All Things Mk5 > Performance Modifications
Fuel pressure deficiency...
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. :stupid:
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:
--- Quote from: Pudding on September 22, 2016, 05:03:05 pm ---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?
--- End quote ---
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
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