fellas,

i recently changed the stock airbox and filter in my 1996 993TT w/29K miles to a K & N filter and a weltmeister performance airbox as shown in the link below.

http://www.automotion.com/productpag...1260#partStart


anyway, now i am getting a strange noise usually during moderate acceleration between 3,000 and 4,000 rpm. it sounds like a drawn out honking. i also get it sometimes when maintaining constant speed in 5th or 6th gear around 2,000 RPM. is this normal? is this the sound everyone is raving about?

btw, i also still have the factory original turbo bypass valves....

any advice?

 

Honking is usually the sound a bad diverter valve makes. Perhaps the new airbox and/or filter has now made this sound that was already there more audible. Try replacing the diverter valves and that should fix it.

If not than then maybe it is a sound unique to that airbox and filter combo? Can you try it with your stock air filter?

 

After looking at that airbox, I'm very curious as to how it works. If I am looking at the picture correctly it looks like they cut away 90% of the airbox cover and ditched the snorkle that grabs fresh air from the spoiler.

Wouldn't that just suck in hot dirty air from the engine bay? Is this a good thing?

 

Hot engine compartment air and oil on the MAF sensor from the K&N element, great upgrade!

 

 

now that i finally got my obc display fixed after not being able to see it for half a decade, i notice that the honking starts precisely when boost pressure reads .3 bar. regardless of the speed and throttle position, whether i'm running the rpms up quick in 3rd gear, or moderately applying throttle in 5th gear as soon as she hits .3 "hooooooooooonnnnnnnnnkkkkkkkk." also, i tried a boost test as have read in some other posts, WOT in 3rd gear from low revs and the highest boost reading I get is .5. is this definitive enough to conclude the diverter valve is the culprit? also, after a few of these boost tests, i noticed it didnt really honk anymore at .3 what do you think?

 

Start by replacing the DVs. The honking noise will be gone. Suggest aftermarket upgraded DV, but you can certainly go with new OEM units. You might even might a slight performance gain as the failing/failed DV's might be leaking boost, but I'm not sure how that will play out since you might be losing power due to that intake, dunno.

Search any turbo form that uses these same DVs(996 Turbo, any Audi 1.8T or 2.7T or any VW 1.8T) you'll find tons of comments about honking and the DV.

Hope this helps.

"The stock diverter valve uses a rubber diaphragm to open and close this pathway. This type of design is prone to unwanted boost escape, honking noises, and surging during part throttle."

http://www.awe-tuning.com/pages/shar...IL=BaileyValve

(You can find them much cheaper than this, but I just wanted to link it so you could read what they have to say about the OEM DVs)

 

thanks for the info..............the only thing that bothers me is that it started immediately after i changed the airbox, which btw, i found out is a fabspeed. would this airbox make the noise more noticeable or cause the valve to fail?

 

I assume you went with an open airbox for more sound not for more performance since it doesn't give more performance.

Since the open airbox is allowing you to hear more engine noise, I would think it is safe to assume the honking was always there, and is now more audible due to the open airbox. I don't see how the box could cause it to fail.

 

The .5bar may not be a diverter issue. It's surprisingly suspicious that .5 bar is also the limit set forth by the DME in "limp home mode." Check with some sort of OBDII scanner to make sure you don't have any codes.

 

billets diverters finally installed. honking gone. .5bar boost limitation remains.