Hey guys. I recently posted about a turbo swap I had to do on my 1.8t due to a bad wastegate valve. Along with the new turbo installation I also did the airbox mod, what a huge difference this combo made!! My turbo (K03)and intake is so much louder, you can definitely here the spool and DV release now!! I also replaced my old DV with a new 710N, cleaned all my charge hoses, TB and vaccum hoses; they were filfthy with oil. Although my car seems to run 100% better (throttle response and overall power), I am not sure my boost is holding consistent psi throughout mid-high rpm range. Now that I can pretty much hear all the mechanics operating throughout the intakeI'mhearing a repeating low honking noise at higher rpm's 3-4k at a consistent speed.IfI am cruising at a steady speed of say 40-45 mph @ 3-4krpm this noise becomes apparent in repetitions.I think this is the DV working but why would it be a constant honking and not just a short burst like if your were under heavy load. If I spool up hard under loadin 1st gear and let off the gas fast I can really hear the diverter valve bleedexcessive boost into the intake which sounds really great anddoesn'thave that honkingsound. Unfortunately I do not have a boost gauge to monitor my boost but I am almost definite that all my hoses are very tightand properly connected. Could this be a bad N75 valve?I alsohad a bad MAF code prior to installation of my new turbo but I didclean itproperly before I reinstalled it. WouldI have to get this cleared for my car to run properly? Any help or advice would be greatly appreciated, thanks guys.

 

Honking noise is usually DV related and would have nothing to do with the N75. There is no point in trying to diagnose boost issues without a boost gauge though.

 

Would anyone know of the primary hoses that I should check, for cracks or leaks that would cause this issue? Someone posted in a prior post about a hose near the coolant resevoir that is prone to fail by cracking that causesa "whoosh" sound...??? Could this sound be related to the DV possibly prematurely opening up?

 

I wasnt joking^

 

I wasn't laughing....And I do understand that this issueis hard to diagnose without analyzing boost gain/loss at certain points. Considering the fact that I just removed and reinstalled my turbo/ assemblywith a NEW DV do you think it could be a misplaced hose or cracked hose causing the DV to bleed early. The noise is definitely coming from DV. I'm going to start with replacing that small vaccum hose that runs from thatnipple to the intake manifold, maybe thats keeping the valve from closing....??

 

most of the smaller once go bad in about 100k, i had to replace only them so far. and if you have some kind or air pump or compressor hook it up to your to one of the hoses and check for leaks.

 

The spring inside the DV makes it close, not vaccum. Did you install it in the same direction as the stock one came out? When I say "I wasnt joking," Im asking you to take my suggestion more seriously. There is really NO point in trying to verify a boost problem without a boost gauge. You simply cannot see cracks in vaccum lines, and often times, if there is a crack in a hose, it doesnt open up and start to leak until a certain level of boost is reached. You might as well just go buy all new hoses and boost lines if your going to do it that way.You can build a boost leak test (read this: https://www.audiforums.com/m_569559/tm.htm) if its a leak you suspect. If youre positive its DV related, which is likely due to the honking noise, make sure its installed in the right direction. My old 710N started honking after less than a year of use. ButI wouldnt expect a new one to do that. I put in a forge valve and it went away.

 

Thanks onepoint8tee!! I just got inside from re-checking all my hoses and connections and noticed that my DV was reversed! I switched that around according to the "all about DV" sticky diagram and took her for a quick spin. Although my honking is no longer so persistent, less noticeable, I can tell that my "spooling" is not as loud as it was before. Oh well, atleast its'installed correctly! I am also going to replace my N75 as well b/c I do notice aninconsistency in boost; sometimes it spools like hell and other times it doesn't. Thanks again for your prompt responses and accurate knowledge...its incredible on what you can get accomplished on this site!

P.S. and yes, I know, I know....I need to install a boost gauge.

 

Unless you have a fault code/CEL refering to boost regulation (positive/negative deviation) then I wouldnt waste your money on a new N75. Get your ecu scanned for fault codes first. If youve never checked for fault codes, and if there are any, have them cleared and get it rescanned again after a week of driving. At least get a boost gauge before you jump to any conclusions about faulty parts. You may be going into limp mode from time to time, and there very well could be a fault code stored (even though you dont have a CEL) that will point you in the right direction. Autozone will scan your ECU for free and print out any codes for you. Replacing parts just based on suspision alone can become costly and is just a bad way to go about troubleshooting/diagnosing.

 

Thanks again, I really appreciate the help. I know I had a bad MAF code stored prior to my turbo swap and never had it cleared, do you think this would cause itto go limp?