Fuel pressure deficiency...

[ROH ECHT]

Hello all...I have a 2007 GTI. Everything is in fine shape. Recently I switched back to my GIAC K04 HO(HO=RS4 fprv and a 140 BAR request for rail pressure) from a trial period with a DriverMotorsport K04 tune. My GIAC tune was fine a few years ago...but not the case when it was reloaded last year. The rail pressure request should be 140 BAR but only hits 110 BAR specified even though the actual exceeds that. 

I have a USP High Flow lpfp(in-tank pump) and the mentioned condition is present with either the USP or OEM pumps...with the OEM pump currently installed. I cannot believe that both of these lpfp's are failing but cannot figure out what the problem is. Again, there are no fault codes and the filter and follower are nearly new. Additionally, with both lpfp's, the actual low pressure will drop below specified nearly 0.5 BAR each time I collect data for group 231 in the upper revs...6k to redline mostly. Earlier the pressure will match requested low pressure.

I've had recommendations to replace nearly everything like: cam follower, filter, hpfp, lpfp, fuel pressure relief valve, and the controller. But I think everything is in good shape other than the controller which I haven't heard of being the culprit to this. Only I haven't heard of anything being at fault for this, so....any others here ever experienced this? "This" being, everything runs fine...it is just that the high fuel pressure request is the stock 110 BAR rather than the tune limit of 140 BAR...

[pudding]

Sounds like either the fuel flow isn't there to support the higher rpms, or the software is commanding a lower pressure.

You've been through the mill with this haven't you!  Have you got S3 injectors to support your K04 conversion?

If I were in your shoes,  I would do this:

Refit a new standard OEM LPFP & controller, latest revision. Early ones overheated.
Fit a Loba HPFP.
Refit standard frpv.
Fit a new OEM fuel filter.

Get a new tune for that and see where you are.  You should hit 300hp easily with a 120bar relief valve and the Loba.  My ED30 does about 310hp with 115 bar request.

If all that holds the right pressure / flow and makes the expected numbers, consider the slate wiped clean and slowly increase things again.  One thing at a time so you don't lose track of what's been done.   The trouble with your situation is you've been changing hardware and software together, so it seems like resetting things back to a known good baseline again would be wise.

[Dan_FR]

ECU/software issue. Hardware won't affect the ECU HPFP request so swapping parts out will not help

[pudding]

I don't think it's solely software related because he said the actual exceeds the requested anyway.  The OEM parts have a tight grip on the pressure differentials.

[ROH ECHT]

I have S3 injectors...RS4 fprv....and the tune for this.
"S3inj_FMIC_TBE_HPFP_140BARreg"

The 6.6 BAR fuel filter is nearly new...CF has less than 2k on it. The actual is below specified from the lpfp and above the specified from the hpfp.

GIAC said it could be readings from a sensor but had no help determining how to locate which one. I've recently replaced the fuel pressure, MAF, and MAP sensors except for the pressure regulator on the hpfp itself. All of my adaptations are done and the tests look to show all is working properly.

My APR-hpfp is believed to be fine as it's actual pressure always exceeds specified by 2 to 10 BAR. Lambda readings looked good in their opinion and the only thing they think it may be is the tune or the lpfp. The lpfp doesn't make sense to me because the ECM doesn't see the lpfp deficiency until late in the revs as actual matches specified up to 6k rpm.

I have been through enough with attempting to solve this and just wish it solved at this point without spending any more unless I have to.

Driveability is normal and I only want to know why the high pressure request of 110 BAR when it used to work at a 140 BAR request. I was at 285 hp at the wheels with this tune before and I am taking it step by step. I think it wouldn't hurt to try another controller...maybe a new oem hpfp and upgrade...last would be the lpfp because I have two and neither correct it.

[ROH ECHT]

The tune GIAC sent was the same that is loaded...guess I need to just wait and see if when I replace a part that the fuel pressure request returns to 140 BAR instead of 110 BAR. 

Just need to figure out what to replace because both my oem pump and the USP hi-flow pumps do this. I don't want to replace another 3rd pump to find I needed to do the controller...and vice versa. The issue existed before buying the USP Hi-flow lpfp and didn't get corrected by it...DM had to adjust the tune to correct it. However, when I ran GIAC before I ran the DM tune it was fine...was only after loading GIAC again that I was faced with the issue that appeared when I switched from GIAC to DM a few years ago. The pressure tests with vcds look correct for both high and low...but those are done at idle. So, there is either a problem with the controller or a restriction somewhere in the feed line that has always existed...←my thoughts at the moment.

BTW...the low pressure actual always begins to fall below specified the moment I go full throttle and throughout the revs during a data pull. Sometimes it only falls 0.2 BAR and the most it falls is 0.5 BAR...and it is a gradual decline and later in the revs.
For example,
rpm = Sp.___Actual
3k = 4.15___4.07
4.5k = 4.15__3.91
6k = 4.11___3.94
6.8k = 4.11__3.48
coasting afterwards
2.4k = 5.60__7.01

Then, as you can see above, when I let off the throttle following a data pull and coast...the low actual goes more than 1 BAR above specified and I assume this is normal.

Plus, the specified high pressure specified will only exceed 110 BAR after I let off, but not when at full throttle.

High pressure during a pull...redline is 6900rpm
rpm = Sp._____Actual
3.5 = 109.99___110.5
5k = 109.99___114.29
6.5k = 109.99__132.25
then coasting...
5k = 122.00____109.17
3.5 = 113.33___113.33

[pudding]

So under full throttle the requested is 110 bar, but when you back off it increases?!   This is all very confusing.  140 bar mentioned, but requested says 110. 

Have you verified full throttle is actually full throttle in the logs?  It's not unheard of for some "linear" pedal maps to not give 100% throttle valve opening.

How are the other readings?  boost pressure, timing, O2 trimming, intake temps, etc.   Just wondering if the ECU is pegging back the fuel request due to an issue somewhere else, in other words some kind of limp mode?

[ROH ECHT]

So under full throttle the requested is 110 bar, but when you back off it increases?!   This is all very confusing.  140 bar mentioned, but requested says 110. 

Have you verified full throttle is actually full throttle in the logs?  It's not unheard of for some "linear" pedal maps to not give 100% throttle valve opening.

How are the other readings?  boost pressure, timing, O2 trimming, intake temps, etc.   Just wondering if the ECU is pegging back the fuel request due to an issue somewhere else, in other words some kind of limp mode?

Throttle angle is 99.6%...boost actual meets or exceeds specified from 2800rpm on and from 2800 to 4500rpm it is 1.55 BAR in the data because of the MAP limit, but is actually 23 to 24psi on the gauge, and then tapers...Lambda is specified at 0.84 and actual meets or is 0.83 throughout the pull from 3k rpm on...intake temps are always great and drop during a pull(I have the S3 and Forge K04 twintercooler)....and all is on point according to GIAC after having looked at all data sent them. 

The car has no fault codes ever...runs strong all the time...and the only issue is it just doesn't request the 140 BAR it used to per the tune installed. After I reported this to GIAC last year...they said "that's odd" and they wanted to figure out why as did I. I was only concerned if it is OK to run as it does run well. The issue is unnoticeable when operating and only revealed itself in the data I looked at after reloading the GIAC tune last year when I switched back to it from two years on the DM tune.

[ROH ECHT]

So, my lpfp actual falls below specified in upper revs...the hpfp actual exceeds specified at the same time...injection timing is at 10.0 there as well...and the long term fuel trim at load is stored at 13.3% - (-1.7% stft) correction of 11.6%. So there is a lean condition correction but for what? The lpfp deficiency or are the injectors not delivering as they should? Or is the lpfp controller jacked?

More data posted here: http://www.golfmkv.com/forums/showthread.php?p=3812507#post3812507

[ROH ECHT]

I've been told that the 110 BAR request is a tune default for when there is a problem with low pressure and it should be regular when I fix the "below 4 BAR issue". Other factors like adaption value and lpfp duty figure into this trigger...likely just need to replace the oem tank pump or integrate another 10psi boost operated lift pump along with the lpfp. Fingers crossed until this is done and I will report the findings at that time.

Right now...I need to decide on a new oem lpfp or this kit minus the pump and I could use the USP hi-flow pump once I remove it from the basket...I think. http://www.giacusa.com/images/MQB_fuelpump.jpg

http://www.giacusa.com/news_and_media/display_news.php?id=208

[pudding]

Is the lpfp controller OEM or aftermarket?

Certainly looks like the problem is in the lpfp area, which I did steer you in the direction of in my first reply 

[cupra_matt]

Hi.

I had exactly this problem with my GIAC stage 1+ map on my eddy. after 4K rpms it would loose power and torque. Its done this since i bought it.

I had it in R Tech yesterday for stage 2+ mapping and when Niki did the first run on the giac map it was requesting 110 bar and going dangerously lean, as a result of this the ecu was closing the throttle to try and richen itself up.

It had a correction factor of 25% and an injection time of 10ms. so very similar to yours.

At first niki thought it was a hardware fault, but he soon realised it was the GIAC mapping.

Stage 2+ completed i came away with 380 BHP and 405 lbs/ft and what feels like a new car. I cannot belive how bad the graph from the GIAC map was!!

So check your mapping before replacing any hardware!! I can almost guarantee its the map at fault.

Hope this helps.

[pudding]

Blimey, that's a bit poo. 

We had exactly the same issues with GIAC 10 years ago when their software came with US supplied supercharger kits for VR6s.   Sh1t rich in part throttle, too lean in boost, and too much timing.  I'm surprised they are still mapping in that way despite all the negative feedback over the years.  Weird.

[jhook661]

I'm having similar issues too I'm Revo stage 3 k04 conversion the car on full boost after 4K is dangerously lean so the ecu is pulling it back and mine has all new parts
Fuel filter 6.6 bar
Loba hpfp
Rs4 return valve
Brand new s3 injectors
No boost leaks or vacuum leaks either
Fuel pressure is good too
And top of all this the idle is shocking to it hunts and choughs but revs never drop or fluctuates 

[Dan_FR]

If the fuel pressure is good then why are you running lean? Logs? You know the fuel request is adjustable, right?