Hi Guys,

Im driving a 997 turbo tip and i would like to share a problem im facing right now;

This happened 2 weeks ago. I noticed a fluttering sound from the rear left whenever i throttle. I have listed down the exact details;

1. Light throttle on even road is fine, sound appears after half throttle or going up slope. On WOT, fluttering is very noticeable.

2. Initially, the mechanic and i were bewildered by the sound. At first we thought it could be a boost leakeage, however subsequent checks on all hoses proved otherwise. And also, im able to maintain my boost level (odometer shows 1.2 bar, but i am running 1.5, 1.6bar on external boost gauge during tuning). For eg, in gear 1, 2, 3, im able to hit 1.2bar..

3. Things took a turn for the worse today. 1st gear, im only able to hit 0.7 then 0.6, 2nd gear 0.9 to 0.7, third gear 1.0 to 0.8bar. 4th and 5th gear im able to hold 1.0, 1.1bar. Something is very wrong now. This was done on highways in the early morning.

4. Funny part is im able to hit 300kmh and still going, no air gushing noise whatsoever. On normal road driving, i could hear the fluttering during initial pick up but when it reaches 100kmh on light throttle the fluttering goes away, till you apply more gas.

5. I have exhaust, ecu, headers, plenum and brv currently.

Anyone here encountered this issue before? I cant send the car back to agent as its modded (exhaust, headers, ecu, brv, ipd plenum) and they will not entertain me unless i change them back to stock parts.

Anyone? very much appreciated. Thanks.

 

Well, I'm happy to offer my thoughts.

I don't think smaller boost leaks affect the boost guages as much, but they do make a "fluttering" sound. As you drive the car more and more, the leak can become more pronounced. You're #3 above seems to indicate that.

For me, my boost leaks have sounded like "fluttering", not air gushing.

Does your present mechanic have a certain smoke machine that can be used to diagnose the leak? Also my first leak was behind a bunch of parts that needed to be pulled out before they could reach the clamps.

 

Check your BRVs. Remove and inspect.

 

BRV's, really? I thought they were pretty much "set and forget" if you get quality aftermarket ones. What would one be looking for?

My dealer just called, they did the smoke test, and no leaks. Perhaps I was just thinking I heard a boost leak and then falsely thinking that my car was a little slower in acceleration.

I know accessing the BRV on the left turbo is a bit more time consuming. Wondering if I should keep the car at the dealer and ask them to check the BRVs.

 

For the record, we have literally over a decade of experience working closely with "BRVs" (also known as Diverter Valves). The stock valves were very problematic on VWs and Audis in the 90s and also on 996TTs when they came out. The factory went through multiple revisions without success. Problems would be tearing of the rubber diaphragm internals and "honking" noises at part throttle.

We were one of the very first US companies to start offering a replacement aftermarket diverter valve (imported from the UK and made by Bailey Motorsport).

However, what we find amusing is how many companies are offering "upgraded" valves for the 997TT. The stock 997TT valves are extremely robust. To date, we have had zero failures of the stock 997TT valves, and we even have co-opted the internal parts as a solution for problematic VW and Audi applications. The 997TT stock valve is bulletproof.

I cannot say the same regarding some aftermarket versions out there. PM me for details if you want more info, as I don't want this to turn into a drama war.

 

What a relief.. problem solved. The culprit - the gasket at the merge collector.

 

so the issue was the header gasket? No cracks on the headers?

So to fix this, you just replaced the header gasket?

After tracking my car this past weekend, my car started to develop the same fluttering/whistling sound just as you described. This noise started on my 3rd session at the track.

My initial thoughts were the brv's. After chatting more with Alex(Sharkwerks), we speculated that it could be either a cracked muffler or cracked headers. I'm currently using the fabspeed headers.

We're going to put in on a lift tomorrow morning to further investigate.

 

I concur with Todd's statement.
Check and inspect BRV. As a former Audi "enthusiast" (owned a 508BHP )
I've tested every stock VW/AUDI and after market BRV (diaphragm and piston types) imaginable. A diaphragm tear would create that flutter sound you describe...

 

Like I said the gasket...check the gasket and replace...LOL...yeah I didn't read the above post until afterward..... oh well flutter flutter...

 

If they worked so well on the 997.1TT, I wonder why they ditched them on the new 997.2TT. LOL

 

Good to hear its just the Gasket, I was going to say there’s probably just an exhaust leak somewhere.

 

Well it was to save $15 ofcourse...

 

so here's an update. Finally got the car on a lift and much to my surprise, the fabspeed headers are cracked at the welds on both sides(close to the engine block). About 2-3 cracks per header. That explains the loud fluttering sound and loss of boost/power.

Such a shame. These things have only had maybe 9K miles on them.

 

Do you think fabspeed will warranty the headers? Or atleast reduce the cost of replacements?

Can you post pics

Mike

 

Hello Mike. I certainly hope so. But I would like a much more robust set. I would be very hesitant to spend the time/money/efforts again to install the same set only for it to crack yet again in the near future.