58 replies to this topic

[vocky]

the fuel pressure regulator on the z22se engine works by vacuum, so at tickover you have reduced fuel pressure and high revs you have full fuel pressure.

if you replace the air filter with a better flowing filter you loose vacuum to the fuel pressure regulator and thus you loose fuel pressure at high revs, this may be why a remap is required with certain inlet systems - too compensate for lower fuel pressure.

there is a very easy fix for this, it involves moving the vacuum source to the inlet manifold and creates a stable fuel pressure = 4 Bar.

very easy to do, there are two blanked take off points on the side of the inlet manifold, simply remove the blanking plug and fit it to the intake pipe and then fit the vacuum pipe to the inlet manifold take off

you might require a new section of vacuum pipe on the vx220, mine was a moulded pipe but any vauxhall at the scrappy can provide a 150mm section of the correct pipe or the main dealer usually has it in stock.

this mod is the same as fitting an adjustable fpr and setting it at 4 Bar, the ecu adjusts for the extra fuelling at tickover and you won't notice any difference, those who have carried out this mod note improvements

here is the link with some pics z22se

[PaulCP]

You can also change the pressure on teh fuel regulator by adjusting the spring on the diaphram to give more flow at the top end. Can't remember how to do it though

[ChazUwe]

Would this make any improvement for me, stage 2 with ITG and miltek? Also I can't quite work out what you need to do from the pictures, can we have an easy step by step guide??

[meo]

Does this help performance? How easy is it to do on the vx thow?

[Anarchy]

A quick read of that suggest low down response will be noticably improved, is that correct? Sounds a bit easy just swap a pipe over and you get a bit more go, am I missing something?

[vocky]

it is very simple to do on the side of the inlet manifold are two small blanking plugs, remove one by pulling it, fit the removed blanking plug in place of the vacuum take off on the inlet pipe to the throttle body, then fit the vacuum pipe to where the blanking plug came from, job done everyone who has carried out this mod reports an improvement, including me when an improved inlet system is fitted (k+n, viper, etc) you loose fuel pressure, simple as that

[luna_s]

i guess you could use a small length of silicon hose in its place if the original isn't long enough

[ChazUwe]

Any negatives at all, if not I will be doing this on the weekend!

[alanoo]

i guess you could use a small length of silicon hose in its place if the original isn't long enough

Silicon hoses (especially small ones) don't like vacuum at all

[andyroo]

it is very simple to do

on the side of the inlet manifold are two small blanking plugs, remove one by pulling it, fit the removed blanking plug in place of the vacuum take off on the inlet pipe to the throttle body, then fit the vacuum pipe to where the blanking plug came from, job done

everyone who has carried out this mod reports an improvement, including me

when an improved inlet system is fitted (k+n, viper, etc) you loose fuel pressure, simple as that

Would this be wise on a car with an ITG that has been remapped? And did you, when you did it, have to get a longer piece of hose to make the vacuum pipe reach its new location?

So to clarify: Pull the vacuum pipe off of the of the inlet pipe to the throttle body and a blanking plug on the inlet manifold (I assume it doesnt matter which?) and swap.

[TangoAlpha]

Any chance of some nice photo's of what/where/etc.?

[vocky]

there is a couple of pics in the 'link' at the bottom of my first post the vacuum pipe was 'pre-formed' on my vx220 and I didn't want to stretch it, so I used a spare straight piece which was laying about in my garage, probably off a vectra I ran this on my 2.2 vectra for a couple of years, no issues at all - including mot

[andyroo]

there is a couple of pics in the 'link' at the bottom of my first post

the vacuum pipe was 'pre-formed' on my vx220 and I didn't want to stretch it, so I used a spare straight piece which was laying about in my garage, probably off a vectra

I ran this on my 2.2 vectra for a couple of years, no issues at all - including mot

What differences did you notice in the car once you'd done it?

[vocky]

the general feelings are 'the tickover becomes smoother and the engine pickup improves'

[Arno]

Just curious.. Most fuel pressure regulators I know decrease the fuel pressure when vacuum is applied to the connection and raise the fuel pressure as it goes to atmospheric or over in case of a turbo or supercharger to compensate for the pressure over atmospheric that's present in the manifold. Most of the time on factory units it's a normal linear increase. Progressive/rising rate regulators can be used as a bodge to stop a car (often tweaked turbo's) from leaning out on high load. Often this variable fuel pressure trick is used with bigger injectors that can flow enough for high power, but would need to be used a too short duty-cycles during idle (<5% or so) to get consistent amounts injected and atomised. By dropping the fuel pressure using the intake vacuum on the pressure regulator the ECU can use much longer duty cycle on the injectors and still get a good control over the amount that's injected (injectors are accurate as long as you stay away from very short or very long duty cycles) and fuel atomisation. Unless the regulator used on the 2.2 works differently then hooking it up to the manifold vacuum would initially lean out the mixture until the ECU re-adjusts. The mapping of the ECU would not be based on this. It's mapped for a constant fuel pressure. Has anyone hooked up an OBD reader after this mod to see how the short term and long term fuel trim is changing or hooked up a wideband lambda sensor in the downpipe with a gauge to get an readout of the mixture? If the ECU needs to adjust too much then it may throw an engine management light and error code after a while. Bye, Arno.

[vocky]

the z22se fpr does indeed work back to front at tickover a bog standard engine has 0.2 mBar of vacuum to the fpr, at 4k rpm it raises to 6 mBar. so the vacuum increases with engine load until the fpr has reached full pressure moving the vacuum take off restores the missing vacuum caused by a non standard inlet system

[ChazUwe]

I have had a look on the VX and it doesn't look very accessible on the VX. Whats the easiest way to get to it, also where can I get a suitable cable from? Looks like you might need a longer one. Would like to try this out though!

[vocky]

prop the engine cover open with a broom handle, then access is fine a longer piece of vacuum hose can be found at the scrappy in most vauxhalls or buy a new piece for a few quid from the dealer - ask for vectra vacuum hose as they have loads under the bonnet

[andyroo]

For the super unmechanically minded (i.e: me ), can someone do a photo guide with red circles and arrows and stuff? Thanks in advance

[ChazUwe]

Ok sounds good, can I check that I am looking in the right area. Above the inlet manifold on the passenger side?? Sorry for all the questions!