# Inconsistent Boost? Opinions or suggestions?



## GTiSurgeon (Mar 10, 2010)

*Inconsistent Boost? Opinions or suggestions? **SOLVED***

Hey guys,

I have read up by searching a lot of the many boost issues that exist on the vortex, I've also seen similar youtube vids. - Couldn't find many definite answers though. 

I'm have and idea what of what could be the problem - the DV or the N75. I found a leak previously and fixed it but it sounds like there might still be a leak. (the other possible cause)

My TT is bone stock at the moment. I read that they should be boosting around 14psi (.96Bar).
A buddy and I connected a boost guage and went for a drive while my buddy kept an eye on the boost and this is what happens:

In 1st & 2nd gear the boost barely reaches 6psi (.4Bar) and is different each time. The boost picks up in the other gears. It gets to about 11psi (.75Bar) in 4th & 5th and drops to under 11psi. This is what gets me - once in 6th the boost picks up to about 12psi and stays constant as long as you have your foot on the throttle....? :screwy:

I'm planning on doing a pressure test over the weekend and also going to check the DV & N75...


Maybe one of you guys could point out something else that I should check while I'm at it?


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## thelmuffingirl (Oct 28, 2007)

Ive heard vacuum leaks are a main cause of this, and is a very common problem among the 1.8 motors, considering we have so many vacuum lines including the secondary air lines as well, its hard to find the leak sometimes. Also, even though you have a slight leak, it doesnt mean the check engine will come on, try to find someone with a VAG system and it will tell you for sure. i have the same problem, and i plugged in VAG and the secondary system has a leak, also i took out my MAF and cleaned it with brake cleaner and she is running so much better. But try not to touch the metal part on the sensor when you take it out.

Also, turbos are exhaust driven, if youre looking for more power, start there. 3 inch downpipe was the best investment i made on my baby. Cause the stock downpipe starts off 3 inch, but seperates into 2 smaller pipes stricting the air flow. But if you change this, you'll need to change your cat to a single cat as well. but its so worth it.

Hope this helps, like i said im no expert, just going off what ive done to my car, and the experience i had.


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## corradojohnt (Sep 16, 2007)

Sounds like a bad DV to me. It is always good to have a back up valve, so I would go the dealer and pick up (~$50.00). Pop it in and test her out. GL! :beer:


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## thelmuffingirl (Oct 28, 2007)

also, i changed my spark plugs today, reminded me of this post, might want to check those as well, just for the hell of it, cause you said you had a leak and if the vacuum leak was really that bad, it could effect your spark plugs, they will look kinda "wet", just pop them out to see, but torque them down between 15 and 21 when you put them back.

how many miles does your TT have anyway?


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## GTiSurgeon (Mar 10, 2010)

thelmuffingirl said:


> also, i changed my spark plugs today, reminded me of this post, might want to check those as well, just for the hell of it, cause you said you had a leak and if the vacuum leak was really that bad, it could effect your spark plugs, they will look kinda "wet", just pop them out to see, but torque them down between 15 and 21 when you put them back.
> 
> how many miles does your TT have anyway?


Thanks so much for your advice!

It has about 72k miles


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## GTiSurgeon (Mar 10, 2010)

*Problem found!*

Thanks for your reply guys, I tinkered about yesterday and found this to be the cause...





































See this pic below where I marked the leak. This little pipe burst all the way along that inner seam, from clamp to clamp.

I'm surprised that the check engine light didn't come on as this in my mind seemed to be quite a big leak. - Oh it got worse that what it was when I started this thread...











Temporary solution: I cleaned the tear up with some thinners to get rid of the oiliness took some superglue and activator and stuck it together again - then I took some insulation tape and wound it around it until I felt that the boost wont blow it off... then I took her out for a drive and man oh man what a great feeling it is to have her boost 100%!!! whoo hoo!!

She's much more responsive and acceleration is a great deal more positive!

Thanks again for your help guys, I appreciate it. eace:


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## thelmuffingirl (Oct 28, 2007)

yay! glad you found the problem! yeah like i said before vacuum leaks are very common, and the smallest leak can make a difference, and my check engine light didnt come on either until my leak got bigger! but my tube under the intake manifold cracked, not fun! But glad, to help! 

oh and 72k, your timing belt will be coming up around 80k!  lol just an fyi, i already bought the kit for my car, and i only have 65k, better safe than sorry.


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## GTiSurgeon (Mar 10, 2010)

thelmuffingirl said:


> oh and 72k, your timing belt will be coming up around 80k!  lol just an fyi, i already bought the kit for my car, and i only have 65k, better safe than sorry.


Thanks for the heads-up, I appreciate it. :beer:
It's always great to get advice from guys that have been there and done that... :thumbup:

I was very careful when I bought the car and I know these 20V have a weak point when it comes to the timing belt. I did a service (oil, plugs, filters, timing belt, tensioner pulley, tensioner) the weekend after I bought it because I didn't want to find myself in a tight spot... 

While I was at it I flushed the engine with new mineral oil then drained that and flushed it with synthetic oil (ran the engine for a while until it was hot) drained that and then installed a new filter and added the new Synthetic oil. It was a bit of a waste of synthetic oil but hey - better safe than sorry :laugh:


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## SteveCJr (Aug 3, 2008)

Wouldn't be the first time I've read about that piece cracking on this forum.

Not trying to thread jack here, but I'm currently having a boost leak issue. About 3 weeks about I noticed I couldn't boost past 10psi. Normally it's around 20psi with an APR93 tune. Took it to the shop a week later and it was down to 5psi and nothing more. They did a smoke test and found a leak. Replaced a whole bunch of hoses and $800 in parts / labor later the that leak was taken care of. But as I drove it home from the shop I still couldn't boost past 5psi.:banghead: I'm hoping that there happens to be a leak they missed and isn't something more. It's now down to 3-4psi /sigh


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## Doooglasss (Aug 28, 2009)

You guys can build or buy a pressure tester and that will get you pretty good results.

www.modshack.info sells one that I used to use.

GTisurgeon - you'll find that under your intake manifold is not only a mess of lines but it will also be covered in baked on oil and most of the parts will be deteriorating due to heat cycles of the motor. A lot of guys go about replacing the whole setup. Just giving you a heads up to the mess that awaits you!

I think there's a rebuild thread in here for the PCV system: http://wiki.quattroworld.com/index.php/TT.Mk1


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## GTiSurgeon (Mar 10, 2010)

DougLoBue said:


> You guys can build or buy a pressure tester and that will get you pretty good results.
> 
> www.modshack.info sells one that I used to use.
> 
> ...


Thanks for the link to a great site, Doug! 
I'm not really looking forward to peeking underneath there! :laugh: But I'll get there, thanks for the heads up! :thumbup:

@ SteveCJr

Yeah, nothing worse than a boosted car that doesn't boost! Hope you get it sorted out!


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## thelmuffingirl (Oct 28, 2007)

SteveCJr said:


> Wouldn't be the first time I've read about that piece cracking on this forum.
> 
> Not trying to thread jack here, but I'm currently having a boost leak issue. About 3 weeks about I noticed I couldn't boost past 10psi. Normally it's around 20psi with an APR93 tune. Took it to the shop a week later and it was down to 5psi and nothing more. They did a smoke test and found a leak. Replaced a whole bunch of hoses and $800 in parts / labor later the that leak was taken care of. But as I drove it home from the shop I still couldn't boost past 5psi.:banghead: I'm hoping that there happens to be a leak they missed and isn't something more. It's now down to 3-4psi /sigh


URGH! same problem basically, dont have a boost gauge installed yet, bought one didnt install, but anyway, im very good knowing the feel of my car and the way it sounds, and i got a bunch of hoses replaced costing me close to $500 and she still isnt up to par, i know they missed a line!


@ DougLoBlue, glad you posted that tester kit because i was about to look for one! :thumbup:


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