Vac pipe

[SILICONEKID350HP]

Can anyone tell me the size of the vac pipe to the fuel regulator cheers

[jojackson4]

Id or od tell you tomorrow

[SILICONEKID350HP]

jojackson4 said:

Id or od tell you tomorrow

ID ..just repositioned the coil packs so I need to try and fit the fuel regulator somewhere else ..Plenum off again ..

[jojackson4]

Tell you tomorow

[Pink_Floyd]

4mm id.

[phazed]

Daz. Running MS this pipe should be left disconnected and the tube hanging off the plenum blocked.

[SILICONEKID350HP]

phazed said:

Daz. Running MS this pipe should be left disconnected and the tube hanging off the plenum blocked.

I`m talking about the fuel regulator vac pipe ...

[phazed]

SILICONEKID350HP said:

I`m talking about the fuel regulator vac pipe ...

So am I!

[GasMunkey]

phazed said:

Daz. Running MS this pipe should be left disconnected and the tube hanging off the plenum blocked.

You sure?

[SILICONEKID350HP]

phazed said:

So am I!

Who told you this ?

[phazed]

Yep, true.

Vacuum was required to alter fuel pressure on te Lucas system.

This is taken care on MS as explained to me by Shaun the mapper and Austecs.

[Bassfiend229hp]

The vac hose is used to allow the fuel pressure regulator to keep the fuel pressure at a specific pressure above *MANIFOLD* pressure (which in itself varies) - otherwise the fuel rail pressure will vary relative to manifold pressure as you open and close the throttle.

I would expect that even with your MS this hose will still be required so that you can keep the fuelling consistent...

Phil

[SILICONEKID350HP]

Phazed your fuel regulator looks the wrong type to me ..Is it a rising rate ,I wonder if that`s why it`s disconnected .

[phazed]

Daz.

It was explained to me in great detail by Austecs why you should block off the vacuum pipe.

From memory, it is to reduce fuel pressure at idle or low rpm, this isn't needed when running MS.

I'm seeing Shaun on Thursday so will clarify why!

[Bassfiend229hp]

phazed said:

Daz.

It was explained to me in great detail by Austecs why you should block off the vacuum pipe.

From memory, it is to reduce fuel pressure at idle or low rpm, this isn't needed when running MS.

I'm seeing Shaun on Thursday so will clarify why!

Hmmm ... as far as I remember the vacuum hose is there to ensure that the fuel rail stays a constant pressure difference from the manifold pressure or the injector duration timing (fuelling) becomes an absolute crapshoot as on a normally aspirated car the injector rails will vary in relative pressure (to the inlet manifold pressure) by 1 bar and generally fuelling becomes excessively rich at closed throttle and weak at open throttle.

See also here...

http://www.ehow.com/facts_7818984_vacuum-hose-fuel...

...and here...

http://www.howstuffinmycarworks.com/Fuel_pressure_...

To be honest I'm really suspicious about how they can map around running a car without the vacuum hose on the fuel pressure regulator!

Phil

[Tavan]

MS installation on my Griff mapped by Sean - never any suggestion of disconnecting/blanking the fuel reg pressure hose.

[phazed]

Hmmm?

[spend]

phazed said:

Daz.

It was explained to me in great detail by Austecs why you should block off the vacuum pipe.

From memory, it is to reduce fuel pressure at idle or low rpm, this isn't needed when running MS.

I'm seeing Shaun on Thursday so will clarify why!

It will do the opposite...

At idle the plenum is sucking hard, without referencing the FP to this 'negative' pressure and leaving it referenced to atmosphere the pressure differential will be greater hence more fuel delivered per injector opening time.