crnrhrd

Not really sure if it's the BOV specifically, its from an FM kit. Anyway just wanted to get a few opinions on this.

Cruising at low rpms in 4th or 5th gear if I go to WOT it will build to about 5-7psi and the BOV starts to flutter. Mid to high rpms no issues whatsoever builds to 15psi with no problems.

Also notice while cruising on the highway in 5th just the slightest pedal fluctuation at or around 0psi it will start to flutter and if I hold the pedal still (like if I'm cruising up a hill) sometimes if will just keep fluttering.

It doesn't so much concern me just something that bugs me a little cause I'm like "what the hell". Any and all opinions are greatly appreciated thanks!

Andy

silvertn350

compressor surge?

nicacus

iTrader: (7)

^ if that's the case try adjusting the spring to a softer setting.

Is it a go fast bits blow off valve??

Braineack

iTrader: (62)

I hope it' fluttering when you lift right? Fluttering typically means the valve is too tight. The boost is pushing against the spring and it's rapidly opening and closing. Are you confusing flutter with surge in this instance. are you for certain it's comming from the BOV and not the turbo? At idle, hold your hand over the bov outlet and rev the motor up, since the boost cannot purge out the valve, you should be able to clearly hear the surge at the turbo. I know I can on my setup when I do this.

I'm going to have to think your valve is hooked up wrong or the diaphragm is bad.

With any sort of throttle opened, the spring pressure on the diaphragm coupled with the vacuum pull on the intake should keep the valve sealed.
In boost, the boost pressure pushing down on the valve coupled with the spring will keep it sealed due to the pressure differentials.
When you lift, the vacuum pull on the diaphragm coupled with the boost pushing back against the spring allows the the boost to purge through the valve.

Please show us how you have you valve plumbed. Pictures beat words.

crnrhrd

The fluttering is occurring when the pedal is still pressed to the floor in 4th or 5th. Was toying with the BOV spring last night and tightening or loosening the crap out of it didn't seem to change a thing. You can't see it in the picture but the vac line on the end of the BOV is running to the intake manifold. Revving up and letting off I can feel the BOV purging plenty of air out of it.

Braineack

iTrader: (62)

check the vacuum line for holes/splits/leaks, otherwise I think the valve is dead. The fluttering you are hearing in this case is the boost pressure forcing the diaphragm open...does you boost levels ever fluctuate or your turbo performance seems lacking/slow?

crnrhrd

Yeah I was looking at it yesterday the line is in real good shape, any recommendations on a decent bov without spending an arm and a leg? I really liked this flyin miata one, but don't want to spend $200 for the new one they carry now.

Boost levels are solid, except for low rpm 4th and 5th.

Jeff_Ciesielski

iTrader: (10)

Hop over to siliconeintakes or ebay and look for one. If you want something PNP, they have forge knockoffs at siliconeintakes that would just slide right in there.

Braineack

iTrader: (62)

Flyin' Miata : Turbodog's deal of the day!


click to zoom
New FM BOV!
We've got a whole pile of these. They were once used in the FM turbo kits, but alas, were replaced by the lighter and better sealing GFB valves. The footprint is 1 3/8" from the 2G DSM turbo cars.
Part 05-90105.
Fits 1990-2005
Price: $50

ZX-Tex

iTrader: (15)

+1. I had an ebay Forge clone that worked fine. Like this one
SS Style BOV Flange

That or snag that FM turbodog deal.

Only reason I do not have the forge knockoff anymore is I felt compelled to buy a Tial-Q which is awesome, but also awesomely expensive compared to the knockoffs.

crnrhrd

Nice find thanks man!