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You can't build boost in neutral. Sorry bud, but them's the breaks.
 

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You can only replace your diverter valve with a bov, but if you do that your car will be losing horsepower. The dv lets the air back into the engine whereas a bov lets the air out into the atmosphere (making that woosh). Unfortunately your ecu adds more fuel to the engine in anticipation of the extra air coming in from the dv. If you put a bov in its place, the ecu still thinks it needs to add extra fuel (because the extra air is thrown in after the maf) so your car will run rich and weak

edit: I might be wrong about the "air is thrown in after the maf" part
 

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Discussion Starter · #10 ·
Guys, im not saying my setup is wrong. My bov is set to the atmosphere, everything is working properly and set up correctly hardware wise and computer wise. im just saying i see cars that rev when they are stationary and the bov goes off. thats what im trying to do.
 

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If you want to run a BOV on the 1.8t, get a MAF-less tune and delete the MAF. OR, add a one-way-valve to the BOV flow path so air can only blow out and not in. It's not so much the air you lose during a pressure purge that messes up the ECM's ability to calculate fueling. It's the air that comes IN through the BOV when the engine is under light or no load (so, manifold is in vacuum thus the valve opens) like you get during a good deal of normal driving. If the valve is open, you've got an intake path leak sucking in un-metered air.

The small stock turbo won't build boost with no engine load. Your bigger turbo will have more lag and be even less capable of boosting with no engine load. If you floor it in neutral, the engine will hit red line before the process needed to build boost can take place (exhaust gasses build pressure on the turbine, turbine spins up and drives the compressor along with it, compressor builds charge pressure on the intake side). It takes longer for the "turbocharge effect" to take place than it does for an unloaded crank to spin up to redline.
 

· I had a steering knuckle in my shed. Really!
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To follow up on Steve's post, no BOV will go "pssssssssh!" as you rev (unless it's not working correctly). It does that when you snap the throttle shut after pressurizing the intake charge.

Many Japanese cars use MAP for fueling (measuring the amount of air that's in the intake manifold). These cars run BOVs. Our car uses MAF (measuring the air as it comes in through the filter). Our car uses a DV.

Your BOV or DV will open when vacuum from the intake mani makes the servo work. When you are revving or boosting, there is little or no vac in your intake mani, and your valve is closed as it should be.

When you are idling or otherwise off the gas or just barely applying pressure, like coasting to a stop or just cruising along a flat stretch of road, the vac cum in your manifold will open the DV. Since it's a sealed part of the intake path, this causes no issues. But a BOV is open to atmosphere as Steve said, allowing in unmetered (and unfiltered) air.
 

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Splitter valve? Mine makes the sound when I snap the throttle.... Don't see what's so complicated about it.

Boost pressure is hardly there because you can't really make it without being under a load..

Maybe your valve is broken? I had a broken spring cause weird issues like that in the past.
 

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You can't build boost while revving in neutral. No boost, no blow-off (or diverter-value acutation if you are running stock.) And, in any case, even if you are under load, you only divert or blow off when you cut the throttle, not on the way up.
 

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Damn that thing was dirty! Like filty, he should have washed it :poke: I don't know man different engine different mechanics involved, I know it's the same basic principal but maybe you need to tweak something to get your desired effect.
 

· I had a steering knuckle in my shed. Really!
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If you pay attention, you only hear the BOV when he lets off the throttle. Our turbos will make a small amount of pressure (only enough to reduce intake vacuum) with no load, but not any boost.

When I was diagnosing a turbo issue I removed the intake snorkel. If I revved the engine up past 4-5k rpm and let the throttle snap shut I could hear the DV let air escape back into he intake.
 

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Im talking about this
how hes stationary and you can hear the bov as he revs
That's not a Passat. The behaviour of your engine may vary. Instead of trying to mess up your car looking for a particular sound effect, why don't you spend the time looking for a BOV whistle to blow? If you can find one, you won't even need the engine running. Whoosh!
 

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One reason you can't hear your revving without a load is your running the t3/t4 Turbo it is a pretty big turbo and spoils up higher than a smaller turbo Hench it needs more load. Now you may beable to rev it to the rev-limiter and might hear it but it still takes a lot to get that turbo spinning
 
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