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This is a short "first impressions" review of the K&N breather "mufflers" on VTA BOV's mentioned earlier in this thread.

I have both (front and rear) BOV's VTA, and I'm not currently running an engine/beauty cover. I installed a K&N breather filter on each of the BOVs, one of which was graciously gifted by @ZSHO.

With breather filters installed, the peak sound level from both BOVs after chopping the accelerator from WOT sounds (subjectively) nearly identical to without breathers. The surprising part was that the bleed seemed to last half as long. I highly doubt the valves are closing sooner, so I suspect the breathers are attenuating the sound from the second part of the bleed as the air velocity drops off, and they just become less audible. It's actually pretty nice; you get the initial loud "PSSH" from the let-off, but it doesn't linger near as long as it did before.

Unfortunately, I don't have any instrumentation to take accurate objective measurements, and the sound clips I took were worthless. My biggest gripe with the VTA is noise from the occasional bleed-off I get when under cruise and going up a steady gradual grade. I'll get an occasional "psh"..."psh"..."psh"... even when using cruise control, like it's trying to regulate boost under partial throttle. I have not yet replicated this phenomenon with the breathers installed, but I will be keeping a close "ear" on this and will report back with any additional observations. I am hopeful though, since compared to WOT, it seems the sound levels from light/partial throttle let-offs are a little quieter (I'd swag 30% lower) with the breathers installed.

I'm curious if @Colorado-SHOBro has similar impressions. I wonder, too, if his change may seem more pronounced, since I think he only has his front BOV VTA, which is already directing sound away from the cabin.

If you had to buy two of your own filters for $45, is it worth it? I'd say "probably not". However, if I can prove that it resolves my partial throttle cruise BOV noise, I might change my answer (it REALLY bugs me - about $50 worth, LOL).

Thanks again, Z, for making this experiment possible and affordable!

Quote from: MiWiAu on February 22, 2017, 07:34:24 PM
Moderators: If you want this as a separate topic, feel free to break it out as a separate thread...

This is a short "first impressions" review of the K&N breather "mufflers" on VTA BOV's mentioned earlier in this thread.

I have both (front and rear) BOV's VTA, and I'm not currently running an engine/beauty cover. I installed a K&N breather filter on each of the BOVs, one of which was graciously gifted by @ZSHO.

With breather filters installed, the peak sound level from both BOVs after chopping the accelerator from WOT sounds (subjectively) nearly identical to without breathers. The surprising part was that the bleed seemed to last half as long. I highly doubt the valves are closing sooner, so I suspect the breathers are attenuating the sound from the second part of the bleed as the air velocity drops off, and they just become less audible. It's actually pretty nice; you get the initial loud "PSSH" from the let-off, but it doesn't linger near as long as it did before.

Unfortunately, I don't have any instrumentation to take accurate objective measurements, and the sound clips I took were worthless. My biggest gripe with the VTA is noise from the occasional bleed-off I get when under cruise and going up a steady gradual grade. I'll get an occasional "psh"..."psh"..."psh"... even when using cruise control, like it's trying to regulate boost under partial throttle. I have not yet replicated this phenomenon with the breathers installed, but I will be keeping a close "ear" on this and will report back with any additional observations. I am hopeful though, since compared to WOT, it seems the sound levels from light/partial throttle let-offs are a little quieter (I'd swag 30% lower) with the breathers installed.

I'm curious if @Colorado-SHOBro has similar impressions. I wonder, too, if his change may seem more pronounced, since I think he only has his front BOV VTA, which is already directing sound away from the cabin.

If you had to buy two of your own filters for $45, is it worth it? I'd say "probably not". However, if I can prove that it resolves my partial throttle cruise BOV noise, I might change my answer (it REALLY bugs me - about $50 worth, LOL).

Thanks again, Z, for making this experiment possible and affordable!

Thanks for the observational notes MiWiau! I've been super busy the last couple days and i literally just came back from the mailbox with my filter. I'm glad to hear it did subdued the sound a little. i wasn't/am not expecting a whole lot of difference but anything would be nice.
Originally i did only have the front BOV VTA but i had to vent the rear to atmosphere when i used the port to hookup my catch can. When i did that i reconnected the front to BOV to recirculating as i'm pretty adamant about only having one VTA to reduce the noise output. It's amazing how much louder it is with the rear valve VTA rather than the front. Definitely a little too loud for my taste so i can only imagine how obnoxious it would be with both vented. A lot of rolling hills here in CO so cruising up and down with those little buggers spitting air out every time you reduce your throttle input even a little is way overkill.  However, it's a good way to let some people know your down for a race when you build some boost and blow it out right next to them! haha

I'm hoping to have time to hook mine up tomorrow and will try to add my input.

Quote from: Colorado-SHOBro on February 22, 2017, 09:59:46 PM
Originally i did only have the front BOV VTA but i had to vent the rear to atmosphere when i used the port to hookup my catch can. When i did that i reconnected the front to BOV to recirculating as i'm pretty adamant about only having one VTA to reduce the noise output.

Ahh, that's right! You opted for the MiWiAu PCV elbow for the catch can.

I flipped the clamp on the breather, so I could access the screw above the charge pipe from the passenger side. It was mostly by feel, due to limited visibility, but not terrible.

Based on my experience, the rear adds a lot of sound relative to the front. If it really bugs you, perhaps you could re-install the original rear line BOV line and tee into it? I was adamant about VTA to break the "oiling cycle", so I didn't look into availability of a tee with 1" pass through with a smaller (1/2" in my case) tee connection.

Edit: found a 1 x 1 x 1/2 tee fairly easily: http://www.pvcfittingsonline.com/pvc-reducing-insert-tee-1401-130.html?gclid=CMjumOujpdICFQ65wAodYK4COw

Reduction to 3/8 seems less prevalent.


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Done. Z 

Quote from: MiWiAu on February 22, 2017, 10:30:09 PM

Quote from: Colorado-SHOBro on February 22, 2017, 09:59:46 PM
Originally i did only have the front BOV VTA but i had to vent the rear to atmosphere when i used the port to hookup my catch can. When i did that i reconnected the front to BOV to recirculating as i'm pretty adamant about only having one VTA to reduce the noise output.

Ahh, that's right! You opted for the MiWiAu PCV elbow for the catch can.

I flipped the clamp on the breather, so I could access the screw above the charge pipe from the passenger side. It was mostly by feel, due to limited visibility, but not terrible.

Based on my experience, the rear adds a lot of sound relative to the front. If it really bugs you, perhaps you could re-install the original rear line BOV line and tee into it? I was adamant about VTA to break the "oiling cycle", so I didn't look into availability of a tee with 1" pass through with a smaller (1/2" in my case) tee connection.

Edit: found a 1 x 1 x 1/2 tee fairly easily: http://www.pvcfittingsonline.com/pvc-reducing-insert-tee-1401-130.html?gclid=CMjumOujpdICFQ65wAodYK4COw

Reduction to 3/8 seems less prevalent.


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Hmm i like that idea actually and i might pursue it in the future. It may be difficult to squeeze a fitting into the short curvy hose back to the intake pipe . . not a lot of room there. So finding a 1" tee with 3/8" fitting might be crucial so i don't have to cram another fitting or adapter in there.
For now i'm gonna give the breather filter a try and see how it suits my fancy.
Thanks for the forward thinking though!

Hmm, yeah, I hope you have better luck, but I can't seem to find a barbed 1" to 3/8" reducer tee. Agree that's tight real estate back there. In lieu of that, perhaps you could shorten the 1" sections of the tee linked above to fit better in the curvy BOV hose, then use a short section of 1/2" hose to get out of the tight area, then reduce to 3/8" using an adapter.



Only downside is you end up with a lot of additional joints for possible leaks. On the 1/2" > 3/8" adapter, for example, I would use RTV on the barbs before installing, then install hose clamps to make it a semi-permanent connection. Probably the same on the tee connection points in the BOV hose (leave the  BOV and charge pipe connections without RTV for removal in the future).

If you still wanted some BOV noise, one other option would be to cobble together a 1" hose and run it from the rear BOV to the front charge pipe connection and VTA the front one again.

Anyways... cart before the horse. Looking forward to your breather muffler impressions.


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I just had mine delivered in the mail yesterday, once I get my car back from the shop I'll put them on. The shop advised against VTA, but I'm young and I like the sound, and I also don't like that oil going back into my intake. I got the filters to catch the oil so it doesn't spray all over my engine bay like it had been. I do plan on cleaning them often. I guess I'll be guinea pig #3!

So i got the breather installed today despite it being 30* and snowing without a heated garage LOL. After eyeballing it for a couple minutes i opted to take the whole charge pipe off and remove the factory pinch clamp and hose off rather than busting my knuckles trying to get the pliers back there. Was way painless and easier that way.
Anyhow, gave it a drive and i'm pleasantly surprised! Seemed to cut down on the noise a decent bit for me. Building small amounts of boost and letting off i'd say it's 50-60% as loud as before. From a WoT let off it's probably 80% as loud but half as long as MiWiAu stated. Makes the car much more bearable to drive under part throttle and definitely maintains the sleeper status more than traditional VTA. You'd probably have to listen for it under normal driving conditions with the radio on low/medium volume. feel like i won't have to explain what that sound is to passengers who don't know any better 

That's great to hear that the breathers worked as designed and diminished the noise levels a bit.  Z

Figured I'd update with my experience as well. I agree, the filters cut down on the noise a ton, both in loudness and duration of the sound. Honestly, when I just had the front one VTA w/filter and the rear still connected, I could barely hear it with the windows down, radio off!

I wish I had opted to take the entire charge pipe off, because I did bust my knuckles trying to get the rear one on. Also, be sure to note which way the screw clamp is facing BEFORE you shove the filter onto the BOV or else you're screwed (like me). Good news is, the filters are such a tight fit from stock, I don't think they're going to fall off anytime soon even without tightening them down 100%.

All in all, this is a good mod for a bit of subtlety and a clean engine bay!