Ford Focus ST Forum banner

What's the slight flutter sound when I let off of the throttle somtimes?

25K views 29 replies 14 participants last post by  aspillz  
#1 ·
Occasionally, when I let off of my throttle, I get what sounds like a slight "flutter" sound. Is this a normal sound related to my throttle body? This isn't the type of noise associated with turbo flutter that you can hear in any number of youtube videos, or at least not to that degree. It also doesn't happen every time.
 
  • Like
Reactions: KonabluST
#3 ·
Even though it's pretty soft (in volume)?
 
#4 ·
Yes that is from the turbo. My car does it too. It's called compressor surge. It happens when there's not enough pressure to open the blow off valve, and the slight flutter you hear is air hitting the compressor blades. Nothing to worry about unless maybe if happens after WOT in boost.


Sent from my iPhone using Tapatalk
 
#5 ·
I have installed a turbosmart bov. Might it need some adjustment?
 
#8 ·
I guess that's possible, but like we said it's completely normal. So it depends on how much gas you giving the car before you let off and hear the flutter.
If it's just a tiny bit of gas and you let off slowly, then it flutters... You are completely fine.


Sent from my iPhone using Tapatalk
 
#9 ·
I removed the symposer and installed a plate that does not have a nipple for a vac line.
 
#11 ·
If you change it to true vacuum you will need to readjust the BOV, I personally changed springs even, but you will always get a little flutter no matter what you do. This is normal when letting off the throttle, but should never happen when putting the pickle to her.
All good info so far!
 
#12 ·
So if I bought the cpe exhale kit with a tial blow-off valve, how/where does that tie in for the vacuum?
 
#13 ·
well it comes with the piece that draws vac on the manifold next to the MAP sensor. special name for the block but I don't know, it is the wierd little block that comes with the kit and the MAP sensor attaches to it and then to the manifold.

Or you can always connect it to the same vac line the stock BPV connects to which is the solenoid block on top of the engine. That is how I setup mine, I have a TIAL BOV.

someone correct me if I am wrong but it works great for me.
 
#14 ·
If I have the turbosmart right now, is it worth ditching it for the cpe kit and the tial?
 
#16 ·
And to throw yet another detail into this, what's the difference between the tial and the hks?
 
#19 · (Edited)
the sounds that they make ... the hks is high pitched.. i personally like the TIAL over the HKS and after hearing them side by side i went with TIAL

I do also like that the TIAL is USA MADE. HKS is Japan which is a good product but Made is USA is cool, says so right on the top
 
#18 ·
I just installed a Boomba adjustable BPV, where you can remove 1, 2 or 3 small screws to get some whoosh happening. Unfortunately I left all three in so I have no BOV sound at all. =< I'm gonna have to figure out how to remove a screw or 2 with the device installed.
 
#22 ·
It is easy enough to remove that at least it isn't a terrible job...like you though I prefer not having to take off a wheel and pull the fender liner and get all "involved" more than I need to. For me though its just because of my damn apartment complex.
 
#20 ·
The Tial BOV on the stock turbo using a true vacuum source sounds like little sneezes between shifts and is drastically different from the Boomba BOV which sounded like an air brake releasing. The size difference is substantial.
 
#21 ·
Lol yeah I describe the sound as a hushed sneeze. It's more of a cccsshhhhhh, not a ptttsshhhhhh like the others.

You'll know what I mean when you hear it.
 
#27 ·
Hey bringing this thread back from the dead (and making my realize sadly my 2015 ST is so old).

I have a Boomba BOV, it was already installed from previous owner, uses stock computer controlled vacuum source. I just started noticing this. But the thing is, the harder I am on the throttle before releasing it, the louder the surge sounds, AND the more intense the BOV "pssst". It's all correlated, louder "psst" = louder high pitch whirring noise. It definitely happens while the BOV BO's. I don't think it's always happened but ever since I noticed it it's all I hear.

Sidenote a little oil is present around the vent holes of the BOV. I haven't been super concerned about it as my oil level is overall not dropping noticibly. But I'm concerned it's gumming up the BOV and it's not opening quickly enough or fully enough.

Should I be worried?
 
#28 ·
I can't tell you you should be worried, but I can tell you that Boomba BOV requires maintenance every six months or so.

 
  • Like
Reactions: MtnMan
#29 ·
Wow thanks yeah that definitely hasn't been done in the 2 years I've owned it and who knows how long beforehand. I did take it off and inspect it and clean up the outside and it looked good but I didn't clean it that thoroughly. Thank you.