The importance of the BPV

[Lex]

I have been investigating SWAS response recently and have found some interesting facts.

The ECU uses the throttle, WGDC, AFRs to limit power/wheelspin when turning and this is more aggressive in lower gears since wheelspin is more prominent - yes we know this.

I was having bucking/poor performance with SWAS active in corners to the point that it was dangerous in the low gears.

I then drove a closer to stock speed3 and the system was not nearly as intrusive. Felt pretty decent actually.

I could chalk this up to BT and heavier modifications but something wasn't adding up as I also wasn't remembering it being this bad in the past and I realized something many people overlook.

When the ECU changes throttle (abruptly) mid corner as the turbo spools this affects the manifold/charge pipe pressure ratio. This in turn triggers/opens the BPV. The OEM BPV is a twin chamber design with a very stiff spring that is very quick acting.

A lot of the aftermarket ones (I run a Forge V1 since the OEM leaked at high boost) do not share the response of the OEM BPV. The forge is notorious for this as it loses lubrication on the sealing o-rings. This causes the response time of the valve to be significantly affected and causes/exacerbates the bucking/sputtering phenomenon and it affects how SWAS interacts. Overall this mismatch between the ESP software and BPV can make you hate SWAS/ESP more than you should.

For those of you where SWAS interferes violently, consider the BPV and that it is an important part of the overall system and it should be tuned to work well with it. Holding boost/pressure is important but so is response time and tunability the multi chamber designs with fast reaction times are better than the older designs with lots of internal friction and slow response. This will affect spool, lag between gears, shifting smoothness, and SWAS. Poor valve response can even cause bucking on throttle tip in or acceleration in a straight line.

I recommend pressure testing your system to the boost level you want to run and stick with the OEM BPV unless you go over 20-21psi (ie bigger turbo).

If you need to swap out the BPV, choose a multi chamber design with a fast response and low friction parts where you can adjust the spring/preload. It will make the car drive better in all conditions.

[LumberJack]

Great read, awesome info

fuckin yo couch

[Mauro_Penguin]

@Lex; forgive my amatuer question, but I thought your GA when paired with the proper BPV would help eliminate leaks associated with loose spring tension. Wouldn't your GA help in keeping the system functioning quickly and properly in addition to the overboost protection?

[jseams]

Heh, this is why I'm happy my stock BPV holds fine at 20psi... although I'm in line to pick up a friends Forge V2 soon when he parts out - I won't be using it until there is a need.

Anyhow, does anybody have a complete link or a list of all the quick reacting two chamber designs currently available? Most reviews seem simply focused on the "sound" and ignore the performance of the unit.

[Lex]

Originally Posted by Mauro_Penguin @Lex; forgive my amatuer question, but I thought your GA when paired with the proper BPV would help eliminate leaks associated with loose spring tension. Wouldn't your GA help in keeping the system functioning quickly and properly in addition to the overboost protection?

The GA does limit vented air if in VTA, stop leaking under high vacuum, and close it faster after a shift. However the response of the BPV itself is always going to be part of the system and that's the main point to get across here. The OE tuned the OEM BPV to work well with the DBW system, SWAS, and how the fuel, spark and throttle behaves during shifting.

If you try several BPVs (with or without the GA) you will notice changes in driving characteristics during these throttle transitions

[ABolewski]

Yes that's the one thing this forum cannot seem to teach me, what a good BPV is to go with. I could give two shits about how it sounds.
Great read though Lex, interesting stuff.

[Mauro_Penguin]

Indeed, thank you Lex!

[Playaj]

Originally Posted by ABolewski Yes that's the one thing this forum cannot seem to teach me, what a good BPV is to go with. I could give two shits about how it sounds. Great read though Lex, interesting stuff.

So ur bpv could scream "I love cock!" And u would be ok with it cuz it works good? Lol. J/k. Lex, u never cease to amaze me. I don't understand half the stuff u try and teach us but I do learn shit I had no clue about. This is why u will be getting my monies when all my parts are finally on!

[ABolewski]

Originally Posted by Playaj So ur bpv could scream "I love cock!" And u would be ok with it cuz it works good? Lol. J/k. Lex, u never cease to amaze me. I don't understand half the stuff u try and teach us but I do learn shit I had no clue about. This is why u will be getting my monies when all my parts are finally on!

Are you saying you know one that does scream "I love cock!"?

[Dash08]

Originally Posted by ABolewski Yes that's the one thing this forum cannot seem to teach me, what a good BPV is to go with. I could give two shits about how it sounds. Great read though Lex, interesting stuff.

We can thank ourselves for that. All of us are to blame for making BPV's synonymous with rice on this forum.

We treat it like it plays no part in engine operation whatsoever. Like it's some bullshit accessory that doesn't do anything.

Lex has overlooked this and delved into the inner workings of them and how they affect our engine's performance on a multitude of levels.

On top of what Lex has discovered here with SWAS and ESP, BPV's have a relatively profound effect on fuel trims as well.

So, BPV's affect driveability, throttle response, SWAS/ESP operation, and fuel trims...

That's not fucking rice, that's important shit.

I think we need a more serious approach to BPV's from now on.

[forcedinduktion]

I suppose Ill be the one to ask, which of the BPVs on the market are dual chambered, if any?

[Big_Burd]

Sooooooo what BOV should I get?!


I kid I kid I don't need one but, seriously.

[Karmat]

So many people were haphazardly replacing oem bpvs without them leaking.

Now we see that not only is it often a waste of money on the ko4 it may actually be a detriment to engine operation.

Great thread.

Sent from my DROID RAZR using Tapatalk 2

[breakfstincluded]

So you're saying...

Stratified Tuning will be releasing a BPV next week? (:

[btstarcher]

What about valves like the HKS? I freely admit I know nothing about them; I don't even remember what factored into my decision when I purchased mine.

[Lex]

A BPV should be evaluated on several performance criteria:

- First, do you need to replace the OEM and how do you know? What I found with the BNRS3 is that once boost pushed past the 21psi mark or so; although boost continued to climb, the airflow did not increase. This is because the BPV had cracked open and instead of the turbo drawing in more air, it was simply recirculating what it had already compressed. So the symptom was not a lack of boost, but rather it was a stall in the increase of airflow. Once the BPV was swapped, it was in line with what the turbo should have been flowing at that boost level and RPM. Boost remained the same, airflow increased. Most aftermarket BPVs are able to seal well under boost but there is more to it than this.

- Controlling compressor surge in all conditions. A BPV should allow minimal to no surge under both heavy and light throttle lift. The HKS seals great under boost since it is a pull type valve but allows for compressor surge under part throttle. The TS valve with the heavy 20psi spring is terrible for surge although it is a push valve. The valve should also flow enough to control compressor surge under high boost and high airflow conditions as well.

- Response time. How quickly a valve is able to open and close with varying pressure differentials is important. Not only does is effectively allow fast throttle modulation without surging or bucking but it works well with drive by wire systems where the ECU modulates the throttle on top of what the driver is doing. Fast valves close under boost quickly promoting spool as well. Fast response time is about low friction lightweight parts, smart construction, multi chamber construction, and high airflow rates out of the valve.

- Ability to tune the valve. This is important for improving driveability and making the valve work well with the electronic control in the car, your turbo, your boost levels. Some of the multi chamber valves allow you to use one or more of the chambers. The ability to replace spring is nice but I prefer a dial where the same spring can be put under more or less pressure as well.

- Construction, fitment, servicing. The valve should not require a lot of attention or servicing because if it does it means that the performance deteriorates as you get closer to the service period. I want the valve to work the same all the time. I've seen plenty of aftermarket valves leak, have poor seals, etc. You want a high quality piece that will last a long time.

- Sounds and VTA. Yes you want a pleasing sound and we all do. It's not a performance feature but it's something to consider since after all we must enjoy driving the car. Some people like VTA and they can use the Guardian Angel to limit the VTA effects on engine operation or use a 50/50 valve. The GA closes the valve much sooner after a shift so if you run the GA in VTA mode you can get some response improvements but the valve should be tunable somehow so that you can soften the spring and walk the fine line between surge and fast response. You can also use the VTA feature on the GA to increase response time of a fully recirculating valve.

[btstarcher]

Thanks, now I remember. I liked that there are no springs to replace and no maintenance. That and I thought that it works for any boost level. Or any reasonable boost level anyway.

Dumb question: would running it as a BOV eliminate compressor surge? Or is my understanding of compressor surge incorrect?

And yes, I understand that I can't use the HKS with the GA....it was the main reason I almost didn't get it.

[starscream]

Just so I understand this right....

STOCK BPV = Good for K04 up to 20psi (basically =<20psi)
AFTERMARKET BPV = Good for K04 beyond 20psi (basically >20psi), BNRS3, Big Turbo (GT30/35...etc)

That would be a good way to look at it?

Seems like the stock valve is the way to go if you want function for up to 20psi, yes?

[btstarcher]

Originally Posted by starscream Just so I understand this right.... STOCK BPV = Good for K04 up to 20psi (basically =<20psi) AFTERMARKET BPV = Good for K04 beyond 20psi (basically >20psi), BNRS3, Big Turbo (GT30/35...etc) That would be a good way to look at it? Seems like the stock valve is the way to go if you want function for up to 20psi, yes?

I hope that's right, because it's the only reason I ordered mine.

[Mauro_Penguin]

@Lex; I love your brain and articulation. That is all.

[Fatguy729]

I can confirm @Lex; 's findings, though not related to swas. I was getting a strange bucking when in stop and go traffic. It would happen when trying to hold a low rpm in 1st and secong gear, and also when going from deceleration to accleleration (lighlty).

I dont want to go through all the details of what i was seeing in logs (trying to diagnose it) because i am on my phone right now, but long story short, i cleaned and lubed my forge v1, and voila! Gone!

[RageATL]

Originally Posted by Lex A BPV should be evaluated on several performance criteria: - First, do you need to replace the OEM and how do you know? What I found with the BNRS3 is that once boost pushed past the 21psi mark or so; although boost continued to climb, the airflow did not increase. This is because the BPV had cracked open and instead of the turbo drawing in more air, it was simply recirculating what it had already compressed. So the symptom was not a lack of boost, but rather it was a stall in the increase of airflow. Once the BPV was swapped, it was in line with what the turbo should have been flowing at that boost level and RPM. Boost remained the same, airflow increased. Most aftermarket BPVs are able to seal well under boost but there is more to it than this. - Controlling compressor surge in all conditions. A BPV should allow minimal to no surge under both heavy and light throttle lift. The HKS seals great under boost since it is a pull type valve but allows for compressor surge under part throttle. The TS valve with the heavy 20psi spring is terrible for surge although it is a push valve. The valve should also flow enough to control compressor surge under high boost and high airflow conditions as well. - Response time. How quickly a valve is able to open and close with varying pressure differentials is important. Not only does is effectively allow fast throttle modulation without surging or bucking but it works well with drive by wire systems where the ECU modulates the throttle on top of what the driver is doing. Fast valves close under boost quickly promoting spool as well. Fast response time is about low friction lightweight parts, smart construction, multi chamber construction, and high airflow rates out of the valve. - Ability to tune the valve. This is important for improving driveability and making the valve work well with the electronic control in the car, your turbo, your boost levels. Some of the multi chamber valves allow you to use one or more of the chambers. The ability to replace spring is nice but I prefer a dial where the same spring can be put under more or less pressure as well. - Construction, fitment, servicing. The valve should not require a lot of attention or servicing because if it does it means that the performance deteriorates as you get closer to the service period. I want the valve to work the same all the time. I've seen plenty of aftermarket valves leak, have poor seals, etc. You want a high quality piece that will last a long time. - Sounds and VTA. Yes you want a pleasing sound and we all do. It's not a performance feature but it's something to consider since after all we must enjoy driving the car. Some people like VTA and they can use the Guardian Angel to limit the VTA effects on engine operation or use a 50/50 valve. The GA closes the valve much sooner after a shift so if you run the GA in VTA mode you can get some response improvements but the valve should be tunable somehow so that you can soften the spring and walk the fine line between surge and fast response. You can also use the VTA feature on the GA to increase response time of a fully recirculating valve.

I went with the GFB Respons and I think it fits all of your criteria. I just don't know if it is multi-chambered though. I know a lot of other people run this bpv as well and like it. It has the dial up top for the spring and it has a knob you turn to control how much you vta so you can crack it like 10%vta and get the sound without causing problems to how to the car runs.

Go Fast Bits Blowoff Valve Dual Port Mazdaspeed 3 6 MS3 MS6

[blackms3_71]

you have done it again lex, good work

[ABSpeed3]

So @Lex; will you be removing your Forge and going back to stock or are you tuning around it?

P.S. blue spring one shim? :p

[Mortose]

NEWB comment:

with the above explanation from Lex explain why i have never had an issue with my SWAS pissing me off mid turn or any issues like that?

I will say that i did have an issue with my OEM BPV giving up on life on a stage 1 OTS map. I would get a bad boost leak and the car would buck constantly under heavy acceleration (not even WOT). I replaced with the Cobb valve, and issues were gone.

Obviously now i'm on the synapse valve, and this thing responds fast as fuck, and like i said, i don't have any issues with SWAS.

[Fatguy729]

Originally Posted by starscream Just so I understand this right.... STOCK BPV = Good for K04 up to 20psi (basically =<20psi) AFTERMARKET BPV = Good for K04 beyond 20psi (basically >20psi), BNRS3, Big Turbo (GT30/35...etc) That would be a good way to look at it? Seems like the stock valve is the way to go if you want function for up to 20psi, yes?

Yes, unless the oem leaks at a given psi, which is common

[btstarcher]

Mine never leaked, but I'll be pushing the limits of the K04....

[Lex]

I mentioned the importance of the BPV earlier this year and finally got to do some testing with one of the fastest valves on the market.

The results were great. SWAS and stability control no longer got in the way. No more bucking, loss of boost, jerkiness when taking a hard corner in a lower gear.

So if you want SWAS and the stability control to work with you and not against you, get a BPV that is as fast as possible. A fast valve also helps response and spool.

[SneakySin]

Originally Posted by Lex I mentioned the importance of the BPV earlier this year and finally got to do some testing with one of the fastest valves on the market. The results were great. SWAS and stability control no longer got in the way. No more bucking, loss of boost, jerkiness when taking a hard corner in a lower gear. So if you want SWAS and the stability control to work with you and not against you, get a BPV that is as fast as possible. A fast valve also helps response and spool.

What BPV is that?

[Lex]

Originally Posted by SneakySin What BPV is that?

It's the Synapse DV.

[Mortose]

Lex = faster than me.

[SneakySin]

Originally Posted by Lex It's the Synapse DV.

That's what I thought it was

[Yatta]

Lex, this is the BPV I am running currently; if you have run and logged this, can you quantify the effects of it leaking while not under boost (it does this by design, essentially bypassing the turbo and IC while under vacuum) I can hear it leaking while in this state, if you take the throttle right to the threshold at atm (no vacuum, no boost) you can hear the transition from it being opened to it being closed.

Given that it uses the bypass outlet as a intake inlet while under vacuum I have wondered if a TIP that brings the BPV inlet closer to the MAF would make sense.

Synapse has claimed positive effects and I believe throttle response is better but it would be interesting to see real test data on this. The sound is definitely like no other BPV I have run (stock, Greddy Type S and a Turbosmart )

[Lex]

Originally Posted by Yatta Lex, this is the BPV I am running currently; if you have run and logged this, can you quantify the effects of it leaking while not under boost (it does this by design, essentially bypassing the turbo and IC while under vacuum) I can hear it leaking while in this state, if you take the throttle right to the threshold at atm (no vacuum, no boost) you can hear the transition from it being opened to it being closed. Given that it uses the bypass outlet as a intake inlet while under vacuum I have wondered if a TIP that brings the BPV inlet closer to the MAF would make sense. Synapse has claimed positive effects and I believe throttle response is better but it would be interesting to see real test data on this. The sound is definitely like no other BPV I have run (stock, Greddy Type S and a Turbosmart )

The OEM is also open under vacuum. Most push type valves stay open under vacuum unless they are under a lot of preload. To log tip in and such transients requires much higher logging speeds than we have available to be able to quantify anything. A fast acting valve will greatly help when throttle is modulated on a turbo car since it won't dump boost, surge, or cause dreaded bucking so in that sense driveability with fast valves is much better.

At the same time the charge piping is at a higher pressure level than the intake itself. By allowing air to bleed in front of the turbo by keeping the BPV open when not under boost there is less load on the compressor which results in less load on the turbine and this decreases pumping losses. Less pumping loss should marginally improve economy.

[SneakySin]

I'm interested to see if Corksport is taking any of the data into consideration with their new bpv that's coming out

[Yatta]

Originally Posted by Lex The OEM is also open under vacuum. Most push type valves stay open under vacuum unless they are under a lot of preload.

I was aware that the stock ones were open under vacuum but thought this was conditional on having positive pressure on the valve face; I know in playing with them I could open/close the synapse with little effort given on the vacuum line (oh how I dread saying I sucked on a hose on MSF) but could not do so with the stock valve. I trust what you say, but still think the off boost behavior of this valve is quite a bit different than stock.

Anyhow, thanks for the analysis, I have been quite happy with mine, it just works and it didn't need any adjustments, just bolted it on and forgot about it until your post.

[Lex]

Originally Posted by Yatta I was aware that the stock ones were open under vacuum but thought this was conditional on having positive pressure on the valve face; I know in playing with them I could open/close the synapse with little effort given on the vacuum line (oh how I dread saying I sucked on a hose on MSF) but could not do so with the stock valve. I trust what you say, but still think the off boost behavior of this valve is quite a bit different than stock. Anyhow, thanks for the analysis, I have been quite happy with mine, it just works and it didn't need any adjustments, just bolted it on and forgot about it until your post.

The OEM is open until quite close to boost but the design is indeed different as it has an internal diaphragm.

What is your port setup on the Synapse? Also are you running it in push or pull mode?

[Yatta]

Tried push and pull; with the stock turbo I think anyone running pull will experience/hear part throttle fluttering on the valve (I did), so I configured it like stock (push), running single port (b used, a VTA) no additional preload.

[Mauro_Penguin]

@Lex; how would you say the synapse DV compares to the cobb bpv? I understand the configuration on the synapse can change from push to pull, but I mean in a apples to apples set up, how is the response and stability between the two?

Just curious as I was sold on the cobb unit for my future upgrade list.

[Lex]

Originally Posted by Mauro_Penguin @Lex; how would you say the synapse DV compares to the cobb bpv? I understand the configuration on the synapse can change from push to pull, but I mean in a apples to apples set up, how is the response and stability between the two? Just curious as I was sold on the cobb unit for my future upgrade list.

I have never tested the COBB unit so it's hard to give you a comparison. I also don't know how it is designed internally. Pretty much any aftermarket valve will hold boost by design so that's not a concern. I would look at a few things:

1. Valve speed
2. Does it need to be serviced or lubricated. I am not a fan of these types of valves as they "lose" performance as the lube wears.
3. Reliability - are there wear or breakable items like diaphragms?
3. Adjustability
4. Fit and quality
5. I prefer push design for least surge