Boost problems...HELP!!!

[00s4slvr]

so i was doing some runs today on stock mode and my boost is going nuts. Im in second going 40 and punch it and then when the rpms get to about 5000-redline the boost like drops from 9-10 to about 6-7... and stays there until i shift to 3rd and so on. THen i did another run and the boost was fine and stayed at 9-10 then dropped a little to 8-9 when i was at 5000-redine then back to 9-10 when 3rd gear kicked in...

Any explanations... i have no idea how to find a boost leak... and if its a small tiny one would my boost be affected??

[Grangalan]

With a GIACX ECU you should be boosting 15-18 psi. You either have a GIANT boost leak or your N75 is shot. Search for boost leak tester. It will cost you less than 20 bucks to make and itll be of GIANT help


Actually I'm nice enough to search for you

http://www.awe-tuning.com/media/pdf/...ure_tester.pdf

[AudiSportB5S4]

Sounds a whole lot like a MAF problem. are you a 2000 year... if so go outside unplug your MAF sensor and try doing a pull see if the boost is more stable. If so buy yourself a MAF (bosch for 2000) for 150.

[00s4slvr]

No its on the stock setting not pump performance... i think you misread it.

What i meant was its on the stock setting which would be 8-9psi of boost. Im in second going 40 and punch it and then when the rpms get to about 5000-redline the boost like drops from 9-10 to about 6-7... and stays there until i shift to 3rd and so on. THen i did another run and the boost was fine and stayed at 9-10 then dropped a little to 8-9 when i was at 5000-redine then back to 9-10 when 3rd gear kicked in... IN STOCK MODE :P if i run the giac x on pump performance im at 15psi

[RolledMySTi]

I haven't been in stock mode for a while, but that sounds about right. If it's running fine in performance mode there is no reason a problem should happen in stock mode.

[00s4slvr]

in performance mode the boost stays at 14-15 spikes to 17 and then jumps to 12-13 then back to 14-15psi when i use drive mode. But it tiptronic mode the boost stays at 14-15 spikes to 17 then drops back down to 14-15.... is that normal?

[00s4slvr]

[00s4slvr]

what is this peice??? there is a wire or vac hose attatched to it..? If this was cut would this cause a boost leak???

[00s4slvr]

[EnviedA6]

Limp mode, I would check for leaks first and then check for hidden codes. This happended to me a few days ago as well. Got the codes cleared, verified that there were no leaks and checked my N75 valve for leaks. Everything is all good now, boosted 5-7psi now I'm back to 17-23psi!!!

[00s4slvr]

apparently for the Giac x ecu 14-15 psi is normal so i guess my car has no boost leaks or anything....?

[00s4slvr]

your at 17-23 in performance mode because you have stage 2 apr i only have the regular stage 1 giac ecu and right now its ok stock mode and my boost is 8-9 psi tapering to 6-7 around the redline then back up to 8-9psi after the shift...

i was told that was normal for stock.

[4RingsCircus]

Your boost drop could be the transmission notifying of impending shift, and the stock mode responding with boost reduction. The other modes may respond less aggressively, giving more performance.

Spray starting fluid on the suspect leak area at idle. If the idle increases, then it is a vac leak. Of course, a hiss or other tell tale signs can give it away as well.

If you have not replaced your N75 and diverter valves, these could be suspect as well.

Oh, and for boost leaks- follow the link.

You are in NJ. There are a LOT of Audis in your general area. Try finding someone with a vag-com or ECU-X. You will want to do a few runs and compare actual boost vs requested. I would disregard any first gear #s, and also any disparities below 2000 RPM.

If you can actually do any gear, 2-5 from 3000 to 6000 at full throttle, and log the data for actual and requested, you may see spikes, or large disparities.

I haven't logged in a while, but from 3K up, my WOT runs between 5 and 20 millibar more actual boost than requested. This is very tight regulation. If I were getting 100mBar differences in either direction, I would start looking.

[00s4slvr]

yeah but my question is if my boost is normal than i obviously dont have a boost leak correct???

ANd when im in park my vac is at 20 which is what its supposed to be at ...

[00s4slvr]

so is that normal then ???