From what i hear ,a Bypass Valve takes that boosted air its venting, and recirculates it back into the intake. But a BOV is removing air once counted and letting it blow in the air, so the car is going to add more fuel thinking that air is still incoming. Generally people end up doing damage to their catalytic converters because of the rich conditions incorporated into running a VTA ( Vent To Atmosphere ) system on a MAF equipped car. Is a BOV a good Investment or a BAD one ????
Bov's good or bad
- Thread starter CocoMs3
- Start date
skatethesea
Member
- :
- 2010 Speed 3
There are a couple guys running aftermarket BOVs in Va Beach. I would wait for them to respond. But if I remember they run a 50/50 vent. Half the time to recirc and the other half to atmosphere. And the easiest way to fix a messed up cat is to install a test pipe 
skatethesea
Member
- :
- 2010 Speed 3
then drop a DP on there too (cabpatch)
well to compensate for the richness just run more boost.. prob solved.. with the cats to..
NocturnalSpeed
Member
- :
- 2003 Mazdaspeed Protege
(ohsnap!)
Could you explain the benefits and/or drawbacks from the BPV?? I found this thread through a search with some info about it, but Id like to know more. Its also from the Protege so maybe the hoses are different in the DISI 2.3T engine?
Please help as your experience will probably help me decide whether to buy the BPV or not...
Thanks in advance!
(iagree)
ok ok lots of noobs in this thread. quick explination
this is a MAF (Mass Air Flow) sensored car. This is the sensor you reuse when you do an intake install or is attached to the OEM airbox. This is probably the most important sensor in the car as it drives nearly everything else..
BOV is VTA (vent to atmosphere) BPV is recirculating.
If your relief valve is upstream (before) the MAF, then you can VTA all day, since the air is lost before the sensor sees it, it doesnt matter
If it is downstream (after) the maf the computer thinks it has X air when it actually has Y
Computer injects corresponding amount of fuel for X air, runs overly rich and the O2 sensors in the exhaust freak out and try to trim it unsucessfully
your car runs like dogs***
you backfire
you clog/damage your cats
backfiring puts extreme axial loading on your turbine, causing premature wear and failure
and all you Gen2 guys need to get a fuel pump before you do any serious modding. Read Cobb's AP notes on their website for further info http://accessecu.com/support/docs/support/AP-MAZ-002/2010 MS3 Support.pdf
and to the shmuck that said raise boost to compensate....explain to me how raising boost will have any effect on your AFR when you let off to shift and are NOT in boost
this is a MAF (Mass Air Flow) sensored car. This is the sensor you reuse when you do an intake install or is attached to the OEM airbox. This is probably the most important sensor in the car as it drives nearly everything else..
BOV is VTA (vent to atmosphere) BPV is recirculating.
If your relief valve is upstream (before) the MAF, then you can VTA all day, since the air is lost before the sensor sees it, it doesnt matter
If it is downstream (after) the maf the computer thinks it has X air when it actually has Y
Computer injects corresponding amount of fuel for X air, runs overly rich and the O2 sensors in the exhaust freak out and try to trim it unsucessfully
your car runs like dogs***
you backfire
you clog/damage your cats
backfiring puts extreme axial loading on your turbine, causing premature wear and failure
and all you Gen2 guys need to get a fuel pump before you do any serious modding. Read Cobb's AP notes on their website for further info http://accessecu.com/support/docs/support/AP-MAZ-002/2010 MS3 Support.pdf
and to the shmuck that said raise boost to compensate....explain to me how raising boost will have any effect on your AFR when you let off to shift and are NOT in boost
oaklandopen
Member
^^^^^hahahah....we have a winner
Yea, I thought the"add boost" comment was really a sarcastic remark....maybe my internutz isn't working
As for the op...I don't know how much you know about how engines work, but modern engines aren't the same as engines of yester-year. There are sooooo many sensors and delicate electornics on modern engines that you can't just go around replacing things because you think it will have a more positive effect. Odds are, it will be more adverse then anything. And if it is positive, something unforseen might get messed up later
Case-in-point, your bpv bov dilema. A bov is going to throw metered air out of the cycle. In a nutshell, your ecu is gonna be in wtf mode all the time.
And unless your stock bpv is bad, an aftermarket one will yield nothing but a sound change, like a first gen's cat back
Yea, I thought the"add boost" comment was really a sarcastic remark....maybe my internutz isn't working
As for the op...I don't know how much you know about how engines work, but modern engines aren't the same as engines of yester-year. There are sooooo many sensors and delicate electornics on modern engines that you can't just go around replacing things because you think it will have a more positive effect. Odds are, it will be more adverse then anything. And if it is positive, something unforseen might get messed up later
Case-in-point, your bpv bov dilema. A bov is going to throw metered air out of the cycle. In a nutshell, your ecu is gonna be in wtf mode all the time.
And unless your stock bpv is bad, an aftermarket one will yield nothing but a sound change, like a first gen's cat back
Wow!, great explanation! thanks for that...
Now another quick question, I posted here that Mexican MS3s might be down on power. All evidence points at the altitude taking its toll on the turbo, so peak pressure in maintained less than 1 second pretty much all the time.
If one of the things the BPV/BOV do, is maintain boost pressure, do you guys reckon itll help minimize (or at least reduce) this altitude effect??
Thanks again!
Now another quick question, I posted here that Mexican MS3s might be down on power. All evidence points at the altitude taking its toll on the turbo, so peak pressure in maintained less than 1 second pretty much all the time.
If one of the things the BPV/BOV do, is maintain boost pressure, do you guys reckon itll help minimize (or at least reduce) this altitude effect??
Thanks again!
oaklandopen
Member
Essentially the job of a bpv/bov is to allow for pressure release once you let off the throttle. The valve is mechanically inclined (by way of springs) to hold a certain amount of pressure from the compressor side of the turbo. Because an open throttle equates to a fast spinning turbo, letting off the throttle doesn't exactly bring the turbo to a screeching halt. All that pressure has to go somewhere even when the throttle plate is closed. Therfore, the bpv recirculates the pressure until it tapers off, and a bov simply releases it
As far as altitude...all I can say about pressures is that there is less atmospheric pressure up high. So that makes me think that there is a loss of boost pressure overall. Just a guess though
I know that there is less oxygen the higher up you go, which I can definitively say equates to a loss of power
Upping the boost can help get your power back, but you're really only gonna be able to do that by way of adjustable wastegate (not recommended by itself), or a tuning option (like cobb ap or hypertech) that will electronically increase boost pressure
As far as altitude...all I can say about pressures is that there is less atmospheric pressure up high. So that makes me think that there is a loss of boost pressure overall. Just a guess though
I know that there is less oxygen the higher up you go, which I can definitively say equates to a loss of power
Upping the boost can help get your power back, but you're really only gonna be able to do that by way of adjustable wastegate (not recommended by itself), or a tuning option (like cobb ap or hypertech) that will electronically increase boost pressure
I know theres no power gains, my main concern was boost pressure which is the problem with the MS3 at this altitude.
Isnt there a advantage of going with an aftermarket BPV rather than the stock? I thought there might be some sort of benefit from an aftermarket but if its mainly the same, I guess Ill just stay with the stock one... no need to change something if it wont get better right?
Thanks again!
Isnt there a advantage of going with an aftermarket BPV rather than the stock? I thought there might be some sort of benefit from an aftermarket but if its mainly the same, I guess Ill just stay with the stock one... no need to change something if it wont get better right?
Thanks again!
oaklandopen
Member
my best guess as to why aftermarket is better would be maybe the higher spring rate set by the user for an aftermarket piece yeilds higher boost between shifts
with the forge, ppl are always going back and forth about the best combination of shims and springs, and which one holds more boost between shifts, and which ones can be detrimental to engine operation
but let it be known, it helps keep more boost between shifts, not at open throttle. perhaps another bpv prevents the tapering effect from happening too quickly. but the application for that would only be essential to someone who needs to have that boost stay with them between shifts, like autox or drag strip
of course, that could be solved with a no-lift-shift program, whereas you'd lose 0 boost pressure between shifts
with the forge, ppl are always going back and forth about the best combination of shims and springs, and which one holds more boost between shifts, and which ones can be detrimental to engine operation
but let it be known, it helps keep more boost between shifts, not at open throttle. perhaps another bpv prevents the tapering effect from happening too quickly. but the application for that would only be essential to someone who needs to have that boost stay with them between shifts, like autox or drag strip
of course, that could be solved with a no-lift-shift program, whereas you'd lose 0 boost pressure between shifts
