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Old 07-14-2013, 07:33 PM   #1
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Default new fluttering sound in boost

During boost I hear a fluttering air noise that increases in volume with pressure.

I thought it might be related to the new EBC that I installed so I removed the EBC and the signal line goes directly to the actuator. The noise still occurs. I inspected the lines, tubes, etc. and did not see anything wrong.

I have a 20 second video and log from today. I also have a couple videos from an autocross yesterday. I have a microphone in the engine compartment to help pickup the sound.

The noise is more noticeable today than yesterday. Has anyone heard this before or have an idea of what it might be?

Today's video, goes with attached log:


Autocross video 1 - Fluttering noise around 5-7 seconds, 17-19 seconds,

Autocross video 2 - noise around 6-8 seconds
Attached Files
File Type: msl travisb_2013-07-14_17.09.53.msl (39.3 KB, 40 views)
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Old 07-14-2013, 08:22 PM   #2
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Take a HARD look at your intake piping for leaks.

Take a HARD look at the security of your exhaust system, especially manifold to turbo and turbo to downpipe connections.

BTW, your BOV doesn't sound right to me, although that's not your complaint.
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Old 07-17-2013, 04:59 AM   #3
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That sounds like your axle/half shaft or whatever it's called where the bolts are on your axle hitting the exhaust pipe to me whenever your engine rocks after you left off on the gas. I've had a noise similar to what's in the video happen to me before with my 3" exhaust when I was trying to get it to not hang so low.

EDIT: in fact, after listening to the 3rd video, I'm pretty sure it's this, because the sound happens even long after your bov should have opened, and it happens during turns when your exhaust could be moving around
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Old 07-17-2013, 08:40 AM   #4
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sounds like your BOV is too tight, and/or plumbed incorrectly.

also, you shift at like 6K; while this is not a contributing factor, it is when calculating your manliness.
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Old 07-17-2013, 03:32 PM   #5
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I don't have a BOV. The only thing that is connected now is the signal line to the actuator. No EBC right now.

I haven't had time yet to check everything again as suggested by hornetball.

I am aware there are other noises that you may hear in the video that I also need to figure out.

The noise I am referring to is most definitely air related. I can make it happen on command by hitting boost while going straight or turning. It's just a f-f-f-f-f-f-f-f sound while in boost and while the WG is open. The volume increases with boost. Not sure if it is an intake or exhaust sound.

--------------------

I do have a followup question on the actuator. Say the actuator is set to open the WG at 7PSI. The pressure in the system hits 7, the WG opens, and the pressure immediately drops. I'm guessing the WG closes and the system builds pressure again.

Does the actuator and WG rapidly open and close as the pressure is hitting the limit and dropping again? Is that a potential cause for the noise I am hearing?

Or, sense this is an analog environment, the WG might not really get the chance to close all the way because as it is closing the pressure is building again. Just curious.
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Old 07-17-2013, 04:02 PM   #6
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Get a BOV then. From the sounds of it, you are destroying your turbo.

None of these noises have anything to do with your wastegate or EBC.
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Old 07-17-2013, 04:24 PM   #7
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Then the noise is compressor surge. It's the compressor blades chopping up all the boost that's being expelled through your intake.
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Old 07-17-2013, 04:27 PM   #8
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I think I kinda hear the noise you describe, it's not a flutter as what's happening when you lift, but I'd ignore it all.
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Old 07-17-2013, 04:35 PM   #9
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Quote:
Originally Posted by Braineack View Post
I think I kinda hear the noise you describe, it's not a flutter as what's happening when you lift, but I'd ignore it all.
Right. It is not the same noise as the surge when lifting. I'm quite familiar with that sound and this new one is very different.

And out of curiosity, any thoughts on my other question? Not so much on the cause of this noise, but just how the actuator and WG work in general at/near peak boost.

Quote:
Originally Posted by travisb View Post
I do have a followup question on the actuator. Say the actuator is set to open the WG at 7PSI. The pressure in the system hits 7, the WG opens, and the pressure immediately drops. I'm guessing the WG closes and the system builds pressure again.

Does the actuator and WG rapidly open and close as the pressure is hitting the limit and dropping again? Is that a potential cause for the noise I am hearing?

Or, since this is an analog environment, the WG might not really get the chance to close all the way because as it is closing the pressure is building again. Just curious.
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Old 07-17-2013, 05:54 PM   #10
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Quote:
Originally Posted by travisb View Post
I do have a followup question on the actuator. Say the actuator is set to open the WG at 7PSI. The pressure in the system hits 7, the WG opens, and the pressure immediately drops. I'm guessing the WG closes and the system builds pressure again.

Does the actuator and WG rapidly open and close as the pressure is hitting the limit and dropping again? Is that a potential cause for the noise I am hearing?

Or, sense this is an analog environment, the WG might not really get the chance to close all the way because as it is closing the pressure is building again. Just curious.
A WG is essentially a P(roportional) controller. A certain pressure- let's say 7psi- will open the actuator a certain amount. If the pressure increases a little - let's say to 7.05 psi- the actuator opens a little more. This is the way it's supposed to control pressure. So even the best and most perfect WG will have some change in pressure.
This means that your boost will be fairly stable- maybe with some initial overshoot and a little droop at higher rpms/loads, but it should NOT flutter.

The quick opening/closing scenario you describe *could* happen if you add a strong T(ime) element to your control system. But that sounds unlikely. Maybe if the hose is kinked or plugged. I never tried, but please check that WG hose to make sure.
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Old 07-21-2013, 12:09 PM   #11
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Quote:
Originally Posted by Braineack View Post
also, you shift at like 6K; while this is not a contributing factor, it is when calculating your manliness.
so, too low.... too high... ?
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Old 07-22-2013, 01:00 AM   #12
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Contrary to popular opinion compressor surge does not destroy turbos. My car has been boosted without a bov for 4 years.
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Old 07-22-2013, 01:24 AM   #13
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It sounds like compressor surge from over working the 2554 you are running. Maybe?

Here is what it sounds like to me in the background of the videos
https://www.facebook.com/photo.php?v=4430838123929
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