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      07-27-2007, 02:34 PM   #45
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ive seen too many srt4 rev next to me with their loud ass BOV's...now ive seem to lose that excitement for that sound...and i want to hear the M54 block (strongest block bmw's ever made IMO) not the turbo honestly...ok i like the slight whine from how it sounds at stock but thats it.
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      07-27-2007, 06:01 PM   #46
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Originally Posted by Won35i View Post
Seems like we need some turbo education in this forum. A wastegate and blow -off valve are totally different and worth totally different. Externally gated turbos are much much better for tuning and also instrumental for large turbos. Wastegates prevent overboosting. BOVs relieve charged air that is useless due to heat soak.
Yes, yes, wastegates affect boost and control creep before the turbo. BOV's relieve backpressure after the turbo (typically off-throttle).

Doesn't the N54 have relatively small turbos? I don't know off-hand how much boost is produced stock, but it would seem an aftermarket BOV would be more a matter of asthetics than need.

quoted from GFB:

"This system means that about 50% of the air is recirculated.... also means that certain Audi/VW, Nissan, Mitsubishi and other cars with sensitive airflow meters can use this valve."

http://www.gofastbits.com/index.php?..._option=hybrid
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      07-27-2007, 06:13 PM   #47
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Small turbos around 8 lbs boost IIRC. Complicated air intake plumbing with BOVs in place on both banks, stock out of the box. See the engine info referenced in this thread.
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      07-28-2007, 01:46 PM   #48
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Quote:
Originally Posted by coolbluelb View Post
Yes, yes, wastegates affect boost and control creep before the turbo. BOV's relieve backpressure after the turbo (typically off-throttle).

Doesn't the N54 have relatively small turbos? I don't know off-hand how much boost is produced stock, but it would seem an aftermarket BOV would be more a matter of asthetics than need.

quoted from GFB:

"This system means that about 50% of the air is recirculated.... also means that certain Audi/VW, Nissan, Mitsubishi and other cars with sensitive airflow meters can use this valve."

http://www.gofastbits.com/index.php?..._option=hybrid
Yes, they arent high capacity turbos by any means. Im sure there will be plumbing and coupler upgrades in the future of they arent already out now.

Dont these cars run two small Air to air intercoolers, opposed to one big front mount?
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      07-28-2007, 02:08 PM   #49
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Pulled from the thread ATR referenced... it mentions intercooler(s), but I only see one.

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      07-28-2007, 05:19 PM   #50
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Quote:
Originally Posted by Won35i View Post
Yes, they arent high capacity turbos by any means. Im sure there will be plumbing and coupler upgrades in the future of they arent already out now.

Dont these cars run two small Air to air intercoolers, opposed to one big front mount?

Piping and coupler upgrades should not be needed unless you are planning on running high boost or upgraded turbos. Even the 14 pounds of boost with the Procede or Vishnu system, the plumbing should be fine. If you wanted to push boost to 21PSI or so, then I would worry about the plumbing. But at 21PSI, those tiny turbos would be so inefficient you'd want to swap them out anyway.

The is only one "large" front mount. I wonder how much room is under the bumper to fit a larger intercooler. The stock one looks fine for mild upgrades, put shooting for 400rwhp I would want a larger intercooler to combat heat soak.
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      08-02-2007, 01:22 AM   #51
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Well im putting a front mount with duel BOV on my alpine white 135i .... BUMP for this one....
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      08-02-2007, 08:59 PM   #52
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BOV are too annoying IMO. its a BMW, not a subaru or mitsubishi. that sound would only make it sound cheap.
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      08-02-2007, 10:51 PM   #53
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This is my first post here so please bear with me. :smile: I own a modded turbo car ('98 Mitsu Eclipse Spyder GS-T) and have messed with the plumbing quite a bit. I feel pretty confident I can answer some questions and clear up a few misconceptions.

First off, the terms Blow-off Valve (BOV) and Diverter Valve (DV) are interchangeable and describe the same thing. They both serve the same purpose: They relieve the pressure spike caused when the throttle plate closes (for example - lifting the throttle between shifts) in order to prevent that spike from causing compressor surge which can shorten the life of or wreck the turbocharger. They can either dump this air back into the intake or directly to atmosphere depending on the particular application. They can also be located either before or after the MAF/MAP/MAS. In my case, the BOV is located after the MAS, so if I dump it to atmosphere then less air than accounted for reaches the cylinders and I run rich. If the BOV/DV is located before air flow is measured...I believe that's the case with the x35i's...then it can usually be dumped to atmosphere because the metering system will see that and compensate. I can't really address the noise issue...my BOV dumps back to the intake and it's still noisy because of intake mods (mostly hardpipe). It's safe to say that a lot of turbo cars have noisy BOV's simply as an aftereffect of true performance mods and aren't intentionally "tuned for sound". However some are and they're usually pretty easy to spot...

A BOV/DV can also help control boost under load if it lifts at a low enough pressure. The BMW stock BOV's may do this; note that I still have a lot to learn about their system. Most aftermarket valves hold such a high pressure (with no vacuum assist) that they are of no practical help with boost control. With the stock turbos this shouldn't be an issue.

The wastegate is the component that is specifically designed to control boost pressure under load by diverting exhaust flow from the turbine, hence controlling compressor speed. In my case, the wastegate is closed until boost pressure reaches 18 lbs, then it begins to open (I have it directly controlled by compressor pressure through a manual boost control valve that bypasses ECU control). If you ever hear the term "boost creep", it describes a condition where the wastegate cannot dump enough exhaust gas when fully open to prevent the compressor from speeding up, hence boost pressure "creeps" up. This is usually an aftereffect of mods that remove restriction from the exhaust path.

I hope this is useful. As I said, I have much to learn about BMW's approach to turbocharging and I look forward to getting some good info here. I plan to be the proud owner of a 135i by the middle of next year!
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      08-02-2007, 10:56 PM   #54
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hey slik. welcome to the club. we're all addicts here. and this is what i call the support center for all 1 addicts.
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      08-03-2007, 08:42 PM   #55
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hey slik. welcome to the club. we're all addicts here. and this is what i call the support center for all 1 addicts.
Thanks for the welcome. There are quite a few good conversations to join in on. :smile:
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      08-03-2007, 10:07 PM   #56
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Quote:
Originally Posted by Won35i View Post
Seems like we need some turbo education in this forum. A wastegate and blow -off valve are totally different and worth totally different. Externally gated turbos are much much better for tuning and also instrumental for large turbos. Wastegates prevent overboosting. BOVs relieve charged air that is useless due to heat soak.
I've been a lurker on this forum for quite awhile now and just registered last week. I have seen some misinformed people on here so far and I figure that many of you have never owned let alone modded a turbo car. I have to say though man that you take the taco. I'm not in any way trying to be disrespectful to you but you don't seem to know a thing you are talking about. You kind of remind me of the high school kid at the Friday night hang out who repeats things he heard in movies and read on the internet and tries to pass it off as his own ideas. Everyone who knows better giggles inside a little but lets him keep on talking. Guys like you are dangerous because people who don't know any better will read your posts and assume that it is the truth and then go and do stupid things thinking that they are doing right. I would venture a guess that more damage has been done to cars due to people getting bad information on internet forums than any blow off valve could ever think of.
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      08-04-2007, 09:57 AM   #57
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My understanding of a Blow off valve is that when the throttle butterfly slams closed and the pressurized air goes racing back up the intake tract toward the turbo impellars which if the air makes it there will shock the turbos and slow down the impellar speed causing more time for the turbos to spin up their previous speed.

The "Blow Off" releases this pressure and does not slow down the turbos RPM. I also agree that the rubber diaphram that is used in the DV will likely fail on cars that have a "box" installed, 15 PSI will kill the rubber and a higher grade unit, be it DV or BOV will be needed. Hello all by the way!
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      08-06-2007, 09:47 AM   #58
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Once you start increasing boost, an aftermarket version is usually needed. The only issue is screwing with the air/fuel ration if you switch from a dv to an bov. Most BOVs vent to the atmosphere while the DVs vent to the intake after the MAF. This can alter your ratios and cause the car to run poorly unless you have a tune to specifically take this out of the equation.
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      08-06-2007, 03:49 PM   #59
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IMO there will be some company that will throw a ton of money into research towards a BOV that will work if the demand is there. Coming from the Subaru world there are the same issues with running rich when 100% atmospheric however there are BOVs that do work just like there are intakes that work when they say you shouldnt run those either however they arent cheap $100 products either. You will get what you pay for.

With a 35k car I wouldnt add anything that would void my warranty especially something that doesnt even add any benefits
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      08-08-2007, 03:24 PM   #60
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Quote:
Originally Posted by fino View Post
IMO there will be some company that will throw a ton of money into research towards a BOV that will work if the demand is there. Coming from the Subaru world there are the same issues with running rich when 100% atmospheric however there are BOVs that do work just like there are intakes that work when they say you shouldnt run those either however they arent cheap $100 products either. You will get what you pay for.

With a 35k car I wouldnt add anything that would void my warranty especially something that doesnt even add any benefits

This car will be the most expensive I've purchased, and I think it'll be plenty fast out of the box. That said, a BOV would be pointless for me, because the most I'd do would be perhaps a cat-back and wheels/tires... and maaaaaybe a re-flash after the initial *wow* wears off.

Even if I was after 400hp though, I'd take a "wait and see" attitude regarding BOVs. Being a former Subaru person has taught me to do that, as aftermarket BOVs are not always a necessity - or a good idea.
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      08-09-2007, 11:55 AM   #61
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Wow. This thread is full of mis-info.

For one, BOV != Wastegate. They are two completely different things with different functions.

An externally venting BOV(not a Bypass Valve, which is what this car will have) WILL mess up your AFRs. No question. It will not help performance and will probably hurt it because of how rich the mix will be. Whether having a noisemaker is worth it is up to you.
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      08-09-2007, 01:07 PM   #62
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Quote:
Originally Posted by Sperm View Post
Wow. This thread is full of mis-info.

For one, BOV != Wastegate. They are two completely different things with different functions.

An externally venting BOV(not a Bypass Valve, which is what this car will have) WILL mess up your AFRs. No question. It will not help performance and will probably hurt it because of how rich the mix will be. Whether having a noisemaker is worth it is up to you.
It's like the N00b forum in NASIOC all over again. :frown:

For some reason, when people unfamiliar with forced induction get a hold of a turbo car, they become BOV-obsessed. Is the Psssshhhhht sound that big of a deal for people? I just don't get it.
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      08-09-2007, 01:47 PM   #63
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I've had my car turbo'd for several years now and I'm still obsessed with BOV's.

I'm not gonna spend money to add a BOV to my 135 any time soon after I get it. Maybe one day after I do enough mods that actually add performance I will put a BOV on.
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      08-09-2007, 11:05 PM   #64
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one of the first thing i will do is slap on my hks BOV as soon as i drive it home from the dealer. Plus its not rice to have a BOV i have had many turbo cars from supras, rx7s, 1st gen eclipse to my last turbo K20 in my civic hatch. It prolongs the turbo's life its not used to annoy but hell when your boostin 25lbs on a 4G63T w/a 20g turbine at almost 550whp it does get hell a loud.
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      08-10-2007, 01:22 AM   #65
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Quote:
Originally Posted by Tech2 View Post
one of the first thing i will do is slap on my hks BOV as soon as i drive it home from the dealer. Plus its not rice to have a BOV i have had many turbo cars from supras, rx7s, 1st gen eclipse to my last turbo K20 in my civic hatch. It prolongs the turbo's life its not used to annoy but hell when your boostin 25lbs on a 4G63T w/a 20g turbine at almost 550whp it does get hell a loud.
Dude, what you said does not apply to all cars. On some cars, the stock "BOV" is actually a BPV (Bypass valve), which vents the air back into the system. Slap a normal, atmospheric BOV on a setup like this, and you are asking for trouble, as the car will temporarily run rich in between shifts... and since it sounds like you have half a clue at least, you'll know that running rich can cause trouble down the line.

Now, I don't know if BMW's twin-turbo engine uses BPVs or atmospheric BOVs, but I highly (no, make that VERY highly) suggest that you check it out before you "slap on" your HKS.
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      08-10-2007, 09:12 AM   #66
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They are BPV or DV as some people have called them.

By the way, people don't listen to reason. They will do whatever Joe Schmoe from Acme Tuning tells them to do. They don't do research, learn about the differences and figure things out on their own.

Go ahead, slap on that HKS and let your BMW psshht like the Fast and the Furious. When you start having problems, remember that we told you so.
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