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Discussion Starter · #1 · (Edited)
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Solution has been reached for both the noises mentioned in the title and for another completely separate issue that comes up later in the thread... Post #39 and #40 detail the whole chain of events, investigations, testing, fixes, etc. so if you don't want to read the entire thread then skip ahead to those (and if you are here from my other thread then just skip to #40). They're basically the TL;DR version, although they are still quite long. The super-TL;DR version is this: noises were caused by an exhaust manifold leak caused by the bizarre occurrence of 1 loose manifold stud and 1 completely missing manifold stud. It shocks me that the leak wasn't bad enough to have more noticeable symptoms but it's fixed...

If you are here from my other thread then this part right below is the TL;DR for you, then skip to #40 and #47 for details on the issue, the diagnosis, and the fix...
The second issue that came up at some point in the thread was a boost related issue that was NOT a boost leak and was NOT any other mechanical reason for lack of boost, it was simply that my tune was too aggressive in the boost it was requesting of the little K03 that the wastegate was unable to hold closed against the exhaust pressure against it and was flapping open, thus thwarting the turbos ability to make target boost at all and also forcing the N75 and turbo to work over-time to correct this (unsuccessfully). Moral of the story: if you have K03 turbo and tuning software that requests, say, ~20 PSI or definitely 21+ PSI, you definitely want to take a look at my post #40 and #47 as you may have the same situation and not even know it. I data-logged a friends Stage 2 Eurodyne GTI right after I fixed my issue and sure enough he is having similar looking symptoms...

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Original post:


There is this strange zip/whistle-ish noise that occurs at times when I press the throttle. It almost sounds as if it were coming from the throttle pedal itself or at least pretty low in the engine bay behind the firewall. It does not occur all the time. It seems to only occur after cruising on the highway for long enough (5+ minutes) and if I sit at a light for a bit or turn the car off, etc. it takes a few minutes of being on the throttle a lot to come back. It is loudest during throttle blips (like when rev matching) at which time it is more of a quick whine/zip noise but it does create a bit of a sputtering noise when I'm on the throttle steadily. It happens during partial throttle or WOT, either way. Acceleration is completely unaffected. NO performance loss whatsoever. Seemingly no boost loss (numbers on my gauge look good but I'm gonna keep a closer eye on them from here out), and no symptoms of vac leak.

A throttle switch was my first thought the very first time I heard it due to location of the sound and the absence of any performance issues/DTCs but it quickly became clear that wasn't it based on the way it sounds... doesn't sound like any pedal switch issue I've ever heard; again it is almost a whine/whistle/zip sound when blipping the throttle to revmatch and it makes this sort of light sputtering noise when I get on the throttle and stay on it instead of blipping it. It only happens after I've been driving for a bit (mainly on highway with constant throttle). Never there after cold start and never there in stop-and-go.

I believe we can rule drivetrain out. It occurs in any gear and out of gear and whether clutch is engaged or disengaged.

My only theory at the moment is the N75 starting to tire a little bit. It fits in some respects, but in others it doesn't (e.g. you'd generally expect boost and power loss with an N75 issue, right?). Is there anyway one could be tiring out but not actually causing boost loss?

I have no other theories at the moment so I am open to any and all suggestions and pointers. If I can clarify or go into more depth about anything else that is lacking let me know.

Thanks for you time!
 

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Any scan info? N75 problems should give faults. I do not have vcds but can get fault info with another scan tool (not obd2, more detailed). Check it out and there are many who can help you.
 

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Discussion Starter · #4 ·
Any scan info? N75 problems should give faults. I do not have vcds but can get fault info with another scan tool (not obd2, more detailed). Check it out and there are many who can help you.
Nah, I scanned with VCDS. There's nothing. I plan to log some data and compare what I see to logged data I've saved previously (I keep tabs on my car religiously). I haven't gotten around to it yet because honestly I don't expect to find a anything out of the ordinary. There's literally nothing different about how the car behaves besides the noise, at least for now. That's why this is tricky.
 

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Discussion Starter · #5 ·
I haven't gotten around to it yet because honestly I don't expect to find a anything out of the ordinary.
I spoke too soon. It seems I am down on boost by a bit. Usually hit 21-22PSI, today maxed at 18PSI (AC off). Oddly I haven't noticed any performance loss, car drives totally normal. What gives.
 

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Regarding the N75 fading and shouldn't that give a code?...it can fade and you get no codes. Mine was replaced last year. I had no codes. My boost would only go to 18 psi max, then drop to about 10 psi but would then climb again to about 14 or 15 psi. This would happen in one gear's rev range. When the N75 is on its way out, it seems the boost behavior varies for each of us. But, if you know all is well with the boost plumbing, DV and vac lines...you can assume to try a new N75 when boost is not right.

Now, with regards to the pulsating noise...perhaps that is also associated with the N75 behavior. It has a signal that controls and allows boost force onto the wastegate actuator to control opening of the WG. So, if the N75 has, or has recently, begun to fade...the sound may be related to the first stage of it failing in your particular case...weird behavior in other words. Where now you may be seeing another symptom of further fading seeing abnormal boost.

Hope to see data soon.
 

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Discussion Starter · #7 · (Edited)
Got it, thanks. Data will be forthcoming soonish. As for the vac lines, the only lines I am at all skeptical about would be the brake booster lines as I had to replace them recently. I replaced the lines from the vac pump to check valve and then from check valve to brake booster because the one going into the brake booster developed a small crack so I figured I'd do the rest (Spulen silicone brake booster hose kit). Well while I was removing the one that goes from brake booster into a part of that 4-way plastic valve pass-through flange thing (part of it passes coolant and the bottom part is just for the vacuum hoses to meet up) I cracked off the end to the flange (so fragile) so I wound up just direct connecting the hoses from brake booster to below check valve which required some hose connectors and a short piece of plain old cheap heater hose (which I figured was sufficient for this application). See the pics below

https://drive.google.com/open?id=0Bzeazv76x9MXTndva2U1aGsxemM

Every connection point has clamps and there were NO issues for a good few months but I suppose something could be up someone along the line. Do you think there is any chance that this has something to do with it. Wasn't my first guess as I find it hard to imagine given how secure the install was on every joining part... I guess one pretty simple answer is take them out and re-install and see what happens but wanted to see what you think of symptoms fitting; would a teansy leak have anything to do with this throttle noise? Again, no performance loss and no brake power loss.
 

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Just a wild swing.....intermittent relay issues? Easy to check and costs nothing. I did break my booster line just as you described but the cars reaction to it was dramatic and obvious, I did not have to guess lol. Misfires and limp mode results, not like yours but again, somethings not right. I was told the N75 when the relay acted up (one of the 100s in the engine bay) and tracing wiring it definitely impacts the N75 performace. Easy check and easy check off that problem if not.
 

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I don't think so...but could be opposed to my thinking. I think when the boost is trying to crack the WG...something is off with either the N75 operating incorrectly or the WG preload calibration. Sound, in my opinion, is waste exhaust pushing and pulsating through the WG by amount of exhaust/spring load ratio or the N75 is opening prematurely.
 

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Discussion Starter · #10 ·
So were thinking a teansy vac leak in the new lines I put it is out of the question for this issue? Still thinking N75/WG even though the noise is happening at ANY level of throttle, not just WOT?
 

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So were thinking a teansy vac leak in the new lines I put it is out of the question for this issue? Still thinking N75/WG even though the noise is happening at ANY level of throttle, not just WOT?
Thinking more it's the N75 based on behavior alone...but there is always a chance it is the WG spring and preload may be light to zero. There's always a chance it is something altogether...but you gotta start somewhere. Data for wgdc, boost, and then fuel trims that will show vacuum leak presence.
 

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Discussion Starter · #12 ·
Ten-four. I'll get the data as soon as I can.
 

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Discussion Starter · #14 · (Edited)
I haven't gotten around to logging yet but I did stumble upon some stuff while researching that is making me wonder about whether my GFB DV+ might have something to do with what is going on. The GFB DV+ is a simple yet elegant design and I do believe that it does all the things they say it does but there are some concerns I've uncovered during some research. These range from simple little things like the brass piston becoming dry over time (even if you lubed it well on install) and thus causing issues, to the more serious functional concern that APR has brought to light which is essentially that the heavier spring actuation method that is integral to the DV+ doing what it is intended to do can actually be its downfall in one area... that is, when the ECU decides based on whatever environmental conditions/factors that is needs to pulse the DV the heavier spring makes this this difficult and the ECU can't anticipate or account for that. The ECU is expecting a certain functionality at times that just isn't there.

That's as much as I care to explain about it, a simple summary, there's more I read about too but, at the end of the day, APR and other tuners are only running Rev D stock DV on their super built big turbo cars so there's got to be something to that, I'd assume. And they recommend just sticking with that DV in all applications with all of their tunes. You could say that they are just saying that so they don't have to be responsible for anything when people use non-OEM parts but, when it comes down to it, would they really use the rev D stock DV on some seriously built cars if it wasn't ideal??

Anyway I'm on a little bit of a tangent there. As far as it relates to my situations... well I'm not entirely sure if the GFB does have anything to do with it. If it does then it's kinda sudden considering I had no issues with it for months. That could be dry piston, could be warmer temps making ECU calculated differently, who knows? Or maybe it has nothing to do with it. To be fair, the stuff I relayed above is all second-hand info and it could also be dated. I am aware the GFB has made some revision to their product but I'm not sure if that was before or after the stuff that has been said about ECU actuation difficulties.

I have no real reason to suspect the GFB is responsible other than conjecture. The conjecture is pretty simple... I'm pretty sure that I don' t have a vac leak because I'm pretty sure I'd be noticing other issues and because the symptoms do seem pretty like a minor N75 or DV issue (as you've pointed out ROH) then I figure I should target the GFB before I target the N75.

The real question will be if putting the DV back to stock doesn't change anything then what lol. I'd be 50/50 since there are decent reasons on both sides of the fence for keep it on or keeping it off lol.

EDIT: Annnnnnd of course I didn't keep the flange piece that you take off the rev D to install the GFB piece so now I can't return it to stock without buying a new Rev D. I usually keep these sort of things just in case but figures the one time I didn't is the time I wish I had..... I guess I could actually just remove the spring for the GFB which makes it go back to a stock open or shut function instead of progression with spring, which in theory would be like having the stock DV but if the issue is with something else about it then that wouldn't make a difference
 

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Discussion Starter · #15 · (Edited)
Addendum to previous post:

The plot thickens. I decided to do what I said at the end of the previous post and remove the main piston spring included in the GFB DV+ solution. Doing so is an intentional optional feature of the DV+ design and allows the piston to go back to the stock DV open or shut function. Why anyone would normally do this, I don't know. I did it because I wanted to go back to stock to test my throttle zip issue but I don't have the stock parts anymore. So anyway, I did remove the spring and re-installed the rest.

Well not 10 seconds after I started my car (totally cold start) to my horror it sounded like there was a very loud hair dryer in my engine bay, a constant noise not a flutter, which I hope means it wasn't some kind of compressor surge. I almost shut the car off right away but I knew I installed everything properly (I mean it's kinda impossible to screw up) and I decided to trust GFB wouldn't lie about telling you that you can safely use their product this way, so I let it go a bit longer as there were also no other signs of any problem. No smoking anywhere, no engine surge, no misfire, no CEL, steady idle, steady and normal vacuum reported by P3. Well by the time my car warmed a bit and idle rested down at 800rpms, etc. it was gone. I gave the car a few revs and notice an additional tone pretty much right on the end of the noise my intake makes. So I heard my typical intake noise and then immediately as that ends I hear a tone not too unlike intake noise except higher pitch but quieter. Sounds kinda like a hawk or eagle or screech owl too be honest. I'm bad with bird noises but it's one of those. I decided instead of putting the spring back in the DV+ that I would drive around the block as the car was not acting up in any way other than these new noises. The original hair dryer noise was gone at this point and was also gone while driving but the noise coming on the end of the intake noise when lifting off the throttle was still there. I drove cautiously for a few minutes and built up confidence that I could go for a normal drive, did that, and gained more confidence that I could go for a hard drive. So I did that too.

All told I drove the car for about 20 mins with plenty of hard pulls and I was astounded when I came to realize that this new noise that was happening when lifting off the throttle at low to mid RPMs was precisely what GFB says to expect to happen when you install the DV+ WITH the spring but I also noticed that my car held more boost between shifts which is the WHOLE purpose of the GFB DV+ if you install itWITH the spring in the first place. During this whole drive my butt dyno told me my car probably wasn't down on power and my P3 gauge data indicated nothing was amiss either so clearly the install was fine and things were functioning as intended. I'm confident the new noise while driving is what GFB tells you to expect. I am however NOT at all sure about that hair dryer noise when I first started that car. That is nowhere in their description of the product nor have I come across it in any readings about the product online. So that is of some concern...

Now as far as the original problem this thread is about, I did not notice the throttle pedal whistle/zip or sputter symptoms at all during this drive. That is NOT yet conclusive though b/c this drive may not have been consistent enough to produce it but I will be taking a drive tomorrow that will definitely produce it if it is not fixed. If I don't hear it tomorrow then somehow doing this change to the DV+ (either deleting the spring or lubing the piston, since I did both) somehow fixed the original problem noises that this thread was about in the first place. However, I'm not holding my breath on that because my boost still hasn't gone back to normal. Even though my butt dyno has been telling me ever since the original noise issue came up a month or so ago that my car hasn't lost any power compared to what it should be at, P3 cars reports that I'm still only maxing 18PSI whereas I should be maxing 22PSI and was before this throttle pedal whistle/zip/sputter thing started a month or so ago.

Hopefully this isn't too confusing since we now have 2 separate issues that are both noises that occur with throttle input haha. I will update tomorrow if the original noises are gone. If they are then I just need to figure out WHY ON EARTH my GFB DV+ WITHOUT spring is behaving like it should WITH the spring, as well as find out why it sounds like a hair dryer on cold start and why I'm down 4PSI boost in the first place.

I had contacted GFB via e-mail but with this new finding a phone call is definitely in order... nevertheless I am interested in what any feedback/input that you guys have on this matter. Let's hear it...
 

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Discussion Starter · #16 ·
Update:

Good bit of driving today. The original whistle/zip noise thing that I made this thread about hasn't changed at all so now I'm still trying to figure that out as well as why the GFB DV+ is behaving the opposite of how it should be in regard to whether it is installed with the spring or not.

On the good side, that crazy "hair dryer" noise I mentioned in the previous post on cold start after taking out the spring to the DV+ did NOT happen today at cold start. I don't know whay that was all about but it's gone now completely.
 

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I don't think the DV has anything to do with the noise. I also don't know anything about the GFB DV...I briefly looked at or into it when it first came out but decided that if my AWE DV ever does wear out, I would go back to oem as well.

"Noise still the same"...I still think the N75 is a good place to start. You don't have a situation where it has been this way all along. Something has changed in your boost behavior. That would point me to the N75 beginning to have problems, as long as there is nothing obviously wrong with the WG actuator or rod, and we aren't completely thrown off as to where the noise originates from. We sort of came to the conclusion it is from near the turbo but it may be something else we haven't thought of. You may want to do more investigation of the location of the noise and I would do a visual to make sure, with the WG rod, all is connected and normal there. Then, after you confirm boost specified and actual data, I'd replace the N75. Then see if fixed or not. If not, hold on to the old N75 as an extra. I would still look at short and long term fuel trim @ idle...trim under load isn't relevant to see if there is a leak. If the N75 fixes the boost and not the noise, then?????, is the noise turbo related? If it is and the N75 is good, I would think to adjust WG preload. But it could need more or less spring preload. Depends on when the noise is happening. Try, when doing the data run, noticing what rpm it is when you first hear the noise. Have your data in front of you. Did the noise start when boost is trying to climb and reach max boost or do you hear it when boost has already reached max boost and has begun to taper down? If you heard the noise begin as boost is trying to reach max boost...likely the WG is pulsing open unable to hold closed. If you hear it when boost tapers...perhaps the preload is too much and is opposing the opening of the WG by boost to allow waste to pass. This is just my thinking with my understanding of how the internal wastegate operates...welcome to any input or criticism.

This stuff we could at least cross off to being the source of the noise...there is the issue of changed boost behavior to correct regardless. You get through this and if still there...you just need to locate the exact source. I'm not sure as I haven't heard it. From your description before, it reminds me of boost pulse I get every time I build boost from a low rpm as boost builds initially to reach max pressure. Mine quits when it has reached mid range rpms to redline. If your noise happens other than what I get...perhaps the noise is elsewhere.
 

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Discussion Starter · #18 ·
All sounds like solid advice and makes sense according to what I know about the WG, etc. too. I'll do as you say looking specifically for those patterns in the data logging. I can tell you right now without logging though that the sputtering noise (which is how it sounds when steady on throttle instead of the whistle/zip noise when blipping throttle) definitely begins the second I put the pedal down, even a little bit, and as the turbo is building up to approach max. It's on the entire time. So yeah assuming this isn't something else entirely then it does sound like the WG is unable to hold closed. But in this scenario boost wouldn't climb consistently right? Although max boost is 4PSI lower it still gets up there consistently, no fluctuation on its way up, at least as far as my gauge indicates, but the data logging will be the final word on that...

Anyway, the reason I went into great detail about the DV+ and what was going on after I removed the spring from it is because it makes absolutely NO sense that it is giving me the benefits it is supposed to when it is NOT supposed to (spring not installed) and NOT giving me the benefits when it is supposed to (spring installed). It's literally behaving the opposite of how it should. It's not the source of the original issue, clearly, BUT I can't help but wonder if that give opposite behavior gives some insight into what IS going on with the turbo/N75/WG situation since they all work closely together. I wonder what the DV+ behaving this way can tell us about the actual/original problem.

The way the DV+ works is quite simple. I don't mean to impose but if you do have a few moments just watch this very well done video from GFB's Brett and everything I said will make sense about how it is behaving opposite of how it should.

https://www.youtube.com/watch?v=3EgXspDfI08
 

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Discussion Starter · #19 ·
Made a new thread about the GFB situation so things don't get to muddled and confusing on this thread... I'll update when I get a chance to data log.
 

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