# what is 3bar psi at idle??



## mveitenheimer (Sep 1, 2007)

what does the 3bar FPR while idling? shouldent it be 43 psi? i have a adjustable FPR and i cant get my fueling tuned rite http://****************.com/smile/emthdown.gif 
am i off somewhere here.ive got it set to 40 psi at idle is this wrong?


----------



## 84_GLI_coupe (Apr 3, 2001)

*Re: what is 3bar psi at idle?? (mveitenheimer)*

Your FPR just keeps a set pressure difference between the fuel in the fuel rail, and the intake manifold pressure/vacuum. Constant pressure difference across the fuel injectors means that you can accurately control the fuel with the ECU.
So basically, your fuel pressure will only be 3 bar when the absolute pressure in your intake manifold is 1 bar (zero boost, wide open throttle in a n/a car). Average manifold vacuum at idle with stock cam(s) is 15"Hg, which is 0.5 bar vacuum. 3 bar FPR + (-0.5 bar manifold) = 2.5 bar referenced to atmosphere = 36.x psi.
If you've got a vacuum section on your boost gauge (if you've got one), what does it read?


----------



## mveitenheimer (Sep 1, 2007)

*Re: what is 3bar psi at idle?? (84_GLI_coupe)*

20 hg but I also have a 270 cam


_Modified by mveitenheimer at 11:51 AM 4-5-2008_


----------



## mveitenheimer (Sep 1, 2007)

*Re: what is 3bar psi at idle?? (84_GLI_coupe)*


_Quote, originally posted by *84_GLI_coupe* »_Your FPR just keeps a set pressure difference between the fuel in the fuel rail, and the intake manifold pressure/vacuum. Constant pressure difference across the fuel injectors means that you can accurately control the fuel with the ECU.
So basically, your fuel pressure will only be 3 bar when the absolute pressure in your intake manifold is 1 bar (zero boost, wide open throttle in a n/a car). Average manifold vacuum at idle with stock cam(s) is 15"Hg, which is 0.5 bar vacuum. 3 bar FPR + (-0.5 bar manifold) = 2.5 bar referenced to atmosphere = 36.x psi.
If you've got a vacuum section on your boost gauge (if you've got one), what does it read?

so if i set my fpr to 34psi (because -.6bar due to 20hg" at idle) that would act as a normal 3 bar stock fpr? 2.4bar=34psi


----------



## BLSport (Dec 24, 2005)

*Re: what is 3bar psi at idle?? (mveitenheimer)*

Just keep it simple...
1. With the engine idling, disconnect the vacuum/boost reference line connected to the FPR
2. Temporarily plug the reference line to prevent a vacuum leak
3. Adjust the FPR until you achieve 3 bar fuel pressure
4. Remove the plug from the reference line and reconnect the line to the FPR
5. Enjoy http://****************.com/smile/emthup.gif


----------



## bdcoombs (Jul 28, 2002)

*Re: what is 3bar psi at idle?? (BLSport)*

what he said take off the vaccum line hold it closed with your thumb adjust fuel pressure to desired psi or 3 bar. then put the vaccum line back on
good to go http://****************.com/smile/emthup.gif


----------



## mveitenheimer (Sep 1, 2007)

*Re: what is 3bar psi at idle?? (bdcoombs)*


_Quote, originally posted by *bdcoombs* »_what he said take off the vaccum line hold it closed with your thumb adjust fuel pressure to desired psi or 3 bar. then put the vaccum line back on
good to go http://****************.com/smile/emthup.gif 
 
thanks that worked great !!!


----------



## derekb727 (Dec 22, 2007)

I know this is old but none the less. 

What adverse affects could I see if my base fuel pressure is off by 2-3 psi give or take?


----------



## TBT-Syncro (Apr 28, 2001)

derekb727 said:


> I know this is old but none the less.
> 
> What adverse affects could I see if my base fuel pressure is off by 2-3 psi give or take?


nothing. fueling would be off a tiny tiny bit


----------

