Interesting noise....

[Rosco]

I have a blitz BOV and you can clearly tell it's sound so I know its not that. I'm trying to figure out what the weird fluttering sound is. To me it seems it is coming from the intake/turbo. I'm just really curious to find out what it is. It happens when I let off the gas. I also have a Mines tuned ECU if that helps any. I was thinking it was the air that did not make it to the BOV bouncing between the blades. Maybe I need to fine tune my BOV? A couple people have told me that it is a normale sound.

[da40]

very normal all turbo make that sound some higher pitched some lower its very normal dont worry about it

[S14-NEO]

i wouldnt always agree with that...make sure you have a solid vaccum source for the BOV the properly operate. from the sound of it you have compressor surge

[sr20detmaybe]

yeh, sounds like compressor surge, is the blitz bov adjustable? (never dealt with 1) if so it could be adjusted to tightly and not opening when u let off the throttle. i know i had to adjust my apexi some bc i had it too tight and it wouldnt blow off corectly under i was at full boost when i let off the gas. hope this helps.

[Rosco]

Yeah it's adjustable, I was pretty sure that you don't want that noise. That will be project one for the day.

[Blown240sx]

Compressor surge = bad

reason being what is happening is the turbo turbine is getting back pressure on it and actually stopping or slowing way down causing stress on the blades and turbo internals.

[Rosco]

Okay I tightened down the BOV and it seems to respond great but I'm still hearing some compressor surge. It's alot quiter now and doesn't seem as bad, but should I tighten further? I mean the allen screw is almost flush with the nut. Is there a too tight spot on the BOV? Could I have a boost leak somewhere that could cause it as well?

[Blown240sx]

Tightening isnt what you should be doing. Compressor surge is caused when pressure is not released from the system. You need loosen it a bit until it stops but not so loose that th BOV leaks.

[Rosco]

Alright, maybe originally it was too loose to begin with because the surge is alot harder to hear now. I will do that tomorrow though. Thanks again.

[S2R4200_ONEVIA]

Just out of curiosity what turbo are you running??

[Blown240sx]

Im gonna guess stock.

[S2R4200_ONEVIA]

Yeah me too, I also have a stock turbo, I run the HKS SSQV and the adjustment screw is almost losened as far as it will go, and I'v never heard any comp. surge.

[drifter_for_life06]

i hear the same thing, along with my stock BOV

but I know what my weird sound is.....my AEM adapater plate for the intake has a port on it(originally for the emissions b/s on the KA) and is now open on the SR..releasing air

[Rosco]

Yup Stock...Still got alot to learn before I decide what turbo I want to upgrade to.

[Blown240sx]

The stock Bypass valve not BOV will make a fluttering sound when boosted higher cause it cant flow all the air off fast enough. The fluttering you get with Aftermarket BOV is usually compressor surge.

[BLKTOPS14SR]

My girlfriends GST, a friends EVO 8, a friends Subey all make that sound. We've been told that its boost blowing by the intake. I know my friend with the Evo made his louder by removing his intake box lid. ?

[rb20det_pwr]

Ive heard it called as "backpressure" before. We used to do it on purpose, by running no blowoff valve, the air that should be going through your blowoff instead bounces off of your closed throttle and all the way back through the system (including the turbine) and out the intake. (open if you want it louder). and there is a lot of contreversy if it is bad for the turbo. TMS will tell you all day that your silly for running backpressure but I, personally, think that turbo blades are made to spin so it isnt that bad. And i have heard of people running this way for a long time with no issues. But I wouldnt do it on anything but a stock turbo just in case it is bad.

[Blown240sx]

Ive heard it called as "backpressure" before. We used to do it on purpose, by running no blowoff valve, the air that should be going through your blowoff instead bounces off of your closed throttle and all the way back through the system (including the turbine) and out the intake. (open if you want it louder). and there is a lot of contreversy if it is bad for the turbo. TMS will tell you all day that your silly for running backpressure but I, personally, think that turbo blades are made to spin so it isnt that bad. And i have heard of people running this way for a long time with no issues. But I wouldnt do it on anything but a stock turbo just in case it is bad.

This has to be the dumbest thing ive heard.... Do you understand what is happening to the turbo fins when you do this. Ok the turbo blades are ment to flow only one way. Now imagine forcing pressurized air onto them in the opposite direct they are suuposed to turn. Its bend the blades and this is why compressor surge is bad. Your compressor is turning one way and the air forcing back through is going the opposite. If you get it bad enough it can cause the turbo to pause for a sec putting massive stress on the blades and internals.

Example which is small scale. Take a pinwheel thing and its made to flow one way now blow air the opposite direction back through the way it is supposed to flow. Bet it stops moving.

[rb20det_pwr]

This has to be the dumbest thing ive heard.... Do you understand what is happening to the turbo fins when you do this. Ok the turbo blades are ment to flow only one way. Now imagine forcing pressurized air onto them in the opposite direct they are suuposed to turn. Its bend the blades and this is why compressor surge is bad. Your compressor is turning one way and the air forcing back through is going the opposite. If you get it bad enough it can cause the turbo to pause for a sec putting massive stress on the blades and internals.

Example which is small scale. Take a pinwheel thing and its made to flow one way now blow air the opposite direction back through the way it is supposed to flow. Bet it stops moving.

Yes, I do understand what is happening, which makes it seem kinda like a bad idea. BUT, many many people here do it all the time with no problems. And I saw an issue of drift tengoku that said people do it for 2 years with no problem.

[sleepin240]

Im done go ahead and do it then. Its your turbo not mine... Why do you think they make BOVs? Its not just a style thing or why do you think they come with them from the factory....

[Blown240sx]

Hey I had a great idea today. Since your into cool noises that hurt your motor setup. Try taking all the oil out, it makes this badass knock noise....