Venting Blow Off Valves - Why Not To Do It

[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.

[Manaz]

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.

Thank you.

[blue_reality]

Well I spent the weekend on the Dyno with a handful of BOVS with some interesting results.

I used and tested:

1. Stock Valve
2. After Market Plumback Valve
3. After Market 50/50 Valve
4. After Market 100% Atmos Valve

I'll post up the video when I finish it - should be an interesting point of discussion. Will be up on www.mightycarmods.com , youtube and itunes in two weeks.

[SoVeReIgN]

Well I spent the weekend on the Dyno with a handful of BOVS with some interesting results.

I used and tested:

1. Stock Valve
2. After Market Plumback Valve
3. After Market 50/50 Valve
4. After Market 100% Atmos Valve

I'll post up the video when I finish it - should be an interesting point of discussion. Will be up on www.mightycarmods.com , youtube and itunes in two weeks.

Isn't that only going to really test whether or not they leak boost in gear?

Or did you do full gear changes etc?

[gareth_oau]

How is pressurised air a dangerous... (RANT)

it is when its hot and coming out of a politician

[99gti]

Car You Have: 99GTI
Basic Mods: Chip, Neuspeed intake, ABD intake, FMIC, 3" DB and high flow cat and APR DV.
Vent (Yes or No) No
Why? I already had issues previously for running rich. My removing air out of the intake it would only run richer. Note: since then I discovered a leak on the ABD instake so any released air probably spat out there anyway instead of spooling the turbo back up again.
Where did you get the information as to why or why not? Didn't realy get the info from any where in particular, just my own research. I'm not the most mecahnicaly minded person, but I get computers. If it believes there is x ammount of air when there is only y ammount of air then it's calculations will be wrong.