BOV questions
 

where do i put the BOV? (ive heard that it should go as close to the throttle body as possible).

also where do i recirculate the blown off air to? (ie. between the air box and the turbo OR between the turbo and the intake manifold.)

it might help to know that this question pertains to a 1.6 with MAF.

thanks.

there is no real need to recirc on a miata.

get a open to atmosphere one...they are cooool :gay:

BOV close to TB
and you recirculate it before the turbo

except there is a need when retaining the AFM.

I'm recirculating on the hotside about 10" from the turbo. BOV works excellent, not the slightest sign of compressor surge. I tried atmospheric - ran like total ass.

mine is on the hot side of the inte ic piping..closer to the turbo...the shop did that..i don't know why...all flying miata have theres close to the TB...i guess they know best...

You want it close to the TB to relieve the pressure near the TB, it's just faster that way. You can install it on the hotside if you like it better. It's just not ideal that way.
When people say close to the TB, anywhere on the coldside pipe will work. It doesn't have to be any number of inches from the TB inlet. Hell you could bolt it to the intercooler if you wanted.

Could be wrong, but I was perusing a '99+ FMII at Mazfest this year and he had his BOV mounted damn close to the turbo on the hotside. It's not optimal, but it makes recirculation plumbing a LOT easier.

I have no AFM/MAF (MAP or go home), so I run mine close to the TB, full vent.

thanks for sharing, ill be deleting my MAF (also94) hopefully end of this month, soon as i get my MS from Braineack, and if you dont mind id like to ask you a few questions about the procedure...prolly just stupid n00b questions, but i do need help and i admit it, the FAQ is great etc. but everyone seems to have questions anyway, and i dont want to start another thread about it if you can help...letmeknow

i was thinking that recircing to between the air box and the turbo might decrease lag as the recirculated air would help spool the turbo from that end.

what is hotside and coldside?

hotside=before intercooler
coldside=after

it will not help any with lag and spool, its insignificant
short explanation-obviously you cant go after the turbo because its all the same pressure throught the piping, so you have to go either athmospheric or recirc.
a lot of people dont want athmo. due to unfiltered air, so recirc. i hope this makes sense

not really sure i follow. there will be boosted air going back into the BOV when under boost, right? is this a problem?

just to clarify: i can recirc to anywhere, right? so i can locate the BOV just in front of the TB and recirc to just after the intercooler?

also where do i connect the vacume hose coming off the BOV?

any pics would be great.

No.

The whole point of the BOV is to relieve air from the pressurized side of the system. That's everything after the turbo. You need to put the air back into the system *before* the turbo, allowing it to flow through the turbo again.

In a traditional recirculated system, the outlet of the BOV goes back into the intake between the AFM/MAF and the compressor inlet.

It needs to be finted to one of the vacume nipples on the intake manifold, after the throttle body.

what is the difference between an expensive and cheap BOV?

About $70.

is there a difference in performance between an expensive and a cheap BOV?

nice Joe!!!
you get what you pay for, go for used name brand if you want best of both worlds, otherwise, go with cheap...i got a HKS for $20 for example, id have a cheap one i got for like $30, let me know if you want the cheap one (its still new)

i think you missunderstood, i said you canTTT go after the turbo, you would be dumping it back into the pressure pipe...you cant do that, it would be the same as not having one...
so after MAF/AFM before turbo...GL

Yeah, it's a tough thing with BOVs. Some of the expensive ones are not-so-good, and some of the cheap ones are great. Short story:

My first BOV was the all aluminum piston type that FM made. It was the DOTD one morning, so I bought it. I think it was around $100 or so. Installed it on the car. After a few weeks it stopped working. Called FM. They said the valve has to be periodically disassembled, cleaned, and re-lubed. I wound up having to do that once every couple of months. Irritating.

So next I bought an ultra-cheap Chinese copy of a Greddy Type-RS BOV from some eBay vendor. Stuck it in the car and it works perfectly. It's been in there almost a year and I haven't had to touch it.

I suggest going this route first. These knockoffs seem to be of surprisingly good quality, and some of them come with recirculation adaptors on the outlet. Examples:
http://cgi.ebay.com/ebaymotors/Type-...QQcmdZViewItem
http://cgi.ebay.com/ebaymotors/Type-...QQcmdZViewItem

perfect, those are the ones i was looking at.

A word of advice-

Most people who buy these (myself included) find that they are set up way too tight, and that you cannot adjust the setscrew loose enough to prevent all compressor surge.

If you take the top off the unit, you'll find that there are two springs, one inside the other. Remove the center spring (the smaller of the two) and re-assemble the unit. In this condition it will leak at idle, but holds 15 PSI just fine and yet vents at the slightest lift of the pedal. This is a good thing.

Since you are recirculating, leaking at idle is not a problem. Some air will simply bypass the compressor, but since it's all downstream of the AFM it's no worry. If you ever remove your AFM and go VTA, simply place a K&N filter on the outlet of the BOV to filter the air that it draws in at idle. The filter also acts as a bit of a muffler, quieting it somewhat.