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Discussion Starter #1
Ok I am trying to solve this damn problem with the HKS BOV and the studder that occurs under easing off the gas under very slight boost (like 2 or 3 psi).

I have the CP-E FMIC, speedie 6's turbo inlet pipe, and an HKS BOV (which I just put in the new generation 3 BOV). Here is the data I have. I know that HKS's have that signature flutter that occurs when they activate under light boost blow off. I have always noticed that but it seems that ever since I installed the speedie6 turbo inlet pipe, that when I am cruising down the highway and want to adjust my speed by accelerating say, 5 to 10 mph, and I'm talking gradual boost/acceleration, just hitting 3 or 4 psi (barely dipping into the throttle). Then when easing back off the throttle, the BOV activates around 0 psi and does the fluttering and as it flutters the car shakes/studders for about a second.

It makes itself most noticeable when the weather is cold (like freezing temps) and as it gets warmer out, it'll still flutter but won't cause the car to studder or quiver. No back fires or anything just a hiccuping feel while it is fluttering. Here is what I had been hypothesizing. Perhaps the fluttering is sending a "ripple effect" back through the intake pipes (I have the CP-E CAI) and this is causing the air flowing over the MAF further towards the front of the CAI to give some temporarily erratic signals. Now the reason we wouldn't notice this under letting off the throttle abruptly and activating the BOV is because HKS activates completely with a single burst but when EASING off the throttle, but still applying SOME throttle, the MAF's signals being interrupted would be noticeable.

Here is what I tried to do: I figured that if I installed some kind of expansion chamber in between the HKS BOV and the turbo inlet pipe, maybe it would dampen the "ripple effect" and not cause the jerking/shaking as the BOV fluttered. I even put a small piece of foam rubber in a make-shift expansion chamber to help slow the air. In short - it had no effect.

I figured the reason I noticed it more after installing the speedi6 inlet pipe was because it was much more free flowing and might allow the ripples to travel back up the intake pipe more readily. I'm half tempted to put the stock turbo inlet back on.

If anyone has any insight into this I would greatly appreciate it. I'm so annoyed with the light-boost blow off studder in colder temps.

Thanks!
 

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I have the exact same issue you are having with my forge. I don't have a solution for you since I have tried various spring setups and they don't help. I noticed this after TIH and custom FMIC. Maybe someone else can chime in.
 

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Discussion Starter #3
QUOTE (Qwik6 @ Feb 11 2010, 11:29 PM) index.php?act=findpost&pid=1636436
I have the exact same issue you are having with my forge. I don't have a solution for you since I have tried various spring setups and they don't help. I noticed this after TIH and custom FMIC. Maybe someone else can chime in.[/b]
I hope someone has cracked this mystery. It wears my nerves thin! LOL What is TIH? Turbo inlet housing maybe?
 

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QUOTE (MattOKC @ Feb 12 2010, 12:46 AM) index.php?act=findpost&pid=1636440
I hope someone has cracked this mystery. It wears my nerves thin! LOL What is TIH? Turbo inlet housing maybe?[/b]
I have the same issue. Not real sure what it is. I noticed it with all of my BPVs i have ran. Forge, Turbosmart dual-port, HKS, Cobb, Greddy, SU/Turbosmart, and Synapse. Idk why it does it but it is irritating. I have the Cobb TIP so it does it with the silicone ones too. Maybe its the FMIC or something causing it.
 

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I had the stock bpv on with my setup and it went away. I do notice it's worse in the cold weather. TIH-Turbo inlet hose. If I hold the boost low and ease off the throttle I can have it flutter for a good 3 seconds. Sounds like the car is laughing.
 

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*FACEPALM*



for the love of god NEVER put anything in any of your piping haha. if that foam had gotten sucked into your turbo you would have smoked it and been fubar'd. i sometimes have this flutter but i just ignore it. its a quirk, every car has them.
 

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Discussion Starter #8
QUOTE (Qwik6 @ Feb 12 2010, 12:47 AM) index.php?act=findpost&pid=1636445
I had the stock bpv on with my setup and it went away. I do notice it's worse in the cold weather. TIH-Turbo inlet hose. If I hold the boost low and ease off the throttle I can have it flutter for a good 3 seconds. Sounds like the car is laughing.[/b]
Exactly! Never thought to describe it like that but yah if you ease off just right and it's right on the threshold of where the BOV activates, it can last a few seconds and sounds like the car is laughing. I'm glad to hear that other people have this going on but it sucks that it's a nuissance. I checked all my connections and everything looks fine. I don't notice any boost leaks at this point.

Yes and I was very cautious about the foam, it was way to big of a piece to fit down the hose, I cut out a chunk of foam rubber and it was the size of the interior of the expansion chamber I built. If that had fixed the problem, I was going to put a metal screen in there too for long term use but unfortunuately it did nothing to alleviate the problem.
 

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I got the problem when I used my synapse with the SB. I dont like it either...
 

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Discussion Starter #11
QUOTE (bova80 @ Feb 12 2010, 11:32 AM) index.php?act=findpost&pid=1636542
Yah that's what it sounds like when I go under significant boost and let off fully, it's more of a light hooting owl type flutter or laughter when it's light boost and easing off the gas right at that threshold where the BOV activates, that's what shakes the car from the studdering. It's really obnoxious in the cold weather. I would love to know what the hell is causing it. I think it somehow comes down to the MAF readings and the fluttering causing some temporarily erratic signals to the fuel injectors.
 

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QUOTE
Yah that's what it sounds like when I go under significant boost and let off fully, it's more of a light hooting owl type flutter or laughter when it's light boost and easing off the gas right at that threshold where the BOV activates, that's what shakes the car from the studdering. It's really obnoxious in the cold weather. I would love to know what the hell is causing it. I think it somehow comes down to the MAF readings and the fluttering causing some temporarily erratic signals to the fuel injectors.[/b]
I've been running the HKS for a good 6 months now. Someone on MSF just posted that they talked to someone at HKS and they said it was normal because it's a dual valve or something. It only really does it at low boost for me too though. Even with the turbosmart I was getting a light flutter unless I was letting off above 10 psi. The only BPV that was nice and clean every time was the stock one. I don't think the flutter is bad for your car but, if your car is shaking when you let off and there's fluttering, I'm guessing you have a boost leak somewhere and are getting surge. I had a GIANT boost leak one time after installing my SPEEDIE TIP over a year ago and I was getting HUGE flutter (more than usual) and then shaking. Checked for boost leaks, found a huge one, fixed it, flutter reduced and shaking (surge) was gone. I'd say check your system man.
 

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Discussion Starter #14
QUOTE (MSP6COP @ Feb 13 2010, 02:47 PM) index.php?act=findpost&pid=1636814
I've been running the HKS for a good 6 months now. Someone on MSF just posted that they talked to someone at HKS and they said it was normal because it's a dual valve or something. It only really does it at low boost for me too though. Even with the turbosmart I was getting a light flutter unless I was letting off above 10 psi. The only BPV that was nice and clean every time was the stock one. I don't think the flutter is bad for your car but, if your car is shaking when you let off and there's fluttering, I'm guessing you have a boost leak somewhere and are getting surge. I had a GIANT boost leak one time after installing my SPEEDIE TIP over a year ago and I was getting HUGE flutter (more than usual) and then shaking. Checked for boost leaks, found a huge one, fixed it, flutter reduced and shaking (surge) was gone. I'd say check your system man.[/b]
Where did you find your boost leak? Today I'm going to temporarily disconnect the recirc. hose, cap it off and VTA the BOV and see if the car still shakes when releasing really light boost. That will at least help me figure out what is going on. I might have to look into the Synapse if there aren't any leaks!
 

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I'm so confused guys.. isn't this NORMAL?! I thought BOVs always made those sound under low boost.... But come to think of it, I had the HKS BOV in recirc and I never had that problem. Lol. I hear it on other boosted cars so I assumed its normal.
 

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When I had the studder I had a good size boost leak right at the turbo/intercooler coupler. Just do a good pressure test from your intake and you'll probably find something.

QUOTE
I'm so confused guys.. isn't this NORMAL?! I thought BOVs always made those sound under low boost....[/b]
Between the stock, forge, turbosmart, and HKS, all of them did it except the stock BPV under low boost. Anything above 10 pi was nice a clean.
 

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I had it when I also had a Standback installed, but when I went back to stock engine management it went away. I always assumed it was my tune/more aggressive BOV behaviour of the standback, interesting to hear people are getting it with stock engine managment.
 

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Discussion Starter #19
QUOTE (bova80 @ Feb 15 2010, 07:30 AM) index.php?act=findpost&pid=1637069
maybe the OP should make a video so we can determine whether its normal or not[/b]
I made one :) I used my phone so I don't know if I'll be able to upload it directly here or I may have to put it on youtube. You can hear the fluttering but I don't know any way to show how the flutters send jolts/studders through the car. They just feel like mini pulsing fuel cuts that coincide with the fluttering.
 

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