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[socal1200r]

For those of you that have removed the stock airbox, is this the type of adapter you used to run a cone-style filter?

http://www.ebay.com/itm/222230887314?euid=e9f7c1f1a2eb4363b7812dead803d346&bu=43191763187&cp=1&sojTags=bu=bu

[Btown]

Yep, that's what I used

[socal1200r]

Yep, that's what I used

Thanks, that's what I needed to know.  Will order one...

[socal1200r]

Got the MAF adapter plate in.  Unplugged the MAF so I could remove the whole assembly to make it easier to work on.  Removed the stock airbox, removed the 4 studs/nuts on the MAF and replaced them with allen heads and washers to mount the adapter plate.  Went to the local auto parts store and got some silicone couplers and hard pipes (90-degree and 60-degree).  Finished product dumps into a small cone-filter that sits almost directly below the MAF sensor, and the hard pipes are resting against some metal areas so the MAF has good support, no need for a bracket. 

Can hear the "whoosh" from the turbo now, and it seems to build boost a little earlier in the rpm range.  One odd thing is there's this sound now, hard to describe, but didn't notice it with the stock airbox on.  It makes this sound under acceleration and at a steady cruise, but not when slowing down.  The left front strut is blown, so not sure if it's related to that or not.  This sound doesn't affect performance at all, and doesn't make it when I rev the engine and the car isn't moving.  So maybe it only happens when the car is in motion? 

Ordered new struts and lowering springs, and will get the front sway bar bushings replaced, so hopefully that odd noise will disappear after those parts are installed.  Should know in a week or so...

[NomakeWan]

Does it sound like a cow mooing? If so, welcome to the moo club, population anyone who messes with the stock intake. It's caused by the bypass valve (that little metal thing that sits between the hose coming out the right side of the intake plenum and the pipe that feeds the turbo intake) resonating. Doesn't happen much on a stock car but apparently becomes much more noticeable once you screw with the intake.

Apparently replacing it with a Bosch BPV from an Audi or such will kill the cow if you so desire.

[socal1200r]

Does it sound like a cow mooing? If so, welcome to the moo club, population anyone who messes with the stock intake. It's caused by the bypass valve (that little metal thing that sits between the hose coming out the right side of the intake plenum and the pipe that feeds the turbo intake) resonating. Doesn't happen much on a stock car but apparently becomes much more noticeable once you screw with the intake.

Apparently replacing it with a Bosch BPV from an Audi or such will kill the cow if you so desire.

Gotta love the internet, that's EXACTLY what it sounds like, lol!  It doesn't affect the performance, it's just kind of annoying to SOME people that drive the car.  Anyone got a cross-reference to the part that will put this mooing cow out of its misery?!

[NomakeWan]

A cursory Google shows the part number is 0280142110. There's an even stronger valve as well, part number 0280142114.

More info: http://www.audizine.com/forum/showthread.php/357594-Everything-you-want-to-know-about-Bosch-Diverter-Valves

Hope this helps!

EDIT: Looks like Audi changed their internal part number a while back, so the original 114 isn't available. They have a newer version, part number 06A145710P. So if you can't find one with a Bosch, look for an Audi.

[Rocketman]

It still happens - but the stock airbox/snorkel are sort of tuned to dampen the noise from it. Moo!

[azgtx]

Switch to the Bosch valve and take out the restrictor in the  bypass hose...moo cow is put out to pasture.

[socal1200r]

Switch to the Bosch valve and take out the restrictor in the  bypass hose...moo cow is put out to pasture.

Is there a writeup on how to do this, or will it be obvious?  What's the Bosch valve part number I need?  Will the restrictor be obvious in this bypass hose?  Hate to ask an obvious question, but what exactly does this bypass valve do, and why does it "moo"?  Is it a design flaw, or is it working like it's designed to, and the sound is just a byproduct of that, or?

[NomakeWan]

See my above post for the part numbers you're looking for. The replacement is super obvious--if you take off the BPV system (which consists of one metal pipe, two rubber hoses, a vacuum hose and the BPV itself), you'll find one of the rubber hoses has a plastic restrictor inside it. Remove it. Then simply place the Bosch/Audi valve where the BPV went since the connections are all exactly the same. The Bosch valve does plumb at a 90-degree angle (the stock BPV is 180-degree) but this really isn't an issue at all. Worst case you'll need a small length of rubber hose, and you'll have a hose on hand to get the size right while shopping.

The mooing is caused by resonance in the rubber diaphragm within the BPV. The stock intake system, as Rocketman mentioned, is 'tuned' to minimize this resonance effect. However, once you start opening things up, resonance results. It's essentially an issue with restriction. The Bosch valve is physically larger with a stronger valve mechanism, so it isn't as susceptible to this resonance effect. It still is--high-boost twin-turbo Audis experience a similar moo--but you won't get there on a Capri.

[socal1200r]

Ordered 1 x 0280142110 thru Amazon, around $46.  Getting new struts and H&R springs installed later this week, so maybe after that's done, I'll take a look at where this BPV is, and prep myself for when the replacement BPV arrives.  And I'll remove the restrictor, and keep my fingers crossed that the "mooing" will be no more...

[NomakeWan]

When you're looking at the front of the motor, look at the metal crossover tube that goes over the middle of the valve cover (and makes changing the spark plugs a royal PITA, if you've ever done it). Note how on the back of it, there are hoses coming off either side. The hose on the right is the bypass valve circuit. It goes down past the right side of the engine, feeds into the bypass valve, then connects to the intake tube on the front of the turbo.



Hope this helps.

[socal1200r]

That helps a lot.  I located the BPV, and it looks like it's held in place by those two large rubber hoses with clamps, and a small hose with a pinch clamp.  So I'm guessing the restrictor is in one of the large hoses?  Seems that removing the rubber hose that goes from the MAF down towards the turbo will make accessing and swapping the BPV a lot easier?   

[Rocketman]

The restrictor is in the vacuum line that controls the BPV diaphragm.

Remove the whole line & replace it with a new piece of vacuum line, it's old & won't flex much anymore.