For those of you that have converted, I have heard the drivability with speed density is a great improvement, but I am curious if it will fix this surging or boost oscillation that I get in higher gears with heavy boost?

When I go WOT the car pulls fine, but if I give it like 75% throttle in 3rd 4th or 5th I get boost oscillation. I am hesitant to call it surging, because I am not sure if that is what it is. Since I ditched the stock turbo and went to bigger boost I have generally had some form or another of this behavior. I can basically hear the car's intake sucking noise go tstststssststtssstssstssstssss as it builds boost, instead of a clean intake noise.

I switched BOV's twice now and it has done it on all of them, even the Synchronic. I am just wondering if going SD will alleviate this problem and if it will, I am all over it. Thanks for any help guys!

 

dont think it will alleviate the problem, that is just BOV flutter. I have the Tial Q on SD and e85. You just have to change the way you drive.

 

Argh...it's just a pain to drive it that way. Either I have to drive like a madman and roll on the boost all the way, or I can drive it like a grandma. There's no in between LOL.

With as much power as I have on tap I don't need to go WOT to pass people, just want to give it a bit of boost, but when I do that on the freeway I get the fluttering. When I am giving it gas and boost, the BOV shouldn't be fluttering at all. Any positive boost should be closing the valve. So I am not sure it's the BOV. I can hear my airbox and filter physically shaking around.

 

When you're doing this, are you rolling on/off the throttle? Typically this happens only when letting off of the throttle.

To answer your question about speed density, no, that will not fix it. What it WILL fix however, is how the car reacts to this stuttering. The bucking that is induced will go away almost entirely, and aside from the noise of this happening, the car will still accelerate and drive a LOT more smoothly.

Speed density is probably the best mod I've done on my car, it is far more driveable in all conditions.

 

Hmmm interesting. Yes it happens on heavy throttle conditions. What happens when I let off is something entirely different. I am talking about building 15-20 lbs with partial throttle I hear the intake sucking noise sound like it is being cut on and off rapidly. I think I need to grab a video for everyone to see/hear. I'm going to get the camera under the hood if possible to see if the motor and intake are actually shaking around.

 

yes I know exactly what you are talking about.

 

Din't know that so many people are suffering the same problem as mine ...
I have the exactly same problem as you JDMevoBOOST ...
I've change my BOV but the problem still there ...
When i go full throttle .. no problem ... but when i half throttle ... the sound tstststssststtssstssstssstssss & my boost gauge will shake ... Here's a video showing the boost gauge shaking like my case (not my car) ...
http://www.youtube.com/watch?v=evGFf...eature=related

 

What turbo? IT could very well be compressor surge caused by the turbo at high load low rpm..If it is the BOV you can actually release the throttle in such a manner that does not cause this surging if your bov is setup correctly, but if you punch it in 5th at low rpm and it surges, most likely it is your turbo..

n/m, you have a BBK full, they really do not surge, so it is your BOV combined with your driving style.. I have been driving turbo cars soley for over 10 years and believe me when I tell you it is possible to tame a BOV with driving style, and no you do not need to mash the gas like an on/off switch..

 

when i went from MAF to MAP sensor with aftermarket ecu i got compressor surge in the high gears at about 4500 with my FP Red, didn't have it with the MAF sensor and stock (flashed) ECU

 

Changing driving style to please your BOV just plain sucks.

 

have you tried APS twin vent? have you replace your throttle body shaft seals? it's common on IX these seals destroyed fast. throttle body shaft seal can cause a lot of issue, boost leak, throttle hang.

 

I had the exact same problem with my 8.5 turbo. Did some research and could not find a definite answer on what it was. It was highly annoying, and sounded terrible. I also had low boost flutter at partial throttle to make matters worse. I got to the point where I didn't even want to drive the car.

Swapped to a BR 35R kit with an anti-surge compressor housing, and the problems went away. I still have no idea what the problem was, but the symptoms sound similar. I still get LBF from time to time, but it's hard to partailly boost a 35R, then flatten it out at that level.

 

There are several similar threads on this board. Blow off valve flutter can be worked with, but what you're describing sounds much more like compressor surge. Tialsport gave a very useful comparison of these two things in the last month in another thread.

 

JDMevoBOOST-
I had issues with both my green and my BBK with flutter and the jumpy gauge. Changing my driving style was not an option as my Evo is my road course car. What am I supposed to do on corner exit - Go full throttle or not accelerate??? Give me a break. I have tried many BOVs and even tried modification after trying each, including the dejon kit.

Some of us put 5 figures ($$$) into our motors just to have a small, yet significant part, compromise the driving experience. My tuner did not have an acceptable answer, other tuners did not have answers, I was off to find my own.

Behold, I finally found a good match for my setup with the BBK! After trying GReddy type RS and subsequently removing it, I took it apart and found it had 2 springs. I installed it with only the large spring (removed the small spring) and adjusted it to about 25% on the soft to hard scale. A little too hard would create the flutter; too much on the soft side would cause me to not hold boost as well (although there was more foregiveness going softer, than harder).

My flutter/erratic gauge was solved with a properly adjusted, single spring GReddy type RS. No compromises, no big dollar solutions. There are jokes in the tuning world about ricers that speak of "BOV tuning" as if it really exists. Well, it exists.

Good luck!!!

 

Robert from FP made a great post about this issue some where.

If you are using ECU controlled boost, that's likely where the root cause is with part throttle surge.