Flutter and/or compressor surge - Hyundai Genesis Forum
Engine and Turbos This section is for discussing engine parts (for example, bottom or top end), turbos (upgrades, porting, etc), or other engine related parts or swaps.

 
LinkBack Thread Tools Display Modes
post #1 of 6 Old 06-28-2010, 05:01 PM Thread Starter
Super Old Timer
 
CrookedH's Avatar
 
Join Date: Jun 2009
Location: Texas
Posts: 1,185
CrookedH is on a distinguished road
(Thread Starter)
Flutter and/or compressor surge

Some good info on bov selection, operation, and issues. Credit goes to Whatnot for the info:

Technically flutter only occurs with a BOV, and surge is with turbo... but that is more semantics than anything.

All fluttering noise isn't bad, as long as it goes away and has a changing frequency, as that is the BOV piston fluttering open and it’s like a ball bouncing, how the frequency gets higher and higher until it stops, and it’s more of a whistling sound.

Instead of gravity pulling on the ball, and the ball having less and less energy, bouncing lower and lower until it stops. The BOV flutter is blowing off some air, and less and less air is released until it stops.

It's basically from too tight of a spring. The air starts to get out, and then the pressure drops too low to compress the spring and keep the BOV open so it shuts, then the pressure builds again, so same process, it just doesn't open as long (why the sounds gets higher pitched), like I explained with the ball and gravity.

Some call it the turkey gobble or the pigeon call or flutter dump, its ok, and won't harm anything, you just have too tight of a spring. You can loosen it if you want to be rid of the sound, but you might have trouble holding higher boost. Here is a great video and you can actually watch the BOV flutter 9 secs in a correlate the "ball bouncing sound" as the BOV increases its frequency and higher pitch, and finally stops.





What IS bad is when the flutter is metallic, generally higher pitched to begin with and continuous, without change, as that compressor blade 'smacking' against the air and is generally a higher frequency as the compressor blade is spinning fast. This is bad for your turbo. It is much like too high of a back pressure, it never actually has the blades moving the other way, and it just puts a ton of strain on the bearings and shaft. There is no, less and less air or and slowing down (ball bouncing effect), it’s a constant frequency beating of the blades.




This is also compressor surge, as you can see the BOV not even open and you hear the surging.


you really start to hear it @ 1:04. And the fluttering sound is constant not "bouncing down", and not as 'whistly' as a flutterdump.

But what is terrible to hear is when you are under load and you get flutter. like this vid.



If you are ever WOT and you hear a flutter, THAT, is VERY BAD. It doesn't even have to do with a BOV, as your BOV should be shut during boost, so how is a BOV causing a surge? It means your A/R is too small for the boost you are running (very unlikely as you engine will most likely blow up before this from the hot air), but most likely, your had some dirt or something that over time rounded off/clipped your compressor blade and the 'seal' (blade tip to housing clearance/tolerance) isn't as good and the blade beats/slaps the air vs., pushing it. Like if you cut the compressor blade in half, it would give you a little bit of boost at first, but then it would lose efficiency VERY fast and then it would slap the air, vs. compress and push it. It is not that 'bad' for your engine or turbo... as you turbo is already F'd lol. So it is bad news, and not good to hear, but you’re not damaging anything when you hear flutter/surge under WOT.




I have heard other opinions, but this is what makes sense to me anyway, and I have some logic behind it, so I am happy with it.
CrookedH is offline  
post #2 of 6 Old 06-29-2010, 08:19 AM
Moderator
 
Tufast's Avatar
 
Join Date: Sep 2008
Location: Columbus, GA
Posts: 10,780
Tufast is on a distinguished road
Excellent post, stuck thread.
Also makes me rethink my BOV choice, this synchronic seems like the shit. I love the quick response & absence of loud whistle after shift. Anybody have any feed back regarding this type of BOV?

Sponsored By: Columbus Body Works / ARK Performance / Modern Automotive Performance / Forged Performance
Tufast is offline  
post #3 of 6 Old 06-29-2010, 10:06 AM Thread Starter
Super Old Timer
 
CrookedH's Avatar
 
Join Date: Jun 2009
Location: Texas
Posts: 1,185
CrookedH is on a distinguished road
(Thread Starter)
Interested in some first hand feedback on the Synapse BOV as well if anyone has used them... I've got the Forge MS BOV I plan on using once I get my car back but was thinking about putting the Forge MS on my wifes car and getting a Synapse for me....
CrookedH is offline  
 
post #4 of 6 Old 04-25-2011, 04:26 PM
Member
 
boostcrzy's Avatar
 
Join Date: Apr 2011
Posts: 14
boostcrzy is on a distinguished road
I've tried synapse when I had my evo and it worked relatively well. It is very temperamental and requires that you figure out what vacuum ports to connect for your particular setup. In my opinion I would go with a tial bov, they perform great and are very easy to install with minimum tuning.
boostcrzy is offline  
post #5 of 6 Old 04-27-2011, 04:29 AM
Moderator
 
Tufast's Avatar
 
Join Date: Sep 2008
Location: Columbus, GA
Posts: 10,780
Tufast is on a distinguished road
Quote:
Originally Posted by boostcrzy View Post
I've tried synapse when I had my evo and it worked relatively well. It is very temperamental and requires that you figure out what vacuum ports to connect for your particular setup. In my opinion I would go with a tial bov, they perform great and are very easy to install with minimum tuning.
I was going to go with TiaL until I learned about Synapse & then changed my mind. I didn't realize that they were that tempermental, but I guess it will worth it once I do have it dialed in.

Sponsored By: Columbus Body Works / ARK Performance / Modern Automotive Performance / Forged Performance
Tufast is offline  
post #6 of 6 Old 04-27-2011, 09:49 PM
Old Timer
 
Join Date: Aug 2009
Location: Illinois
Posts: 428
Red Raspberry is on a distinguished road
My Tial works OK. If I were to do it again I would upgrade the OEM one and not do a cold side BOV. As it is with the BR tune the OEM one works great. The Tial is just a gewgaw now and in the way.
Red Raspberry is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome