what is the stock fuel pressure?

**jrodmk2** · 08-06-2004 10:34 AM

i thought it was stated a little while ago that it was 58 is this correct? then add approx 1 psi for every pound of boost we are running. any help is appreciated. damn i should get a bently manual.

**Daft** · 08-06-2004 01:13 PM

The 1.8T fuel system has a base fuel pressure of 58Psi (Approx. 4Bar).

This is the value seen when the vacuum line is disconnected from the FPR.

Vacuum at idle will cause fuel pressure to sit closer to 50Psi or 3.5Bar.

The FPR is connected to the intake system so that it can see boost and vacuum. Thus, it can receive boost and cause the fuel pressure to increase.

Fuel pressure should increase 1:1 with boost. So, a car making 1Bar of boost (14.5Psi) would make 72.5Psi of fuel pressure.

The one thing I never got straight was the specs of the OEM FPR. Everyone lists it as a 4Bar FPR. No one ever lists what it can handle without getting sloppy. I wonder if we are putting too much strain on the OEM ones????

**jrodmk2** · 08-06-2004 01:35 PM

not sure either, i put a adjustable unit in from eurospec. i am going to check it when i get my gauge in this weekend. i am running really rich with the fpr almost all the way out (low pressure). i may get a aeromotive fpr for nothing, because my friend was going to use it on his vr6 turbo but went with somethig else. i will have to see if i can hook it up with the stock lines. i am running a bar of boost but i am slightly confused why i am still running rich. i will have to get some reading off a vag-com next week.

thanks

**ki11switch** · 09-26-2007 11:01 PM

I know this is an old thread, but what should i be running my fpr at with a stock k03 and giac programming? And i would set it while the vacuum line is off right?

**solowb5** · 09-27-2007 06:38 AM

Its 3 bar if it is dbc and 4 bar for dbw engines

**mike-2ptzero** · 09-27-2007 06:55 AM

Originally Posted by solowb5

Its 3 bar if it is dbc and 4 bar for dbw engines

All B5 A4 1.8t's came with a 4 bar fpr, only 1.8t's that came with a 3 bar have a VW badge on them.

ki11switch - yes you want to set the fuel pressure with the vac line removed since it should be set at atmos pressure. Another reason you dont want to set it with the line is because any changes in the idle can cause a change in how much vacuum is being applied to the FPR. If the idle is bouncing you would never be able to set it with the vac line on since the fuel pressure gauge would also be bouncing.

**_audible_** · 09-27-2007 07:40 AM

My fuel pressure is at 62psi at idle with vac line connected (I have'nt checked with is disconnected yet). K04 turbo, neuspeed 1.2bar chip, 5bar fpr and stock injectors. Does that sound right? I am not getting enough fuel as I'm running lean when under load. Wideband gauge reads 14.8 at idle and 15.8 - 17 under load! Also getting misfires in the upper RPM after 4500 at wot. No lean codes thrown though, but will get multiple misfire codes after it throws a cel. Wtf? Had a maf code once, cleaned the maf, never got that code again, but still have the same problems. Changed plugs 3 times, checked gaps, regapped them and everthing, nothing works. Idle is smooth. Weird huh?

**mike-2ptzero** · 09-27-2007 08:15 AM

Originally Posted by _audible_

My fuel pressure is at 62psi at idle with vac line connected (I have'nt checked with is disconnected yet). K04 turbo, neuspeed 1.2bar chip, 5bar fpr and stock injectors. Does that sound right? I am not getting enough fuel as I'm running lean when under load. Wideband gauge reads 14.8 at idle and 15.8 - 17 under load! Also getting misfires in the upper RPM after 4500 at wot. No lean codes thrown though, but will get multiple misfire codes after it throws a cel. Wtf? Had a maf code once, cleaned the maf, never got that code again, but still have the same problems. Changed plugs 3 times, checked gaps, regapped them and everthing, nothing works. Idle is smooth. Weird huh?

15.8-17 while at full boost?

**_audible_** · 09-27-2007 08:22 AM

See, that's the thing. I know I have a boost leak somewhere and will need to check for one soon as I'm not seeing anywhere near 17.5lbs. Boost gauge is only reading 15lbs and holding. I used to hit 17.5 and hold with this chip and the K04 which has been in the car a little over a year now. I never had a wideband gauge until I installed it with a high flow cat a week ago. Never logged the car since I don't have a vag tool. All of this stuff is coming out soon when the gt28rs goes in and a tune from c.tapp, but for now I'd like to at least figure out what's making it lean out so bad. Fuel filter will be changed tonight. Only other thing if that's not it would be injectors, but I'm not having any idle issues and I'd think if it was a injector problem I'd have idle issues(?). Same thing with a bad coil pack right, I'd have issues at idle if one was bad wouldn't I?

But yes, that is at full boost, or as close as it will come to hitting full boost.

**ki11switch** · 09-27-2007 10:35 AM

so should i set my fpr to 58psi with a stock set up and giac programming?

**mike-2ptzero** · 09-27-2007 11:44 AM

Originally Posted by ki11switch

so should i set my fpr to 58psi with a stock set up and giac programming?

Yes, the K03 chips are tuned for 4 bar with stock injectors.

**ki11switch** · 09-27-2007 04:37 PM

alright thanks for the help

**jessechuy** · 09-27-2018 01:16 PM

so I'm getting ready to install a stage 3 ecu ko4 turbo 550 injectors I have a aftermarket fuel rail I wanted to use but I'm unsure how to set up a aftermarket fuel regular and how many psi to set it at? I will be running about 24psi of boots can someone help me?

**Seerlah** · 09-30-2018 10:22 AM

If it is an adjustable fuel pressure regulator you remove the vacuum/boost reference line from the (a)fpr. At that point you adjust the fuel pressure to the fuel pressure written for the tune to run on (ie ~58psi for 4bar).

When you remove the reference line you adjust the fuel pressure to atmospheric pressure without vacuum influence from the engine. Then when you place the reference line back into the afpr, the fuel pressure will drop because of the vacuum by the motor. You are basically mimicking fuel pressure with engine vacuum/boost at 0 in/hg (inches of mercury) with the reference line removed when dialing in fuel pressure. With the engine running you are at ~-20 in/hg, so your fuel pressure will be innacurate if dialing it in with the reference line hooked up.