Fuel Pressure Regulator lag. A15 SOHC

[MaXiMiZoR]

Yes! I finally got all parts I needed and I finished this mod

The blue fuel rail adapter is for Nissan (http://cgi.ebay.com/ebaymotors/ws/eBayI ... K:MEWNX:IT) and the piece that fits into the fuelrail needed 0.1mm to be sanded of in diameter and 0.4mm in lenght to fit in the hole of the fuelrail.
The OEM fuel return line was hard PVC, so I had to cut it and attach a 8mm rubber hose to it that goes to the Malpassi.
To fit the Malpassi, I found a convenient place at the back of the intake manifold. Drilled 2 holes in the aluminium and fitted the FPR.

For the rest, it was easy...

Original OEM plastic fuel line with GM-connector:


OEM FPR:


Malpassi Rising Rate FPR fitted at manifold backside:


I cut off the 8mm (outer diameter) PVC original fuel return line and shove it into an 8mm (inner diameter) rubber fuel hose, secured it with 2 fuel line clamps:


Some more pics:



After a first testrun it's noticable that throttle respons is quicker and mid-range to high-range power has increased. Also any dead spots have disappeared. I've yet got to fine-tune it but the first test results are promising... It's now running at 3 BAR, I think (previous owner set it to 3 BAR, he said). Got to give the screw a few turns clockwise (+) to see if it makes a difference...

[MMamdouh]

will i get the same results as you did if i used a single membrane regulator rather than dual membrane regulator? ( standard FPR rather than RRFPR)

MMamdouh

would you please give me your opinion regarding this?

MMamdouh

[MaXiMiZoR]

A stock fpr with a vacuum port decreases fuel pressure when vacuum is present. For example, it's 55psi with no vacuum (open throttle) and 47psi with vacuum (idle). An adjustable fpr is just that, an fpr that you can adjust the pressure. You set the high pressure and vacuum does it's thing at idle.

A rising rate fuel pressure regulator adjusts the fuel pressure disproportionally from the change in vacuum or more often pressure. They have set ratios like 10:1. For every 1 psi of vacuum/pressure change, the fuel pressure goes up 10psi. They are useful in boosted cars when you can't reprogram the injection for larger injectors or higher pressures. At idle, the car runs around stock pressures, with high boost and load it runs very high pressures.

From what I understand from this quote is that an FPR (single membrane) allows you to set a static boost pressure, while an RRFPR (2 membranes) allows for variable boost pressures depending on the amount of pressure on the vacuum line.

With my mod I didn't notice a night and day difference, but I can tell the engine get's more fuel pressure by the changed sound of the injectors/cylinders. Sounds like the engine pushes itself harder. Next week I'm recieving a 0-6 BAR glycerine filled pressure meter. In the meanwhile I'm just blindly adjusting the pressure step by step. More feedback will come if I got the pressure gauge installed
Thinking of changing my fuel filter also (small cost), maybe a clean filter gives a bit more pressure. Mine got 100.000km now, so it's seems worth changing. Still wondering how much pressure an OEM fuel pump from a Lanos will give.

[Daniel]

Still wondering how much pressure an OEM fuel pump from a Lanos will give.

In the Pierburg catalog the fuel pump KFM 7.02552.05.0 for Lanos 1.6DOHC is gived for 4bar/56PSI.

[MaXiMiZoR]

Thanx for the info Daniel.

When I got the RRFPR it was set at 3 BAR. I turned the screw 2 half-turns clockwise and not much difference. Today I turned it another half-turn clockwise and it made a huge difference! Power increase was surely noticable up to 4000 RPM. But at 4000 RPM it seems to hold itself in. Also an annoying high-pitch noise was coming from the RRFPR and after the testrun the car wouldn't start as easily. The fuel pump seemed to struggle... Maybe too much boost?
I now turned the screw a bit back and the high-pitch noise has almost dissapeared but also power is less now.

Anybody know why it's making a high-pitch noise under heavy boost?

Note: I read somewhere that the RRFPR has got to be placed in series after the stock FPR. I didn't do that. I swapped the stock FPR for the RRFPR. Can somebody explain why you should place them in series???

[benzino]

4 bar stock seems way too high

most cars including the 1.5 and the 2.0 run at 3 bar

[MaXiMiZoR]

Power increase was surely noticable up to 4000 RPM. But at 4000 RPM it seems to hold itself in. Also an annoying high-pitch noise was coming from the RRFPR and after the testrun the car wouldn't start as easily. The fuel pump seemed to struggle... Maybe too much boost?

I talked to a friend on the phone and he says the holding back at 4000RPM has to do with the fuel pump running out of pressure. It simply can't provide enough pressure at high RPM. Bit of a dissapointment really...
But I still want to know what the whining noise is about. It makes that high-pitch noise at idle. Injectors? FPR? Fuel pump?

[benzino]

maybe look around the car to pinpoint the noise when it's occuring

[MaXiMiZoR]

It occurs only at idle, when I open the throttle the sound disappears. I've set the pressure a little less now and the sound vanished but also the power I had...

[Fltofancy]

The squealing noise you hear is likely the RRFPR poppet valve opening and closing very fast. Kinda sounds like when you squeeze a ballon neck and let the pressure out, SKWEEEEEEEEEEEEEEEEE! Very typical for a pressure regulator trying to regulate from high pressure (AKA full fuel pump pressure) to a low pressure for idle.

I'm curious to know what difference, if any, if you disconnect the vacuum from the factory FPR and just run at the high pressure factory setting.

Fltofancy

[MaXiMiZoR]

The squealing noise you hear is likely the RRFPR poppet valve opening and closing very fast. Kinda sounds like when you squeeze a ballon neck and let the pressure out, SKWEEEEEEEEEEEEEEEEE! Very typical for a pressure regulator trying to regulate from high pressure (AKA full fuel pump pressure) to a low pressure for idle.

I'm curious to know what difference, if any, if you disconnect the vacuum from the factory FPR and just run at the high pressure factory setting.

Fltofancy

Thanks for the info, it's exactly that noise
I disconnected the factory FPR... should I place it back in series with the RRFPR?

[MaXiMiZoR]

will i get the same results as you did if i used a single membrane regulator rather than dual membrane regulator? ( standard FPR rather than RRFPR)

MMamdouh

would you please give me your opinion regarding this?

MMamdouh

Honestly, I think you get similar results with a single membrane adjustable FPR.

[MMamdouh]

i remember we got a ticking sound from the RRFPR we put on the turbo 2.0 nubira and it was consistent with the injector opening and closing... actually it was matching the fluctuations we saw on the pressure gauge of the RRFPR.. .we thought this happened because it was a cheap ass RRFPR but now it seems to be a normal characteristic for an RRFPR at high pressure

MMamdouh

[Fltofancy]

What happens if you just disconnect the factory FPR from vacuum and run it like that (i.e. without installing a different FPR)? Wouldnt it supply fuel at the higher pressure setting at idle and all other times? Would this be enough pressure boost to eliminate the slow acceleration from idle?

Fltofancy

[MaXiMiZoR]

Great thinking
Since the vacuum line's main purpose is to let the FPR know when the motor is at idle or not, I believe when the vacuum is disconnected, the FPR doesn't regulate anything and just delivers max. pressure all the time.
Probably runs far too rich at idle this way.