Fluttering sound is completely normal. It's the electronic wastegate actuator regulating boost levels. It's still there with the stock intake, but you're unable to hear it. Only way to eliminate that would be to change your turbo and wastegate actuator. As for the compressor surge, what intake and BOV did you install?

 

First off all thanks for the response
Now I don’t know what to say, I was sure the fluttering sound was turbo surge…
I have stock BVP but openly vented so BOV. Got an AEM big filter and install it on the stock intake pipe surrounded with heat shield.

So is there any way to differentiate between the electronic wastegate actuator regulating boost and turbo surge?

 

You're not getting surge then. I had surge when I had my Forge BOV and it wasn't opening and also when my Synapse pre-load spring broke. Surge is a much louder and more distinct sound and you'll know when something isn't right.

 

I think you are confusing surge with flutter there, MM. If your BOV doesn't open... that'd be flutter. Flutter isn't dangerous because it only happens when you let up off the gas. There's no exhaust gas pushing your turbine so you don't have two sets of pressures twisting on the turbine shaft. As a matter of fact, you can actually safely run the car with no BOV. Although by running with no BOV you can actually cause the compressor wheel to stall and thus it takes more energy to spool it back up again resulting in more lag, no actual harm will come to the turbo. The BPV/BOV's primary function is to relieve the pressure in the charge pipe to reduce the amount of momentum loss experience by the compressor.

Compressor surge only happens when you are on the gas. Your BOV should never open when you are on the gas. When the compressor surges, it is because pressure inside of the charge pipe is pushing back against the compressor wheel at the same time exhaust gas is trying to rotate the turbine and the compressor is trying to push more air. This puts an enormous strain on the turbine shaft and ultimately will cause the shaft to fail. Typically the most common reason for compressor surge is a wastegate failure. Your wastegate is designed to open up at a certain pressure to prevent overpressurization of the charge pipe and intake. If it doesn't open up when it should, that overpressurization pushes up against the compressor wheel and bad things start happening at that point.

What we cannot say is that the OP is experiencing compressor stall as we don't have enough perspective on the problem to know what the OP is hearing or what the OP is doing at the time the sound occurs. It could very well be that the OP is correct that this is happening on all 13+ 2.0Ts and the reason why most don't realize it is because most folks are not listening for it, hear it and ignore it (assuming the sound is normal), or have an aftermarket exhaust system.

Regarding the last item... you know that the 13+ electronic wastegate will open during normal operation to regulate boost even before the system reaches max pressure. This mode of operation is a little different from the way the 10-12 wastegates operated in that the 10-12 wastegates stayed closed during normal operation up to peak boost. We also know that the 13+ exhaust system from the downpipe to the back is the same as the 10-12s; however, much more exhaust is being shoved down the same sized pipe due to the higher power outputs of the 13+. We also know that the exhaust on the 10-12s were a huge choke point for those cars at those power levels. When we add all this up, that would mean that the exhaust system on the 13+ models are even more inadequate.

So, when we add all these things together, it could very well be that Mr. David has discovered a problem with the 13+ models that nobody ever stopped to consider. If the turbo is being choked by excessive back pressure it may very well be that the wastegate design on the '13+ combined with the the small exhaust is causing a stall. Excessive back pressure could be preventing the wastegate from fully opening, thus the turbine overspeeds and the system overpressurizes. This is all theory at this point, but I wouldn't be so quick to discount the possibility that a problem actually exists by blaming a faulty BPV or BOV which would have nothing to do with flutter under powered conditions.

 

I am speechless.. lol

From Garrett Website,
"Blow-Off (Bypass) Valves
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it.
Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure; helping to eliminate the phenomenon of surge."

From Turbonetics Website,
"Q: Should I run a Blow-Off/By-Pass Valve (BOV) on my turbocharged car? What does it do?
A: Yes, all turbo cars can benefit by running a BOV on their vehicle. A BOV works by relieving the compressed air pressure trapped in the piping when the throttle body closes. The turbocharger continues to spin from the exhaust gasses exiting the engine and the compressed air has nowhere to go. The BOV opens and prevents the compressed air from "backing up" onto the compressor wheel causing surge. By venting or re-routing the trapped air, the BOV allows the turbocharger to spool up quicker between shifts and prevents long term damage from continual surging of the compressor wheel.
NOTE: If your vehicle has a Mass Air-Flow Sensor, it is important to re-route or By-Pass the air back into the inlet of the turbocharger (behind the MAS) so that the vehicles computer does not raise/alter the air-fuel mixture, causing the car to potentially run rich between shifts."

 

Great info thanks to everyone
I think I understand the BOV related surge, which is not the problem here! No surge at all when I lift the gas pedal or when the BOV is supposed to open.

The problem I am experiencing is surge/fluttering when at WOT
In the range of 13-16 PSI or 3000 to 4000 RPM (aprox)
It’s a distinct flutter sound that I´ve also hear in these forum on a couple of videos tagged “2013 leaking BOV” or similar

It would be nice to hear from someone else who had this problem
However, im still intrigued by +MM+ theory of that sound been just “the electronic wastegate actuator regulating boost”

How would you try that hypothesis? How can you determine if there is surge or is the wastegate that produces de sound?

 

In formulating an answer, I think perhaps I was unclear... so allow me to elaborate:

There is a moment when you first let up off the gas and the throttle body slams shut where exhaust gases are still pushing the turbo... this can cause a momentary surge if the pressure is not relieved... this is what the BOV does. While it does prevent the momentary stall associated with the throttle plate closing, It's primary function is to allow the compressor to continue to spin while there is very little exhaust to push the turbine... if the compressor stays spinning, it takes less energy to spool back up again. In any case, this is not the kind of flutter that the OP is describing.

The air backing up into the compressor happens after the throttle body is closed... if the pressure isn't relieved somewhere in the charge pipe, it will work it's way back through the compressor causing the compressor to stall...... but.....

The compressor is not being pushed by the turbine at that point. The stress on the thrust bearing is momentary as there is only residual exhaust pressure pushing the turbo at that point.

The dangerous kind of compressor stall that I'm talking about is the kind where the turbocharger is being pushed by the exhaust (throttle body open) and the engine cannot pull in enough of the charged air and overpressurizes. The pressure that the turbo produces is regulated by the wastegate and not the BOV.

With a traditional wastegate that uses a diaphragm and spring to open and close, a wastegate failure results in a prematurely opening wastegate.... not a big deal. In the case of an electronic wastegate, however, the wastegate is controlled by an electric actuator. If the wastegate is closed at the time the actuator fails.. guess what the wastegate isn't doing anymore? The wastegate's primary function is to prevent the turbine and compressor from overspinning (see the compressor map below)... that is to keep the turbo from going past the surge limit.. or surging. This is the speed at which real damage can happen really quick:

I know this goes against conventional wisdom because traditional wastegate design typically prevents the wastegate from failing in a closed position; however, we are not dealing with a traditional wastegate in the 13+s. We are dealing with an electronic actuator that is directly controlled by the ECU.

The OP is complaining about a fluttering sound when the gas is applied. He stated that he has a normal blow off when he lets off the gas with no fluttering sound. That sounds to me like he doesn't have a problem with the BPV.

A fluttering sound when the gas is applied could be a fluttering wastegate.... but a fluttering wastegate would not improve by reducing the backpressure on the system. It would continue to flutter. The OP stated that he had heard someone else having the same problem that was relieved by removing the muffler. While I agree that this is hearsay, I'm willing to entertain the OP and assume what he is saying is true for the moment.

So... the question is... why would relieving back pressure affect compressor stall while the OP is accelerating?

 

If you relieve back pressure the engine would be able to process more air.
But I guess faster flow would spin the turbo even faster testing the wastegate witch is probably the cause of the problem



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http://youtu.be/1daDZVQkORY

I want to get to the bottom of this
What do you guys think?


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That is your electronic wastegate controlling your boost under WOT like every 2013 Gen on the road. It is never going to stop unless you go External and a new turbo and tune.

It will not do it half as much if you go stage 2 tune and run max boost. Mine almost never does that anymore after the tune.

 

That looks like your wastegate partially opening when you let off the gas a little... which would make that wastegate flutter.

 

Let off?
But yes I think you are right
The wastegate starts opening a bit at the time the flutter sound began
Thanks


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Stage 1 full 3" exhaust checking in.

Under WOT (and only WOT) I get fluttering under 4k RPM. I read many times this is typical for us 13+ 2.0Ts. Whether it is "normal" or not is another issue, but "typical" it certainly is.

My solution: don't go WOT under 4k.

 

But why won’t you WOT under 4k?
Do you still believe its compressor surge? or does the flutter sound bother you?
now that I know it’s not harmful I even like it