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My 03 is NA with 30lbs injectors, SVT focus pump. It has TFS heads and comp 270 cams. I was thinking of going to a return style fuel setup since it’s just plan better than returnless for tuning and drivability. Is the conversion really worth the money? Seen guys swap a 98 hat/assembly and use a C5 vette fuel filter and would have two lines go to that filter and call it return style, not going all the way to the rails. Do you keep the FRPS. Do you have to get another pump? What is a budget friendly setup?


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I don’t think the stock FPS would work anymore because you wouldn’t vary the pump speed. The corvette filter would make it return, but that puts the pressure at 58psi. There would be no regulator needed as its internal to the filter. You could do that as long as you retune for the injector psi. Then I think you tune for the fpdm to run 100% instead of changing pump speed. I’m not entirely sure on that part though.
 

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you have to be careful. You can induce new problems doing this. My 95 would boil the fuel after driving for a long time and I switched to a deadhead system to fight this. For me it was the right move. I can now drive my car for hours without the fuel getting really hot.
 

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Never heard of the deadhead fuel setup. What does it consist of?


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its a fancy term for returnless but mine isnt truly returnless. The pump runs all the time like any OBD1 mustang but the regulator is in the back of the car so the fuel never goes into the hot engine compartment until is about to be used. The whole recirculation length is less than 3ft. I just have a feed line going forward that connects to both rails through a nice Y adapter. With a return style, 95% of your fuel is being returned to the tank when cruising and this happens over and over and over and when you have a big intank pump its happening faster than it would with a stock pump. The turbo just added so much underhood heat combined with recirculating constantly through the engine compartment, the fuel would boil after 1 hour of driving on the interstate. I tested it this year with a 2 hour drive and it didnt boil. Im pretty confident i fixed it.
 
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With my coyote swap, I’ve got a 340lph pump in the tank. It’s a return setup with an adjustable regulator. Feed line to one side of the regulator, the other side of the regulator feeds the rail, then the regulator returns from the bottom. I had an external pump and after 3-4 hours it would vapor lock and kill the car. I went to the in tank pump and have so far gone on a 6 hr trip, almost 80mph the whole time and no issues. The fuel keeps the pump cool.
 

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Never heard of the deadhead fuel setup. What does it consist of?


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A deadhead is a returnless system.

Here's the best read on how to setup a return system to minimize hot fuel issues:

The best way to set up a returnless is to have excess fuel return to the tank before entering the engine compartment where the excess fuel may soak up engine heat like in the bottom view. The top image is a modified deadhead system but is becoming the standard for what is considered a deadhead. The bottom image has all fuel going into the engine compartment before returning to the tank which causes the fuel to absorb heat from the engine.
Rectangle Font Parallel Slope Diagram
 

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FPR = Fuel Pressure Regulator
 

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Unless you can't meet the fuel flow, stick with returnless. There is no disadvantage to returnless outside of your options for pump/flow requirements.

When you run a return style, you are still in essence deadheading the pump. The difference is, instead of varying the speed to reduce the pressure, you have a mechanical device that opens and relieves pressure to ensure a constant pressure. The flow is still blocked to an extent. By having the pump produce work on the fluid, for it to return to the tank to not do any work, creates heat. This is why when you see a simple hydraulic circuit that doesn't have a variable displacement pump, you have either a massive oil cooler or you have a bypass circuit that allows the pump to move fluid at near zero pressure.

On a returnless style system, you vary pump speed to maintain pressure. Near 100% of the work done to the fluid, the fluid immediately returns back into the engine. You basically have a variable displacement pump, but done electrically vs. strictly mechanically. The automakers did this not only to save money on piping, but also to minimize making the fluid hot since returning fluid that was once pressurized back to the tank will do more to heat the fluid than a quick run around the engine. Doesn't help to run around the engine bay, but you get a significant reduction in heat by only pumping the amount of fluid you need.

Again, unless you need more flow than what can be provided with a returnless style, you will actually be making a big compromise by going to a return style. The only downside again to returnless is the component selection to provide necessary flow is limited. That said, between dual GT/Cobra pumps, that line when a return style becomes necessary is very high.
 

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Keep the returnless.
 
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