FI fuel upgrade options

phunk

You are right that the return system is the strongest solution to pressure drop. Tuning around a pressure drop can be reasonable if the pressure drop is extremely mild and consistent, but these are rare qualities of pressure drop. Once a piece of the system has reached the edge of its capacity, it will generally be pretty inconsistent as many day-to-day variables can shift the limits up and down.

A stronger fuel pump can sometimes alleviate the issue, but the nature of a returnless system really taxes the fuel pump output. No matter how hard your fuel pump works, the best it can do is hold 52psi inside the fuel pump module. When the flow restrictions through the fuel system begin to show as fuel is in high demand, the fuel pump's hands are tied, as it is allowed to output no more than 52 psi and anything extra will simply bleed out the regulator that resides right next to it. The pressure drop through the system will continue to grow as fuel demands grow.

A return system allows the pump to work harder for you by placing the regulator after most of the flow restrictions in the system, and blocking off the factory regulator port in the fuel pump module. Now the fuel pump is no longer regulated directly at it's output, and it will operate at a higher immediate pressure allowing it to push "harder" through the fuel system.

You can set the regulator to the factory fuel pressure setting and it will run the same pressure profile until where fuel pressure used to fall off, it will no longer fall (until much higher fuel demands).

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phunk

There is no boost referencing the factory fuel system or regulator.

The factory fuel pressure settting is ~52psi. At 12 psi boost, the effective/relative/differential fuel pressure is about 40psi. There is 40psi more fuel pressure than there is intake manifold pressure, assuming no pressure drop in the system.

40psi with 650cc injectors isnt exactly a ton of fuel. If the pressure is dropping in the system, its even less. To resolve a case of pressure drop might extend the 650s into your required output. But if there is currently little-to-no drop occurring, than you just need larger injectors.

To investigate the minimalist remedy for your car, you would need to acquire some data. Is fuel pressure dropping below 52psi at the fuel pump module? This means the fuel pump is out of steam. Is fuel pressure holding steady at the pump module, but falling at the rails? This means you need upgraded plumbing or a return system. Is fuel pressure holding everywhere but the injector duty cycle is topped off? This means you just need injectors.

Most often, customers rather spend their money upgrading all of it in one shot rather than investing in detailed diagnostics to precisely locate the problem.

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EliteXpress

That's exactly what I'm doing with my build.

Jinxx

Now if I'm following this right ..... I know I need info for the duty cycle and fuel pressure to pinpoint the issue .... However from the nature of the stock fuel system is maintain 52lbs of pressure but at 12lbs of boost there would really be 40 lbs of pressure which to feed the motor and therefore leaning out as the boost increases from 0-12 .... So the real weak link is the stock system ... Switching to the return system gives the ability to increase the fuel pressure to the injectors to maintain 52lbs or greater if needed as boost increases .... Wouldn't changing the pump or injectors at this point be useless ?... The stock system would still regulate 52lbs and still starve injectors .... And changing injectors at this time would still only have 40lbs of fuel pressure to use and as result causing richer condition on the lower rpm side that would have to be tuned out .... Am I correct on this way of thinking ?

phunk

yup & yup.

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