I have a supply/return to and from the throttle body using the Sniper internal regulator to maintain PSI. My plan was to remove the Sniper internal regulator and install a return style regulator - the Trickflow 27001 Universal Bypass Regulator (see below) at the block-off plate that covers the factory mechanical pump hole. I'd run a supply/return up to the regulator and then the single line to feed the TB. Would this be a problem?

https://www.trickflow.com/parts/tfs-27001

[Scott65]

Better to run through the TB to the regulator and return from there.

[LKLusza]

Originally Posted by grivera

OP - how accurate is the fuel pressure gauge and what brand?

Hi grivera,

I used an Earls liquid filled gauge: https://www.holley.com/products/fuel...arts/100187ERL. IMO the liquid gauges are safer and more accurate than the dry ones. As far as accuracy goes, I can't say as it's the only one I have. I know that I haven't had any problems with it and it does seem to be on the mark.

[JLMounce]

Originally Posted by grivera

OP - how accurate is the fuel pressure gauge and what brand?



Can you elaborate on this? I had planned on reconfiguring my fuel lines on my Sniper. Currently I have a supply/return to and from the throttle body using the Sniper internal regulator to maintain PSI. My plan was to remove the Sniper internal regulator and install a return style regulator - the Trickflow 27001 Universal Bypass Regulator (see below) at the block-off plate that covers the factory mechanical pump hole. I'd run a supply/return up to the regulator and then the single line to feed the TB. Would this be a problem?

https://www.trickflow.com/parts/tfs-27001

Yeah I wouldn't recommend that. What is occurring there is that your pressure reference to your ECU is happening before any fuel is delivered to your injectors. Your ECU thinks the injectors are receiving 43-58 psi (depending on regulator type, run state etc.) but because the pressure is indexed prior to the injectors, which each successive injector pulse in line, you lose a little bit of line pressure in the fuel rails.

The fuel rail in a Sniper/FiTech is pretty small, so I can't honestly say how big of an issue this would be, but it's certain in this type of setup that the final injector in line will not have the same amount of pressure as the first injector.

Placing the regulator after the final injector allows the regulator to account for those holes (injectors) in the fuel rail.

[grivera]

Thanks for the detailed response!

[Formulajones]

Actually, I've been running the fuel system like described for a couple years now on 2 different cars and it works absolutely perfect.

To start with, I prefer a return style system, always have whether it's a carb or EFI.

To plumb the EFI, I use a 13301 return style Aeromotive regulator. I hide that regulator in the engine compartment. Usually somewhere near where the original mechanical fuel pump resided and run a full length return from there.

From the regulator I run either a stock appearing fuel line or hide the -8 braided to keep a stock appearance. Either way, it's a single line coming up to the Sniper.

2 other things I do is put a pressure regulator sensor at the Sniper unit and monitor fuel pressure at the EFI unit. Not down where the regulator is.

The other thing I do is install the Radium dampener that the OP mentioned earlier, which is excellent at stablizing the pulse issues you get from injectors opening and closing.

There are no drawbacks to running the fuel system this way as far as worrying about running fuel flow through the unit trying to equalize pressure to all the injectors. In fact in the Holley instructions it tells you this EFI unit is designed to be plumbed this way if desired, it's why this particular unit doesn't have a regulator built in on the EFI unit itself.
That's what makes it stealthy as you don't need a bunch of fuel lines running in and out of the EFI which is nearly impossible to hide. In fact, I didn't have to change my fuel lines at all when I installed the Sniper Stealth. I already had the system plumbed this way with the carb on it and a big pump in the tank. I just simply hooked the fuel line to the Sniper and it was off to the races.

One other tip I got from Chris at EFI System Pro, since I run a boost referenced fuel pressure regulator, even though I don't run boost, Chris recommended I run the vacuum line to the engine anyway. The vacuum readings at idle and light cruise tame the fuel pressure a bit and will give more accurate fuel delivery in those light load conditions where a bunch of fuel isn't necessary. Doing this really calmed things down in the fuel tables.

[Formulajones]

Here is a picture that helps describe, and gives an idea, what can be done with the Stealth setup and why I chose this unit specifically. However, this can be done with any EFI unit that uses an external regulator.

I run a return style fuel system, but it's only returned from the regulator back to the tank, and the regulator is hidden in the engine compartment. The feed line to the EFI from the regulator, is dead headed at the EFI unit, which is a short run.

This allows a lot of things but what I did with it, is put a mechanical fuel pump and the factory steel lines back in place to make it appear as though it still has a carb on it. It's all non functional of course but complete and intact just as I used to run the car back when it was fueled by the mechanical pump.

The main fuel line to feed the unit is hidden. No need with this system to run a fuel line in and out of the unit and back to a regulator. That would be nearly impossible to hide and completely out of the question for what I wanted to accomplish. This engine makes a pinch over 600hp and it's been flawless and easy to tune.

I plumbed dad's car the same way and his makes over 700hp with the same setup. No tuning issues or funky injector problems or pressure readings.

Can't believe it's been a couple years already since the switch on both cars, seems like yesterday.

[Scott65]

FJ, I feel like you really should highlight boldly the section about the pulsation dampener. Without that it reverts back to being a way that's been recommended against for a long time.

[Formulajones]

The pulsation dampener is something I added to both cars maybe a year after the systems were up and running.

I did that to stabilize the fuel pressure readings at idle, which is primarily what that is intended for.

The odd thing is that the autometer mechanical gauge I ran on both cars was rock steady at idle. Ran and drove perfectly, you'd never know it was any kind of issue. It wasn't until I later switched over to a Holley sensor to monitor fuel pressure through the Sniper that I noticed the fuel pressure fluctuating at idle. Cruise was fine. I quickly found out that the injectors open and close so fast at idle it causes a pressure wave. The Holley sensor is so sensitive it picks it up, where as the mechanical gauge never did. At cruise it's gone as injector pulse width increases.
So I installed the dampener which settled down the fuel pressure pulsing at idle. I didn't notice any drivability change or see any need for fuel table changes at all, as the correction was still only 1-2% so I left it alone.

It's just nice to have the fuel pressure steady at idle so I don't think there is something wrong with my eye balls