# COMMON Question: Boost Surge - Fluctuation - Flutter



## DMVDUB (Jan 11, 2010)

I'll start by saying I know this is a very, VERY addressed subject. The reason I'm addressing it again is because there are so many threads that have questions, speculations and no proven answers. The intent is for this to be the end all to those who suffer from boost surge or fluctuation. This is to be a discussion that had DEFINITE and PROVEN results not just speculation. If you are just throwing out an idea or regurgitating the common knowledge behind this issue, please state that you haven't used the idea to fix the problem but it could be a viable option to fix this issue.

That stated I will list the common thought's behind these gremlins or what (we think) causes them:

#1. SOFTWARE 

There is a general consensus that the software causes the problem.

_I have owned several software packages for the K03s and the K04 and I have always suffered from boost fluctuation. Some software acted a little different but the problem still existed. So I know by experience that it's not just a software issue._

#2. N75 VALVE

There is another train of thought that says the N75 is to blame for this. Now sometimes this is true. Some people may see a significant change by replacing a faulty N75. (This is a good thing to check, the problem lies behind the fact that most shops will not take back a N75 if it didn't fix your problem. I got lucky with the shop I use. Best thing is to swap with someone who doesn't suffer from this problem before buying a new valve.)

My personal experience with this hasn't been good. I bought a new N75F to replace mine. It didn't change anything. I have been told that some people have had success with Unitronic's tune STG2 and the "J" valve to alleviate this problem. I generally steer anyone away from using any N75 that isn't OEM for their engine. But, I will be trying a "J" valve to see of it in fact does help.

#3. BOOST LEAK

Another very common thing to blame is a Boost Leak. This is a very viable option to this issue since the fluctuation you see (example) 20-15psi 15-20psi 20-15psi and so on.) could be the pressure rising and causing one or more of the rubber couplers to expand releasing enough boost for it to seal again, then reach the level of boost where the seal breaks again. This is very possible, where I have a problem with this lies in the presence of a "whistle" sound when the boost is escaping. Or, the obvious issue that if the coupler is expanding enough it will eventually come free of the pipe, leading to a loud "POP" and loss of power.

_This is not something I've encountered on my own car, so I can't really give a 100% solid answer from experience. I can say that this does happen. So, checking your couplers doesn't hurt and changing rubber to silicone doesn't hurt either. _

#4. WASTEGATE MALFUNCTION

One place you can look if you're seeing a fluctuation or general loss of boost is the wastegate nut. Mainly the outside nut. (furthest from the actuator). If this nut comes loose, and it does occasionally you will definitely notice something "fishy" going on. Mainly you will see a big drop in your max boost, but second you may see it fluctuate.

_I have experienced this many times. The nut closest to the end of the rod has a tendency to come loose (especially if you have ever "cranked your wastegate"). This isn't commonly, or let me say, hasn't ever been the solution to the fluctuation problem. A slight improvement IF the nuts aren't tight on either side of the flapper._

#4B WASTEGATE MALFUNCTION 2

The second kind of wastegate malfunction could be inside the actuator itself. Meaning the diaphragm inside had torn. (I have never replaced a wastegate and had it fix the surging issue, I ran a Forge Wastegate on my K04 and still had the same issue.)

I'll throw out a few other speculated causes for this issue, I'm not going into detail on them but I will note a few common others.

1. FAULTY MAP SENSOR
2. FAULTY MAF SENSOR
3. FAULTY O2 SENSOR
4. WORN OR TORN GASKET (TURBO 2 MANIFOLD)
5. WORN OR TORN GASKET (MANIFOLD 2 HEAD)

***ONE WAY TO NARROW DOWN THE SEARCH FOR THE CAUSE OF YOUR SURGE IS TO INSTALL A MANUAL BOOST CONTROLLER, SET AT YOUR COMMON MAX PSI (MINE IS 20PSI). THOUGHT BEHIND THIS IS, THAT IF THE TURBO HOLDS 20PSI ON MANUAL BOOST CONTROL YOU HAVE KNOCKED OUT ALOT OF THINGS THAT COULD BE THE CAUSE. 

_What becomes very annoying about this is 1. the MBC and your ecu won't like each other due to the lack of part throttle control. 2. the MBC may tell you that everything is fine except the N75 or your Software, this becomes very painful when you install new software or a new N75 and the problem is there still._

Let's try to make a end all to this issue. If you have suffered from this and have fixed the problem tell us how. Please include your mods and specifically which software and what fixed the problem.eace:


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## redefine6 (Jun 24, 2009)

Yep, we've been over this plenty. My specs are below. Had the little 20psi-15psi -- 15psi-20psi surging going on. I had limited available n75's to test at my disposal. I tried nearly every revision (except J, couldn't get ahold of that one) and none solved my problem. To take a guess, the aggressive onset of boost from my unitronic tune was too much for the n75 to respond in time therefore causing a soft limp after boost rose above 20psi.

Solution: MBC by itself (very squirly, but fun)

or

MBC(BoostValve Overboost kit) + N75 in parallel, I bought the boostvalve from HStuning for like 40bucks, worked like a charm (Very very smooth, no partial throttle issues)

I used the following Diagram for this setup:










Note: I wouldn't consider my n75 to be faulty, perhaps it just wasn't designed for that level of boost / pulse frequency considering the majority of these 1.8t tunes are pushing nearly double the amount of factory boost.

DMV: When you try out that J valve let me know how it goes. Is the J type from the audi TT ?


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## DMVDUB (Jan 11, 2010)

No the "J" is from the AUDI 5cyl turbo (I think that's where it comes from) That's just a shot though.

And you're very right about the overboost setup. I ran this for SO long, but my car didn't like it too much. It does work though with some tweaking. 

Thanks!

EDIT* I am running the J valve now and it runs perfectly no more fluctuation, no overboost just runs well.  (not that this would be the case for others. But if you have a Gonzo tune you may be able to take advantage of the J valve too. Seems to respond a little quicker.)


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## 4bagels (Feb 10, 2009)

One thing it always felt like to me is rising exhaust backpressure AFTER the wastegate, which affects the calculations of what position the N75 should command.

So it would go like this... You hammer the throttle, let's say the ECU tells the wastegate to open 30%, and boost rises right up to 20psi (so far so good). But the exhaust backpressure then rises, so after one second, 30% isn't doing what it did before and boost falls off to 15psi. The ECU sees that, and starts closing the wastegate to bring boost back up to 20psi, and this whole process starts cycling.

So I guess a question would be - has anyone seen this problem diminish when they installed a less restrictive exhaust system?


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## DMVDUB (Jan 11, 2010)

Good question and theory:thumbup:

I know personally when I've run straight downpipe dump the problem still existed, that's about the least restrictive it gets. 

But, if anyone has had an exhaust remedy the problem let us know!eace:


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## simangunsong (Jan 23, 2007)

*Flutter question*

I just installed a neuspeed cold air intake on my 05 GTI. The car seems to run well with it, but the wastegate, is much louder and ends with a flutter. is this normal because of an increase in the air flow? or do I have wastegate issues? ( I am new to the 1.8t) Thanks for any help and advise, sorry if a million people may have asked the same question.
Shawn


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## Vince.:R (Nov 15, 2009)

Yeah it's normal, I have the neuspeed p flo short ram and it makes a flutter noise. It could be your DV but from my understanding if your DV was bad you'd have a CEL


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## DMVDUB (Jan 11, 2010)

If you're hearing a flutter, sounds kinda like "cha cha cha" when you let off the throttle you are experiencing compressor surge. This is very different.

Compressor surge (which is what both of you are speaking of)

Comp' Surge is the air backing up on the turbo and causing the turbine to come to a stop (or close to it) it's bad. Thing is a lot of K03 cars have this issue after being "chipped". The solution is either a fresh 710N DV or an aftermarket performance DV ( I use a Forge 007). 

I still get a little surge now and then, but having the proper spring rate in the DV makes a big difference. Also I have found that the return line that goes to the DV from the intercooler pipe is restrictive and will most likely fail over time.

By using a larger diameter hose for the return line you will see a slight improvement in this area. I have a 1" heater hose that after running for some time retains its shape from the heat.

Thanks Guys and your questions are fine, I made this thread to try and have an end all to the many repetitive threads on the same subject. Hence the name (more words easier for searching.)eace:


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## simangunsong (Jan 23, 2007)

*Flutter question*

cool, thanks guys, I am looking into a APR R1.eace:


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## DMVDUB (Jan 11, 2010)

The APR DV is very good because it it a fast acting valve, being a diaphragm style valve. The only issue is you can't fine tune it for your setup. You would be better off with a piston style DV like a Forge product. For one the piston type are good forever, you only need to keep up on the service (keeping it lubed, I clean and lube mine every oil change just for good measure.) The second big advantage to the APR valve is the ability to fine tune it for your output levels. By switching between springs and shims and also running in reverse or not you can really reduce any compressor surge that may still be lurking around. Also whichever valve you choose, I recommend Forge but either way buy a length of at least 1" heater hose and make a new return line from the DV to the IC piping. It makes a world of difference.

Also deleting the N249 can have a positive effect when it comes to remedies. eace:


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## redefine6 (Jun 24, 2009)

I've searched and googled and still can't understand why one would bypass/delete the n249 in order to remedy surging. I can see this would be viable if the n249 is malfunctioning, otherwise, wouldn't the n75 be responsible?

Any insight with regards to surging and the n249 mod?


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## redefine6 (Jun 24, 2009)

p.s. Not sure if this in considered a bypass. BUT, I had capped the line going to the diverter valve and spiced the FPR vacuum line and ran it to the diverter valve instead for testing purposes. Saw NO difference.


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## DMVDUB (Jan 11, 2010)

I have a new solution to the flutter some of us experience from out diverter valves. 

By first connecting the DV to the intercooler pipe directly. ( I used a couple clamps and about 1.5" of heater hose).

Second, run a pipe (I used dishwasher drain hose, it's very strong and can hold the heat well) to a 90* bend going into the TIP, where the DV is normally located. 

I am currently using the blue spring in my forge 007 with this setup and vacuum source from the throttle body. Ever since I have swapped locations I have experienced no flutter whatsoever.

**Another member has noted that by lubricating the N75 with some penetrating oil you can revive the N75 to some extent. He can explain further if he feels so inclined.


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## LGDUBR (Mar 13, 2007)

I have a hyperboost hx diverter valve which comes pre-lubed from the factory with silicone grease. It seems to me that, once that lube wears out (about every 3k miles) my boost surge gets a lot worse. But, after I crack it open and re-grease it, the car feels 100x better. It's not 100% cured, but definitely a significant difference. I've been meaning to install the factory 710p valve just to see how it feels but need to figure out where I put it first lol


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## jannepower (Jun 28, 2011)

What I have seen:

Boost oscillation in fullthrottle.
Wrong moded pid maps in ecu.


Driving in highway then push gaspedal about 50-70% boost rises 1700-2100 mbar you see hesitation and afr drops 9.5-10 and ecu starts closing tb.
Wrong moded vg calibration or tightened vg.
Remember 50% duty in n75 is not 50% vg position.

I hope someone knows what I mean sorry for my bad english.


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## madmax199 (Oct 28, 2009)

Good thread:beer:!

One thing you haven't touched though is OEM turbos (KO3/K04) having too weak of a wastegate springs to have good enough control when higher boost(24+ psi) is targeted. That conditions makes boost "yo-yo" up and down because the wastegate flap is creeping open even before n75 request or full boost is reached. 

For those that suffer from this, I have added external 5lbs springs to the acutator rods to give it more strength and control(max boost had to be adjusted down but boost is controlled much better with no fluctuation). It's a common mod on other platforms and works like a charm.



Uploaded with ImageShack.us


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## Audi_Mechanic (Mar 24, 2012)

I experience the same problem after installing GIAC software into my stock 20AE. Would spike to 21 and fall down to 17psi when under high load. No flutter from the recirculation valve when shifting, I could hear the turbo spooling up and slowing down, and could feel the car pull & let off.

Larger SMIC smoothed it out a little but didn't fix it.

3inch catless downpipe made it worse, would spike up to 22.5 when under high load and fall flat on its face down to 14 psi and go back and forth. After the ECM adapted, it wouldn't spike past 17 -18 but was far more annoying since it then occured in all gears, not just under high load.

Regapped recently installed Audi/NGK plugs to 0.028" and it smoothed it out a lot and would only surge between 17-15 or 17-16psi. 

Replaced the N75 wastegate solenoid with the correct replacement from ETKA (06A 906 283E, same part # for 180 & 225 1.8's) and the surging is GONE! Smoothly builds boost to 15, when under high load it will smootly build to 17 without hitting soft limp mode.


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## Slimjimmn (Apr 8, 2006)

here is the problem on vortex:
1-person has a problem
2-person goes on vwvortex and makes an account
3-person starts a thread about their problem
4-people reply some, op responds some
5-person obviously fixes their car and never gets back on to post a fix
6-repeat steps 1-5
it happens 75% of the time with diagnostic issues


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## northdakotablows (Aug 22, 2011)

good write up. Still havent found out why mine is still acting funky, threw in a mbc left it at 0 and it went away. Now the tune is pointless because i have no mediation without flooring it:screwy:


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## [email protected] Performance (Jul 20, 2011)

madmax199 said:


> Good thread:beer:!
> 
> One thing you haven't touched though is OEM turbos (KO3/K04) having too weak of a wastegate springs to have good enough control when higher boost(24+ psi) is targeted. That conditions makes boost "yo-yo" up and down because the wastegate flap is creeping open even before n75 request or full boost is reached.
> 
> ...


 I've noticed that this is a common occurrence with the newer production year cars. For example, 2001 (AWW) and 2002-2003 (AWP) have no issues holding boost perfectly, but 2004 and 2005 MY's have issues holding boost properly sometimes, even with the same exact software. Its not 'surging' by definition, its a mere fluctuation due to the wastegate opening and closing, but it only happens is SOME cars. Not all.


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## groggory (Apr 21, 2003)

Looks like a good thread.

Adding it to the FAQ for stock boost flutter and surge


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## rodgertherabit (Apr 16, 2009)

madmax199 said:


> Uploaded with ImageShack.us


makes sense to me, but there must be a better way to add more load to the Springs...:beer:for the effort!


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## SweetRide (Jan 7, 2004)

Subscribed!!

I have this same issue, I was recently upgraded to APR stage 2 and I was hitting 26psi (where before it was 21psi and holding 18)and holding 21psi after to many runs like this it would put me in soft limp and I also started fluttering at times. I then hooked it up to vagcom and saw an over boost code also saw that the MAF was not reading accurately. Also at this time the car would only boost to around 15psi and would jump up and down like crazy. So I replaced the MAF and the N75 valve just in case, but there was no change and its still fluttering like crazy! Curious now if it is not my waste gate spring! I'm in for more answers!


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## Audi_Mechanic (Mar 24, 2012)

The boost fluctuation may be caused by the simple fact that aftermarket software is being installed with stock hardware that was designed by Audi and borg warner systems to work within audi's design parameters. Audi increased power output with the 210 and 225 models by changing compression ratio, piston/rod design, intercooler design, and the size of the turbo. Those higher output engines don't have a problem with surging, unless they have a problem with hardware. 

So anyone who has made major changes like a larger turbo and/or external wastegate and still had surging or alleviated their surging by doing such, should chime in.


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## Audi_Mechanic (Mar 24, 2012)

Installed a FrankenTurbo F23 with GIAC 380cc k04-23 software, and surging was insane. Would spike past 25psi and eventually fall to 14psi when soft limp mode activated. New TT 225 MAF sensor and injectors, new turbo inlet hose, new exhaust gaskets & nuts were installed with the F23. Installed a ball and spring type manual boost controller in parallel with the N75, set to crack open at about 20psi, and surging is gone.


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## AnniGTI3194 (Mar 25, 2005)

*surge at low rpm...*

thank you for this informative thread. 

I read through all of the posts here and didn't see anyone with this problem yet... its a problem I've had for the past 2-3 years with my car but I've ignored it. When I accelerate lightly in first gear, I put my foot on the pedal and my boost immediately shoots up and then down, causing my car to jerk around. However, I'm fairly sure my car does not suffer from a boost leak, because when I am accelerating in 2nd gear and beyond (more pedal to the metal), it holds boost like a champ. 

A shop recently tried switching out the spring in my Forge 007 but it did nothing. I'm also running Revo Stage 2, Eurojet Street FMIC, Forge Boost Hoses, N75H, etc. 

Here is my complete setup listing: http://www.parts4vws.com/registry/registry_detail.asp?MemberCarID=11819 

Does anyone have suggestions on what this problem could be? Maybe try switching the N75 to a J valve? 

Thank you! -Cameron


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## groggory (Apr 21, 2003)

AnniGTI3194 said:


> However, I'm fairly sure my car does not suffer from a boost leak, because when I am accelerating in 2nd gear and beyond (more pedal to the metal), it holds boost like a champ.


 Wrong. 

You can have a boost leak and still hold boost just fine. 

Do an intake pressure test per the threads at the top of this forum to verify. 

Also, do an exhaust leak test per the threads at the top of this forum. 

Post back any leaks you found. Then fix said leaks. 

Then clear codes with vag com. 

Then drive around for awhile. 

Then post up your block 032 values


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## AnniGTI3194 (Mar 25, 2005)

groggory said:


> Wrong.
> 
> You can have a boost leak and still hold boost just fine.
> 
> ...


 Thanks so much for your input, I definitely will do this.


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## Rivals Inc (Jul 30, 2009)

Ok, here we go....i have a problem and just may have found solution.

2001 jetta 1.8t
Mods
evolution cold air intake.
Ported & polished intake manifold & head.
NGK laser platinum plugs
Forge DV 007 with blue spring.
Ko4.
3 inch exhaust with cherry bomb & borla muffler
I do not know the software im running, sorry!

Problem. I would loose boost a lot, i run up to 24 lb's it would go from like 24 to 15 lb's. THEN it would hardly build any boost at all! the turbo acts as if there is a limiter holding it back. Ok so i replaced the OEM diverter valve with the forge thinking it would stop, but no still does it. My MAF sensor is bad. i have a new one on the way. BUT! You know the elboy hose at the back of the motor that goes from the intercooler pipe to the turbo? I used to have a problem of that slipping off under high boost, and the hose clamp managed to tear about 2 inches of the lip off the hose. Could this also be the reason i am getting no boost at all?


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## 2.8 guy (Aug 10, 2005)

A manual boost controler hooked up in parallel to the N75 is how you can stop these fluctuations. The N75 is just to slow to respond to the quick onset of boost the turbo makes at higher psi. Most of these tunes are for 17-22psi and theses little snails can make that very quickly...faster than the N75 can control. The car starts to see boost higher than requested/tuned, (i.e. your 22-25 psi spikes) and tries to cut back, it then is lower than requested and tries to turn it back up....enough of this and it goes into limp mode. 

I was having this issue with my uni 1+....spikes around 23psi. Tune was set for 20psi, this caused my limp mode and annoying boost fluctuations. I installed a mbc (boostvalve) in parallel to the N75, set it to 20psi and have not had limp nor a single fluctuation since install.

:beer::thumbup:

edit: basically what redefine6 said...


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## Rivals Inc (Jul 30, 2009)

^ yeah but....mine wont even go past 5 lbs =(


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## Glasser (Jul 24, 2010)

Rivals Inc said:


> ^ yeah but....mine wont even go past 5 lbs =(


That means that your car is in limp mode.


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## 2.8 guy (Aug 10, 2005)

Rivals Inc said:


> ^ yeah but....mine wont even go past 5 lbs =(


this information only applies to engines in proper working order...that tear in your elbow absolutely must be repaired before you can even start to question or diag your limp mode.


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## Rivals Inc (Jul 30, 2009)

I'm going to check it out tomorrow hopefully. My car us at my college in the shop. So i have to get a ride there & what not. And that N75 valve....hm i will be looking at that too. 

ALSO, something this thread lacks is some videos. With my problem i will be doing vids, and posting them on here. Vids will really help, especially clueless people like me, lol.


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## AnniGTI3194 (Mar 25, 2005)

Hey guys, update on my problems with this power loss/boost surge issue. 

I first replaced the N75 valve on my own. I went with the ECS Tuning N75 race valve. It didn't help. 

I just took my car to EUROWURX in Burbank, CA. Let me say, I am extremely impressed with this shop and the owner and staff are all very knowledgable on issues like this. :thumbup: 

They found that I am experiencing a giant exhaust leak... the system on my car is a piece of junk and I'm currently researching new 20th AE turboback exhausts. 

I'll post up after I install the new exhaust. Thanks for everyones help!! 



groggory said:


> Wrong.
> 
> You can have a boost leak and still hold boost just fine.
> 
> ...


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## diesel66 (Aug 7, 2012)

hi, i am experiencing the exact problem but cant fathom how a leaking exhaust can cause our problem. can you explain what the eurowurx told you to convince you this is the right path, i haven't done the seafoam thing yet but laying under the car whilst running i cant see,hear or feel a leak so i am very keen to see your outcome.


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## groggory (Apr 21, 2003)

diesel66 said:


> hi, i am experiencing the exact problem but cant fathom how a leaking exhaust can cause our problem. can you explain what the eurowurx told you to convince you this is the right path, i haven't done the seafoam thing yet but laying under the car whilst running i cant see,hear or feel a leak so i am very keen to see your outcome.


 Exhaust leak = bad o2 data

Bad o2 sensor data = lose


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## AnniGTI3194 (Mar 25, 2005)

diesel66 said:


> hi, i am experiencing the exact problem but cant fathom how a leaking exhaust can cause our problem. can you explain what the eurowurx told you to convince you this is the right path, i haven't done the seafoam thing yet but laying under the car whilst running i cant see,hear or feel a leak so i am very keen to see your outcome.


 they said that I am experiencing power loss in the low end of things due to a massive exhaust leak. once that leak is fixed, they can move on to diagnose the problem if it is still happening. could also be a variety of things contributing to the problem, since I have a lot of other bolt-on mods the car. 

again, the car holds boost fine when I am punching the gas to the floor ... the boost just sort of flutters when I am lightly accelerating the car in 1st and 2nd gear, making the car jerk around a bit. 

still working on finding a moderately priced aftermarket exhaust system for my 20th... if anyone has any suggestions, please let me know


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## Andaloons (Apr 16, 2004)

AnniGTI3194 said:


> still working on finding a moderately priced aftermarket exhaust system for my 20th... if anyone has any suggestions, please let me know


 Check this one. 

I've had mine now for over a year and put 35k miles on it with no problems! :thumbup: 

Get your own band clamps for this system; the ones that come with it are crap.


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## diesel66 (Aug 7, 2012)

car was recently at VW in New Zealand and they never picked up on O2 readings being out but i am in the process of ordering my own vag-com(vcds) but living here its a $500+ investment


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## groggory (Apr 21, 2003)

diesel66 said:


> car was recently at VW in New Zealand and they never picked up on O2 readings being out but i am in the process of ordering my own vag-com(vcds) but living here its a $500+ investment


 Why so expensive? Currency weak? Shipping?


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## diesel66 (Aug 7, 2012)

all of the above, we only get 80 cents to your dollar and i wanted to future proof by getting the version that will do later model vw's as well (hex+can-usb)


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## groggory (Apr 21, 2003)

When you get it register in the vag com owners thread, help out your locals


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## diesel66 (Aug 7, 2012)

will do thanks


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## diesel66 (Aug 7, 2012)

have since done the seafoam exercise with no discernable leaks so that rules that out for our problem


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## DMVDUB (Jan 11, 2010)

Diesel66, please post EXACTLY what's going on along with what you've done to try and fix it. When I say what you've done to try and fix it I mean EVERYTHING even things you think are insignificant, as every little thing matters. Once we know what you've done, we can start to lead you in the righ path. 

So, use a format:
Car ( make model etc )
Engine code 
Upgrades / performance 
Tuning software / "chip"
How many miles
What you've replaced maintenance wise
How Long it's been going on


Thankseace:


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## Slimjimmn (Apr 8, 2006)

I had a pretty large pre-front o2 sensor exhaust leak with no performance problems or fuel trim problems. 
It SHOULD cause a rich condition for sure, but for some reason didn't for me.


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## jthomas (Nov 9, 2012)

*Nooby Questions on boost flutter*

I recently purchased a 02 GTI 1.8t that already had some mods done. Now Im new to gas turbo engines so please bare with me. 
The car has what looks to me to be a K04 turbo w/ EuroJet intercooler. Forge DV, AEM cold air. Im assuming it has had some programming work done cause when I can keep the boost in it will hit around 22psi. Im having a surging issue most of the time. The only time I can get the boost to hold is when the thorttle is to the floor. Any other time it surges from 20-22psi to 0 then back to 20-22psi. it is very annoying and it has a full magnaflo exhaust so everyone around me knows it is doing something silly. I have also noticed that if it is at full boost with the thorttle wide open it tends to flutter a little. I took everyones advice and cleaned/lubed the DV (it was nasty)I am very fortunate I have played with beetles for the last couple of years and I have a spare complete engine so I swapped out the N75 valve. It still surges. Im really wanting to know what exactly will happen if I go to a manual boost control? Its a manual tranny so what will limp mode do? Im really wanting a smooth steady boost. Is this even possible? Please keep in mind I dont know all the abbviations. Thanks for any imput.


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## radlynx (Jan 4, 2007)

bump...


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## diesel66 (Aug 7, 2012)

to AnniGTI3194 i fixed the exact same problem you had with boost flutter, i did two things so am unsure which one fixed it. the throttle body was clean on the intercooler side but when i took it off it had oil residue on the otherside so i cleaned and polished both sides but i also cracked open the tps and sprayed contact cleaner on it


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## MGs05GLI (Oct 4, 2006)

Hi,

I recently purchased a 2005 GLI (49,xxx) with the following mods.

GIAC (most recent version I believe)
Turbo back 2.5" Techtonics exhaust
Forge DV (not sure which spring)
Forge TIP
Eurojet FMIC
Power gasket

It has the stock N75 valve and I am experiencing boost surge only under partial throttle to mostly full throttle. I don't seem to have any WOT issues. I will spike to 18-20 and drop to 13-15 and then back to 18-20. If I press down on the throttle boost settles lower than if I had been WOT from the get go.

I contacted ECS about their N75 Race and they, as they had mentioned in another thread, said that the valve reacts differently depending on several factors which have already been discussed (chip, mods, MY, etc.). I'm interested to see if the valve will work on my car and if it does, I will report back my successes or failures.

I do like the setup mentioned in the second post about the boost valve MBC partnered with the N75. If the ECS valve doesn't work, I may go that route.

Thanks again for creating the thread.
-Mark


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## Audi_Mechanic (Mar 24, 2012)

you have to re-gap your spark plugs to a smaller dimension. doing this makes a big difference. 

increasing boost pressure allows more air & fuel to be injected into each cylinder, which increases the resistance of the air/fuel charge, requiring more spark energy to ignite it. since there aren't any simple ignition upgrades, you have to shorten the spark plug gap. 

the 'race' N75 isn't going to help. it actuates too slowly and won't allow the ECM to properly control boost. The factory N75 wasn't designed to maintain the higher boost pressures, it's just too slow. Using a ball & spring type manual boost controller plumbed in parallel with N75 is the most effective way to control boost IF there isn't anything wrong with your engine such as boost leaks or worn out N75.


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## DMVDUB (Jan 11, 2010)

The part throttle boost issue is because of the software trying to match the request boost level with the actual. 

the turbo boosts faster than the ecu expect at part throttle so it cuts boost then in goes below requested so it goes back up and so on. 

GIAC does that.


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## MGs05GLI (Oct 4, 2006)

Thanks for the comments. I've only had the car for a few weeks so there may be some driver adjusting as well. I understand that the K03 spools quickly and with the boost hitting 20 PSI the system tries to correct things but just reacts too slowly. I'm most likely going to keep the stock N75 and see if a spark plug change helps, or just deal with it since it doesn't happen all the time.

My other options would be to just get a bigger turbo and have a different tune that I'm sure would alleviate a bit of surging. 

Thanks again.
-Mark


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## DMVDUB (Jan 11, 2010)

You can "uncrank" your wastegate a tad and it will usually alleviate the spike and boost hunting issue from a mechanical standpoint. You don't want to do it so much that you lose boost, just a couple threads at first, drive it and then adjust to the better side of things. :wave:


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## jetta021.8t (Feb 13, 2009)

Put this post up and was told to check out this one so he is the deal maye some one has and idea..

Just took my car for a wick ride after installing my surge tank and happen to notice my boost pressure acting up. 

Did a pull in 4th and boost will hit 24 ish then drop to 20ish and do that back an fourth til.. Seems to get a little better when the rpm gets closer to redline.

Check for boost leaks and I have nothing..
I have a boostvavle controller to a tial 38mm wg... The one hose rip so it's 1/4" one side and 5/16" on there other.. Could this be the issue?(going to change anyway)

Can a wastegate spring get weak over time and cause something like this?
I have this video but it's a bit shakey form holding with one hand but u can hear it and see it at the end of the video ..
http://youtu.be/Qv_bSLAD54A
Thanks for any info


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## DMVDUB (Jan 11, 2010)

jetta021.8t said:


> put this post up and was told to check out this one so he is the deal maye some one has and idea..
> 
> Just took my car for a wick ride after installing my surge tank and happen to notice my boost pressure acting up.
> 
> ...


both answers are yes... Look at the bold in the quote


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## jedge1.8t (Jan 27, 2012)

Whats the cause of the part throttle boost drop when you run a manual boost controller?

The n75 delivers boost smoothly on partial throttle, it was cool because at partial throttle my car would actually feel like it was it was WOT at times.

when i run my AEM tru-boost at nearly any duty cycle my boost builds until whats requested is met then boost drops to about half of what what was achieved. Its like the car accelerates really fast then just stops abrutely at the set speed. 

WOT spikes 23-24psi then tapers to about 18-19psi under and holds it though.


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## DMVDUB (Jan 11, 2010)

jedge1.8t said:


> Whats the cause of the part throttle boost drop when you run a manual boost controller?
> 
> The n75 delivers boost smoothly on partial throttle, it was cool because at partial throttle my car would actually feel like it was it was WOT at times.
> 
> ...


AEM tru-boost us an EBC but...

MBC's are made for all or nothing boost. There's no in-between. No matter what you do the N75 will ALWAYS be the smoothest option. Think about it, it's controlled by the ecu that knows how much throttle the engine is getting and how much boost it's to request at that level. 

A boost controller can only guess at what you want. If the turbo is big enough you will have lag that will make it seem smooth though


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## jedge1.8t (Jan 27, 2012)

I guess the N75 has the beauty of knowing where the throttle body position is at, its weird because when the N75 is on and half way on the pedal feels very similar to pedal to the floor. 

is it possible to run a boost controller and a N75 parrallel to eachother to retain the smoothness?


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## DMVDUB (Jan 11, 2010)

jedge1.8t said:


> I guess the N75 has the beauty of knowing where the throttle body position is at, its weird because when the N75 is on and half way on the pedal feels very similar to pedal to the floor.
> 
> is it possible to run a boost controller and a N75 parrallel to eachother to retain the smoothness?


Yes


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## groggory (Apr 21, 2003)

DMVDUB said:


> AEM tru-boost us an EBC but...
> 
> MBC's are made for all or nothing boost. There's no in-between. No matter what you do the N75 will ALWAYS be the smoothest option. Think about it, it's controlled by the ecu that knows how much throttle the engine is getting and how much boost it's to request at that level.
> 
> A boost controller can only guess at what you want. If the turbo is big enough you will have lag that will make it seem smooth though


The N75 seems like a pretty weak sauce valve...especially for big turbo applications.

Maybe someone can build a 1.8t specific EBC that uses the N75's ECU control as an input so that it can remap that to a better valve and BT wastegate actuator friendly boost curves.

Good idea or no?


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## jedge1.8t (Jan 27, 2012)

groggory said:


> The N75 seems like a pretty weak sauce valve...especially for big turbo applications.
> 
> Maybe someone can build a 1.8t specific EBC that uses the N75's ECU control as an input so that it can remap that to a better valve and BT wastegate actuator friendly boost curves.
> 
> Good idea or no?


Im surprised apr doesn't offer this, with switchable programs they should at least offer switchable boost, a ECU and N75 kit I feel would be extremely popular to the 1.8t mild tuning crowd.


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## DMVDUB (Jan 11, 2010)

Since APR doesn't care about us anymore they would never have something like that.

Also, Gonzo has been able to use the N75 on BT tunes just fine so I don't see why there isn't anyone else that can.


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## Slimjimmn (Apr 8, 2006)

DMVDUB said:


> Also, Gonzo has been able to use the N75 on BT tunes just fine so I don't see why there isn't anyone else that can.


Just hope he copywrites his maps and tuning and encrypt locks them so people in china or elsewhere don't steal


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## DMVDUB (Jan 11, 2010)

He does


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## jedge1.8t (Jan 27, 2012)

When i get some free time im going to test this out and see how it compares, hopefully no boost will be lost when set to 90% but gain that smooth throttle response you lose with a MBC


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## henryhendrixx (Aug 16, 2012)

I seem to be having a combination of a few problems. When I'm just driving around town normally, my boost will shoot up to 0 psi and then drop to about 10hg. It's very annoying and it only happens when my foot is in one place on the gas accelerating. It usually happens around 2k rpm. I'm also getting boost fluctuation when I'm wailing on it. It's done the first problem since I got the car completely stock except a Forge TIP as it's only modification.

As the car sits:
2003 GTi 1.8 AWP
Seafoam
Pretty sure a leaky valve cover gasket
3" Tsudo Turboback 
K&N Ram air
APR Stage 1 tune
APR R1 DV
3Bar FPR
No boost leaks (Pressure tested)

This problem is really annoying and any help would be appreciated. I'm planning on regapping my sparkplugs and possibly getting a FMIC soon. Will post back with regapping results.


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## DMVDUB (Jan 11, 2010)

0 psi eh? 

You need to explain more... sounds like you're just not getting into boost. Press the go pedal harder:wave:


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## henryhendrixx (Aug 16, 2012)

No, that's when I'm just accelerating in town


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## Slimjimmn (Apr 8, 2006)

My car and many others do this on a stock ko3s. No solutions yet. I believe it's a programming thing.


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## DMVDUB (Jan 11, 2010)

Gonzo's k03 software doesn't do it and most others shouldnt either. Its 90% of the time hardware related.


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## Slimjimmn (Apr 8, 2006)

I think mine is due to weak wastegate so I bought some springs and doing that spring mod


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## jedge1.8t (Jan 27, 2012)

okay so now i am running a AEM tru boost in parallel with a N75. nothing sees pressure first, its all split off equally.

Review:

Boost spike - The spike now comes on more progressively, although I still managed to hit the same 23.8 PSI spike, It actually smoothed out rather than becoming instantanous and drop quickly, came on smoother and tapered down slower+++

WOT - nothing much has changed here despite a smoother boost spike. Car seems faster between 3.2k - 5.4k however the torque seems to fall after that point, but i expect that witht he small KO4.

Partial throttle - heres the best part, the car has really smoothed out and is much easier to drive around normally. Shifting is alot more fluid, and partial boost requests dont just drop once there met.

Boost settings - Reluctantly I still have boost setting functionality, with the EBC in off mode, I actually hit and hold 10psi. set at 90% duty cycle I spike at 24psi and average out around 18psi. I would imagine it would only be N75 settings or higher duty cycle but fortunatly I retained the EBC off setting functionality, which is what I use on a relaxing drive.

Overall- I will keep this configuration for now, it seems to be much smoother. Though theres a vacuum line mess now i still enjoy having a smoother daily and a smoother boost curve. 

***Now i need to work out my AFR's, its around 12a:f at 5.2k rpms and down to 10a:f at 6.2k rpms***


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## henryhendrixx (Aug 16, 2012)

Replaced spark plugs with double platinum iridium Bosch gapped at .028, it made no difference :banghead:


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## groggory (Apr 21, 2003)

henryhendrixx said:


> Replaced spark plugs with double platinum iridium Bosch gapped at .028, it made no difference :banghead:


What model plugs?


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## jedge1.8t (Jan 27, 2012)

i used run those plugs, they ended up giving me misfires, i switched to NGK iridiums and they run good. 

I would check your wastegate? Maybe do the spring mod and see if the strengthened spring will hold your boost.


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## Rod Ratio (Jun 6, 2012)

henryhendrixx said:


> Replaced spark plugs with double platinum iridium Bosch gapped at .028, it made no difference :banghead:


Coppers work best. Those platinum a will cause misfires. In this case you DON'T get what you pay for


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## henryhendrixx (Aug 16, 2012)

Currently, I'm not getting any misfires, but when I do, I'll go with the NGK plugs, I had a feeling it was something with the turbo though, how would I check the wastegate and where would I buy new springs?


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## groggory (Apr 21, 2003)

henryhendrixx said:


> Currently, I'm not getting any misfires, but when I do, I'll go with the NGK plugs, I had a feeling it was something with the turbo though, how would I check the wastegate and where would I buy new springs?


The wastegate spring is sealed. You don't replace it.

Worst case, you adjust it with a pair of nuts on the wastegate actuator arm.

...but I doubt that's your problem. I bet you have a vac leak or exhaust leak or torn dv or ....


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## Rod Ratio (Jun 6, 2012)

NOBODY wants to do a simple pressure test anymore:screwy:


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## groggory (Apr 21, 2003)

Mechanics with a grease allergy


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## Rod Ratio (Jun 6, 2012)

Pretty much


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## ExtremeVR6 (Sep 6, 2001)

groggory said:


> The wastegate spring is sealed. You don't replace it.
> 
> Worst case, you adjust it with a pair of nuts on the wastegate actuator arm.
> 
> ...but I doubt that's your problem. I bet you have a vac leak or exhaust leak or torn dv or ....


Putting your nuts on the wastegate would be a worst case!! 

I'd be willing to bet a lot of people end up chasing a lot of different fixes for a couple different causes... I'm betting weak wastegate on 211k car for mine


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## Laswell2001JETTA (Oct 17, 2012)

just reviving this thread. I'm experiencing the same issues too. I recently made a hybrid out of a k03s and a k04. Before the insillation the car had a plane ol k03s. It held 20 psi and then tapered off from there. Now with the hybrid will spike above 20 psi, hold at 17 for a few seconds, then alternate from 5 to 15 psi. for the rest of the rpm range.


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## sadairk2 (May 26, 2013)

I'm getting boost surge and drop off at partial load. Jump to 20+ quick, then drop to 15, then 20, then 10. I have an N75 valve coming. I'm going to test a different N75 valve before trying a MBC in parallel. Should be here this week.


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## DMVDUB (Jan 11, 2010)

sadairk2 said:


> I'm getting boost surge and drop off at partial load. Jump to 20+ quick, then drop to 15, then 20, then 10. I have an N75 valve coming. I'm going to test a different N75 valve before trying a MBC in parallel. Should be here this week.


If you're in Sterling, VA I could meet you somewhere and scan the car as well as check some common problems. This is really a hard one to diagnose over the internet.


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## sadairk2 (May 26, 2013)

SWEET!! I just picked it up about 6 weeks ago. I'm new to VW's but not to turbo's. My other cars always bypassed the stock boost solenoids and went with a Greddy Profec. Is this not common or recommended for the 1.8t for some reason? I figure, take the computer out of it completely. Dedicated boost control just seems logical.


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## ray4624 (Jul 23, 2010)

So I gues it's my turn to share my problems haha

My car seems to boos fine. Occasionally boosts above the 18psi I normally get to about 20-22 psi. My vacuum however does not go to more then 10mm Hg where it used to be at almost 27 mm Hg. The main issue I have is that my dv flutters when I let off instead of a quick purge like it usually does. From this thread I gather that it's either my n75 or dv? Just wondering what I should look to swap out first or if there are any other possibilities. 

Thanks.


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## DMVDUB (Jan 11, 2010)

sadairk2 said:


> SWEET!! I just picked it up about 6 weeks ago. I'm new to VW's but not to turbo's. My other cars always bypassed the stock boost solenoids and went with a Greddy Profec. Is this not common or recommended for the 1.8t for some reason? I figure, take the computer out of it completely. Dedicated boost control just seems logical.


Any type of external boost control may or may not work with certain states of tune. Meaning, if boost request ins't met or overshot it can throw you in limp. A proper tune can make great use of the N75


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## sadairk2 (May 26, 2013)

Understood. I have an N75 coming in and I'll swap that out and test before anything else.


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## DMVDUB (Jan 11, 2010)

sadairk2 said:


> Understood. I have an N75 coming in and I'll swap that out and test before anything else.


Also check that the wastegate nuts are both tight against the "flap". If they aren't it can cause boost fluctuation and low boost.


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## sadairk2 (May 26, 2013)

I think my new N75 should be in today. I was swapping out the cabin filter last night and poked around a bit. The nuts on the actuator are flush and tight. Spring feels strong. I poked around a bit for leaks or tears but didn't see anything. I will have to remove the IC pipe to dig any deeper. When I switch out my N75, I'll post results.


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## sadairk2 (May 26, 2013)

So, I did a few things yesterday. Took of my bumper, re-attached the Curpa R lip to my R32 bumper. It's super solid now. Removed the Intercooler pipes and VHT'd them flat black. Installed the Tyrolsport and 42DD shifter bushings. Wow what a great feeling! I also swapped out the N75 "H" valve with a brand new N75 "E". WOW what a difference! I still get a slight bit of surging but it is night and day! 

I never got a video of the boost gauge before but it fluctuated between 15 and 5 on partial boost. Now at partial boost it sticks. Super manageable and the best modification I've made to the car so far. I can't speak for everyone but it really helped for me. Wouldn't call it a fix but I'm 90% there. No leaks. No codes. And now holds boost better than ever on a GIAC X-Plus tune. I'm very happy. I'm having a love affair with the car all over again and that is worth it for me.


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## DMVDUB (Jan 11, 2010)

sadairk2 said:


> So, I did a few things yesterday. Took of my bumper, re-attached the Curpa R lip to my R32 bumper. It's super solid now. Removed the Intercooler pipes and VHT'd them flat black. Installed the Tyrolsport and 42DD shifter bushings. Wow what a great feeling! I also swapped out the N75 "H" valve with a brand new N75 "E". WOW what a difference! I still get a slight bit of surging but it is night and day!
> 
> I never got a video of the boost gauge before but it fluctuated between 15 and 5 on partial boost. Now at partial boost it sticks. Super manageable and the best modification I've made to the car so far. I can't speak for everyone but it really helped for me. Wouldn't call it a fix but I'm 90% there. No leaks. No codes. And now holds boost better than ever on a GIAC X-Plus tune. I'm very happy. I'm having a love affair with the car all over again and that is worth it for me.


For the most part unless you have a big turbo you'll always have a little fluctuation. Once it gets minimal enough it's only noticeable by seeing it on the gauge or logs.


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## sadairk2 (May 26, 2013)

DMVDUB said:


> For the most part unless you have a big turbo you'll always have a little fluctuation. Once it gets minimal enough it's only noticeable by seeing it on the gauge or logs.


Which is pretty much where I am now. Very happy with the car's response and boost hold at partial throttle. It's a little blippy but it's slow enough that you can control it. Boost comes on quick and holds for the most part. 

Next job is trans fluid change to MT-90.


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## vwdirector (Jan 31, 2006)

I've done the SAI delete but haven't added any resistors, could this cause the boost fluctuation? I've already replaced DV and N75.


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## virgo (Mar 11, 2014)

DMVDUB said:


> No the "J" is from the AUDI 5cyl turbo (I think that's where it comes from) That's just a shot though.
> 
> And you're very right about the overboost setup. I ran this for SO long, but my car didn't like it too much. It does work though with some tweaking.
> 
> ...


Hello guys,

I'm having some boost spikes since it was stock, now I've narrowed the problems to the N75 and my intake and I'm willing to give a try to the "J" revision if its worth.

Mine is the 06A906283*F* version.

Should I go with the J revision or just stick with the latest version E for my vehicle?

I did a boost leak test and I might have a leak on the intake manifold, I use a power gasket and I had the intake removed twice and reinstalled without any sealant.

No codes on vagcom. Producing 165 whp, see the graph, shows exactly whats going on.



Regards.


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## DMVDUB (Jan 11, 2010)

Use the N75 for YOUR car. Do NOT use the J valve or any other "race" valve.

I always keep a ball and spring manual boost controller around for checking this. I set it at whatever the tune requests. Normally 22psi for all but APR and 20 for APR (I think it's 20 or 18, I'd do 18 for APR at first since they keep the over boost protection and you'll go into limp of you over boost). 

Here's an easy test I do for my friends if they have this issue. It's quick and simple. 

Hook up MBC set to 20psi (just keep it set at 20psi so no fiddling each time) take the car for a spin. If the boost holds at 20psi and drops off as usual (depending on turbo) without fluctuation then you've got a tune or N75 issue. If it Fluctuates on the MBC you've got a leak most likely. Since you have the MBC in place if there's no fluctuation you can drive it like that until you get the correct part or find out if the tune is doing something wonky. When I say "the tune" I just mean the ecu is trying to alter the level of boost because of a number of reasons which should be easily found by logging. It has nothing to do with your choice of tuning company (there actually are a few oddball ones that actually are the tune but I think they are more or less gone now) I say this because people love to immediately blame the tune. 

One thing about running the MBC while getting the peopler N75; they do not regulate boost on a small turbo in a linear fashion. A larger turbo takes time to spool so it's less violent, but a K03S (stock turbo) will have an ON/OFF feeling. As soon as the rpm reaches enough for spool (instaboost) you're going to be all in it. It will take a little getting used to on a small turbo but it's not too bad. Second, for those running APR, after testing with the MBC at 18-20psi LOWER IT to 15psi or else the APR tune will run into Over and Under boost issues since it's not seeing the proper boost at the proper time and the jerky way it comes on. Your other option with APR is to set it to stock mode and the MBC to 10-11psi (8psi for non 180hp models). This will be less jerky if at all and it won't run into any issues. 

With the other files you can play a bit and raise boost if you want  Just check your fuel trim to make sure you're not leaning out and knocking. Without WMI and / or a good FMIC anything over 25psi on stock turbo is going to be worthless after a few minutes since IAT's will be insane and you'll inevitably be puling a shˆtload of timing therefore losing any benefit of higher boost.

Obviously your other option is to do a leak test. I find that the MBC thing works great since you can keep it in the glove box for anytime testing. Having a leak tester is a great thing though so building one is a good idea.

Hope this helps. :wave:

****NOTE****
Depending on the mods you've done primarily removal of the N249 valve (I think it's that one... can't remember off hand right now) essentially you want to delete that little black reservoir on the valve cover and the solenoid that controls it. You want the diverter valve to be connected directly to the intake manifold. 

When the DV is directly connected to a VAC/BOOST reference the ECU can no longer open the diverter valve and dump all your boost when it gets mad at you. It can still do other things to protect the engine so removing this isn't going to hurt and it'll save you a bunch of headaches later. *It can still take boost from you while running the MBC if it freaks out but it's really just slamming the throttle shut. So, if it does really feel that it's in danger (lean for example) it can still protect itself.
**When the ECU closes the throttle plate the DV will open because it's going into VAC so your boost will release. Just wanted to note that if you wonder how in the hell your boost gets taken when the ECU no longer is in control of the Boost Control or the Diverter Valve

************

Another thing to check anytime you're having issues with fluctuation is the diverter valve itself. Normally it's pretty obvious that it's the culprit but it's something to be aware of. 

-VIRGO, I wasn't just answering your query.
I tried to make this an open answer for anyone having issues while still giving you a solution to the problem. eace:


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## mccutter (Aug 13, 2008)

DMVDUB said:


> ...I tried to make this an open answer for anyone having issues while still giving you a solution to the problem. eace:



Good Job! Thanks for the info!


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## virgo (Mar 11, 2014)

DMVDUB Great info, thanks a lot, I appreciate all your help! I'll take from here and I'll reply back once I have it fixed.

As a starter I'll fix the intake gasket, following with a DV replacement (just ordered a forge 008) and a N75 revised version for my car (E) version.
I'll look up for a MBC, is there any specific one you recommend (a link or model number will be great)? 

Thanks again!


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## DMVDUB (Jan 11, 2010)

virgo said:


> DMVDUB Great info, thanks a lot, I appreciate all your help! I'll take from here and I'll reply back once I have it fixed.
> 
> As a starter I'll fix the intake gasket, following with a DV replacement (just ordered a forge 008) and a N75 revised version for my car (E) version.
> I'll look up for a MBC, is there any specific one you recommend (a link or model number will be great)?
> ...


Here's a couple links. I personally have a nice TurboXS one as I gave my cheap one to a friend but here's some links on amazon ranging in price. The main thing is to know it's a Ball and Spring style valve. 

*$10-$30*
*These first three work as good as any of the high end MBC's I just get a deal on TurboXS and Turbosmart stuff that's why I pay extra*

http://www.amazon.com/Voodoo-Manual-Turbo-Controller-Anodize/dp/B00883N7AQ/ref=sr_1_9?s=automotive&ie=UTF8&qid=1410186910&sr=1-9&keywords=manual+boost+controller

http://www.amazon.com/Subaru-Manual-Turbo-Boost-Controller/dp/B002KAXO7Y/ref=sr_1_1?s=automotive&ie=UTF8&qid=1410187107&sr=1-1&keywords=manual+boost+controller

http://www.amazon.com/Volkswagen-Jetta-Manual-Boost-Controller/dp/B002KB00OI/ref=sr_1_41?s=automotive&ie=UTF8&qid=1410187171&sr=1-41&keywords=manual+boost+controller

*$30-$100+*

http://www.amazon.com/Voodoo-Controller-Aluminum-Ceramic-Installed/dp/B008GUDMII/ref=sr_1_15?s=automotive&ie=UTF8&qid=1410187242&sr=1-15&keywords=manual+boost+controller

http://www.amazon.com/Turbosmart-TS-0101-1001-Boost-Tee-Boost-Controller/dp/B001N1KV22/ref=sr_1_3?s=automotive&ie=UTF8&qid=1410187314&sr=1-3&keywords=manual+boost+controller

http://www.amazon.com/Grimmspeed-Manual-Boost-Controller-Red/dp/B0054RG4QI/ref=sr_1_4?s=automotive&ie=UTF8&qid=1410187343&sr=1-4&keywords=manual+boost+controller

*I've had this one and it was very good. I just left it connected in the cabin hidden under the dash and sip tied the vac lines away in the bay when I wasn't using it. *

http://www.amazon.com/TurboSmart-TS-0106-1002-In-Cabin-Manual-Controllers/dp/B001C3K1NK/ref=sr_1_1?s=automotive&ie=UTF8&qid=1410187428&sr=1-1&keywords=manual+boost+controller

*This is the current one I have and at $105-$120 I love how precise it is. It has a rough and fine tuning setting (knob and allen key) as well as lockable to the boost setting you want. That way you know when you pull it out it's locked in at whatever PSI you set it to last.
*
http://www.amazon.com/Turboxs-Parts-BCHPBC-Performance-Controller/dp/B004TQY35O/ref=sr_1_14?s=automotive&ie=UTF8&qid=1410187534&sr=1-14&keywords=manual+boost+controller

There's more than enough options here for MBC's. I figured I'd throw a few at you so you can make the choice you want. I would say if you're planning on going BT get a decent in cabin like the last 2. They can all technically be "in cabin" but these look better and are nicer to control. Not to mention the tunability of the last one (TurboXS HPBC) is great. You can actually get a more linear feel from the HPBC from the dual settings on a small turbo.


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## das.ist.derrick (Aug 5, 2014)

Great thread everyone! I seem to be having an issue with my MK6.

2012 MK6 GTI
CBFA Eng code
Apr Stage 2
42dd turbo back
forge intercooler pipes
forge intake
R8 coilpacks
Piston Style Dv (from VW)

When I first got my tune I would peak around 20lbs and hold around 18lbs. Now I peak at 15lbs and holds around 13lbs. I haven't received and CEL's for boost leak or anything at all. When I put the car into stock mode, its holds stock boost pressures like a champ ( but stock mode is no fun). Makes me think there isn't a leak anywhere. Im gonna check the wastegate nut and fiddle with the n75 tomorrow. Any suggestions let me know!!


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## jolfdriver01 (Sep 1, 2006)

diesel66 said:


> to AnniGTI3194 i fixed the exact same problem you had with boost flutter, i did two things so am unsure which one fixed it. the throttle body was clean on the intercooler side but when i took it off it had oil residue on the otherside so i cleaned and polished both sides but i also cracked open the tps and sprayed contact cleaner on it


I've kinda thrown together a 82' convertible w/aeb outta a 99' passat. As it stands right now ive only got a 2.5" downpipe w/pre cat sensor tapped in so the rear sensor isn't installed, just hangs there right now. When I take it for a ride it'll pull pretty good, losing traction even but will eventually (typically right away) will buck. hard. Falls on its face really until I let go of the throttle then it comes back to life. My tps will only read max 77% @ WOT. Its a DBC. I haven't driven it in a little while but i think it was boosting somewhere under 1 bar. The engine has the factory tune, Ive swapped out the n75 and it seems to helped something in the way it runs but definitely did not fix it. I'm thinking aside from the obviously poor readings from the post o2 that the msd 2225 inline fuel pump isnt holding enough psi. Has anybody experienced the "falling on its face" problem before? 
Also, im running the stock tranny from the rabbit so, short gear ratio. Not that that should matter. The wife recently bought me vagcom so I'll get some more in detail info soon. After reading some of this thread, I'm begining to think I might try installing a MBC to see if the n75 is just tossing it into limp due to the short downpipe letting the turbo spool so fast. i dunno.


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## cmdshft (Oct 17, 2011)

Bumping this useful thread.

I am having this problem myself:

https://www.youtube.com/watch?v=51JjndOTWq4

I have smoke tested the car after the video was made, and found a leak in the upper turbo inlet hose. Replaced that and the problem shifted itself to the 5k range, where it drops from around 15-16psi after starting to taper off to sudden drops around 5-10psi and back.

As of now, I have done the following:

No vac leaks
No Boost leaks (holds 20psi in 4th and 5th gear fine until 5000rpm and hits the "out of breath" wall)
New OEM coils
New MAF
3" turbo back straight pipe
No smoke out the tail when driving
CTS 450HP FMIC
Forge 008 DV with yellow spring (18-23psi)
Cold Air Intake
Stage 2 Single Mass Clutch
Stock Fuel Injectors
Stock Fuel Pump

The only things I can think of are MAP sensor, wastegate nuts, air intake temp sensor, coolant temp sensor or fuel pump.

A friend of mine has the nearly same setup as me and had adjusted his wg nuts by 4 cranks and reported that the fluctuation has gone away. He's going to keep driving it and see what happens but so far it seems maybe that might be what I have to do as well.


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## 2001BlueVDUB (Mar 26, 2017)

I'm having a problem with my boost. I just bought a 2001 Volkswagen Golf (first turbo car). I've been told it's has an aftermarket down pipe, it has a cold air intake and a bov/dv and a boost gauge, ( which read 20 psi and now 8-10) the other day I took my intercooler off and there was a good amount of oil in it. Could my turbo be going bad or just seals leaking. Also can that cause me to loose 10-12 psi of boost?


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## Supersized22 (Nov 6, 2016)

2001BlueVDUB said:


> I'm having a problem with my boost. I just bought a 2001 Volkswagen Golf (first turbo car). I've been told it's has an aftermarket down pipe, it has a cold air intake and a bov/dv and a boost gauge, ( which read 20 psi and now 8-10) the other day I took my intercooler off and there was a good amount of oil in it. Could my turbo be going bad or just seals leaking. Also can that cause me to loose 10-12 psi of boost?


How much oil? K04 and k03s tend to spit quite a bit of oil without a catch can 

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## Supersized22 (Nov 6, 2016)

Is anyone seeing this anymore? 

Mk4 golf gti 1.8t

Gonzo tuned

Annihalator kit?

Gttx-052 turbo with 660cc injectors bigger exhaust mani. 3 inch downpipe to 3 inch straight pipe 

The issue im having is: car is in first gear right? I go from a stop, at about 1
5 to 2.5 grand the turbo just spools to 5 psi and the engine starts stuttering a bit. But im barely pushing the throttle when it does this. I have no clue. Im gonna check the wastegate nuts, and maybe replace a few sensors. Any ideas let me know! 

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## MK6Hicks (Jan 25, 2016)

Its an old thread but I need some insight..

I'm having a weird issue with my 03' 1.8t quattro 5 speed. AMB 1.8t. Or lack of problem I guess you could say. I'm the second owner, the first owner was an old guy, so I really don't see how the car could be chipped. But i push 14-16psi when it initially spools at 3k rpm and then after around 4500 rpm it settles around 12psi. (where it should be, 11-12). And then it drops off closer to redline as would be expected with the stock ko3. My boost gauge is accurate, I compared it to live data on the car, and the cars requested and actual boost are within 100mbar from eachother, and no lean codes or anything. I only have one intermittent code for the cat, but as it's original with 136k on the car I know it's getting to the end of its life span, but I don't think that would cause this. If I boost and hold it at 11-12psi, like 85% throttle, it feels quick and how stock power should feel. Then I push the pedal the remainder to the floor and it boosts to 15psi and holds, and doesn't rly feel any faster. I know with 15-16psi on a tune it would be around 200hp and it's definitely not pushing that much hp. The boost comes on totally smooth and holds, no jumping around. Like the car runs perfect, except that it pushes 15psi and does not feel tuned, so I think it's an overboost condition. Never been in limp mode or anything, which I thought occurred after 13psi on a stock tune. I unplugged the n75 and the car pushes 3-4psi so I know the wastegate on the turbo is good. The turbo has a slight whistle sound, but not like a dentist drill, it boosts perfect. More sounds like a boost leak, but since I put the boost gauge in 3-4k miles ago, it always has done the same thing, consistently pushing 15psi, then after 4500 rpm tapers to 12psi where it should be. I know it should surge to 12 or 13psi max and settle around 11. I've inspected all the turbo piping and vacuum lines and all look fine. Also the car has perfect vacuum at 20 at idle. No vacuum leaks. Silky smooth idle. The car is perfect besides pushing more boost than it should and not feeling any faster like it's tuned. I've thought maybe n75 valve is faulty, but the boost is so smooth and always consistent. I don't wanna spend $80 for a part that is most likely fine. Any ideas?

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## topemu (Mar 6, 2017)

Im having a nasty similar issue. Any thoughts on a fix without using a mbc?
Just got a tune, expecting 18psi. Which i get. But onky from 3-5k. Then it dies down to 10 and stays there.

also if i start boosting in a low gear, then itll drop to 10psi at 5k and stay at 10psi in the next gears i rev through.

check all hoses and pipes, no leaks found.
Tried 4 different n75, stock and forge dv. Different TIP. Added cone filter. New colder plugs, added new r8 coils. 

now i have the wg actuator off. It actuates in/out with some force smoothly.
Wg flapper closes fully.
wg flapper arm bushing is solid.

ONLY thing i see is that the wg flapper arm has a tiny but of play when everything is unbolted.
Like 1mm side-side. The bushing is firm tho. So this is side play of the arm in the bushing.
Is that normal?


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## Vegeta Gti (Feb 13, 2003)

K03/04 won't and soundness be five to hold boost to redone. You're just throwing lava out of the turbo at that point. Which is stated in a multitude of threads over the last 20 years. 

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## Vegeta Gti (Feb 13, 2003)

As far as checking..

Did you smoke check the system? Not just a10psi pressure check, but smoke check?

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## topemu (Mar 6, 2017)

Vegeta Gti said:


> K03/04 won't and soundness be five to hold boost to redone.


 I think you have some typo in there. Not sure what you mean .

No I have not smoke tested yet. But I've literally replaced every single vac hose with a new one.
I'll look for a place to do a smoke test though


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