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10-29-2003, 07:32 AM

#11

IGY

Senior Member

Join Date: Dec 2001

Location: Okinawa Japan at McDonalds

Posts: 472

Quote:

Originally Posted by little rotor' date='Oct 29 2003, 08:48 PM

Shouldn't the regulator just allow the extra fuel to flow down the return line to keep the desired pressure? i.e its not just a fixed size hole. Obviously at some point you would get to the point where the regulator could physically not pass enough fuel to maitain the desired pressure, but this would be more of an issue at idle when the injectors are not passing much fuel and if the two stage pump speed is not being used.

In regard to JSpecs post, I realise you will have higher fuel pressure at higher boost, my question was relating to the effect of changing the fuel pump only.

With out the vaccuum line attached it is just a fixed hole. More fuel through the same size hole means higher pressure before the regulator, at the injectors. All the vaccuum line does is push a plate over the hole matching fuel pressure increase or decrease to manifold pressure increase or decrease with a 1:1 regulator(stock).

I give this info as FACT because I have actually seen it many times, I didn't read it in a book and I didn't give it as an opinion or theorize it.

10-29-2003, 10:19 AM

#12

Silver Ninety Three

Senior Member

Join Date: Oct 2001

Location: Clifton, NJ

Posts: 1,675

You need an intercooler bad. I'd keep it at 10 psi untill you can build up the fuel system and get a proper intercooler.

10-29-2003, 04:54 PM

#13

little rotor

Member

Join Date: Aug 2002

Posts: 65

Hmm. I assumed that a FPR would be a bit more technical than that. Guess I'll have to pull one apart some time. I'll be putting a higher flowing pump in a car next week, so I'll pay close attention to exactly what the pressures are before and after. For now, I guess I'll take your word for it.

10-30-2003, 10:41 AM

#14

roadkill669

Senior Member

Join Date: Jun 2003

Location: Culpeper, VA

Posts: 572

Quote:

Originally Posted by IGY' date='Oct 29 2003, 05:23 AM

[quote name='sleeper7' date='Oct 29 2003, 06:54 PM'] Is what I think should of been said was, with a bigger fuel pump you increase fuel volume, not pressure. The stock fuel pump runs out of fuel under higher boost. Just my .2 cents

chuck

Have you ever tried to measure fuel pressure on a stock system with an upgraded fuel pump? I have and you will ALWAYS see more pressure at the rail with a pump that has a higher flow rating. [/quote]

It makes sense. I have 2 fuel pumps on my car now and the fuel pressure rose 15 psi and stayed there. It doesn't drop anymore, plus I have it wired to the battery.