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Regulator placement -- EFI setup

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Old 04-28-2012, 01:49 PM   #1
notenoughcash
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Regulator placement -- EFI setup

Looking at options for fuel regulator placement, it's the last thing I need to sort out to finish shopping list for plumbing parts, as expensive as that is, don;t want to buy any more than I need.

Accel EFI (full sequential)
Mallory 11106M Compact pump (pre and post filters in place)
Mallory 4305M Regulator
-10 AN feed line, -8 AN return

Option 1a
Feed from pump to one fuel rail. Crossover at back of manifold to other rail. Come off of second rail to input of regulator, return to tank

Option 1b
Feed from pump to Y-block to both rails, feed from back of both rails to Y-block into regulator, return to tank (this was someones suggestion locally, to me it seems like it would be done more for appearance and just costs more in plumbing parts)

Option 2
Feed from pump to regulator, feed both fuel rails independently from regulator, return from regulator to tank

Option 1a seems like the choice given most factory setups are this way, just wanted to see what others opinions are here and if there is a better way to do it.
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Old 04-28-2012, 02:24 PM   #2
MRL Performance
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Option 1a is how we ran it on the dyno. Easy and effective.
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Old 04-28-2012, 06:08 PM   #3
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1a it is....worked out easiest to draw up, it works and saved a few $$ in the plumbing costs
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Old 04-29-2012, 09:00 PM   #4
The Toad
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I ran the Accell Gen 7 on one of my projects. I did plan 1a. Pump to rear fuel rail. Crossover at front fuel rails and regulator at rear fuel rail that returned to tank. I had no problems with this set up.
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Old 05-01-2012, 02:48 PM   #5
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Option 1aa would be simplest - fuel pump to regulator w/ return to tank, then single line to TBI. No need to run up and back to TBI and that saves a lot of plumbing. Indeed, since ~2000 new cars must have a "return-less" system, i.e. a single fuel line to the engine for less emissions from hot gas. If you run 3/8" tube from reg to TBI, should be minimal pressure drop. For an inexpensive reg, many people use the Corvetter filter/reg (19 O-Reilly's) which maintains a fixed 56 psi if that works w/ Accel's TBI. Has 3/8" quick-connects. I use on my Dart.
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Old 05-01-2012, 03:26 PM   #6
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As several slanters running port injection over at .org have stated, running the regulator after the injectors, but before dumping the excess fuel into the return line (like most factory systems not having the more complicated pumps required when there is no return line) per example 1a above, works best and saves some tuning headaches.

Last edited by twofosho; 05-02-2012 at 01:18 AM.
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Old 05-01-2012, 04:14 PM   #7
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No matter how you choose on an efi system you want the regulator placed after the fuel gets to ALL of the injectors. Guys have run lean not doing it like that especially on boosted applications.

I ran a 10 an feed to 8 an Y, brought those two 8an lines to the front of the fuel rails, mounted the regulator on the back of the pass side fuel rail then the drivers side on the back of that rail I ran an 8an cross over back to the regulator with an 8an return. I am using 3 walbro GSL-392's that are good for over 1400 Boosted EFI HP. 1 pump comes on to start, second one at 3PSI and the 3rd one at 8PSI controlled by a Mega Squirt MS3 extra.
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Old 05-04-2012, 02:17 PM   #8
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You guys are losing me and I am an engineer who has published papers on fluid flow. As long as there is minimal pressure drop due to flow from the regulator to each injector, all injectors will see the regulated pressure. At 1400 HP, there may be enough fuel flow that you need 1/2" tubing (haven't calculated), but most people should be fine with even 5/16" tubing. In current cars, the regulator is at the tank and most use 5/16" tubing to the engine.

If the fuel gets hot and turns to vapor in the lines, you could get a distribution problem, but unlikely at >50 psi, especially once flowing. With smaller tubing, the fuel passes thru the tubing faster so less heating.
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