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Old 06-30-2010, 05:26 PM   #1
Badler
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Default The NO BOV/BPV thread. Not one or the other. None. Zero. Zip.

This thread is about the pros and cons/facts, lies, and opinions of running without a BOV/BPV. I have seen many threads get derailed by/to this subject and then get locked. I have derailed a few myself and for that I'm sorry. This may get locked as well. No biggie.


This is what I can gather. I can/will add to it.

PROS:

Maintain boost in the charge pipes.
Less lag when shifting fast/racing.
One less thing to fail.


CONS:

Loss of some driveablity in a DD.
Turbo wear and tear.
Compressor stalling.


Curious to hear from others what their take, experience, flame, etc... is on this subject. I know guys have been running Crawford kits on here for years and DDing them. Modaddict where are you!?!? I've seen a few others that were doing it on various setups as well. Most of which got DD as well. Some of you have just been around cars and are familiar I would really love to hear some firsthand experience.


Disclaimer: These are the sole thoughts and views/interpretations of Badler and are in no way shape or form set in stone, just observations and pot stirring.
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Old 06-30-2010, 05:33 PM   #2
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You pretty much hit it on the head.
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Old 06-30-2010, 05:36 PM   #3
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edit:

i see. i thought this was another thread about running WITH a bov/bpv.

my bad d00d

Last edited by happs subi; 06-30-2010 at 05:45 PM.
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Old 06-30-2010, 05:38 PM   #4
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Quote:
Originally Posted by happs subi View Post
WTF does that have to do with this? That is a BOV faq silly, this is the opposite.

Please read the thread title and understand what this thread is about before posting.
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Old 06-30-2010, 05:42 PM   #5
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So you want to do this on a street car?


Quote:
Originally Posted by happs subi View Post
OP is talking about completely removing the BOV/BPV
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Old 06-30-2010, 05:43 PM   #6
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Quote:
Originally Posted by Aphex28 View Post
So you want to do this on a street car?
Possibly. Still weighing in.
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Old 06-30-2010, 05:50 PM   #7
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Man seriously, what makes you think that all the stuff I posted isn't from personal experience?

You don't want to do this on a street car if you want to keep it running.

Going from 80k rpm and jamming it to a stop is not good for the turbo.

You will get tired of overhauling them. You will also get tired of shifting without throttle lifting.

I had to do it after every race... and I mean have to not want to.

Even a super tight bov is better than none at all.

Good luck
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Old 06-30-2010, 05:54 PM   #8
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Quote:
Originally Posted by 08GRSTi View Post
Man seriously, what makes you think that all the stuff I posted isn't from personal experience?

You don't want to do this on a street car if you want to keep it running.

Going from 80k rpm and jamming it to a stop is not good for the turbo.

You will get tired of overhauling them. You will also get tired of shifting without throttle lifting.

I had to do it after every race... and I mean have to not want to.

Even a super tight bov is better than none at all.

Good luck
Because the way you presented yourself in the other thread shows you don't even fully understand how a turbo system works.

Move along. This thread is for people who get it.

Last edited by Badler; 07-01-2010 at 02:22 PM.
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Old 06-30-2010, 05:57 PM   #9
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Quote:
Originally Posted by Badler View Post
Because the way you presented yourself in the other thread shows you don't even fully understand how a turbo system works.
You are entitled to your opinion, as am I
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Old 06-30-2010, 05:58 PM   #10
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Round 3?
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Old 06-30-2010, 05:59 PM   #11
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Quote:
Originally Posted by 08GRSTi View Post
You are entitled to your opinion, as am I
Well unfortunately your opinion on how a turbo system works is completely wrong. Don't treat your opinion as fact.


This thread wasn't started to bicker with you so cool it please.
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Old 06-30-2010, 06:00 PM   #12
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Originally Posted by 04WRX_GUY View Post
Round 3?
Nah, I'm done. He was the only person arguing in there in the first place and the cause of the thread going in a downward spiral.
He's entitled to believe what he wants
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Old 06-30-2010, 06:02 PM   #13
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Quote:
Originally Posted by happs subi View Post
edit:

i see. i thought this was another thread about running WITH a bov/bpv.

my bad d00d
No worries my good man, no worries.
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Old 06-30-2010, 06:11 PM   #14
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Quote:
Originally Posted by 08GRSTi View Post
Man seriously, what makes you think that all the stuff I posted isn't from personal experience?

You don't want to do this on a street car if you want to keep it running.

Going from 80k rpm and jamming it to a stop is not good for the turbo.

You will get tired of overhauling them. You will also get tired of shifting without throttle lifting.

I had to do it after every race... and I mean have to not want to.

Even a super tight bov is better than none at all.

Good luck
The turbo does not jam to a stop.

What happens when you get the turbo spinning as it does around idle and then all of a sudden jamming on the throttle? Compressing air is not trivial. Why are you not worried about the stress put on the turbo?!?!?!?! This is serious you could be seriously damaging your turbo.

Seriously, F1 cars ran turbos in the late 80s for a couple years. The are reported to have run around 4 bar. That is like 58PSI. The ran this without a BOV/BPV! Now before you say they were race cars and were being rebuilt and components replaced regularly, think about how many shifts occur over the course of a race. Think about how many times the drivers go from full throttle to no throttle and back. They did this all without turbos failing left and right. Now one could posit that the engineering on these turbos were such that they were designed to handle this stress. But, if as an engineer, I told you that you could cut x grams from the turbo's rotating assembly by simply putting a valve in your system would you do it? I know I would. Cutting weight on the rotating assembly would mean faster spool up meaning more power earlier. This could be the difference between winning and losing. Just look at the crazy engineering that goes into F1 (or many other forms of racing). These guys are paid to develop the best car. It is safe to assume that these guys explore everything to ring out the most performance out of the car. Hell Group C cars ran enduro races without issue.

Please show me a turbo that has failed due to "compressor stall". Please tell me how long a turbo should last so there is a basis for comparison. There is no fixed lifetime, just like engines. Some go early and some last forever. Please show me some facts about this. Find some metallurgy exposing the increased wear. Find some speed data that shows the compressor is actually stalling in this case. Find some proof.

If you want to talk about personal experience, I have a friend with an RX7 (FC). He autocrosses (sees DD time in the summer too) his car without a BOV/BPV. Guess what. The turbo hasn't failed and I have heard it surge plenty. There are countless examples of people who do not have issues with not running a BOV/BPV. Please, from your vast experience show us an example where a turbo has failed due to this.

Know why cars come with a BPV? It is so people who don't know cars don't get freaked out by strange noises. Know why companies make BOVs? Because people like the noise.

Added: To the OP, if you want to run without one, go for it. There are plenty of people who don't. This topic, however, has been covered ad nauseum....

Added 2: Food for thought, what do turbo diesel engines do without one of these?

Last edited by van_dutch; 06-30-2010 at 06:18 PM. Reason: added
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Old 06-30-2010, 06:17 PM   #15
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Quote:
Originally Posted by van_dutch View Post
Added: To the OP, if you want to run without one, go for it. There are plenty of people who don't. This topic, however, has been covered ad nauseum....
I know but it never made it into one thread. Most of the ones didn't really discuss it, just touched on it, got derailed, and then locked. When I was searching there were just bits and pieces all over. I was trying to more or less compile them.


Thanks again for your contribution!
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Old 06-30-2010, 06:58 PM   #16
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Old 06-30-2010, 07:01 PM   #17
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Excuse me as I'm the nubiest of newbies, but it looks to me like Badler and 08GRSTi should probably get a room and do a cage match to the death or something. I read the other thread that was smartly closed by one of the moderators.....seems like you two brought the fight outside the bar and are finishing it in this thread.

LGT
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Old 06-30-2010, 07:03 PM   #18
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Quote:
Originally Posted by van_dutch View Post
Added 2: Food for thought, what do turbo diesel engines do without one of these?
Instantly explode?

Somebody in another thread said something about them not having throttle plates? Sounded iffy to me but I have zero knowledge on diesels. Havent had a chance to further investigate.
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Old 06-30-2010, 07:05 PM   #19
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Quote:
Originally Posted by unamused LGT View Post
Excuse me as I'm the nubiest of newbies, but it looks to me like Badler and 08GRSTi should probably get a room and do a cage match to the death or something. I read the other thread that was smartly closed by one of the moderators.....seems like you two brought the fight outside the bar and are finishing it in this thread.

LGT
If you bring that idiot into this thread again I am going to be even more pisseder.


Thanks for your awesome contribution though.


BTW a cage match on here is when we do it via PMs.
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Old 06-30-2010, 08:03 PM   #20
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Quote:
Originally Posted by van_dutch View Post
There are countless examples of people who do not have issues with not running a BOV/BPV. Please, from your vast experience show us an example where a turbo has failed due to this.

Know why cars come with a BPV? It is so people who don't know cars don't get freaked out by strange noises. Know why companies make BOVs? Because people like the noise.
http://www.turbobygarrett.com/turbob...o_tech101.html

"Blow-Off (Bypass) Valves
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it.
Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure; helping to eliminate the phenomenon of surge."


http://www.turbobygarrett.com/turbob...o_tech103.html
"◊ Surge Line
  • Surge is the left hand boundary of the compressor map. Operation to the left of this line represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor. Continued operation within this region can lead to premature turbo failure due to heavy thrust loading.
  • Surge is most commonly experienced when one of two situations exist. The first and most damaging is surge under load. It can be an indication that your compressor is too large. Surge is also commonly experienced when the throttle is quickly closed after boosting. This occurs because mass flow is drastically reduced as the throttle is closed, but the turbo is still spinning and generating boost. This immediately drives the operating point to the far left of the compressor map, right into surge.

    Surge will decay once the turbo speed finally slows enough to reduce the boost and move the operating point back into the stable region. This situation is commonly addressed by using a Blow-Off Valves (BOV) or bypass valve. A BOV functions to vent intake pressure to atmosphere so that the mass flow ramps down smoothly, keeping the compressor out of surge. In the case of a recirculating bypass valve, the airflow is recirculated back to the compressor inlet.
  • A Ported Shroud compressor (see Fig. 2) is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left (see Fig. 3) by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency."

Garret seems to think they are important.
Quote:
Originally Posted by van_dutch
Food for thought, what do turbo diesel engines do without one of these?
They don't have a throttle plate.......
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Old 06-30-2010, 08:12 PM   #21
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Subaru also thinks only running 14.5psi on an sti is important. Does that mean you can't run more safely? They are stating that for warranty concerns IMO.

What does Garrett say to Crawford about this? Serious question.


That's two on the no throttle plate diesel thing.
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Old 06-30-2010, 08:23 PM   #22
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Quote:
Originally Posted by quazimoto View Post

SNIP

Garret seems to think they are important.
Ok. I would still like to see that turbo failures occur because of this. Just because company x says it doesn't make it true. Corky Bell, author of Maximum Boost, says it isn't a big deal. We can go back and forth finding a person that says this and a company that says that but it doesn't change the fact that it is not proof. I see this all over the place that surge/stall (technically two different concepts...) leading to bearing failure or shearing a shaft. I have yet to see analysis done on a turbo that broke from this. I have seen discussion of ones that had oiling issues, or ones that contacted the housing. Garrett said that it can lead to premature failure. What is the expected lifetime? How does that compare to the premature failure lifetime? Without these, there can be no actual discussion about failure rates. Please, show me. Stop with the I heard this or I read this somewhere on the internet. I'm not going to try to prove that it is not necessary (can't really prove a negative). Prove (find evidence - quotes by companies like Garrett are kind of evidence, but they are not nearly as strong as scientific study of these things) that turbos fail more quickly without a BOV/BPV (by short order, I'm talking about they fail in 100 hours compared to the 1M hour expected lifetime - a noticeable change - 100 hours versus 105 hours is within what can be reasonably be expected).

Quote:
Originally Posted by quazimoto View Post
They don't have a throttle plate.......
I was just being a pain and seeing if anyone would bite. Some confusion the pssshh from the airbrake system with a BOV on large trucks.

Last edited by van_dutch; 06-30-2010 at 08:23 PM. Reason: added.
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Old 06-30-2010, 08:37 PM   #23
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I'm gonna try for a few more negatives
From Peter Media Synapse Engineering:
"* A wide open BPV in bypass mode under vacuum negates much of the
capacitance generated by the intercooler and all of it's surface area
* An unloaded compressor by way of an open BPV under cruise means less
energy being wasted at the turbine end to compress air against a mostly shut throttle, which ultimately leads to unnecessary exhaust backpressure, which leads to bad scavenging, which leads to bad volumetric efficiencies, etc.

But one of the biggest factors that most people don't realize is that a
properly placed BPV between the intercooler and throttle plate will lead to
a higher pressure differential across the throttle plate under braking.
This leads to an additional ~2" of vac behind the throttle plate which helps
the brake booster under heavy braking.

The other reason for BPVs in the future is that it is one of the only
fail-safes if you have wastegate failure via diaphragm, or controls. A BPV
can be the fuse the saves the motor. As far as racing goes, there's no way
you can finish a race spanking fuel cut in every gear if your wastegate
fails. But using a BPV as a compressor-side wastegate can run gear after
gear.

None of these benefits can be realized with BPVs that are always closed and only vent under heavy vac and throttle lift. A properly designed BPV should have reaction times in the sub 70 millisecond range, and be able to close within the same window. As far as our testing has gone, none of the
aftermarket units have been able to achieve this. Synchronic opens or
closes in ~20ms."

Also are we limiting this to stock turbos without surge porting?
And to street cars not race cars since the conditions are different?
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Old 06-30-2010, 08:53 PM   #24
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^ I know you are directly that about the OP, but for the purposes of what I am going for:

Ok. Nothing there has anything to do with failure (the biggest alleged necessity - as the others are nice but you can deal with).

Race cars are perfectly acceptable to discuss as they run much harsher conditions and if they don't see drastic failures, why would it matter on the street?

Ported, unported it doesn't matter. It's a funny noise.

I'm not interested in discussions about drivability, increased lag etc. I'm talking about failure due to the evil compressor surge.

Last edited by van_dutch; 06-30-2010 at 08:58 PM. Reason: added
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Old 06-30-2010, 09:04 PM   #25
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Quote:
Originally Posted by Badler View Post
PROS:

Maintain boost in the charge pipes.
Less lag when shifting fast/racing.
One less thing to fail.


CONS:

Loss of some driveablity in a DD.
Turbo wear and tear.
Compressor stalling.
You have it pretty much dead on. I have nothing to add except my agreement. I ran a super tight forge bpv on my wrx. The spring was supposed to be for 35 psi and the thing hardly ever opened except lift from wot/high boost.
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