Venting Blow Off Valves - Why Not To Do It

[blue_reality]

Hey Gang.

Over at Mighty Mods we're doing a video on Blow Off Valves. While the common practice in VW/AUDI land is that you do not vent to atmosphere and most people either use the stock DV, or those with chip upgrades us an AUDITT/S3 DV or after market plum-back, can you post up why you don't vent, and the source of that information.

You may have run a BOV and then car ran like crap and spat our fault codes.

Or

You may not have one but was told by your mechanic etc that your car would run rich etc etc.

Please, I am not interested in whether you like/dislike the sound/aesthetic/art/philosophy of it or whether you think it is cool/rice/try hard or any other non-scientific information. This info will be used to help us develop a script for the video and get a gauge on what information people have been given about BOVs. We're hoping to make one video that will give everyone all the basic information they need with video evidence on BOV function in one easy to understand video.

So please post up:

Car You Have:
Basic Mods:
Vent (Yes or No)
Why?
Where did you get the information as to why or why not?

Thanks guys. Video will be up in two weeks.

[BL33SU]

Car You Have: Passat 1.8T
Basic Mods: Chip, BOV
Vent (Yes or No): Yes
Why?: Coz it sounds good and it works
Where did you get the information as to why or why not? just tried it and it works and have not turned back

[SoVeReIgN]

Car You Have: Passat 1.8T
Basic Mods: Chip, BOV
Vent (Yes or No): Yes
Why?: Coz it sounds good and it works
Where did you get the information as to why or why not? just tried it and it works and have not turned back

Car You Have: A3 1.8t
Basic Mods: Max'd out ko3s, peaks at 24psi
Vent (Yes or No) : Yes, Dual port
Why? Only tossers drive with BOVs, but as soon as you get one it is fuxxing addictive, I love the sound. And it gets on boost faster after a gear change.
Where did you get the information as to why or why not? : Around on the net, talking to a few in person

Note : Big difference in a dual port BOV and a fully atmospheric BOV on VW/Audis.

[ntails]

Car You Have: 01 GOLF GTI
Basic Mods: Chip, BOV and vactory DV
Vent (Yes or No): Yes and No
Why?: Because it was on the car when i purchased it. Have been meaning to take it of since i got it but keep putting it off, plus it hasn't given me any issues that i know of.
Where did you get the information as to why or why not?

[RhysQ]

Car You Have: Polo GTI 1.8T
Basic Mods: Chip, BOV, SEAT intake, BMC panel filter
Vent (Yes or No) : Yes, Dual port (Turbosmart Kompact Series)
Why? Firstly, my car was leaking boost under full throttle with the standard BOSCH plastic diverter so I needed to upgrade to a metal one....which has proved a treat and holds boost very well now. Secondly, growing up around cars I just always wanted a turbo car that goes pshhhht...haha... now I've got it. I know I'll get sick of it but for now I couldn't really care and like the sound. I love the look on people's faces when they see a Polo drive past making that noise..... "WTF?!, did that come from that! "
Where did you get the information as to why or why not? : good ol' VWW.

[Manaz]

I'll assume everyone realises that atmospheric venting BOVs are illegal (you'll fail an emissions test with one). Important to some, not to others, I make no judgment either way here.

My understanding of why you wouldn't use a BOV on certain cars is because the MAF has already measured the amount of air in the intake side of the engine by the time it reaches the BOV, and if you're venting air back to the atmosphere rather than recirculating it, the engine will run rich because it thinks there's more air available for burning fuel than there really is.

[Mr Messy]

Car You Have: 2001 GTI 1.8T
Basic Mods: Forge 007P, K&N filter. No chip yet...
Vent (Yes or No) No!
Why? Seemed to be the over-ruling wisdom here to re-circ as it doesn't throw CELs or affect the legality of the car. Plus, my metal DV makes plenty of noises that I can enjoy, without advertising to every other car around that it's a turbo.
Where did you get the information as to why or why not?
Here, the 'tex, coppers (told me atmo bov is not on)

[D3bb4]

Why? Only tossers drive with BOVs, but as soon as you get one it is fuxxing addictive, I love the sound. And it gets on boost faster after a gear change.
Where did you get the information as to why or why not? : Around on the net, talking to a few in person

What's this based on?

If you have a non-atmospheric BOV venting into the turbo inlet, it helps spool the turbo = faster boost after gear change.

[Manaz]

What's this based on?

If you have a non-atmospheric BOV venting into the turbo inlet, it helps spool the turbo = faster boost after gear change.

Rightly or wrongly, I think most people assume BOV to be an atmospheric venting device, even though you can get plumb-back BOVs.

[SoVeReIgN]

What's this based on?

If you have a non-atmospheric BOV venting into the turbo inlet, it helps spool the turbo = faster boost after gear change.

I'm led to believe the piston is quicker than the standard DV

Based on my arse dyno and swapping between the two.

[fuzion]

Car You Have: 2002 GTI (1.8t obviously)
Basic Mods: Chip, K03S, adj FPR, AEM Intake+Dry Filter, GFB DV +more?
Vent (Yes or No) No (plumback)
Why? - Minus you can throw codes, and legalities of a BOV running a recirculated diverter throws back in the intake which with the AEM makes a "shh" sound anyhow. i WISH i could shut mine up, the stock, forge, bailey was louder!

Where did you get the information as to why or why not? few mechanics with tuning experience, vw-vortex (vw bible/encyclopedia).

a dual port bov, is 50/50
50 in and 50 out.

i have ran one before, and say i hold a lot more boost up top with a full recirc as well. i have ran about 5 diferent branded (including OEM) diverter valves and definitely noticed the differences and have logged it too.

[gavs]

I'm led to believe the piston is quicker than the standard DV

Based on my arse dyno and swapping between the two.

Ha ha, arse dyno!!

Technically an atmospheric venting bov is illegal due to "emmisions" but it's primarily due to noise pollution as all it is venting is air.

And people wonder why anyone here at work wants to stab the writers of ADR's with blunt instruments.

How is pressurised air a dangerous emmision.....Oh no, my air tools are venting excess compressed air, it must be an illegal emmision... (RANT)

[Manaz]

Technically an atmospheric venting bov is illegal due to "emmisions" but it's primarily due to noise pollution as all it is venting is air.

That's not my understanding. You can actually get quiet atmospheric venting BOVs. The real reason is that it's possible (though I have to admit, highly unlikely) that you will vent something other than just compressed air from the BOV.

[D3bb4]

That's not my understanding. You can actually get quiet atmospheric venting BOVs. The real reason is that it's possible (though I have to admit, highly unlikely) that you will vent something other than just compressed air from the BOV.

gavs is right

Violates EPA noise pollution rules/laws. Same as when you get done for having modified air intakes; it's because they generate more induction noise.

There is also argued fuel emission variations, as some cars manage to run rich with atmospheric venting bov's, but cars have cat convertors, etc. so it's not often tested.

[Blitzen]

Car I Have: Polo GTI.
Basic Mods: SEAT intake, K&N Panel Filter Forge TIP, I/C hose, duel port BOV, APR V2 ECU Tune.
Vent(Yes/No): 70% intake, 30% atmosphere.
Why: Cos I love the sound. The Forge one isn't that loud, but it is fully adjustable, and it holds the extra boost of the tune really well.
Where did I find the info: Mates, on here, and work.

Another reason BOV's arn't legal, and isn't just due to sound, is due to oil residue and and vapours that can be expelled into the atmosphere due to the way it is venting.