I have read many posts on here about BOV flutter and have heard testimonial about the Greddy Type-S being difficult to tune with our application. I myself just experienced similar problems. After installing the Portfuler on my car and increasing the boost to 15psi, my Type-S that had worked for so long at 10psi began to flutter miserably. No matter how tight or loose I set the screw on top, it would flutter.

I ended up trying the "one spring mod" which has been written up on the Evo forums and used sucessfully by many Evo tuners and it worked great. This just requires taking off the top of the BOV, removing the smaller of the two springs, and putting it back together. I tightened the set screw 3 full turns after it first touches the spring plate and this also seemed to work well. The sound is not quite as intense is it used to be, but I no longer have any flutter.

Also, one last tip. If you want to maintain the whistle sound that the Type-S is known for, make sure that you line up one of the 4 holes on the inner plate with the lower port on the BOV.

For a more detailed description of this mod check out:

http://www.evomoto.com/tech_info.php?tPath=1&tech_id=7

1999 Eclipse GS
Built motor
Hahn 16G Turbo w/ FMIC
Hahn Stage 5 Portfueler (270's & 500's)
Zeitronix Zt-2 wideband w/ 3.5bar MAP
3" SS Turbo Back
CM Stage 4 Clutch and Fidanza Flywheel
Baer Big Brake Kit

Shoulda took pictures and did a wiki write-up!

I contributed to the Wiki.

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http://www.2gnt.com/quote_db.php?id=278

Outside of Corona: "That sucks, peace out..." (jamie walks away)... "Sweeet, what we doin?" -Zac
Tim's garage (prior to motor install): "Im gonna smoke real quick, that way if you fuck up I am already nicotined up" -Tim

Yea, I def should have, but it is a pretty straight forward mod and there is a good write up with pics on the link I added.

1999 Eclipse GS
Built motor
Hahn 16G Turbo w/ FMIC
Hahn Stage 5 Portfueler (270's & 500's)
Zeitronix Zt-2 wideband w/ 3.5bar MAP
3" SS Turbo Back
CM Stage 4 Clutch and Fidanza Flywheel
Baer Big Brake Kit