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Thread: New Project Dual Quad Sniper - Fuel System Question

  1. #1

    Default New Project Dual Quad Sniper - Fuel System Question

    Hi Guys. Parts are arriving for the latest project. Swapping out the old carbs for a Sniper Dual Quad EFI (550-527). It's going on a cross ram, and I've already identified a couple of areas that need to be modified from the tunnel ram design (reconfiguration of throttle brackets and longer connecting wires). Those will be other threads later.

    My first question was around fuel system for the car. Car already has an Aeromotive A1000 pump. Curious if I should run -10AN line all the way to the engine and split it to the two -6AN feeds to the throttle bodies and a -8AN return? It's a big block Chevy with a healthy roller cam. I wanted to make sure the dual throttle bodies were fed with enough fuel volume, but wanted to get feed back if it was overkill or would cause any other issues. RPM range won't be too crazy, but l'll be shifting 6500/6800 range. EFI is a bit new to me so I'm sure this is the first of many questions. Thanks in advance.
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  2. #2

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    No, you don't need a #10 fuel line. Actually a #6 fuel line is all you need, but you could use #8 if you want. You won't need a return line if you put the regulator in the back of the car. Use Holley 12-876 and mount it next to the fuel pump with a short return line back to the tank and that's all you need. Just plug the return ports on each Sniper. The front Sniper doesn't have a crossover, so you need to make sure you feed both sides.

  3. #3

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    It really depends on how much HP you want to make. I don't feel like getting into now, but there's a lot of information on the internet about calculating what your asking. Look into BSFC: https://en.wikipedia.org/wiki/Brake-...wer%20produced.

    Not exactly what your looking for, but another cool article in the ballpark of your question:
    https://www.dragzine.com/tech-storie...eans-big-fuel/.

    As you can see, a lot goes into your question. The easiest answer is to talk to people who have similar setups and find out what works for them. The toughest solution is to start doing the math and it's going to start with calculating the power potential of your engine.

    In short, if your planning on making below 600 HP, naturally aspirated without power adders, and on high test pump fuel, -6AN will be fine. Above 600 HP and below 800 HP, naturally aspirated without power adders and on high test pump fuel, I would go with -8AN and then split to -6AN. If you start playing with power adders and/or types of fuel that require much richer mixtures then of course the formula changes.

    Some people just want a simple answer and others want to figure it out. If you just want a simple answer, it may be best to just pay someone who knows how to calculate it, so you don't have to use your brain power for what's not your forte/money maker.

  4. #4

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    Andy & ABC, thanks for the help. It is a healthy setup, not 1000 HP, but north of 600. With Carbs, I would run the -8 or -10 and split it at the dual carbs. Carbs are pretty easy, not a ton of pressure required and they are happy as long as they're fed. My concern came in with if the added volume of -10AN would impact ability to maintain pressure or cause any other hiccups when it came to the EFI.

  5. #5
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    The difference is 7-9 psi (carburetor) versus 43-60 psi (EFI) fuel pressure. EFI high fuel pressure doesn't need those large diameter hoses.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  6. #6

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    @Imanut: You don't need #10, but if the car is already plumbed with it you could use it. If you're plumbing the car from scratch then follow my advice from above. One #8 high pressure line from the back with no return line. That's the easy solution.

  7. #7

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    I run the dual Sniper setup on a 427. -8AN from a tank mounted pump (80+ psi) to the regulator (60 psi) in the engine bay. -8AN return from the regulator to the tank. There's a crossover on both Snipers, so a single -8AN to both Snipers from the regulator. No loss of pressure at RPM peak.

  8. #8

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    @Ken: This is a little off topic, but I have to ask, how much HP are you making?

    If I read and understand your setup correctly, you're not going to see a pressure loss at the regulator if your only measuring the pressure from the pump/tank to a regulator mounted/plumbed before the injectors.

    I assume your system is working fine, but for all else looking, the regulator in this type of system should be after the injectors. If the regulator is before the fuel rail or injectors your not accounting for increased fuel demand when pulse width and duty cycle increase.

  9. #9

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    You're correct. I looked into this quite a bit with many systems plumbed both ways. Since it was this way with the carbs, but at 7 psi, I kept it the same with the EFI (I've had the in-tank HP pump for awhile). I've seen no lean situations or unusual duty cycle increases beyond normal at this point, but haven't had it on a dyno. Guestimate on horsepower would be just north of 500. Online horsepower calculator says 600, but that seems rather overly optimistic.

  10. #10

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    My car that has the Sniper in it was setup as a drag car originally. So it had a #10 fuel line and a #8 return. I left both in place when I switched over to the Sniper. It works fine, it's just much larger and heavier than it needs to be. When I built by second car I used a single #8 line and put the regulator in the rear of the car next to the fuel cell. I might eventually convert my first car over to a self contained pump module inside the gas tank and get rid of the #10 line. I'll just use the existing #8 return line as my pressure feed line and pull the #10 line out of the car.

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