has this ever been done??? cause in runing pig rich!! and i mean PIG! if anyone knows how much of a difference it makes usually lemme know... it doesnt run as rich with mt pfc but still pig! should i just get the stocker back in there?

 

Do you still have the stock Fuel Pressure Regulator?

If you are over-powering the regulator, it will run rich.

 

how rich??? like, pissing out fuel through the exhaust? like 1/8 of a tank in piont 2 miles??

 

It probably would depend on how far the FPR would be overpowered as to the results. I would guess that overloading the FPR too much would make the car run like it was disconnected from the MAP sensor. However, I have no personal experience with that situation so it's only a guess.

Keep in mind, I'm not suggesting this is exactly what is happening; but it's a possibility.

 

I'm running the 20B pump with no problems. It might be a little richer at idle but still runs great.

 

still on the stock fpr???

 

Right... I've just bought a '96 FD3S RS. 1 previous owner, completely standard, no modifications what so ever.

Now I've got a few items left from my previous car ('94 GTO or 3000GT as you might call it), and as I'm certain the modification bug will hit fairly soon was wondering if I can reuse these parts...

Cosmo 20B fuel pump (Denso 195130-0771 248lph@ 13.5V)
Malpassi Rising Rate Fuel Pressure Regulator (1:1 Ratio)

Will I run too rich like xxfetusmanusxx if I swap fuel pumps? And will the Malpassi FPR solve this? (If it even works with the FD)

Thanks

 

I don't think your fuel pump is causing you to be too rich. I suspect that the 20B pump is capable of flowing more fuel, but at the same pressure as the stock pump.

 

In general, pump capacity has no effect on the amount of fuel delivered except under these specific circumstances:

1. The fuel pump is inadequate. For instance, if the FPR wants 50 psi and the fuel pump can't supply enough fuel to keep the pressure at 50 psi the pressure will drop and the amount of fuel delivered will be reduced.

2. The FPR is too restrictive and the enormous flow of the pump leads to elevated pressure. This is most likely to happen at idle or right after the pump switches to "high speed" on the FD's two-speed dual voltage system. In this case, you have some massive pump pumping a lot of fuel through the system. The FPR only wants 30 psi, but the FPR or the return line is such a restriction that the pressure rises to 40 psi and thus the amount of fuel delivered increases.

But again, in general, so long as your fuel pump is adequate and your return path is not overly restrictive, the pump has nothing to do with the amount of fuel delivered. Consider these examples of two different pumps in the same car:

#1. Pumpzilla flows 90 GPH at 30 psi and 80 GPH at 50 psi. At idle, the FPR wants 30 psi, and the fuel computer holds the injectors open enough to deliver 1 GPH at that pressure. So, of the 90 GPH flow, 1 GPH is injected into the engine, and 89 GPH are returned to the tank by the FPR. At redline under full boost, the FPR wants 50 psi and the fuel computer holds the injectors open long enough to deliver 50 GPH at that pressure. The pump flows 80 GPH, so 50 GPH gets injected and 30 GPH are returned to the tank by the FPR.

#2. Pumpcilla flows 65 GPH at 30 psi and 60 GPH at 50 psi. At idle, the FPR wants 30 psi. The pump flows 65 GPH, the engine drinks 1 GPH and 64 GPH are returned to the tank by the FPR. With the pedal floored at high RPM, the FPR wants 50 psi, the pump flows 60, the engine drinks 50 GPH, and 10 GPH are returned to the tank by the FPR.

Two pumps with different capacities in the same car, and the amount of fuel delivered to the engine is exactly the same. That's how the fuel system is supposed to work. And it does work so long as you choose components that are appropriate for your setup. I wouldn't expect either of these issues to be present on an FD with a Cosmo pump and an otherwise stock fuel system.

-Max

 

Like others have said here, FPR is the fuel pressure regulator. Btw, what type of fuel system do you have? If it's all stock, there's no reason to change pumps(unless yours went bad).