Recirculating BOV do i really need to replace?

[Ranton]

If so why?

And whats the difference between these three?







apparently they all fit the MPS3?

How can i tell if mine is leaking?

[MattMPS3]

The BOV debate has been going on for some time, there has always been a question mark over the boost holding capacities of the stock bpv over an aftermarket unit, particularly if raising boost levels, I will ask though, do you trust a piece of injection moulded plastic in a high temp scenario to hold your boost.

As far as aftermarket valves, aside from the additional psssshhhhht noises hybrid valves offer, users have commented on better response and reduced lag on shifts, whether there is any real world evidence to support these claims is where the debate lies.

[Ranton]

The BOV debate has been going on for some time, there has always been a question mark over the boost holding capacities of the stock bpv over an aftermarket unit, particularly if raising boost levels, I will ask though, do you trust a piece of injection moulded plastic in a high temp scenario to hold your boost.

As far as aftermarket valves, aside from the additional psssshhhhht noises hybrid valves offer, users have commented on better response and reduced lag on shifts, whether there is any real world evidence to support these claims is where the debate lies.

I think the main Difference in changing to a hybrid is all in the users head.. no offence to any one.. but yeah..

From my experience with Volkwagens etc the First Factory Released Recirc valve was shit.. the housing cracked and the spring and diphram was weak..

People would replace them with Forge Piston type Recirc valves.. for the first month they are fine altho the piston is no where near as responsive as a diphram but people tend to forget about pulling apart and servicing the valves so they keep a good seal...

The revised plastic Recirc valve released by VW ended up being the best Recirc valve you could possibly fit to your car.. it wouldnt leak and had a heavily weighted/sprung diphram and it was only 65NZ$ to replace if it ****ed out.. not that mine ever did after 120,000 kms dealing with 22psi boost spikes etc.. and harsh driving...

I just wonder thats all..

because with my CAI it almost sounds like the Recirc valve is taking some responsibility for boost regulation so i assume mine may be ****ed..

[LittleredMPS]

I bought the forge BPV in the first picture.

The difference is not staggering, but there is one.

You will find lag when changing gears is a little less, and that the engine seems to pull harder further into the rev range than the standard plastic fantastic BPV does.

The side mounted Forge BPV also makes no real noise at all. I was told to expect a cash register sound, but nup, nothing.

Personally I recommend it.

[Nepharius]

Well I cant tell you any advantages but I can tell you the difference between the top two. The top one is the revised Forge the second one is the old one. The main difference or at least the one they set out to rectify was that the old one (the second one) makes a kind of swords clanging style sound when you change gears which annoyed people. The third one I have no idea... is that a BOV instead of a BPV?

[MattMPS3]

I was running a GFB Hybrid in mine for a while, it was a good valve, but regular servicing is a must, and I only ever used it set to full recirc anyway, I ended up switching for the lower maintenance HKS diaphragm style valve as the GFB was a bit of a battle to get to with the FMIC in place.

[langer5489]

Ive got a turbosmart one... Its changable to Psshhh... to no Psshhh. If you ever get a chance to hold the stock in one hand and the aftermarket in the other... needless to say you'll know which one to use. Compared to the turbosmart, the stock felt like it came from a toy truck. Boost reponse was a bit 'sharper' (i guess is the word) too.
Have fun, just make sure you dont crossthread your bolts on install

[Ranton]

The main differences i believe you will find in the first too is that (From what i can judge by the exterior of the valve)

Top Picture the Valve operates with a Piston like all the others.. however then the piston is UP (The Sealed position) the boost loads up against the side of the piston untill the Piston is drawn upwards by the connecting Vaccume Line
This design has very little reliance on Spring Pressure holding the piston in the sealed position as the boost is side loading on it. its probably more responsive and moves more freely

the Second Design is where the boost loads up directly against the base of the piston (unsprung side) and the Piston remains sealed against the boost forcing it open due to a heavy sprung Spring on the other side.. & the Vaccume line pressurising the opposite side also.. untill the throttle is released and the vac line ends up sucking the piston back up...

The Design of the top one makes more sense to me than the second one.. i think the second one is more suseptible to leaks if a soft spring has been used..

---------- Post added at 04:22 PM ---------- Previous post was at 04:21 PM ----------

Are there any other Diphram types available

im still not a big fan of piston types

[Doug_MPS6]

The appeal of using after-market as opposed to OEM is that some after-market BOV's are adjustable so can be made to operate to suit your mod configuration. While some good sources seemingly in the know will tell you that the OEM unit leaks boost above ~15psi as a protective measure (though that won't often be admitted by those close to the manufacturer), I still have issues with this argument.

Firstly, the wastegate is designed to bleed boost when it exceeds a certain value and secondly the OEM BOV (and aftermarket BOV's too) operate in neutral pressure mode when on-throttle (on boost) as it has the vac line off the top and boost in the main body, which equal each other out, so even if you were feeding 50lbs of boost in, the BOV wouldn't know about it as it would still be in equilibrium. Some folks think still think the BOV is a boost controller - it's not. It's what its name says it is.

The only time the BOV is under differential pressure is when the throttle is closed. The vac line sucks the piston up and the boost in the main manifold blows the piston up at the same time.

[Ranton]

I completely agree with you doug!

Althou just my luck i was giving her a bit of stick on the way back from the Local Snow Dome Tonight.. and notice that in 6th at about 3000rpm and upwards it almost seemed to be loosing boost and there was a fluttering noise..

just my luck the day i query the use of after market valve it almost seems astho the diphram has worn out on mine and is now flapping about slightly....