what is 3bar psi at idle??

[mveitenheimer]

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
am i off somewhere here.ive got it set to 40 psi at idle is this wrong?

[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?

[mveitenheimer]

20 hg but I also have a 270 cam


Modified by mveitenheimer at 11:51 AM 4-5-2008

[mveitenheimer]

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]

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

[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

[mveitenheimer]

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

thanks that worked great !!!

[derekb727]

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]

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