2 BOVs

[trbotaln]

whats up guys, I was looking through an old issue of sport compact car magazine and I noticed their was an old single turbo supra with 2 BOVs right next to eachother on the intercooler piping. Has anyone tried this on a dsm or is it not a good idea?

 

[deeeep]

i dont see what the point whould be

 

[blcknspo0ln]

yes you can, my friends VR4 has done it. although he has two seperate charge pipes, i'm sure you can rig it to work.

just weld two flanges to the same charge pipe and stick the BOV on

 

[CanadianTSi]

Pointless unless you are flowing MASSIVE amounts of air, but ya sure you could make it work.

 

[Shadowfax]

yes you can, my friends VR4 has done it. although he has two seperate charge pipes, i'm sure you can rig it to work.

just weld two flanges to the same charge pipe and stick the BOV on

Who's your friend?

The point I'd have to ask, more than running two BOV's is why would you put them besides eachother? The point of the BOV is to relieve pressure on the TURBO, not the Throttle plate. your biggest intake tract restriction is the IC- so technically running the BOV as close to the turbo is your best idea

I know of a few 3/S turbos that run one BOV near each turbo, and at least one running 3 - the stock location and one by the turbos.

If you have insane long piping, then venting ALL the air might be pointless, however that's not the way a BOV works anyway- it vents only as much as needed to drop pressure below actuation.

Sum it up- if you have ever heard your BOV actuate more than one per shift or have heard psh-psh-ps-ps-p-p... then you should likely consider moving the BOV before the IC, or installing a second one there

 

[trbotaln]

I have always been told that having the BOV closest to the throttle body would be the best way and eliminate compressor surge.

 

[blcknspo0ln]

Who's your friend?

The point I'd have to ask, more than running two BOV's is why would you put them besides eachother? The point of the BOV is to relieve pressure on the TURBO, not the Throttle plate. your biggest intake tract restriction is the IC- so technically running the BOV as close to the turbo is your best idea

I know of a few 3/S turbos that run one BOV near each turbo, and at least one running 3 - the stock location and one by the turbos.

If you have insane long piping, then venting ALL the air might be pointless, however that's not the way a BOV works anyway- it vents only as much as needed to drop pressure below actuation.

Sum it up- if you have ever heard your BOV actuate more than one per shift or have heard psh-psh-ps-ps-p-p... then you should likely consider moving the BOV before the IC, or installing a second one there

dorian, aka sundown13x ? over at 3si had a dual BOV for a while, dunno if he still does.

i guess the question at hand is not IF its possible, cause it is, but whether or not it's beneficial

 

[vtracer20]

the bet the supra was running alot of boost...it might help with getting rid of the pressure in the UICP thus making it benefitial

 

[Shadowfax]

I have always been told that having the BOV closest to the throttle body would be the best way and eliminate compressor surge.

Find a guy with a 2.2Turbo Dodge- any of them that are stock and go for a ride see if they have come surge they never came with a BOV - I never had comp surge in my 2.2 Turbo II and it was a Garret T3 50 trim with IC from the factory. I put a BOV on and it did help quicker shifts by a ton, but never had comp surge. A lot of the 3/S guys have comp surge, and almost none of them attribute it to tiny stock IC's and high boost - I know at least one 3/S'ers got rid of his by putting a stock DSM bov on each IC pipe just after the turbo (course he's running 14B's too ).

The point is that there were many turbo cars without BOV's and typically they didn't have comp surge issues- they had blown turbo issues- without a BOV the air stacks up when you slam the throttle plate closed (btw good way to have fun- learn to speed shift- use the clutch, but keep the gas hammered No BOV actuation) that air still compresses- yes right at the TB, which is why a lot of people run BOV's there- you will vent a considerable amount of air if you have the BOV at the TB- however a second spike is happening at the IC and the ultimate issue isn't pressure spikes - but simply that pressure builds up on the comp wheel, trying to arrest it's movement - don't think I need to tell you what happens if it ever succeeds

you want to vent your pressure spike, great- keep a BOV at the TB - but if you want to make sure your turbo has the longest life possible- either make sure you have an VERY well flowing IC tract- or stick a BOV inbetween the IC and the Turbo- I honestly will do both

 

[dave99gst]

i no somone with 2 bov's on a 2g. works out ok. ( but ya pointless )

 

[suicidal2af]

Find a guy with a 2.2Turbo Dodge- any of them that are stock and go for a ride see if they have come surge they never came with a BOV - I never had comp surge in my 2.2 Turbo II and it was a Garret T3 50 trim with IC from the factory. I put a BOV on and it did help quicker shifts by a ton, but never had comp surge. A lot of the 3/S guys have comp surge, and almost none of them attribute it to tiny stock IC's and high boost - I know at least one 3/S'ers got rid of his by putting a stock DSM bov on each IC pipe just after the turbo (course he's running 14B's too ).

The point is that there were many turbo cars without BOV's and typically they didn't have comp surge issues- they had blown turbo issues- without a BOV the air stacks up when you slam the throttle plate closed (btw good way to have fun- learn to speed shift- use the clutch, but keep the gas hammered No BOV actuation) that air still compresses- yes right at the TB, which is why a lot of people run BOV's there- you will vent a considerable amount of air if you have the BOV at the TB- however a second spike is happening at the IC and the ultimate issue isn't pressure spikes - but simply that pressure builds up on the comp wheel, trying to arrest it's movement - don't think I need to tell you what happens if it ever succeeds

you want to vent your pressure spike, great- keep a BOV at the TB - but if you want to make sure your turbo has the longest life possible- either make sure you have an VERY well flowing IC tract- or stick a BOV inbetween the IC and the Turbo- I honestly will do both

I really hope this post was a joke.

 

[99gst_racer]

I really hope this post was a joke.

I 2nd that......

so technically running the BOV as close to the turbo is your best idea

This is so bass-ackwards. You DO want to BOV to be mounted close to the throttle body, not close to the turbo. Thats how it's always been. The newer Turbo Dodge's put the BOV near the TB.....

 

[drivemusicnow]

Did either of you actually read it??? makes sense... it may not be correct, but neither of you are providing any explanation as to why its not...

 

[Shadowfax]

guys - know why there are guys on 3/Si running two BOV's and suddenly their comp surge is gone? cause they listened to me. I'm not making this up- find out for yourself- take your BOV off and cap it- then tell me what it does. If you find a 2.2 or 2.5L turbo dodge (daytona, lebaron, OMNI GLHS, turbo caravan) they don't have BOV- the bov was designed to relief pressure on the turbo, not to stop any pressure spikes. The Throttle plate is closed- who the hell cares if there is pressure on the other side?! Your engine doesn't. What happens if that air is there? You might run a bit rich for a moment if you flat out open it back up - you might pop the IC hose off the elbow... but for all other intents and purposes- the only thing that not relieving the air will do is back up and try and stall the compressor- is it possible? Not really, most turbos will not enjoy the comp trying to stop and the exhaust still spinning the turbine.

I'm not going thru all the links and threads and related work just to prove something to you guys that should be halfway common sense- why would the BOV be located on the intercooler on WRX? Oh, perhaps because you don't give a shit about the pressure spike at the throttle plate. Will it make a difference on most cars- not really, you aren't running enough airflow, or you will simply open it back up and start cramming into cylinders again... if your turbo lasts 100,000 miles with the BOV near the TB then you've got a system that is okay- but if you keep looking at turbos, you'll find that some have BOV's mounted RIGHT OFF the comp outlet- know why?

 

[psychlow]

Pressure is pressure. There's not going to be enough of a restriction in the intercooler to cause a BOV near the turbo to be much more beneficial.

I agree that not all cars came with BOVs, but I don't understand how you say you're not dropping below the compressor surge line when you drop the throttle plate at WOT. If your pressure spikes to 25PSI+ on the compressor side and your exhaust pressure drops to near nothing, your compressor wheel is going to slow down drastically - against its own inertia at over 100K RPM. Your pressure ratio can go to 1:2 or worse.

 

[Shadowfax]

Pressure is pressure. There's not going to be enough of a restriction in the intercooler to cause a BOV near the turbo to be much more beneficial.

That depends entirely on how good your IC is

I agree that not all cars came with BOVs, but I don't understand how you say you're not dropping below the compressor surge line when you drop the throttle plate at WOT. If your pressure spikes to 25PSI+ on the compressor side and your exhaust pressure drops to near nothing, your compressor wheel is going to slow down drastically - against its own inertia at over 100K RPM. Your pressure ratio can go to 1:2 or worse.

I am exactly saying that will happen- but that isn't going to hurt a damn thing other than the turbo

 

[psychlow]

I am exactly saying that will happen- but that isn't going to hurt a damn thing other than the turbo

OK, I may have misread this:

Find a guy with a 2.2Turbo Dodge- any of them that are stock and go for a ride see if they have come surge they never came with a BOV - I never had comp surge in my 2.2 Turbo II and it was a Garret T3 50 trim with IC from the factory.

So, you probably had surge, but it wasn't hurting anything except slower shifts and a shorter turbo lifespan, right?

 

[92redman]

The point is that there were many turbo cars without BOV's and typically they didn't have comp surge issues- they had blown turbo issues-

And what is your explanation for the blown turbos if it isn't compressor surge?

 

[Shadowfax]

So, you probably had surge, but it wasn't hurting anything except slower shifts and a shorter turbo lifespan, right?

I didn't have noticible comp surge on my TurboII - doesn't mean it didn't exsit - the airflow on those turbos was mostly higher boost- I know the stock turbo could push out upto 26psi (on the TII) while the T3 super60 was more like 30psi...

again, the point of the bov is longer turbo life. That it does it's job is unquestionable. Whether you put it near the TB or the turbo is most likely largely irrelvant- however that doesn't mean that there aren't some instances where it's a good idea- like with stock sidemounts on a 3/S with a pair of 14b's- the piping from the rear turbo to the IC is 1.5" and it happens to be nearly 5 ft long!

Edit- yes, yes, I should have clarified NOTICABLE COMPRESSOR SURGE! There is a difference between a 3/S bucking wildly at 2000rpm and 1psi boost for 5-10 seconds, vs feeling nothing at all but slowly killing your turbo.

Still better yet- if you have a crappy flowing 8 valve 2.2L motor with a garrett T3 50 trim and a 2.5" turbine outlet- how much exhaust flow do you really have- would you actually notice if the turbine wheel was forced to spin backward (keep in mind what a 1989 Garrett designed turbine wheel looks like- nothing like anything you've seen.

 

[suicidal2af]

I didn't have noticible comp surge on my TurboII - doesn't mean it didn't exsit - the airflow on those turbos was mostly higher boost- I know the stock turbo could push out upto 26psi (on the TII) while the T3 super60 was more like 30psi...

again, the point of the bov is longer turbo life. That it does it's job is unquestionable. Whether you put it near the TB or the turbo is most likely largely irrelvant- however that doesn't mean that there aren't some instances where it's a good idea- like with stock sidemounts on a 3/S with a pair of 14b's- the piping from the rear turbo to the IC is 1.5" and it happens to be nearly 5 ft long!

Edit- yes, yes, I should have clarified NOTICABLE COMPRESSOR SURGE! There is a difference between a 3/S bucking wildly at 2000rpm and 1psi boost for 5-10 seconds, vs feeling nothing at all but slowly killing your turbo.

Still better yet- if you have a crappy flowing 8 valve 2.2L motor with a garrett T3 50 trim and a 2.5" turbine outlet- how much exhaust flow do you really have- would you actually notice if the turbine wheel was forced to spin backward (keep in mind what a 1989 Garrett designed turbine wheel looks like- nothing like anything you've seen.

Compressor surge will not make your car buck. Compressor surge is when the pressure that builds up at the throttle plate "shockwaves", for lack of a better word, back to the turbo and violently halts the movement of the compressor. You lose your spool. You DO hurt the lifespan of the turbo everytime it happens. Did some cars come from the factory without one? Yes, but it doesn't mean they didn't get compressor surge. That's EXACTLY the reason they blow turbos.

Your argument about location of bov is quite, quite flawed. The IC might be a minor restriction, but the air is still flowing through it and stacking up at the TB. As long as you release the pressure near the TB, the compressed air is still going to flow through the IC, and not cause surge. If it caused surge in that condition, you would have surge ALL the time, not just during closed throttle plate conditions. Air flows from high pressure areas to low pressure areas, and your highest pressure under normal conditions is going to be where the air is being compressed. A bov simply keeps the low pressure area near the TB.

I think you're very, very confused as to what compressor surge actually is. Anytime air get backed up in the intake tract, and collides with the compressor and halts the wheel, that is compressor surge. The only noticeable effects you will see are the neat sound it makes, and the turbo losing spool. And after a while you'll notice the blown turbo.

 

[fulanititoo8198]

I just read about this in the recent issue of Turbo and high tech performance. They have 2 HKS SS BOV's on a HKS T51R SpL. on a stroked 4G63 Evo.

 

[InfamousEclipse]

My buddy has one on his 2G, but he's runing a Frank 5 Turbo so... I'm sure it helps

 

[Shadowfax]

Compressor surge will not make your car buck. Compressor surge is when the pressure that builds up at the throttle plate "shockwaves", for lack of a better word, back to the turbo and violently halts the movement of the compressor. You lose your spool. You DO hurt the lifespan of the turbo everytime it happens. Did some cars come from the factory without one? Yes, but it doesn't mean they didn't get compressor surge. That's EXACTLY the reason they blow turbos.

Again, I should have mentioned that when I said they don't get surge- they don't get noticable surge- however if you've never been in a 3/S complaining of comp surge- you don't know that they can severely buck when at low boost and higher gears due to comp surge- it's not JUST when the throttle plate is CLOSED- it's anytime that boost stacks up enough to cause it.

Your argument about location of bov is quite, quite flawed. The IC might be a minor restriction, but the air is still flowing through it and stacking up at the TB. As long as you release the pressure near the TB, the compressed air is still going to flow through the IC, and not cause surge. If it caused surge in that condition, you would have surge ALL the time, not just during closed throttle plate conditions.

BINGO! That's what I've been seeing- comp surge under MORE than just 100% off throttle conditions!

Air flows from high pressure areas to low pressure areas, and your highest pressure under normal conditions is going to be where the air is being compressed. A bov simply keeps the low pressure area near the TB.

And I did say that assuming you have a well designed IC piping setup there is little to nothing wrong- however it's also wrong to assume that the DSM is as bad as it gets- you don't have nearly 20 feet of IC piping to deal with- only about 7. There are more cars than just the DSM, and they have problems beyond those of DSM's. Just because on a car with a decent flowing tract and a decent sized IC you can see these traits doesn't mean the issue doesn't happen otherwise. If the BOV actuates 3, 4 or 5 times when you let off the throttle- what does that tell you is happening?

I think you're very, very confused as to what compressor surge actually is. Anytime air get backed up in the intake tract, and collides with the compressor and halts the wheel, that is compressor surge. The only noticeable effects you will see are the neat sound it makes, and the turbo losing spool. And after a while you'll notice the blown turbo.

me thinks that you assume much. I made the mistake of not signifying between noticable and not noticable comp surge- again, if you only think that it makes a little noise and the turbo loses spool, you've not seen really bad comp surge. I know what causes comp surge- I'm simply saying that your IC is the biggest restriction in the IC pipes, and that there can be a larger pressure difference between it and the IC than the IC and TB. Again- answer why there are BOV's mounted directly on the turbo? IHI's I think. You can say what you want about typical setups, and the fact that they work isn't in question- but when push comes to shove, you are still technically relieving MORE pressure on the TURBO by venting it at the Turbo than at the TB.

 

[n0va91TSI]

I cannot see how putting it far away from the turbo is better. the only reason mitsu put the stock BOV on the UPIC pipe is the convient location for recirulation to the intake pipe. Remember that normally BOVs recirculate, so the air is moving in a circle thru the intake/turbo/piping. you want the shortest path with the least resistance so the air can flow better with as even pressure distribution as posible. Its a closed system and you want it to have the least restrictions so if you can not involve the resistance of the intercooler and extra piping it will flow better and keep the turbine from slowing down as much. The point of getting rid of compressor surge is keeping the turbo spinning as quickly as posible between shift so you wont has as much turbo lag after you shift into the next gear. Many of you people believe these old wives tales about putting a BOV near the throttlebody. It makes no sense! use you head!

also people put 2 BOVs cuz they think its cool. same reason people tell me i should get twin turbos even thought my car is obviously an inline 4 with one exhaust manifold. people are stupid.

 

[suicidal2af]

The reason you put it closer to the TB is because when the throttle plate is closed, THAT is where pressure is going to build highest the fastest. You want to vent the pressure as it STARTS to build, not after it is already backed up all the way through the intake tract.

If your intercooler is THAT restrictive that the path of least resistance is back towards the turbo, then you have an issue that you don't solve by putting a bov there. It's counterintuitive. Turn the boost down to a level where it ISN'T a restriction...all keeping it up and venting through a bov is doing is making the turbo work harder to see the exact same pressure going into the engine. You should not have this problem. If you do, you don't bandaid it with a bov.

Longer IC piping should make this even less of an issue, not more. Shorter piping is going to make pressure at an obstruction build more quickly throughout the tract, and surge will be much more apparent. What overflows first, a shotglass or a wineglass? And as far as the bov actuating multiple times, that means you have it adjusted too tight. It isn't opening fully, and is fluttering as a result.

Back to the topic, the only reason I could see for 2 bovs is to utilize smaller, faster reacting valves, but still have enough overall area to release all the pressure in a high boost scenario.