Sniper Plumbing

[B767]

If you want the fuel pressure regulator located at the rear of the vehicle, so you only
have to run one fuel line all the way to the engine compartment, you can use this:
http://documents.holley.com/199r11014.pdf (Holley EFI 12-875/12-876 Filter/Regulator)

It's been discussed on this forum before. It's not a good idea for every application. There's still a return line, it's just very short, since the fuel pressure regulator is located at the fuel tank. It only works well on mild performance naturally aspirated applications. Unless it's nitrous oxide, a forced induction engine (turbo/supercharger) requires a boost referenced fuel pressure regulator. And because it's not a vacuum/boost referenced FPR, the Base Fuel Table lb/hr values will be skewed under & above WOT (zero vacuum/100 kPa).

I prefer a vacuum referenced fuel pressure regulator in the engine compartment:
https://aeromotiveinc.com/frequently...fi-regulators/ (Aeromotive EFI Fuel Pressure Regulator FAQs - Read Question #8!)
http://aeromotiveinc.com/wp-content/..._Gauges_01.pdf (Aeromotive Tech Bulletin 903 - Liquid Filled vs Dry, The Problem & Solution)

The Terminator's fuel pressure can be safely increased to 60 psi (from 43 psi).
And with the FPR at the rear of the vehicle, it preferably should be set to 60 psi.
FYI: 60 psi may require a higher output fuel pump due to higher pressure/lesser volume:
http://documents.holley.com/holleyfu...ems_chart1.pdf (Fuel System Selection Chart)

Aeromotive (FAQs - EFI Fuel Pressure Regulators): "Be careful using a factory OEM style filter-regulator, like those used in the Corvette, if your fuel pump flows more than 250 LPH. The stock part is unable to handle the excess flow provided by high flow Aeromotive fuel pumps, causing false high pressure and reduced fuel pump service life. For high performance applications, most prefer to replace the stock “returnless” fuel rail with an Aeromotive Billet Fuel Rail."
Danny Cabral: Yes, the Holley EFI 12-875/12-876 Filter/Regulator's fuel pressure regulator (LINK) is the same type of OEM fuel pressure regulator. It's too small to support the high flow volume of a high output/racing fuel pump.

175 GPH is the flow size of the fuel filter, and it's Holley's 2nd largest fuel filter. The filter flows more than the FPR due to its size (for filter life/service longevity). You wouldn't want their 100 GPH fuel filter regardless of fuel flow, because it's too small and would require replacement more often. -8AN refers to the o-ring port thread size (3/4-18). It's large for a non-restrictive transition from filter to hose fitting. Most users will install -6AN fittings (AT985068ERL) & plumbing (LINK).

This & some of Danny's other posts almost answer my question, but I would like a clear directive for my installation.

I'm replacing a brand “X” EFI on a new build 500 HP 427. I currently have your preferred setup with an Aeromotive vacuum regulated return regulator downstream of the TBI unit. 255 LPH in tank pump with 3/8" line both directions, pressure gauge on the regulator. The current EFI is not controlling timing, I would like to replace it with a Sniper EFI in the same configuration.

My question is, how to plumb it using the Aeromotive regulator? It appears to me I should be able to use two of the fittings designated “inlets” on the Sniper for the feed & return lines, capping the fitting designated “return” where the built in regulator is, thus bypassing it. Is there any reason this would not work, such as internal valving I'm not aware of? Thanks and God bless, Brien

[351C Sniper]

Yes. You can deadhead the Sniper EFI. Be sure to use Holley or Earl's fittings for the Sniper unit, because the fittings have o-rings and traditional AN fittings don't. Use one of the three fuel inlets and plug the outlet/return. Sniper expects 58.5 PSI at the injectors. It's a good idea to verify the fuel pressure is about 58.5 PSI near the fuel inlet.

[B767]

Yes. You can deadhead the Sniper EFI. Be sure to use Holley or Earl's fittings for the Sniper unit, because the fittings have o-rings and traditional AN fittings don't. Use one of the three fuel inlets and plug the outlet/return. Sniper expects 58.5 PSI at the injectors. It's a good idea to verify the fuel pressure is about 58.5 PSI near the fuel inlet.

Thanks, but that is not what I asked. Most manufacturers, including Holley, recommend plumbing TBI injection units upstream of the regulator. Fuel should flow from the in tank pump (through a 10 micron filter) to the fuel rails (internal on TBI) to the regulator and back to the tank. This arrangement results in the most stable fuel supply pressure to the injectors. Although it will work, they do not recommend deadheading as an ideal setup, a return system is preferred.

My question is, can I do this by routing the fuel into one of the inlets and out another one of the inlets to my external regulator, thus bypassing the internal regulator? There is no reason this would not work UNLESS there is internal baffling or a one way valve that I am not aware of. Anyone have any concrete information on this? I would like it plumbed this way for four reasons:
1. I trust the Aeromotive regulator more. (See one of Danny's links above.)
2. My Aeromotive regulator has a gauge.
3. A vacuum compensated regulator is preferable. (Again, see Danny's post above.)
3. My system is already set up this way.
Thanks for any info you may have to share on the subject.

Yes. You can deadhead the Sniper EFI. Be sure to use Holley or Earl's fittings for the Sniper unit, because the fittings have o-rings and traditional AN fittings don't. Use one of the three fuel inlets and plug the outlet/return. Sniper expects 58.5 PSI at the injectors. It's a good idea to verify the fuel pressure is about 58.5 PSI near the fuel inlet.

Can I run a return system using two of the inlet ports?

[Matt]

Thanks, but that is not what I asked. Most manufacturers, including Holley, recommend plumbing TBI injection units upstream of the regulator. Fuel should flow from the in tank pump (through a 10 micron filter) to the fuel rails (internal on TBI) to the regulator and back to the tank. This arrangement results in the most stable fuel supply pressure to the injectors. Although it will work, they do not recommend deadheading as an ideal setup, a return system is preferred.

My question is, can I do this by routing the fuel into one of the inlets and out another one of the inlets to my external regulator, thus bypassing the internal regulator? There is no reason this would not work UNLESS there is internal baffling or a one way valve that I am not aware of. Anyone have any concrete information on this? I would like it plumbed this way for four reasons:
1. I trust the Aeromotive regulator more. (See one of Danny's links above.)
2. My Aeromotive regulator has a gauge.
3. A vacuum compensated regulator is preferable. (Again, see Danny's post above.)
3. My system is already set up this way.
Thanks for any info you may have to share on the subject.

Can I run a return system using two of the inlet ports?

Yes you can, and the way we suggest to do it is on page 12 of of the Super Sniper Instruction Manual. Super Sniper Instruction Link
Feed from one of the front ports, and return from the other front port. Cap the two ports on the rear when using an external fuel pressure regulator. Matt

[B767]

Perfect, thanks Matt.