TunerMaxima3000

iTrader: (4)

I'm having a difficult time with the whole BPV idea. I've been researching the crap out of it and I can't really find any good answers to my questions.

Summarize - A BPV uses Manifold Pressure (vacuum for the bulk of operation) to hold OPEN the BPV. This bleeds off boost in the charge pipe.

Once the throttle valve is opened to a certain point vacuum drops off enough to allow the BPV to CLOSE and boost begins to build in the charge pipe.
If the boost in the charge pipe exceeds spring pressure and/or throttle valve closes (shifting, letting off throttle) the valve opens again to purge this excess boost.



My main questions about the setup:

1. Why the heck do we want to keep this valve open at less than about 60-70% throttle? Seems like this setup would create a lag, once you punch it WOT from a cruise or off the line, you have to build boost up and get RPM up to get going.

2. With this valve being open most of the time when cruising/idling, isn't it possible that the engine could pull in un-filtered air?


The only thing I can think is when comparing SC to Turbo, turbo builds boost under load primarily, load is most present when the throttle is opened and manifold pressure increases (vacuum goes away).
SC builds boost anytime it is spinning, obviously RPM dependant, but has nothing to do with load.

So my guess reasoning for the BPV would be to 'sync' the engine's load/demand for air with the SC's production of it. If we left the BPV closed and ran it like a BOV then the compressor would be building boost all the time, and the engine would see boost rather than vacuum at cruise and part throttle, hurting fuel mileage to some degree.

The only other thing I can think is somehow it's potentially harmful for the SC to be exposed to constant boost, but this logic makes no sense as long as it's not seeing surge, which it wont with a BOV or a BPV.





Excessively long post? Can you tell I"m a bit mixed up? Converse,

TunerMaxima3000

iTrader: (4)

I have an idea for a boost controller that would allow me to run the BPV normally, and for track days, or times where I want more boost 'on demand' I'd have a controller just close off the Manifold Vacuum line to the BPV. The BPV would still operate via spring pressure for safety and close-throttle, jes?

Just a random idea, until I get a better idea of the concept and it's function I'll assume it needs to be a BPV and it needs to stay like that.

TunerMaxima3000

iTrader: (4)

No ideas, Wizard? Other long time SC gurus? Anyone able to lend some insight?

HotshotVQ35

iTrader: (5)

asking for advise on this forum?

TunerMaxima3000

iTrader: (4)

Quickywd01

iTrader: (16)

Unfortunately

TunerMaxima3000

iTrader: (4)

Thought we had some SC genuis' on here, wtf happen?

Quickywd01

iTrader: (16)

You missed the thread where there was a discussion about having a system that would let out air during shifts. Anywho, how are you going to control your AFR if you start playing with the boost controller and you go from 5 to 12 psi? Your idea is good but you have to cover more things which is why most people don't do things like this. It could be as simple as a FMU but now things start getting complicated and depends on a lot of variables.

vipervadim

iTrader: (10)

what's the matter? nobody wants to respond to your post on a G35/350Z forum??? so you're posting this here?

and YES, you are mixed up, and you even answered your own question.


what's the difference between BOV and BPV? does it apply to ALL SC types?

connect the dots and figure it out, no spoonfeeding here.

TunerMaxima3000

iTrader: (4)

Linky? Would love to read that, thanks!

How does the AFR have anything ot do with it? You're purging air before the MAFS, my understanding is that it would have no relation to AFR.

I have a Haltech so I have that stuff covered. There's no difference though, you'd just see boost earlier so you set tuning different, right? Max boost doesn't change, so you need no difference in fuelling supply

TunerMaxima3000

iTrader: (4)

So, you're trying to say, you don't know.

I don't have a post there. I've found the .org to traditionally be much more intuitive than driver, even my350z for most parts.

I have had a few maximas, own a 5th gen, and yes this particular question is pertaining directly to the g35 I own and am prepping for boost, but the premise is the same for all centrif. sc's pretty much. This is the same engine, not sure where your issue is.

I could post on a mustang forum too if I wanted, what's the difference? If you don't know the answer that's fine, but don't play the 'no spoonfeeding' card dude.

Chris Gregg

iTrader: (59)

It's late and at the risk of having only skimmed your post, I'm left with the belief you misunderstand the function of the BOV and BPV to some extent. I'm actually running a Greddy BPV that can be set up to be a BOV, just either run a hose from the BOV into the intake = BPV or leave it open to atmospher = BOV. So I will speak based on my experience as well as use of this Greddy unit.

I say I think you're confused because both BOV and BPV remain closed, even at idle and even with vacuum. They operate on a dual vacuum and boost pressure system. I mean to say that both will be closed and remain closed at idle even with vacuum and without boost. Now, you get into throttle and build boost, the valve should remain closed. It is only when you introduce boost and when you let off the throttle, introduce also vacuum, that the valve will open up.
Also, the valve will also open up in absence of vacuum, when only there is high boost pressure, that is because the boost over rides the spring and opens the valve. So yes, it functions under both sets of situations to bleed off excess boost. However, this functionality is solely determined by how you adjust and set the spring pressure of the valve.

If you set the spring pressure too low, you could start seeing boost fail to build or drop off quickly because effectively you have a leak. I suppose if it is set low, you could see the valve open at idle just due to vacuum. This is all easily resolved by increasing the spring pressure. Naturally, too high spring setting will both prevent the valve from opening during boost spiking, but also cause the valve to either fail to open or open up enough to adequately vent enough boost. Guys tend to hear fluttering due to the boost working backward and stalling the turbo propellers.

All this is why adjustment of either BOV or BPV should be a natural part of all tunes, especially on the dyno.

Hope all that made sense, and didnt fo into circles, past bedtime.

McSteve

iTrader: (3)

I think what you are referring to is the difference between push type and pull type BOVs. Push types get pushed open once pressure in the pipe exceed a certain amount, which happens by the air pushing against the throttle plate and pull type's are open at idle and get sucked closed as soon the throttle opens.

I guess the advantage is that supposedly the pull types operate somewhat faster and the valve closes tighter and tighter the more pressure u pull into the engine. The traditional type could sometimes fail by having too much pressure for it to handle.

A popular pull type is the HKS SSQV or less popular the Synapse BOV.

TunerMaxima3000

iTrader: (4)

Thanks for the responses guys, but if seems, at least to me, you guys are both talking about BOV's, not BPV.

Part of the big confusion and reason I can't straighten this out, is it seems to be common to confuse a BPV for a Recirculating BOV. People think (I did) that BPV is just the recirculating setup.

The truth seems to be that a BPV is a completely different animal all together, one that has very little info available, most of it seems to be confusion with the normal BOV, such as happening in this thread already.

The BPV is DESIGNED to bleed off boost at low load (vacuum) before the metering device. This is making more sense the more I go though it, because a a supercharged car can run very high RPM with very little load during most of it's operating. This would create an excess boost level, which is un-needed at such low load.

Where-as a Turbo car creates boost BASED on load (exhaust temp/velocity/density).

Chris Gregg

iTrader: (59)

Ahhh. I see. Learned something. The only other thing I had in my mind was a pop off valve. Thanks for the clarity!!

TunerMaxima3000

iTrader: (4)

If I could see a cut-away/diagram of a BPV (not a BOV) it might help, but I cannot find one. I'm going to call vortech maybe and see if I can dig any info out of them. Best I can tell there's an atmospehric inlet with a filter on it on one port, Vacuum (IM) on one port, and then obvoiusly the piston/cylinder face on the Charge side.

Chris Gregg

iTrader: (59)

Are you talking about something like a Greddy Type-r? With the dual ports? This is what I've got (older version) and the design seems to coincide with what you're talking about in a supercharged setup for recirculating built up pressure at idle.

Just re-read my earlier post, what jibberrish, need to fix that crap! LOL!!