yoshimitsuspeed said:

Was your boost leak test done up to the pressure of boost you were running? Did it include the BOV circuit to make sure the BOV wasn't bypassing under full boost?

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Yes it was done up to 40psi, 10psi past my highest boost pressure in my logs.

It included the whole system.

I'm sorry, but I will be running a BOV no matter what. The ill effects (whether or not you accept their existence), will just harm your turbo and cause you more money in the long run.

Hey guys! Why not run your WASTE of space T-25s with no waste gate? Or unhook the line off of it and see how long your turbo lasts :rollseyes:.

They made it for. Reason. Like some cars came w/o intercoolers. Yeah they might work. But why would you want to? The factory "tune" is set up for that air. Keep it. You where really happy to run a t-25? I don't understand? I can't ####ing wait to throw mine off a brodge.

I'm no wagon scientist. But ok, your throttle plate closes while your turbo is still spinning, that air hits your butterfly. Where does it go? Take a blow gun. And put your palm over it. Now imagine that in a not so closed system.

yoshimitsuspeed said:

It is a little bit different though.
If you vent your BOV the ECU is dumping fuel for air that has already passed past the AFM/MAF but is not going into the engine.

Without a BOV if you let off the gas the volume of air is going the exact same place it would with a recirc BOV it's just taking a different path. It should have a similar effect. If the air was still fluttering while you stepped on the gas it could confuse the ECU a bit but that overlap should only be a few ms if anything.

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I'm not saying the effects are the same, Venting was merely an example. When the turbo flutters, the pressure waves flow back and forth past the airflow meter, so the same air is counted multiple times. I'm not debating this fact, I have logs that prove this is an issue. This is further backed by the fact that the only BOV-less car produced by Toyota had a Harmonic Intake, most likely to block the pressure waves from confusing the MAF.

It also seems odd to me that these guys use the All-Trac as their basis for reasoning. Yet all the All-Tracs and GT-Four's I've worked on (including the most powerful ST205 in the US) had an aftermarket BOV added for the sake of the turbo. Not just for the sake of making noise, some were as simple as a stock Audi diverter valve recirculated back into the intake.

And while I can appreciate a Devils Advocate for the sake of conversation, it seems your arguments are merely reaching for the sake of poking the bear.

WES_393 said:

I'm not saying the effects are the same, Venting was merely an example. When the turbo flutters, the pressure waves flow back and forth past the airflow meter, so the same air is counted multiple times. I'm not debating this fact, I have logs that prove this is an issue. This is further backed by the fact that the only BOV-less car produced by Toyota had a Harmonic Intake, most likely to block the pressure waves from confusing the MAF.

It also seems odd to me that these guys use the All-Trac as their basis for reasoning. Yet all the All-Tracs and GT-Four's I've worked on (including the most powerful ST205 in the US) had an aftermarket BOV added for the sake of the turbo. Not just for the sake of making noise, some were as simple as a stock Audi diverter valve recirculated back into the intake.

And while I can appreciate a Devils Advocate for the sake of conversation, it seems your arguments are merely reaching for the sake of poking the bear.

Click to expand...

Well said.. On another note, you safe over there in black forest man? We've been getting smoke all the way in Downtown Denver from the fires. Hope all is well.

To the OP, I'm open to anyone trying new things if they happen to work. Advancements never get made if no one ever tries to challenge the status quo. If this is something that was absolutely proven, I would be all over it. I think the problem that DSM'ers have, and I will venture to say nearly all people who run turbos have(with the exception of the mr2 clan),is they run a BOV because it just makes sense from a physics standpoint.

You seem like a pretty intelligent person gauging by the responses you've returned to some people on here. Based on that that, why don't you do multiple tests with identical turbos being stressed the exact same way in a lab test? That is the only definitive way to get your answer. See what gains you get from each and then break each one down(if you still have two to break down), and see which is worse for wear. This has to be done in a lab style, repeatable setting with multiple turbos. I don't think anyone here would be willing to do that because we are afraid of the results(dead turbo, money down the drain only to get expected results).

It seems to me based off your logic that there would be a "sweet" spot for bov's that is much different than what we all consider it to be. That tuning your bov in a new way could net substantial gains. Please test that for all of us. Be that guy that makes what would be a giant leap in bypass tech-since there really hasn't been any since they've been in use. I am convinced there is a reason why there have not been any real advancements....but I could be wrong. Prove us all wrong.

jakelandry said:

FWIW, I toasted a hx40 (factory surge-ported and designed for a non bov vehicle) from doing the dgm bov mod and not running the bottom port. 80 mph on the highway created enough surge to cause journal wear signifigant enough to eat my compressor cover and billet wheel up. Ask justin, he rebuilt it... twice. Not saying no bov kills turbos, just adding my experience.

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That's what exactly happend to me on my mhi Evo 3 16g, it had the DGM mod on the bov and it and was not opening up at 24 psi for a while and it started to get in and out play and ate the compressor cover up and blade as well. This had to be caused by the air being forced back out on the turbo and creating pressor that is forcing the whole rotating assembly to want to push out creating thrust bearing ware. Journal bearings were fine so it was getting the oil it should.

Similar effect to what is desired with no BOV can be reached (theoretically) by having an air tank where the BOV will be emptied into. Then as throttle is opened (WOT, or somewhere around there) a valve opens, letting the pressure out of that tank to dump into the intake, thus creating boost pressure while turbo is spooling. Upon releasing the pedal the valve would close allowing BOV to dump into the tank to release extra pressure from intake.

Will a system like that work? Don't know, this is only a theory.

WES_393 said:

I'm not saying the effects are the same, Venting was merely an example. When the turbo flutters, the pressure waves flow back and forth past the airflow meter, so the same air is counted multiple times. I'm not debating this fact, I have logs that prove this is an issue. This is further backed by the fact that the only BOV-less car produced by Toyota had a Harmonic Intake, most likely to block the pressure waves from confusing the MAF.

Click to expand...

But is that fluttering causing a problem? I don't doubt it's there but when it is you are off the gas. Have you noticed this happen while you are on the gas or seen a negative effect on pressure?

WES_393 said:

It also seems odd to me that these guys use the All-Trac as their basis for reasoning. Yet all the All-Tracs and GT-Four's I've worked on (including the most powerful ST205 in the US) had an aftermarket BOV added for the sake of the turbo

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But who added that BOV?
Was it the engineer who designed the car? Or maybe the engineer who designed the turbo?
First people say I shouldn't question the people who designed the car but when I come up with an example of one without it then it's perfectly acceptable that someone added a BOV when the car didn't come with one. Was the person who added it qualified to know that it absolutely needed one? Or did they just add it because it's standard practice?

WES_393 said:

And while I can appreciate a Devils Advocate for the sake of conversation, it seems your arguments are merely reaching for the sake of poking the bear.

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I'm sorry if you guys feel that way. I have been trying to provide arguments either based on scientific fact or others personal experiences. I have tried to maintain as passive a position as possible and when I read many of the responses in this thread I feel like I have been one of the least rude, least aggressive and least defensive people in this thread.
I have no desire to poke the bear and if you can tell me how to not come across that way I will try my best. I am looking for ideas and open minds.

I'm no wagon scientist.

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I'm looking for scientists, not Dbaggy responses with no educational value or legitimate information to back up their claim.
I'm looking for people who can actually come up with an articulate counterpoint and some scientific background for their beliefs.
Your posts and information have been greatly valued and I appreciate everyone's input who has had valuable information to add.

AwD4g63TsI said:

To the OP, I'm open to anyone trying new things if they happen to work. Advancements never get made if no one ever tries to challenge the status quo. If this is something that was absolutely proven, I would be all over it. I think the problem that DSM'ers have, and I will venture to say nearly all people who run turbos have(with the exception of the mr2 clan),is they run a BOV because it just makes sense from a physics standpoint.

You seem like a pretty intelligent person gauging by the responses you've returned to some people on here. Based on that that, why don't you do multiple tests with identical turbos being stressed the exact same way in a lab test? That is the only definitive way to get your answer. See what gains you get from each and then break each one down(if you still have two to break down), and see which is worse for wear. This has to be done in a lab style, repeatable setting with multiple turbos. I don't think anyone here would be willing to do that because we are afraid of the results(dead turbo, money down the drain only to get expected results).

It seems to me based off your logic that there would be a "sweet" spot for bov's that is much different than what we all consider it to be. That tuning your bov in a new way could net substantial gains. Please test that for all of us. Be that guy that makes what would be a giant leap in bypass tech-since there really hasn't been any since they've been in use. I am convinced there is a reason why there have not been any real advancements....but I could be wrong. Prove us all wrong.

Click to expand...

You are the kind of person I like to hear from and you think like I do.
Unfortunately I don't have the means to do these tests right now. I agree that this would be the only way to prove for a fact that there was no increased wear or decreased reliability. Maybe some day I will be able to do some proper testing.

The title of this thread states it's purpose pretty well. I wanted to see if anyone did run without one, if the conversation had ever come up and what peoples general thoughts were on the subject. All of those have been answered very clearly at this point.

It is very interesting how many failures here seem to be attributed to BOV failure or problems when so many have successfully run turbos for tens of thousands of miles at high pressure ratios on the MR2 boards with no issues.
As you said this is no scientific proof either way.

Can people tell me what the DGM mod is?

91-GS said:

Similar effect to what is desired with no BOV can be reached (theoretically) by having an air tank where the BOV will be emptied into. Then as throttle is opened (WOT, or somewhere around there) a valve opens, letting the pressure out of that tank to dump into the intake, thus creating boost pressure while turbo is spooling. Upon releasing the pedal the valve would close allowing BOV to dump into the tank to release extra pressure from intake.

Will a system like that work? Don't know, this is only a theory.

Click to expand...

It wouldn't work very well because you would want to relieve all or at least most the pressure. An air tank big enough to allow this would have no pressure to feed back into the system. A small air tank would equalize pressure very quickly and once it equalized the rest of the pressure would be forced out past the turbines to where there was the lowest pressure in the system.

I'm sure they added it for the turbos sake for reliability and effenciancy. question is why not run a BOV? Once it gets to a certain psi it still start to bleed air. You may not need one running 7psi. but some people run 20+ and thats a lot of air to back up. if that air backs up into the turbo wouldnt that put your wheel in a bind by forcing it in the oppost direction? But since my claims have no educational value. I would like to see your numbers.

yoshimitsuspeed said:

I'm looking for scientists, not Dbaggy responses with no educational value or legitimate information to back up their claim.

Click to expand...

...yet you respond with condescension when given examples from those who have had turbo failures from faulty blow off valves or valves which were adjusted too stiff and didn't open as designed.

The majority of DSMers are not scientists, so you're probably going to get answers like:

"Well do you think it could've been this instead?" No.

"And why not?" Because shit didn't blow up when a working valve was on the car.

Not trying to start a flame war here, just making you realize you may be stepping on some toes if you ask too many questions. It's a never-ending debate much like the necessity of balance shafts- may go on until the end of time...who knows?

Just because something works well on one platform doesn't necessarily mean it carries over into another. As some have pointed out, what if there's a different intake design on the MR2 which combats compressor surge? Who knows. You'd need extensive testing on an identical platform to prove any theory wrong or right.

Hai guys! I have an idea.. lets take the diverter valve off your charge pipe.

This way, when you slam the throttle shut that entire column of pressurize air slams into the butterfly and tries to expand backward through a centrifugal pump thats just coming off peak wheel speed!

I saw where some doods over at this other forum did it, so it must be legit!

That is a great way to shock load the thrust surfaces and the shaft assembly in an expensive piece of turbo-machinery. You have basically dead-headed the pump when you come off WOT. There is still exhaust being applied to the turbine, and there is inertia in play. BOVs do indeed help recovery and response, in addition to fighting compressor stall on lift and the documented damages that occur as a result.

That "chirp" that so many love from the BOV.. all the energy is otherwise being applied to the throttle body, which has a large cross-sectional area as well as the compressor wheel.

This whole thread reads like a concern troll. Ask this question to some turbo pro-mod guys.. then time how long it takes them to stop laughing.

Congrats you started some dialogue, here's a cookie. While you are at it, you should remove the oil pump too. Just fill the block, seal the galleys and call it a day. Think of all that parasitic loss you will save!

Take off your waste gate. And eliminate your intercooler. So more air gets in there faster.

Not trying to be a dick here. But turn the boost up on your t-25 without and bov. I have had with personal experience witnessed a perfect t-25 on an eclipse pushing 12-14psi run for years constantly. Run yours double what your doing now with now bov and DD it for a couple of years and we can compare shaft play. But then again, some turbos last, some don't. So unless we put both setups In an controlled environment. Then both of our viewpoints are mute.

How Blow-Off Valves Work

A quick search yielded this response.

LandSpeed-DSM said:

Hai guys! I have an idea.. lets take the diverter valve off your charge pipe.

This way, when you slam the throttle shut that entire column of pressurize air slams into the butterfly and tries to expand backward through a centrifugal pump thats just coming off peak wheel speed!

I saw where some doods over at this other forum did it, so it must be legit!

That is a great way to shock load the thrust surfaces and the shaft assembly in an expensive piece of turbo-machinery. You have basically dead-headed the pump when you come off WOT. There is still exhaust being applied to the turbine, and there is inertia in play. BOVs do indeed help recovery and response, in addition to fighting compressor stall on lift and the documented damages that occur as a result.

That "chirp" that so many love from the BOV.. all the energy is otherwise being applied to the throttle body, which has a large cross-sectional area as well as the compressor wheel.

This whole thread reads like a concern troll. Ask this question to some turbo pro-mod guys.. then time how long it takes them to stop laughing.

Congrats you started some dialogue, here's a cookie. While you are at it, you should remove the oil pump too. Just fill the block, seal the galleys and call it a day. Think of all that parasitic loss you will save!

Click to expand...

Ha ha! Love it! Ain't that the truth brother!

To the OP....

JusMX141 said:

I'm a bit confused- are you here looking for input as the last line of your first post suggests, or are you only here to tell us all that we're idiots for using a blow off valve?

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Isn't it obvious?

LandSpeed-DSM said:

Hai guys! I have an idea.. lets take the diverter valve off your charge pipe.

This way, when you slam the throttle shut that entire column of pressurize air slams into the butterfly and tries to expand backward through a centrifugal pump thats just coming off peak wheel speed!

I saw where some doods over at this other forum did it, so it must be legit!

That is a great way to shock load the thrust surfaces and the shaft assembly in an expensive piece of turbo-machinery. You have basically dead-headed the pump when you come off WOT. There is still exhaust being applied to the turbine, and there is inertia in play. BOVs do indeed help recovery and response, in addition to fighting compressor stall on lift and the documented damages that occur as a result.

That "chirp" that so many love from the BOV.. all the energy is otherwise being applied to the throttle body, which has a large cross-sectional area as well as the compressor wheel.

This whole thread reads like a concern troll. Ask this question to some turbo pro-mod guys.. then time how long it takes them to stop laughing.

Congrats you started some dialogue, here's a cookie. While you are at it, you should remove the oil pump too. Just fill the block, seal the galleys and call it a day. Think of all that parasitic loss you will save!

Click to expand...

This is THE description and the undeniable reason why you need a BOV. Period. Awesome description man

I have a simple question. How many no bov mr2 guys are running over 30psi of boost? Many of us over here are running 30, or even 40 psi of boost on expensive aftermarket turbos. I for one am not about to put that kind of pressure on my surging turbo, or throttle plate.

Those mr2 guys are nuts...i tried it on my mk2 for a short time, wasn't a fan at all. drivability completely took a dump, other than that i didn't notice a big difference at all. In my opinion, those guys just need to learn how to shift. The only time i could possibly see it as being a benefit would be on a road course in a big sweeping turn when you're feathering the throttle, other than that like i said, learn how to shift. Since ill probably never be on a road course with any of my cars I reinstalled the valve after about a day and a half.

LandSpeed-DSM said:

Hai guys! I have an idea.. lets take the diverter valve off your charge pipe.

This way, when you slam the throttle shut that entire column of pressurize air slams into the butterfly and tries to expand backward through a centrifugal pump thats just coming off peak wheel speed!

I saw where some doods over at this other forum did it, so it must be legit!

That is a great way to shock load the thrust surfaces and the shaft assembly in an expensive piece of turbo-machinery. You have basically dead-headed the pump when you come off WOT. There is still exhaust being applied to the turbine, and there is inertia in play. BOVs do indeed help recovery and response, in addition to fighting compressor stall on lift and the documented damages that occur as a result.

That "chirp" that so many love from the BOV.. all the energy is otherwise being applied to the throttle body, which has a large cross-sectional area as well as the compressor wheel.

This whole thread reads like a concern troll. Ask this question to some turbo pro-mod guys.. then time how long it takes them to stop laughing.

Congrats you started some dialogue, here's a cookie. While you are at it, you should remove the oil pump too. Just fill the block, seal the galleys and call it a day. Think of all that parasitic loss you will save!

Click to expand...

Where's the damned Like button for this post?

Op and the folks considering or doing this this have gone full retard.

donniekak said:

I have a simple question. How many no bov mr2 guys are running over 30psi of boost? Many of us over here are running 30, or even 40 psi of boost on expensive aftermarket turbos. I for one am not about to put that kind of pressure on my surging turbo, or throttle plate.

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I was thinking this the the whole time I was reading this thread.

yoshimitsuspeed said:

My Baby for the last 10 years has been a MK1 MR2 which is now running a blacktop 4AGE at 11:1 compression and 7 PSI boost on a DSM T25.

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I have had farts flow more air than a T-25 @ 7psi. Even most of the lightly modded cars on this forum are pushing MUCH more boost and airflow than what you run on through you're T-25. Go ahead, run without one. At those levels, you won't be breaking anything.

T is for TURBO said:

I was thinking this the the whole time I was reading this thread.




I have had farts flow more air than a T-25 @ 7psi. Even most of the lightly modded cars on this forum are pushing MUCH more boost and airflow than what you run on through you're T-25. Go ahead, run without one. At those levels, you won't be breaking anything.

Click to expand...

My point exactly.

This thread is a funny read.

I won't even start. Lol.


Okay maybe i will.

In what world is pressure pushing your compressor the opposite direction than it was designed, a good thing. There is so much turbulence going on in those pipes when things are surging it's pretty logical to see why it would wear down a turbos chra bearing assembily. And it's been explained in this thread numerous times. The reason a bov is used.
Plus in all honesty. Is it really worth it to risk your indiction system for 100rpm quicker spool?

What are the REAL gains these mr2 guys believe, that having a sealed pipe system is better?

I'll bet a few things in regards to the mr2s

1. Intake design accounts for surge

2.They aren't running nearly as much boost as us

3. They use cheapo turbos and dont care (100-500$)

4. They don't want to announce their turbo failures in fear of being wrong

Or 5. they are ####ing idiots like most these honda kids out there.

I will just say this, my friend has built an skyline r32 gtr race car barely street legal but goes to some meets and he has NO bov(s) and he keeps complaining of problems such as turbo issues and pipes blowing Off from excess pressure. He is going to add 1-2 bovs to get rid of this problem as he has gone to so many places but he cannot afford a race specalist so its cheaper to install bovs! And it will work,

I have seen it before but I did not really ask them how they got it set up though

urbansmoker1 said:

This thread is a funny read.

I won't even start. Lol.


Okay maybe i will.

In what world is pressure pushing your compressor the opposite direction than it was designed, a good thing. There is so much turbulence going on in those pipes when things are surging it's pretty logical to see why it would wear down a turbos chra bearing assembily. And it's been explained in this thread numerous times. The reason a bov is used.
Plus in all honesty. Is it really worth it to risk your indiction system for 100rpm quicker spool?

What are the REAL gains these mr2 guys believe, that having a sealed pipe system is better?

I'll bet a few things in regards to the mr2s

1. Intake design accounts for surge

2.They aren't running nearly as much boost as us

3. They use cheapo turbos and dont care (100-500$)

4. They don't want to announce their turbo failures in fear of being wrong

Or 5. they are ####ing idiots like most these honda kids out there.

Click to expand...

Yeah and if you've ever ripped a half of a gear at high boost on a turbo much bigger than a T-25, then let off and your bov has never been louder from releasing excess pressure, then it's obvious that it serves more than a 'cool sound' purpose and not having one could take it's toll on your turbo over time.

ec17pse said:

I will just say this, my friend has built an skyline r32 gtr race car barely street legal but goes to some meets and he has NO bov(s) and he keeps complaining of problems such as turbo issues and pipes blowing Off from excess pressure. He is going to add 1-2 bovs to get rid of this problem as he has gone to so many places but he cannot afford a race specalist so its cheaper to install bovs! And it will work,

I have seen it before but I did not really ask them how they got it set up though

Click to expand...

Pics of that bad boy or I call BS