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Discussion Starter #1
I was just wondering why anyone would want a BOV. I installed the CP-E intake today and it pretty much sound like some of the SRT-4's i've seen with a bov. I actually thought something was wrong with it when i did it because it was so loud. Seriously, any louder and it would be too much. I will say something about CP-E, they did an awesome job designing this intake. Its of way better quality than the intakes ive had from Injen and AEM. I applaud them and appreciate the time and effort that they took to design and manufacture this product. Perfect fit and definitely the best 300 bucks ive ever spent. So really, can someone answer me, why would anyone want a BOV on our car, it seems totally pointless.
 

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I dont know why anyone would want one on any car. Unless you want people to think your car is sneezing.
 

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The same reason ANY turbo car wants one, to prevent compressor surge and keep the turbo spinning as fast as possible between shift... :shrug:
 

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I grabbed this from turbosmart.com.....

Blow-Off Valves eliminate compressor surge when changing gears. Excessive back pressure is created when the throttle is closed during gear changes or deceleration, causing turbo cavitation. This is detrimental to the life of the turbocharger. Fitting a BOV will substantially improve this problem. Installing a BOV will also significantly reduce turbo spool-up time. A substantial improvement in response from the turbo between gearshifts and a quicker boost delivery will result in an increase in torque at lower RPM.
 

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Once you replace the BOV you will know why you did it... as soon as you take off the stock piece you will be thinking.... "Is this a joke? Who engineered this?"

EDIT: Also, this needs to go in the Engine section...
 

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Discussion Starter #7
i dunno, I have been doing some reading about them and the seem pointless on a stock or close to stock MS6. I could see if you had alittle more boost or HP but at out level(according to the articles ive read) is pointless unless you want that sound. The real thing i was trying to ask was, If you want a bov for the noise, just get a cp-e intake. Its as loud as some bovs ive heard.

Once you replace the BOV you will know why you did it... as soon as you take off the stock piece you will be thinking.... "Is this a joke? Who engineered this?"

It may not be well engineered, but its not hurting performance and i havent heard of anyone having any problems with the stock recirculation valve. So your saying to change it because its not engineered well? Im not being a smartass, im just trying to figure all this out. Im fairly new to forced induction.
 

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you're right. it is pointless on a stock ms6. but those of us that will be increasing boost must have a metal bov that can hold more pressure. plastic bovs are normally rated at 15psi. for instance the 2g dsm bov is plastic and rated for 15psi while a crushed 1g dsm metal bov is rated for 25-30psi. if u dont plan on increasing boost, then u dont need to upgrade unless u just want the sound.
 

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I was just wondering why anyone would want a BOV. .... So really, can someone answer me, why would anyone want a BOV on our car, it seems totally pointless.
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I believe what you're saying is why anybody would want to change out the stock BOV (or bypass valve) for another, not why there is a need for a BOV at all. As stated above, the BOV helps to protect the expensive turbo from damage caused by a huge pressure spike when the boost it's being generating hits a brick wall (clsoed throttle plate) and bounces back, and to reduce turbo lag because this built up pressure with no where to go will slow down or even stall the turbine. This means when you open the throttle again the turbine has to spin up from a dead stop.

People swap out the stock BOV for two main reasons:
1. Sound - they want that "pssshhh" sound when shifting
2. Performance - the stock BOV is fine when new, but can deteriorate and "leak" due to the inferior quality of materials used, losing some of the precious boost the turbo works so hard to generate. The stock BOV is spring loaded to handle a certain amount of pressure; running higher boost than it's rated for will again cause it to "leak" bleeding off the boost.

So, if you don't care about the sound, leave the stock one in until:
1. it gets old and starts to leak
2. you crank up the boost and the stock valve starts bleeding off this increased boost
 

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Discussion Starter #10
I really just trying to learn about the bovs. I havent looked at mine yet, but are you guys telling me that our stock bov is made of plastic? If it is, then i can sort of see replacing it. I didnt start this thread for the reason that it sounds like. Me and my wife had a couple shots of canadian mist and I really didnt type what i meant. Truthfully, all i should have put for the title was the CP-E intake sounds like a bov, so if you want the sound, why would you buy a bov instead of a intake. I was just blown away with the sounds of a turbo. I can guarantee that i will never own a car without one again. Im totally addicted,lol. Anyways, back to bov's. I am going to really modify my car as parts come out for it so if i was going to buy a bov, what model would you guys recommend? Greddy, HKS, Etc? Thanks guys, and sorry for sounded like a jackass, Canadian mist is the only alcohol that does that to me.
 

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No problem. Everyone needs to learn from the beggining.

JUSt did a quick search for you with the BOV and these pages here, after going through them you will know a lot more.

http://forum.mazda6club.com/index.php?act=...mp;highlite=bov

BTW, when you posted this I thought you had it with the "tone of cheek" on, that's why I posted my clip to make fun. Sorry if it sounds dumb to you :)

Anyway this is the clip again : http://members.optusnet.com.au/m6gr8/Wrx.amr ...but seems like no one finds it funny :unsure:
 

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A metal BOV is a good thing for long term use as well, also a recirculated BOV is a good way to lower the air release sound (which is a sound i love). like the MS6, the EVO also has a recirculated BOV, instead of just releasing the air, it puts the released air back into the system at the front end of the turbo. there is no increae in power by doing and no big benefit, just alot less sound. Unlike the STI and the SRT4 whos BOVs you can hear a block away at high RPMs, its all about taste really, if you have ever heard an EVO/STI with after market intake/exhaust (especially an STI) and a full release BOV, it sound so agressive on every point on accelerating and shift points. but again, its all about taste. Even though the EVO comes with a plastic BOV like the MS6, yet the evo is doing 21 psi, they still perform well for casual driving, hard driving they will bleed air and even though they are recirculated you still lose compression. but not a major loss.
 

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Discussion Starter #13
i appreciate the search man, and i thought it was funny. I might get a bov at some point because i love the sound the intake makes already. And after i found out if was plastic, it may make sense to upgrade. Also, im a machinist and I wonder how hard it would be to make one. Id like to get one and find out what its about and then draw one up and make one out of billet aluminum. They dont sound like that they would be that complicated, but I could be wrong

oh yeah, does anyone know why it says Warn(0%) on my avatar.
 

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Getting an HKS BOV was my first mod. I wasn't expecting an hp gains, but I was suprised that it actually felt a little stronger up to . The HKS holds boost at least 500rpm longer than the stock bov did. I don't know if my stock valve was messed up, but it definatly wasn't strong enough to hold even the stock boost levels in the higher rpms.
 

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you're right. it is pointless on a stock ms6. but those of us that will be increasing boost must have a metal bov that can hold more pressure. plastic bovs are normally rated at 15psi. for instance the 2g dsm bov is plastic and rated for 15psi while a crushed 1g dsm metal bov is rated for 25-30psi. if u dont plan on increasing boost, then u dont need to upgrade unless u just want the sound.
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+1

stock is 15.6psi, not exactly low for a stock setting. most guys running a MBC are already pushing 17-18psi with boost spiking to 20psi in some cases.
 

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like the MS6, the EVO also has a recirculated BOV, instead of just releasing the air, it puts the released air back into the system at the front end of the turbo. there is no increae in power by doing and no big benefit, just alot less sound. Unlike the STI and the SRT4 whos BOVs you can hear a block away at high RPMs, its all about taste really
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Where do you get your information? Being a former WRX owner I can tell you that there is a reason that the BOVs are recirculating and it all has to do with the MAF sensor. When the turbo spools the MAF measures the amount of air that is going into the engine and adjust the fuel ratios accordingly. So, if you switch to a pure atmospheric BOV the car will run rich and KILL your CATs, not to metion your performance.

The stock BOV on the Subaru is good to something similar to what you stated with the EVO's, and as a matter of fact most people don't switch to an aftermarket BOV until they are pushing serious boost(20 psi or more) and have a aftermarket EM. Also, neither the STi nor the SRT4 have a atmospheric BOV stock. They both start life with a recirculating due to the MAF. The reason you can hear the stock on the STi is due to the owner removing the silencer from the intake.

I know that this is personal choice and maybe more necessary on the MS6, but I would personally rather have a fully recirculating or 50/50 before a 100% atmospheric. If you want to read more about the BOV debate you can find alsorts of information on nasioc.com
 

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Where do you get your information? Being a former WRX owner I can tell you that there is a reason that the BOVs are recirculating and it all has to do with the MAF sensor. When the turbo spools the MAF measures the amount of air that is going into the engine and adjust the fuel ratios accordingly. So, if you switch to a pure atmospheric BOV the car will run rich and KILL your CATs, not to metion your performance.

The stock BOV on the Subaru is good to something similar to what you stated with the EVO's, and as a matter of fact most people don't switch to an aftermarket BOV until they are pushing serious boost(20 psi or more) and have a aftermarket EM. Also, neither the STi nor the SRT4 have a atmospheric BOV stock. They both start life with a recirculating due to the MAF. The reason you can hear the stock on the STi is due to the owner removing the silencer from the intake.

I know that this is personal choice and maybe more necessary on the MS6, but I would personally rather have a fully recirculating or 50/50 before a 100% atmospheric. If you want to read more about the BOV debate you can find alsorts of information on nasioc.com [/b]
You're correct, neither the WRX/STI (both use the exact same BPV) nor the SRT-4 use an atmospheric BOV. When I had my WRX it was pushing 19.6 psi at peak tapering to 16.4 psi at redline on a VF34 turbo setup custom tuned at MZM Performance in Austin, TX, all of which was done on the stock bypass valve without a problem. In the WRX community, there were several people that actually had problems with BOVs, even if the rest of the car was bone stock. Because their ECUs are calibrated to receive the extra air between shifts, when it's vented into the atmosphere via a BOV, the ECU still sends the extra fuel to the cylinders, which causes a momentary run rich condition. Occasionally people even had problems with their cars studdering between shifts due to this condition as well.

The rich condition often causes "afterfire" (not to be confused with backfire) which can be harmful over the course of time. There are several members over on nasioc with aftermarket BOV's that have deteriorated their stock cats due to this run rich condition, most notably the pre-cat located in the up-pipe before the turbo. There are people whose pre-cats have fragmented sending substrate shards into the turbine housing itself, ruining the turbo. Not only can an extreme run rich condition deteriorate cats, it can also foul both your spark plugs & O2 sensors more quickly than they would in a run stioch condition. Our cars may need a BOV in order to hold higher amounts of boost, but I can assure you a WRX/STI does not, unless they have a more extreme setup.

Also, if anyone has noticed a lot of SRT-4's making a fluttering sound rather than the traditional "psshhh" sound, it has to do with them modifying the stock external wastegate rather than a BOV. Subies (as well as most other turbo cars) have internal wastegates which are more difficult (ie expensive) to modify. Me personally, I would prefer the aggressive external wastegate flutter over a BOV anyday, but that's just me. A lot of Subie owners put BOVs on their cars, but for most, it's only for the sound and nothing more, as they yield no performance gains on stock or lightly modified Subies.
 
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