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Power loss - turbo not building boost as before!

Whitedemon

Passed Driver's Ed
Location
Miami, FL
Hey guys, I need some help here, my car is 08 GTI TFSI, recently I've been adding some mods to it but the main one being a water/meth kit. I have a Borg Warner K04 installed with Revo stage 3 software (have had it for almost 4 years now), my car would usually boost at peak 25-26 psi and hold around 23 psi, but ever since I installed the WMI and changed the settings using the SPS switch (upped the timing from 4 to 7) my car hasn't been boosting as before. Now, I don't know if it's just a coincidence that this happens at the same time I installed WMI, I also replaced the oem throttle body pipe with the CTS turbo one and replaced the intercooler hoses. I've checked every boost pipe/hose, make sure all the clamps are tighten up, visually at least I haven't been able to find any boost leak.
Other things I've done trying to fix the issue:
. Deleted PCV valve (replaced with oil catch can)
. Replaced DV valve with GFB DV +
. Checked for fault codes using VAGCOM - nothing comes up

I did some logging (requested vs actual boost) with the settings at B8 T7 F9
1598498270118.png


Once I reverted the settings back to stock, this is what I got
1598498445418.png

You can see how when the ECU is in stock actual matches up with specified easily and even passes it. So could it be the ECU map?

Any other ideas of what it could be???
I appreciate any help you guys could provide me, this issue has been driving me insane for quite some time now. Thanks.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
here's another log I did the other day, notice how actual doesn't meet specified until really late in the RPMs(almost redline), it's like the turbo would be spooling really slow.
1598499932263.png


Also, it's odd that requested peak boost is only 1500 mbar (21.7 psi), for a stage 3 K04 that seems kinda low, like I said before I was hitting 25-26 psi normally.

Another thing I forgot to mention, at the beginning right after I finished installing all my mods, it was boosting 22-23 psi, coincidentally this happened right around the time weather in my area went to shit, it got really humid overnight so I let it pass thinking it was just due to the bad weather since it wasn’t that much difference from before (only like 2 psi less) but then..I decided to do some WOT pulls (to adjust timing for the WMI) and RIGHT AFTER I did this the boost went down from 23 psi to 19-20....

anyone got any idea what This could be?
 
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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Right, it could be the weather. But like you say, when weather changes and it still has the issue, it may be something else.

Putting faith in all you said you checked...I would say grab a multi-meter, set it to ohm, and check the N75's resistance. Unplug it and test at its two tabs. VW spec range is 20 to 30 ohm. I was told replace if not right at 25 ohm. Mine was 22 ohm and I replaced the N75 and all was better. But I do not see yours behaving like mine did before I replaced it. Mine would not reach peak and then drop before trying to build again. It's possible yours has just begun to act up...but I see it more as a WG-Actuator issue.

Not sure how long you've had the car with it's current set-up. But again, it may be affected a bit by weather.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
Right, it could be the weather. But like you say, when weather changes and it still has the issue, it may be something else.

Putting faith in all you said you checked...I would say grab a multi-meter, set it to ohm, and check the N75's resistance. Unplug it and test at its two tabs. VW spec range is 20 to 30 ohm. I was told replace if not right at 25 ohm. Mine was 22 ohm and I replaced the N75 and all was better. But I do not see yours behaving like mine did before I replaced it. Mine would not reach peak and then drop before trying to build again. It's possible yours has just begun to act up...but I see it more as a WG-Actuator issue.

Not sure how long you've had the car with it's current set-up. But again, it may be affected a bit by weather.

thanks for replying. I’ve had this setup (revo Stage 3) for over 3 years now, never had this issue before, also, don’t think a 5-6 psi loss would be due to bad weather, that’s way too much.

I was also thinking about it being the WG actuator, I don’t think it’s the n75 as when it’s set to low boost actual matches specified with no problem, also it does build boost steady, don’t see any sudden drop in boost, It’s only when it tries to reach high boost (20psi or more) that it struggles to get there.

I have some n75 duty cycle datalogs as well, I’ll be posting them in a bit.
 
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Whitedemon

Passed Driver's Ed
Location
Miami, FL
1598574986474.png

1598575138452.png


That's what I get, not sure if that's correct but it will always stay between 40-70% under load. Also, not sure if it's supposed to zig zag like that.
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
That appears very normal. More so when the WGDC first drops...as it will attempt to regulate more so when the actual boost peaks you'll see the WGDC less smooth than later on. Just know the WGDC is a command...a report of what the ECU is requesting. The N75 can do its own operating of the valving depending on the resistance. When the resistance differs from where it should be...the power supplied can operate the WG at an inaccurate opening.

It is still possible the N75's resistance is just a tiny bit off. There was some time when mine was just a bit lower than normal before it began doing the obvious and weird behavior.

Now, you have REVO and isn't it adjustable? Are you certain the boost deficiency isn't due to the settings? I just do not want to lead you down an unnecessary road because I am unfamiliar with the REVO settings if it has this ability and how it can affect the boost. I know a way to contact Fran Revo if your REVO dealer has no direction for you so to eliminate that it could be the settings.

Regarding the WG...you could try adding a bit of preload to see if it makes a difference. I have a vid and pic that may help if you reach the point of trying this.

Remove the clip (it pops off when using a flat screwdriver between the clip and linkage) and turn the 10mm nuts the direction for the result you seek. I generally loosen the nut nearer the end of the threaded WGA rod first and make the adjustment with the other inward nut based on a number of turns. One turn is 1mm...so I may say increase preload 2mm or 2 turns. Preload; "Increase" should hold the WG closed a bit longer as it will take more boost to begin opening the WG. And then; "Reduce" allows it to open more easily.


My vid on WGActuator preload:
 
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Whitedemon

Passed Driver's Ed
Location
Miami, FL
Now, you have REVO and isn't it adjustable? Are you certain the boost deficiency isn't due to the settings? I just do not want to lead you down an unnecessary road because I am unfamiliar with the REVO settings if it has this ability and how it can affect the boost. I know a way to contact Fran Revo if your REVO dealer has no direction for you so to eliminate that it could be the settings.

Yes, I did check the settings, even played around with them, tried different configurations, no change in boost, even after increasing boost from 8 to 9 (max setting), it would still boost the same, no more than 20-21 psi, so I don’t think it’s the map.

I will test the N75 valve as you said, to at least opt that out. If it’s not that then I guess I’ll try adding preload to the WG..is it possible these WGA nuts can become loose over time? Thanks for all the help
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Yes, I did check the settings, even played around with them, tried different configurations, no change in boost, even after increasing boost from 8 to 9 (max setting), it would still boost the same, no more than 20-21 psi, so I don’t think it’s the map. OK, good.

I will test the N75 valve as you said, to at least opt that out. If it’s not that then I guess I’ll try adding preload to the WG..is it possible these WGA nuts can become loose over time? Thanks for all the help
Great, report the N75 ohms you see. Yes, there have been some reporting they found the rod-to-linkage had loosened. May not be the case for yourself, but you can still increase the preload by 2mm and just see how much, if any, change it makes. It you do see it looking much more normal...then you know the WGA spring has weakened.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
Ok, will try that when I get a chance (too busy with work lately).

also, I just noticed the MAP sensor on the throttle body pipe when I touch around it, it feels a little oily? It’s not a lot, but definitely feel the oil..like surface is not completely dry.Do you know if that’s normal? I did take it out and o-ring looks good, also made sure it was tighten up good. What are the chances of it being a bad/leaking MAP sensor?
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Possibly, could be the MAP sensor. You would want to know if it leaks from the seal or through the sensor. If the pipe is aftermarket...the receiver for the sensor may not be a great fit for allowing the seal to completely do its job. I found my intake leaked a tiny bit. Was as though the receiver is too deep. I added an o-ring to it and it sealed. The seal cannot be replaced on the MAF sensor as it is not a true o-ring. So to try sealing it better...you work with it or replace its o-ring. I doubt it is why boost is lower...but it depends on how badly it leaks. I mean, the same thing occurs with the oem boost hose couplers and those seals. They seep oil but usually aren't losing pressure.
 
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Whitedemon

Passed Driver's Ed
Location
Miami, FL
Possibly, could be the MAP sensor. You would want to know if it leaks from the seal or through the sensor. If the pipe is aftermarket...the receiver for the sensor may not be a great fit for allowing the seal to completely do its job. Ifound my intake leaked a tiny bit. Was as though the receiver is too deep. I added an o-ring to it and it sealed. The seal cannot be replaced on the sensor as it is not a true o-ring. So to try sealing it better...you work with it or replace. I doubt it is why boost is lower...but it depends on how badly it leaks. I mean, the same thing occurs with the oem boost hose couplers and those seals. They seep oil but usually aren't losing pressure.

that's what I thought as well, it doesn't seem to be losing pressure through there, I have the CTS turbo pipe, the sensor does look to be sealed good, even when I took out the sensor and put it back it took a little bit of force to push back in the o-ring which is a good sign, just had that little concern, but even if it was leaking through there.. it doesn't look big enough to amount for 4-5 psi loss. Also, I have the water/meth bung right before the sensor's, so that oily substance could come from that too ??
lol I'm just trying to rule out all possibilities here since this thing's been going on for weeks
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
So...I decided to take out the MAP sensor again today to have another look, and this is what I found, I know oil shouldn’t get past the o-ring and there looks to be plenty of it (and some methanol too) on the inside surface of the sensor so there does look to be a very small leak, now...I don’t know if this alone would be responsible for the almost 5 psi of boost loss?
 

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ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Well, it's definitely leaking. Yeah, there should be no oil beyond the o-ring. Not sure if you can find the correct sized o-ring to try replacing it. I would at least try that so you'll know if it leaks boost there or not. O-rings do eventually harden and hold their shape and their flattened spots. My guess is if you put the MAP into its socket in the pipe without the two bolts and wiggled it about...you'd feel some slop in the fitment.
 
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Whitedemon

Passed Driver's Ed
Location
Miami, FL
Well, it's definitely leaking. Yeah, there should be no oil beyond the o-ring. Not sure if you can find the correct sized o-ring to try replacing it. I would at least try that so you'll know if it leaks boost there or not. O-rings do eventually harden and hold their shape and their flattened spots. My guess is if you put the MAP into its socket in the pipe without the two bolts and wiggled it about...you'd feel some slop in the fitment.
Yup, I did feel the slop, it wasn’t a very tight fitment, I thought that was normal...

I think I’ll just go ahead and replace the whole sensor since I can’t find that o-ring being sold separately...also to have a complete peace of mind.

I’ll post an update after I do this to let you know how it went, thanks again!(y)
 

GIACUser

Master Wallet Mechanic
Location
SoCal
Just to clarify, this problem came into being seemingly after WMI install?
If so, can you post up a diagram of your WMI plumbing/assembly/specs?
 
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