Making The Blow Off Valve Quieter?

[xr_velocity]

I don't think saying go back to NA will achieve much. Would you want the worlds hottest chick who farts in bed constantly?

It's all about how much your BOV flows I guess. I don't think the shape of the filter will change much. It is still the same intake.

You need to expel x amount of air through a valve (BOV) that flows y amount of air. x = y in a perfect world equals no back flow through the turbo causing that fluttering noise.....

That is the theory anyway. So who can work out what value x is for 15psi and what value y is for a 20mm BOV hole (25mm is external diameter). I can't work out exactly what it is...so I plan to just use two stock BOVs on two separate outlets on the intake. Hopefully doubling the flow, greatly reduces the back flow of air through the turbo.

Edited 20/01/10 01:45 AM by xr_velocity

[ravenhard]

So you are using the stock BOV?

I have an adjustable BOV, depending if I want more "phisht" or flutter. Either way there is a bit of noise

Edited 20/01/10 01:45 AM by ravenhard

[xr_velocity]

I am using the standard BOV. I didnt see the point in buying the same sized after market one because it would not flow much more from what I read on this forum anyway.....

So you are saying with your after market BOV, you can turn it all the way soft so it flows more quickly....but you still receive a lot of flutter?

[howitzer85]

IMO the problem is due to the 25mm inlet for the BOV on the piping, its just too small to allow all the pressure to vent so alot is still forced back to the turbo, hence the flutter.

You need to get a bigger blow off valve (with a 38mm inlet) and get the matching adapter welded to the piping, this will allow more air to exit through the BOV.

I haven't done this yet but in my mind it makes sense... please correct me if I'm wrong

[xr_velocity]

Is 38mm big enough though? Has anybody done this and what is their experience?

[ravenhard]

the reason I got an adjustable BOV was that I wanted to try out the venting to atmosphere and the associated noise it came with but I knew I didnt want to live with that noise all the time. So most of the time its fully plumb back

I have also saw a video on youtube that shows the stock bosch unit failing when reaching 15psi at the top end and loosing a few psi on a dyno. Simply replacing to an aftermarket unit solved this issue. But the internet being the internet and youtube its not the best source of factual information so take it with a grain of salt

[xr_velocity]

So does your turbo flutter reduce at all when you vent to atmosphere? Or is it drowned out by the shhh noise?

[howitzer85]

My BOV vents to atmosphere and the flutter is still louder. (currently running low boost tune to save the clutch so there may not be enough pressure to fully open the BOV)

38mm is the standard for most hi performance BOV's not sure if you can get bigger

[RSK]

Is 38mm big enough though? Has anybody done this and what is their experience?

Wanting confirmation on this aswell. Does it totally elimate flutter? Do you need to run a 38mm plumb back pipe to your Cai, so effectly needing to mod that aswell?

[ENVYOSXR]

I have a 38mm BOV and it still flutters a bit, some BOV's you have to cut the spring inside them as they are way to strong and wont let the BOV open under light throttle.