fuel pressure mod (with modified inlet systems)

sdbutler10

rite i have been trying to under stand this for a while now but everyone seems to have diffrent ideas so what do i do when i come to fit my manifold with this pipe lot.
do i leave the fuel rail open with nothing on it and block up the holes on the inlet pipe and manifold or have it all connected as normal.
thanks scott

vocky

with 2.0 sc injectors and the 2.4 inlet manifold you need to do the fpr mod, but with a standard tb and injectors it appears best to connect it as normal dunno..

Daz

Are the 2.0sc injectors similar to those used in the z20net neil?

Europa_Blue_SE1

I think I know where the dip in my torque came from I forgot my pipe and had done the FPR mod on the 2.4 inlet seems to take a bit of torque away for sure can't wait to get her back on the rollers and see if my torque goes beck up both Jon and Mark said I was losing the torque mibbe because my injectors could do with a clean Daz did you have the mod done when your car went on the RR mate? 🙁

rik1083

glad I don't need to bother with this for now 🙂
Tomorrow may finally be the day I fit it

digger

right another thicko... right now i have the 2.2 tb and manifold and the fpr is on the manifold side plug.

but next weekend im putting on the 2.0sc tb to the modded 2.2 manifold, so where does fpr pipe go ???
top, middle or off and inlet blanked???

Europa_Blue_SE1

Digger I have just took my pipe off and blanked the air intake don't know if you've got an Astra or Veccy and don't know if this makes a difference but that's the way I done mine think Daz has done something similar but notsure? Sure someone will be on soon and be able to help you a bit more...

digger

its the astra

Europa_Blue_SE1

If it's the Astra Baldie just take the pipe off completely mate and blank off the air intake I blanked mine off with one of the nipples from my 2.2 inlet trying to think what you could blank yours off with mate notsure.gif but sure someone will be able to give you an idea of something to use to blank it off mate hope this helps some...
Alan

digger

ive got an extra nipple so i can blank inlet and remove pipe and leave the rail open, but will it be the same once 2.0sc tb fitted?

vocky

today I fitted a fuel pressure gauge to the fuel rail on my vx220 🙂

At tickover, with inlet manifold vacuum connected it's 3.2 Bar, revving the engine caused the fuel pressure to rise to 3.8 Bar.

Then I temporally disconnected the vacuum pipe, the pressure increased to 3.8 Bar, my air/fuel gauge showed the ecu adjusted to the increased pressure - this took only 10 seconds

Next I refitted the vacuum pipe and the ecu once again adjusted the fuelling to the new fuel pressure.

So the fpr mod does lower the fuel pressure at lower engine load and the ecu does adjust very quickly to the lower fuel pressure.
Also the fuel pressure does rise to maximum with engine load.

markv

Don't forget that this is the short term fuel trim. It hasn't learned ANYTHING in 10 seconds. The table that is in memory with the long term fuel trims takes WAY longer to get updated. So if you've driven around with the lower fuel pressure at lower revs, then in memory it will have long term fuel trim values that lower the values that were mapped into your ECU. Short term it will compensate, but it will take time to up the learned values.

Ofcourse you can also take the power of the ECU, it will forget all changes 😉

Mark

vocky

yes you would be best to reset the ecu after changing the fpr vacuum pipe 🙂

I was just amazed how quick the ecu adjusted the fuelling :shock:

ANARCHY

This certainly is confusing now.

So is this correct:

A modified air intake reduces the vacuum pressure?

Reduced vacuum pressure increases the fuel pressure?

The vacuum pipe totally removed/blocked would produce the highest fuel pressure?

On some configurations higher pressure is better and on others low pressure is better.

Just trying it to see what happens is the best thing to do.

vocky

ANARCHY said:
This certainly is confusing now.

So is this correct:

A modified air intake reduces the vacuum pressure?

Reduced vacuum pressure increases the fuel pressure?

The vacuum pipe totally removed/blocked would produce the highest fuel pressure?

On some configurations higher pressure is better and on others low pressure is better.

Just trying it to see what happens is the best thing to do.

yes, lower vacuum equals greater fuel pressure, proven by the fact with the vacuum pipe removed there is maximum fuel pressure.

it does depend on what mods you have to where the vacuum take off comes from, with 2.0 sc injectors you must have vacuum at tickover, whereas with a 2.4 inlet you seem better with no vacuum.

but the reason why the fpr mod works on a standard (ish) engine is the vacuum, which lowers the fuel pressure at tickover, is lost by fitting a modified intake system - no vacuum raises the fuel pressure.
fitting the fpr mod restores the lower (tickover) fuel pressure.

it's very confusing to say the least :?

ANARCHY

Thats clearer now. I need to restore the lower fuel pressure at idle because mine is pretty much standard apart fom big holes in the airbox.

So on the standard air intake pipe on a XV220 oppsite the FPR pipe is a large 10mm pipe, is this pipe also expecting a vacuum?

vocky

the large pipe is the oil breather, it puts the oily gunge on the tb puke..

some people fit an oil catch tank instead

2-20

vocky said:
today I fitted a fuel pressure gauge to the fuel rail on my vx220 🙂

Hello Neil,

Could you explain what is needed to connect it... Did you connect it to the existing pipe pick-up or do you have a different setup.

Thank you

vocky

nothing special, just bought another fuel rail, drilled and tapped a hole and fitted the gauge 🙂

[the gauge is filled with fluid, thats what you can see in the pic]

Europa_Blue_SE1

Vocky sorry it's a totally off topic question but what kind of coolant is that you are using mate?
Thanks
Alan

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