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Who is NOT running a BOV?
I just upgraded my cold side piping from 2" to 2.5" (For mad horsepowerzz)
And since I didnt feel like doing any welding at the moment, I now am running with no BOV. I know the general consensus is that at low boost you dont need one, but at high boost you do. But, I have no reason to believe this is actually true, in addition to the fact that there are lots of examples of high boost cars running without them for seemingly long periods of time. So because of this I dont think I am going to bother putting a BOV back on. So, 2 questions: 1) Am I alone? 2) Am I crazy? |
These guys didn't run a BOV and it worked well enough for them :)
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Originally Posted by Full_Tilt_Boogie
(Post 575259)
So, 2 questions:
1) Am I alone? 2) Am I crazy? OEMs run them for a reason. Namely because they have warranties to watch-out for. I am sure that some guys somewhere got away without one. But a lot of engineers much smarter than I think they are an absolute neccesity. My logic there is some of the absolute crap OEM turbo setups out there. Where the cheaped out as much as they could. Yet even then they still had a BOV. IIRC you can get a short section of pipe from places like ATP thats already flanged for a BOV. Just cut out a section from your pipes, put a lip on there, get yo-sef some clamps and silicone and viola, BOV without welding.
Originally Posted by kday
(Post 575265)
These guys didn't run a BOV and it worked well enough for them :)
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I've heard people argue that they're not needed every now and then, but when 99.9% of all turbocharged cars in the whole world use them I'm going to go with "yes, they are required"
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How else would you avoid compressor surge?
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One could argue that OEM cars have them today because of the flutter/turkey gobble.
I havent gotten into boost at all yet, but just letting off the throttle with my boost gauge reading atmospheric and I get a couple seconds of fluttering sound, which would be totally unacceptable for a factory vehicle. Also, what about the OEM turbo vehicles before BOVs were standard? Did they tear though turbos constantly? I doubt it. Im not trying to be close minded, I ant this to be an open forum, but I have never seen any evidence of damage from compressor surge, and neither has Corky. |
Heres some RX7 folks, many of whom are running without them. They seem to have drawn the same conclusion as myself.
http://www.fdowners.com/showthread.php?t=217 |
Originally Posted by Sparetire
(Post 575266)
Time between engine/turbo rebuilds?
The OEM argument isn't too convincing since NVH is a major issue for OEMs, and the "turkey gobble" is definitely a NVH problem. |
Very interesting. I do find compressor surge annoying though, so I'll keep mine.
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NVH is pretty much handled with the retarded intake tracts you tend to see on factory vehicles. They have to have these to avoid spooling sounds anyway, and recircing just before the turbo also creates noise there. I could hear my bone stock DSMs BOV quite well as soon as I removed a lot of crap from the intake tract and left it recirced to the stock location just before the turbo. So I dont think the noise component is the reason. Though I can see the point that a car is much more driveable with one, which may actually be the primary reason the OEMs run them. On the other hand, I have 0 trouble beleiving that many pre-BOV OEM turbo cars were nightmares in terms of relaibility, or at least would be by modern standards. People used to think 100K was super high mileage and that any car lasting that long was great.
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Originally Posted by Full_Tilt_Boogie
(Post 575259)
1) Am I alone?
In BEGi's description it says: Bypass Valve: The Bypass valve is used to eliminate compressor surge. On the smaller turbo, GT2554, it is not a necessity. However, it is a good idea for the larger turbos. |
Of course the Rotary guys don't care about the longevity of their turbos, the apex seals will be gone long before they have to worry about the turbo.
I'd like to see spool data with and with out. |
I'd like the "surging doesn't cause damage" argument be proven. By that I mean: we all know knock causes engine failure. Enough of it and you blow your shit up. and YET lots of cars run with a bit of knock here and there for their whole lifetime. So can it be the same thing here?
low pressure and you probably can get away with it, yet raise it and you MAY damage stuff? |
Originally Posted by Sparetire
(Post 575266)
Time between engine/turbo rebuilds?
I am open-minded though. I think you'd be a bit of a guinea pig on this forum running without one but I'd be curious to hear some long-term results. |
Originally Posted by 18psi
(Post 575328)
I'd like the "surging doesn't cause damage" argument be proven. By that I mean: we all know knock causes engine failure. Enough of it and you blow your shit up. and YET lots of cars run with a bit of knock here and there for their whole lifetime. So can it be the same thing here?
low pressure and you probably can get away with it, yet raise it and you MAY damage stuff? With axial turbines compressor stall can cause premature wear if it occurs for long periods of time because it causes more vibration. Whether or not this is true for radial turbines, I dont know. We can safely assume that if a turbo is in constant surge non-stop, that the vibrational issues would cause damage over some amount of time. But that not what is happening, for our application its only surging for a second or two. |
1. No
I am running without BOV, but i'm only running @ 6 psi. It is plumbed for a BOV, but not for recirculating (stock Greddy intake elbow). I plan on running it this way until I increase the boost. |
My Grand Nationals didn't have a BOV.
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http://www.turbobygarrett.com/turbob...r/faqs.html#t9
What is compressor surge? The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side. Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are: * A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body * The outlet plumbing for the bypass valve is too small or restrictive * The turbo is too big for the application |
Originally Posted by TurboTim
(Post 575349)
My Grand Nationals didn't have a BOV.
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Mullets still rule.
Many people I drive with dont run BOV either. They said the effect is minimal and worth it not having to worry about one more thing.. I have a big ass Tial BOV |
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