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FMIC installation after affects

gts-wpn

By gts-wpn,
in Engines & Forced Induction

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gts-wpn Enthusiast

gts-wpn

Posted
Posted

I recently had a front mount intercooler installed on my r33, and i did notice that after the front mount was bolted on the flutter noise changed and the noise difference was that the original flutter was faster, and the new flutter was slower. I have an atmo venting blow offf valve so thats why original i had some flutter, but in the last week or 2 the flutter has changed back to its original faster flutter. So my question is, is it normal for a car to do that? or is there something that has changed the noise after the FMIC was put on.

Another question, I also put my stocko blow off valve back on and even with the FMIC it makes no flutter whatso ever, is that normal even with a FMIC?

Any advice appreciated. Cheers.

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https://www.sau.com.au/forums/topic/66137-fmic-installation-after-affects/
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Nozila Grand Master

Nozila

Posted
Posted

i have a stock bov on my r33 and there is no flutter what so ever just a loud whoosh coming from the pod filters. On the other hand, with my brothers cars there are flutters. One has a r32 with a sequential hks bov - flutters off boost but wooshs under load while the other has a very loud flutter on his sr20. Obviously both has fmic but neither of them have had stock bov's on so i wouldnt know if it flutters or not. Hope that helps.

inissane Proficient

inissane

Posted
Posted

firstly a BOV's job is to vent a back pressure wave from a suddenly closed throttle under boost say in a gear change. This wave returns towards the turbo through intercooler piping, and ofcourse the intercooler (if BOV is on turbo side of cooler).

Larger FMICs can resonate or echo the flutter sound which is by the way compressor surge, the very thing that BOVs are designed to prevent! The FMIC's effect upon sound is irrelevant, the problem is that you are experiencing compressor surge, or the flutter sound which is the pressure wave finding its way to the turbo. This means that BOV probably isn't venting enough air (or the timing or somthin along these lines), whether it be plumback or to atmosphere. Whether the BOV is plumback or to atmo is in terms of compressor surge, irrelevant also.

However, for RB25DET which has an airflow meter (AFM) a plumback BOV may work smoother under a range of conditions, because if BOV vents to atmos the computer assumes it has still received this air and may inject too much fuel in some conditions (and possibly stall).

Truth is flutter may sound alright but its compressor surge which will reduce throttle response when gas is applied after a gear change and reduce the life of a turbo. May work for ages but i think you may end up increasing turbo shaft play.

Hope this helps!

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