Fuel Pressure...

[djwimbo]

I was curious about my fuel pressure when I installed my new clutch b/c I noticed the inside of my turbine housing and my 02 was white or showing signs of a lean condition.

Yesterday I tapped into my fuel line and monitored my fuel pressure while driving.
Idle: ~48psi
light accel: 52-55psi
full boost: 70psi peak and 5K-redline it will lower down to 63-64psi
high vacuum/hard engine braking: 43-44psi

My car has a stock fuel system, rail, injectors, pump, probably filter, etc.
actual performance mods: Unitronic Stg 1+(1bar/14.7psi) and TBE.
I know fuel pressure is supposed to rise as the regulator sees atmospheric pressure in a N/A application and increase even more in a boosted application, but is my fuel pressure too high?
I know my boost is lowering as my rpm's increase due to the fact that I'm running a K03 and they run out of power top end. My fuel pressure seems to follow/taper down as my boost does, but I don't have a boost gauge yet to know for sure.

Is this normal? anything I should be concerned about? I don't have VAG-Com yet or a wideband. So I don't know for sure if there's an issue, but I also don't have any CEL's either.

Thanks.

[djwimbo]

So I take it this is normal?

[creechsa4]

you must have an in cabin fuel pressure gauge. i'm not sure if any of us have that style. mine's in the engine bay. how's your spark plug color? any hesitation? hopefully you have some brown on your plugs.

[mike-2ptzero]

So I take it this is normal?

Yes it is normal, your fuel pressure changes with your boost pressure and seeing that your still running a stock turbo your boost will taper in the higher rpms which is why your seeing your fuel pressure taper down too. Believe me the K03 tapers off in the higher rpms, you wont need a gauge to tell you that much is true. Well unless you are only running 5psi.


No your pressure isn't too high since you are running a 4bar fpr at atmos pressure which is 58psi and the pressure changes 1:1 when boost is added, so this means your fuel pressure will go up 1psi with every 1psi of boost is added.

[djwimbo]

I know the boost tapers, that's a given. The car runs out of power at 5500rpm.
The stock FPR is a 4Bar? B/c I haven't changed anything in the fuel system, just the ECM software. I was just curious if this is normal, and it looks like it is. I was just surprised that it was hitting 70psi peak.

We went over the FPR's and stuff awhile ago in school I just never tested my vehicle on site. I had a fuel pressure gauge layin on the windsheild of the car coming off a 1/8"NPT tap into the fuel line.

Yes it is normal, your fuel pressure changes with your boost pressure and seeing that your still running a stock turbo your boost will taper in the higher rpms which is why your seeing your fuel pressure taper down too. Believe me the K03 tapers off in the higher rpms, you wont need a gauge to tell you that much is true. Well unless you are only running 5psi.


No your pressure isn't too high since you are running a 4bar fpr at atmos pressure which is 58psi and the pressure changes 1:1 when boost is added, so this means your fuel pressure will go up 1psi with every 1psi of boost is added.

[mike-2ptzero]

I know the boost tapers, that's a given. The car runs out of power at 5500rpm.
The stock FPR is a 4Bar? B/c I haven't changed anything in the fuel system, just the ECM software. I was just curious if this is normal, and it looks like it is. I was just surprised that it was hitting 70psi peak.

We went over the FPR's and stuff awhile ago in school I just never tested my vehicle on site. I had a fuel pressure gauge layin on the windsheild of the car coming off a 1/8"NPT tap into the fuel line.

Yeah your reading of the fuel pressure at idle with the vac line removed can be +/- of the 58psi depending on the adjusted altitude.


Just think of the fuel pressure the K04 guys that run stock injectors with a 5 bar(72.5psi) FPR and try running even just 1 bar of boost which puts their fuel pressure at 87psi. This is why all the tuners went away from using a 5 bar FPR and went with a 3bar fpr with larger injectors.

[djwimbo]

I know some of the guys are using 5Bar FPR's and I WILL NOT use anything that high.

Being that I'm getting an insurance check here soon, I'm thinking K04. Difference is, I'll be using larger injectors and a 3Bar FPR.
A stock fuel pump can't handle that high of pressure. At least not for OEM longevity. A stock fuel pump is designed to run at X.psig and be considered "dead headed" at about double that pressure. The added pressure is obviously more stress on the pump than it's used to.

[_audible_]

I run a 5bar fpr with a 1.2bar chip on stock injectors and i run lean. Would switching to an adjustable fpr (lowering it down to 3bar) and 440 injectors be a better option? I would like to think it would be and I've thought about it in the past, but wouldn't upgrading to a fuel pump with better flow capacity correct the situation too?

I didn't change anything because I wan't planning to stay K04'd originally, but now I am.

[djwimbo]

440's are huge, those are big for a 28RS, and AFAIK great for the 2871 and 3071 guys. Hence the reason I has purchased a set for my future plans.

How lean are you running, and on what turbo? Are we talking 14.0:1 or higher? On a K04 a set of 310/317's are great. But once again, I haven't done it personally, just what I've read. At this point I'm planning on running a k04 here soon, maybe an eliminator turbo, but not sure at this point. My stock turbo is about dead at 160K. At this point I can't afford to buy a manifold and stuff, just the turbo. I like the idea of the K04 b/c It'll look stock.

And personally I wouldn't build a car to use anything but a vacuum/boost assited 3Bar FPR just b/c of the stress a higher pressure puts on the pumps. That's why they make bigger injectors, and SEM's that allow the use of 5th, 6th or even 8 injectors.

I run a 5bar fpr with a 1.2bar chip on stock injectors and i run lean. Would switching to an adjustable fpr (lowering it down to 3bar) and 440 injectors be a better option? I would like to think it would be and I've thought about it in the past, but wouldn't upgrading to a fuel pump with better flow capacity correct the situation too?

I didn't change anything because I wan't planning to stay K04'd originally, but now I am.

[mike-2ptzero]

I run a 5bar fpr with a 1.2bar chip on stock injectors and i run lean. Would switching to an adjustable fpr (lowering it down to 3bar) and 440 injectors be a better option? I would like to think it would be and I've thought about it in the past, but wouldn't upgrading to a fuel pump with better flow capacity correct the situation too?

I didn't change anything because I wan't planning to stay K04'd originally, but now I am.

Are you running a K04 chip and if so which one?

Like djwimbo said the correct size injectors are 310-317cc, even the 380cc injectors are too big and were only used for the K04 "hammer" file for the 2001.

[_audible_]

Are you running a K04 chip and if so which one?

Like djwimbo said the correct size injectors are 310-317cc, even the 380cc injectors are too big and were only used for the K04 "hammer" file for the 2001.

It's a 1.2 bar K04 chip from Neuspeed which called for a 5 bar fpr on stock injectors.

Idle a/f is at 14.8-9 and driving is in 13.XX-14.XX... This is at half throttle. Full throttle will a/f will bounce really quick to 16.XX and then go back to 13.XX-14.XX.

Either way, it's not safe at those numbers and I feel I'm pushing my luck with it. It's been this way for a little over 2 years. Lol.


I also have an Upsolute file for a gt28rs that runs well on 440cc's and a 3bar fpr.
I'd rather be running a little rich than as lean as I have been. Since I'm keeping this as a DD and not doing anything with it, I'd like to fix it.

[mike-2ptzero]

It's a 1.2 bar K04 chip from Neuspeed which called for a 5 bar fpr on stock injectors.

Idle a/f is at 14.8-9 and driving is in 13.XX-14.XX... This is at half throttle. Full throttle will a/f will bounce really quick to 16.XX and then go back to 13.XX-14.XX.

Either way, it's not safe at those numbers and I feel I'm pushing my luck with it. It's been this way for a little over 2 years. Lol.


I also have an Upsolute file for a gt28rs that runs well on 440cc's and a 3bar fpr.
I'd rather be running a little rich than as lean as I have been. Since I'm keeping this as a DD and not doing anything with it, I'd like to fix it.

Sounds like there is something else causing it to do this, maybe a maf that is reading lower then it should be because that chip should still hit 12:1 or richer when you go WOT and get to full boost.

I dont the issue you are have running lean being due to running 5 bar with stock injectors with the stock pump. It would be if you were seeing a lean issue at very high rpms but it sounds like it is never reaching the correct AFR when getting into boost.


Have you checked your fuel trim reading on black 032 lately?

[_audible_]

I don't have a VAG right now so I can't check it. I'll try to get someone local who has one and log it. It's the original MAF so that definitely could be an issue causing it. A long time ago (maybe a year ago) I did throw a code for the MAF. I cleaned it and never got the code again. I'll replace that and see if it corrects it. I also have a hfc. Would that affect the numbers (other than placement of the 02 sensor affecting it)?

I'm do for a fuel pump anyway, so I was thinking about just going with a 255lph. I thought that because I figured the stock fuel pump couldn't keep up with the 5bar fpr and was being starved for fuel(?).
I'll start with replacing the MAF first and go from there.