Give Enough Pressure To Bypass Ecu Protection

[BHDave]

I though the stock fpr ran of the vacuum from the plenum chamber not the actually pressure in the fuel rail?

<{POST_SNAPBACK}>

It does, the stock reg is set to provide about 2.5bar (i think) base fuel pressure at atmospheric pressure.

The vacuum/boost signal off the plenum maintains that set pressure differential by increasing/reducing the restiction in the fuel line created by the reg, so if you are running 1 bar boost at any given time, you will have the reg holding 3.5bar fuel pressure and you still have a 2.5bar difference in pressure.

There are minor differences as it's a dynamic system and changes in flow (say by adding a bigger fuel pump) effect it a bit which is part of why you see a higher base pressure on the stock reg when running a higher flowing pump.

[rmahnovetsky]

Well that is how I though it worked. let me just re explain to make sure what Im thinking is right with you line of thinking.

The fpr is controller via the plenum. If you adjust the idle screw you will see a drop or increase in pressure if you have an inline in guage. The fpr basically acts like a valve, how far open it is, is determined position via the vacuum. Thus the stock fuel pump and the fpr go hand the hand, they are dependant on each other to give the correct factory fuel pressure to the injectors.. for eg

fuel pressure = 50 psi

fpr is open at 50% ... 25psi to injectors , 25psi back to the tank.

Increasing decreasing the fuel pressure will alter the pressure to the injector and back to the tank.

The fpr is just a valve which open and closes via a vacuum thats it. Therefore changing fuel pressure will change how much pressure goes to the injectors..

if Im wrong please set me straight.

[Cubes]

I was told of issues that have been seen with the 044 pump and std regs.

'Apparently' the std reg has trouble passing enough fuel to keep pressure low on idle, as a result fuel pressure *slowly* increases until what pressure I don't know. Closed loop is able to handle the increase in pressure 'apparently'.

It only causes a problem on non closed loop ecu motors.

How much of a problem.. I don't know. Tim Possingham mentioned he had come across this problem. Not really a problem just an annoyance.

[rmahnovetsky]

well Im using a 040 so ok for me

maybe the diapham can't sustain that amount of pressure and slowly opens up?

[Tangles]

Mines all going on my Stagea from tomorrow...

Hopefully by thursday/friday night I can post up a dyno graph in the Stagea section.

[rmahnovetsky]

bwilkeson: good luck, I'm sure it will go great.. Post up the results..

[Sydneykid]

I have run a Bosch 044 at 13.8 volts with a standard FPR on a number of cars. That's double the flow of a standard GTR pump at the standard 11.2 volts. NONE of them had more than the standard fuel pressure of 36-38 psi.

The exit orifice from the standard FPR is ~6.5mm, compared to the 7.5mm outlet orifice of an 044 pump. The piston in the FPR moves ~10mm so that is not an issue either.

If you are getting a true 44 psi in the rail at idle, with the standard FPR and the vacuum line disconnected, then something is wrong. There is a blockage or some other restriction in the return system (inc the FPR) to the tank. This will give unpredictable results and is therefore very dangerous. I strongly suggest that you find out what the problem is and fix it.

cheers

[rmahnovetsky]

no, the vacuum line was not disconnected when I checked it. I'll check it with the vacuum off. Could explain why I have an idle problem on hot and humid days.

[rmahnovetsky]

actually I can notice the fuel pump wine when fuel gets low. ..

[rmahnovetsky]

OK so I tested the fpr it is 44 psi when I take the vacuum off. 34 When I put it back on. ~38psi when my idle is screwy..

[rmahnovetsky]

I have finish an anround town fuel usage test with the new pump..

$30 of fuel at 1.16/L of 95 ron gave me 277ks and still counting maybe 10 more... so at 277 ks = 9.33 L / 100ks .. Adding a bigger fuel pump has no effect on fuel usage - as expected ... Mine you I didn't go over 4500 once.