Since we are measuring pressure after the turbo but before the engine, flow through the engine will be the same for any given pressure, regardless of how the pressure got there. Doesn't matter it was from a TD04, a Roots blower, or six thousand Moroccan women blowing through a straw.

There are two things being discussed here. The "amount of air" that we care about for making power, the number of O2 molecules entering the engine, is not completely dependent on pressure, but rather pressure, volumetric flow rate, and temperature. The bov, however, only cares about pressure, and couldn't care less about temperature, flow rate, etc.

bailey sells nice cheap ones.

Volumetric flow would be the determined by the "bottleneck", the enigine.

Pressure was accounted for.

Air temp was somewhat accounted for by the compressor efficiency statement. More would play into it but I figured my simplified explanation would be enough to discount the much regurgitated misinformation that a big turbo flows more at a given pressure than a small one.

:inout:

A big turbo does, however, flow more oxygen molecules at a given pressure than a small one.

SO it will be a lonnnng time before I am at 15psi or more anyone got a part # of which Bosch BOV to use?

Bosch part #: 0280142108

Can usually find them for ~$40-60.

Once I get my new BOV I will have two of these forsale.

Ben, Given the FIXED consumption of air the engine is using (proportionate to rpm) 15 psi is 15 psi. A larger turbo doesn't have to flow any more or less cfm to make 15psi on a Miata or any car. For example if an NA motor draws 250cfm then pumping 500cfm into it would make 14.5lbs of boost. Not counting VE of the engine or any of that. Any gains at all might be from a larger turbine having less resistance in the exhaust. Think about it like a bucket. The level of water in the bucket is the pressure and there's a hole in the bottom representing your engine's consumption. The amount of water required to fill the bucket depends on the size of the hole. Not the pump filling the bucket.

m2cupcar, where's the sound samples?

I'll do some after the new IC is installed.

I went ahead and bought the VTA version of the BOV m2cupcar listed by the same seller. I'll let everyone know how it works out/sounds once I get it installed(but it may be a while......).

ima get one too i think, Ive finally started upping the boost on a cheapo diy boost controller to ~11 psi now, but it spiked to 15 a few times so im gonna chill here, but i dont wanna loose any efficency or spool on my 2554

To answer the question on will a Bosch hold XXpsi on XX turbo - I am pretty sure I lost my BOV after the equivalent of four track days this weekend (two drivers, two days). It used to make a very clean woosh when I lifted off above 0psi, but now it makes a quieter hiss when I lift at low pressures, and the clean woosh followed by a quieter hiss at higher pressures. I haven't had time to get it off of there yet, but I'll be looking into an all-metal replacement.

My setup is a T25 at 13psi, poorly tuned at 200rwhp.

I think the VW / Bosch Replacement the Adjustable Turbo one are the same valve. They have exactly the same description.

EDIT: Ordered a red "adjustable turbo" one. I'll let ya'll know how it goes.

-Mike

Ryan, You should try a helper spring, maybe that can solve your spike problem a little bit

I agree. Tho there wasn't one for auction when I bought mine.

Got my valve. It's definitely different from the recirc bosch-replacement. Looks like a solid unit, though. Turbo install is this weekend, I'll post again at some point after I've got it in and tuned enough to care about how well the BOV works. :)

-Mike

Two things:

1. My Bosch valve was fine. The noise changed because the check valve cemented to the end of the BOV gutted itself a few weeks at Buttonwillow.

2. The new metal BOV is very nice, quieter than the Bosch, and a direct replacement.

Anyone want to buy a Bosch? I have two. :D

As promised, here's some vid of the acceleration for the bov sound. No silly noises, just a good release of boost - just the way I like it.
http://i158.photobucket.com/albums/t...h_108d72e2.jpg
http://i158.photobucket.com/albums/t...h_0bbf16b4.jpg
Yes, that was "unmarked" crown vic in the second vid. :doh:
Photobucket's video encoding sucks! First vid gets the idea across, but the second one is almost useless. Maybe I can encode the flv files myself and pbucket will leave them alone?