Boost issues

[Jcornelius]

I have a 2007 GTI with the 2.0t Fsi motor. I bought the car a little over a year ago now from a Volkswagen dealer for dirt cheap cause it was having some problems. Long story short, it ran perfect after about $300 worth of work. It made about 12psi of boost completely stock. Over the winter I decided I wanted to make it faster so I ordered a bunch of performance parts and maintenance parts to put on in the spring. It has a new pcv valve and gasket, new o rings on all boost pipes, all of the vacuum lines were replaced, CTS cold air intake, eBay catless downpipe, CTS coil packs, ngk spark plugs can’t remember the PN for those but it was what was recommended for my tune and they’re gapped correct, N75 valve, MAP sensor, MAF sensor, GFB DV+, autotech HPFP upgrade, and a boost dynamic tuning Stage 2+ tune

Now it just doesn’t seem right. The tuner says the car should be making 23psi of boost 17psi tapering but it maxes at 17psi and doesn’t feel as quick as it should. Around 3000rpms it starts to break up like crazy if I’m really light on the throttle but if I’m WOT it’s smooth as butter until it falls on its face at 5100rpm for a split second then it picks itself back up and starts pulling again for a second till it hits about 5500 where the stock K03 turbo loses its juice. I can’t seem to figure it out. I have no vacuum leaks that I can find or boost leaks. It’s been smoke tested and pressure tested. It spikes to about 17 and holds 15 psi afterwards. Idk what to do next honestly. I asked on a mk5 group on fb and nobody seemed to have an answer that made sense (what a surprise) so I’m coming here hoping for someone more knowledgeable to point me in the right direction. Thanks in advance

 

[Michael gti07]

Are you using the heavy spring for the GFB valve?
It sounds lame, but the carbon buildup might finally be getting to this direct injection engine.
Gotta put a camera down the valve area to double check.
Weak possibility of having oil contamination on maf/map, clean them with Quickdry electronic spray. (Maf cleaner is the same stuff, just a bit more expensive.)

 

[Jcornelius]

Are you using the heavy spring for the GFB valve?
It sounds lame, but the carbon buildup might finally be getting to this direct injection engine.
Gotta put a camera down the valve area to double check.
Weak possibility of having oil contamination on maf/map, clean them with Quickdry electronic spray. (Maf cleaner is the same stuff, just a bit more expensive.)

I don’t think it’s the valve cuz I put the stock one back in and it’s the same results. I’ll check the carbon buildup in a little while here.

 

[ROH ECHT]

I (Brad Roberts) responded to one of your posts on VW GOLF GTI MK5 a year ago, but the issue was for codes p0171 and p0507. Then to another post back in April, where you state it is a 2008 FSI, regarding some top-end ticking. What you describe here now, isn't mentioned in those fb posts in VW GOLF GTI MK5. Was this mentioned on another fb group?

Regarding the issue mentioned here, did it ever boost to 23 psi? You haven't clearly said; only that the tuner said it should and that you notice it only reaching 17 psi. If all is sealed up as you claim, the lower power may be caused by any number of other systems.

If you want to be pointed in the right direction, do you have VCDS or other similarly capable data logging device?

Do you know what both fuel pressures are making, both high and low pressure reports at full throttle throughout the rev range?

Do you know how hard the LPFP in the tank is working both at idle and throughout the rev range? The LPFP data shows its Work Load %.

Do you know what the N75 Duty Cycle % is, at full throttle throughout the rev range?

What is the specified/target boost compared to its actual boost?

Where is the timing's cam phase at?

What is the N75 resistance? Because even a few new ones can be faulty. Should be 25 Ohm...even though VW states within a range of 20 Ohm to 30 Ohm.

What is its PCV setup? Is the PCV paired correctly with its rear vent tube? https://www.golfmkv.com/forums/inde...r-pcv-to-crankcase-breather-tube-info.378931/

There's more yet to question; such as how was the smoke testing done. Were all tubes connected to the intake manifold separately tested when disconnected from the manifold and from the upstream side of their one-way check valves?

Has the waste-gate been tested:

Has the LPFP and fuel filter check valves been checked with a gauge? This is only done with a gauge because when using VCDS the key must be on. The key being on doesn't allow those two to be checked for it continuously primes:

 

[ROH ECHT]

You may consider trying this group...mentioning the year model etc..
https://www.facebook.com/groups/529405700525327