Blow Off Valve Shutter

[Speeedy]

I have asked around about blow off valve shutter and if its bad (causing back pressure) or not. I have seen many videos and wondering if its a certain valve itself?? Any opinions leave a comment.

[SlidingSideways]

If you remove your bov completely, it makes a shutter/fluttering noise, and it doesn't harm your engine, although your turbo tends to slow down between shifts and has to spool up again

The flutter is the sound of the air pressure "bouncing" back and fourth between the turbo to the pod filter. The more airspace you have in between, the slower the shutter sounds.. I.e. bigger intercooler.

I did this on my rb25 for half the summer, it sounds pretty mean. I cut a little flange out of thick ish metal, I believe it was 18ga, and drilled holes where the bov bolts go through and I just put it in place of my bov, and then bolted my bov back on so no air could escape due to the metal plate flexing under pressure.

I would've kept it on, but I had a track day coming up and wanted to keep the turbo spinning quick between shifts while I was there. Just never got around to putting it back on.

[gezed]

it doesn't harm the engine, but doesn't it harm the turbo?

[Skym]

Flutter sound = compressor surge / turbo hitting surge line and can get that sound by blocking little hole (boost goes through that little hole and helps BOV to quick release) next to main valve on stock BOV. But from my experience that mod makes engine less responsive off boost.

I thought the flutter sound is air going backwards over the compressor blade. But I found out it's the sound of turbo hitting compressor surge line that you see on a compressor map and that sound can be heard through podfilter.

Hitting compressor surge line is bad for a turbo. More so at higher boost levels / rpm's where compressor surge can do more damage to bearings in CHRA (more load on bearings), damage engine -

http://www.youtube.com/watch?v=nCj6Spwl1CU

[r33_gtst]

Compressor stall and compressor surge are two complete different things
Many high hp cars run no bov

[Skym]

I see what you mean by stalling when engine can't inhale enough air at higher rpm, but I see it as the same way as throttleplate shutting during shift's. From what I understand, in both cases mentioned in my post the turbo hits surge line on compressor map. The shock of turbo speeding up, slowing down during shift's puts excessive load on bearings, but at higher rpm / boost levels where it speeds up, slows down is where it does the most damage due to higher load on bearings. Both are bad for turbo bearings.

I use a Synapse BOV that result's in 0 surge. It feels like a factory engine (smooth), but more responsive (engine accelerates car quickly). Similar to modified stock BOV, but better response off boost (similar to a NA engine with 0 lag).

From what I understand, on some racecars (24 hour R35GTR racecar for example) they can keep turbo spooled via quick shifting. But it requires playing with trans shifting programming.