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GUTA KING

By GUTA KING,
in Engines & Forced Induction

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Kinks Grand Master

Kinks

Posted
Posted

I ran my RB20 for over 3 years with no BOV. And the previous owner ran it like that as well, it was boosted for most of its life and handled backing off at 1 bar just fine. Chuffed like a mofo, and sounded great.

Got bored with the turbo and replaced it with an R33 S2 one, and continued running without a BOV. It was fine as well.

NO BOV = NO WORRIES. Anyone who tells you your turbo will blow up has been brainwashed by the "your car needs an aftermarket BOV for better performance (and more money in my hip pocket peddling junk to idiots)" brigade.

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cmerr0411 Rookie

cmerr0411

Posted
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i personally suggest running one. why would you want all that air slamming into your turbo fins then once you get back on the gas you got the little lag from you turbo slowing down. i kno people who ran no bov and their turbos are still ok then i know some that had their shit blow up. you never kno you could be next. id rather spend a couple hundred bucks on a bov versus buying a new turbo sooner than i have to

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R34GTFOUR Mentor

R34GTFOUR

Posted
Posted (edited)
I ran my RB20 for over 3 years with no BOV. And the previous owner ran it like that as well, it was boosted for most of its life and handled backing off at 1 bar just fine. Chuffed like a mofo, and sounded great.

Got bored with the turbo and replaced it with an R33 S2 one, and continued running without a BOV. It was fine as well.

NO BOV = NO WORRIES. Anyone who tells you your turbo will blow up has been brainwashed by the "your car needs an aftermarket BOV for better performance (and more money in my hip pocket peddling junk to idiots)" brigade.

no bov = stupid

yes its not going to "blow up" your turbo, bit it WILL create more lag in between gearchanges than necessary, i would never run any turbo car that i have without a bov. If you dont want the ptttch sound, plumb it back, easy.

search, this has been covered to death

Edited by R34GTFOUR
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Kaido_RR Grand Master

Kaido_RR

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lol!

it does not created more lag between gear changes lol it does the opposite. nothing wrong with running no bov most drifters dont use bov, and i have personally seen many cars go for years without a bov and big power and no problem what so ever with their turbo.

its a urban myth ...

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funkymonkey Grand Master

funkymonkey

Posted
Posted

cefiro's and other nissan family cars equipped with RB20DET's run no BOV's (plumb back or atmo) and have worked fine for their entire lives (all 17 years of it). Granted they always ran on stock boost on stock turbos. Once you start changing factory boost levels and turbos etc, it'd be wise to put one in.

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R34GTFOUR Mentor

R34GTFOUR

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lol!

it does not created more lag between gear changes lol it does the opposite. nothing wrong with running no bov most drifters dont use bov, and i have personally seen many cars go for years without a bov and big power and no problem what so ever with their turbo.

its a urban myth ...

aahh wat??

your telling me air being forced back into a turbine thats spinning the other way wont slow that turbine down, then once that turbine's rpm has been reduced it doesnt take more time to spool up the turbo the the rpm which is would still be at if there was a bov there???

im the one lol

a mate of mine has a xr6t with no bov and the compressor surge is huge inbetween gearchanges when hes at 20psi, and there IS lag when he changes gears because of this. A bov in this situation WILL reduce spool up (or lag whatever you want to call it) time in between gearchanges when your on boost in the previous gear

its not a myth, its plain old physics

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Kaido_RR Grand Master

Kaido_RR

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aahh wat??

your telling me air being forced back into a turbine thats spinning the other way wont slow that turbine down, then once that turbine's rpm has been reduced it doesnt take more time to spool up the turbo the the rpm which is would still be at if there was a bov there???

im the one lol

a mate of mine has a xr6t with no bov and the compressor surge is huge inbetween gearchanges when hes at 20psi, and there IS lag when he changes gears because of this. A bov in this situation WILL reduce spool up (or lag whatever you want to call it) time in between gearchanges when your on boost in the previous gear

its not a myth, its plain old physics

where does the air go? if the air is not vented, it stays in the pipe. therefore once you jump onto the throttle again and the throttle body opens, and because the pipe is already fulled with air, it goes straight into the throttle body, unlike if you vent it.

this is one of the main reason why pro. drifters don't run bov as it helps with lag between gear changes *weather its noticeable or not is another issue*

also how fast is the turbo rotating/spinning ? 100,000rpm or more, do you think that the amount of air remaining in the pipe has enough force to slow down the turbine when it is speeding at such a high rate?

yes its physic, the air must apply a force on the turbine blades. the turbine blades are rotating which means they also have a force...

so we have:

Air:

F= ma

m= mass of the body (kg)

a = resultant acceleration of the body (m/s^2)

now because the turbine blades are rotating they have a torque.

t=mr^2a

m=mass(kg)

r=radius(m)

a=angular acceleration (rad/s^2)

but that is assuming the turbine blades are a point mass system and we don't consider the mass moment of inertia

what im tring to get at is that one force will be alot larger than the other, so the impact of the small force on the larger force won't be that great....

also their are other issue to consider but its late and i can't remember this stuff off the top of my head would have to go grab my uni books and start quoting lines etc

just to summaries my point. the Force exerted by the air is not great enough the reduce/impact the turbine blades , due to the relative large force it creates (creates is not the best word but you get my point)

Edited by [Michael]
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R34GTFOUR Mentor

R34GTFOUR

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Posted (edited)

where does the air go? if the air is not vented, it stays in the pipe. therefore once you jump onto the throttle again and the throttle body opens, and because the pipe is already fulled with air, it goes straight into the throttle body, unlike if you vent it.

this is one of the main reason why pro. drifters don't run bov as it helps with lag between gear changes *weather its noticeable or not is another issue*

also how fast is the turbo rotating/spinning ? 100,000rpm or more, do you think that the amount of air remaining in the pipe has enough force to slow down the turbine when it is speeding at such a high rate?

yes its physic, the air must apply a force on the turbine blades. the turbine blades are rotating which means they also have a force...

so we have:

Air:

F= ma

m= mass of the body (kg)

a = resultant acceleration of the body (m/s^2)

now because the turbine blades are rotating they have a torque.

t=mr^2a

m=mass(kg)

r=radius(m)

a=angular acceleration (rad/s^2)

but that is assuming the turbine blades are a point mass system and we don't consider the mass moment of inertia

what im tring to get at is that one force will be alot larger than the other, so the impact of the small force on the larger force won't be that great....

also their are other issue to consider but its late and i can't remember this stuff off the top of my head would have to go grab my uni books and start quoting lines etc

maybe i've lost my point i was tring to get across but yeah

i know what your trying to get at, your thinking along the lines of the force required to slow down the turbine because of its weight cannot be produced by the force that the "trapped" pressurised air stuck in the intercooler piping, i studied physics aswell haha

But think along these lines,

The turbine is spooled from the load that the engine produces, no load = pretty much no boost as you would know with free reving (lets not get too technical and mention antilag)

I dont know why im saying this cause by the look of your post count you've been here for sometime and you know your stuff but anyway,

so when you get off that throttle and slam shut that throttle body butterfly, that compressor doesnt have the driving force from the exhaust turbine that it had when the throttle was on and the engine was under load, so the inlet charge WILL overwhelm the compressor wheel and slow it down. Theres not a matter of ifs or buts, the inlet charge will reduce the turbine rpm, maybe not all that noticeable at lower boost levels, but when the intake charge is up there, i've noticed a difference.

I've noticed with all my cars an instant improvement with a bov, atmo or plumbback. The same xr6t i mention above has a tad over 500rwhp and you can feel it slowing down in each gearchange, then have to spool again. Another mate had a stockish s14, no bov he ran a mid 13, nothing else changed expect a bov and he shaved .2 of a second off his time. If only every noticed nothing but improvements with a bov attached, and that why i stand by my original comment that i will never run a turbo car thats under my name without some sort of vent valve.

Its got abit off topic, and its late so im heading off haha

Edited by R34GTFOUR
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Kaido_RR Grand Master

Kaido_RR

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i know what your trying to get at, your thinking along the lines of the force required to slow down the turbine because of its weight cannot be produced by the force that the "trapped" pressurised air stuck in the intercooler piping, i studied physics aswell haha

But think along these lines,

The turbine is spooled from the load that the engine produces, no load = pretty much no boost as you would know with free reving (lets not get too technical and mention antilag)

I dont know why im saying this cause by the look of your post count you've been here for sometime and you know your stuff but anyway,

so when you get off that throttle and slam shut that throttle body butterfly, that compressor doesnt have the driving force from the exhaust turbine that it had when the throttle was on and the engine was under load, so the inlet charge WILL overwhelm the compressor wheel and slow it down. Theres not a matter of ifs or buts, the inlet charge will reduce the turbine rpm, maybe not all that noticeable at lower boost levels, but when the intake charge is up there, if noticed a difference.

I've noticed with all my cars an instant improvement with a bov, atmo or plumbback. The same xr6t i mention above has a tad over 500rwhp and you can feel it slowing down in each gearchange, then have to spool again. Another mate had a stockish s14, no bov he ran a mid 13, nothing else changed expect a bov and he shaved .2 of a second off his time. If only every noticed nothing but improvements with a bov attached, and that why i stand by my original comment that i will never run a turbo car thats under my name without some sort of vent valve.

Its got abit off topic, and its late so im heading off haha

fair enough i can see where your coming from :P

from my personal experiences i notice no difference from running no bov to running a blitz bov (350rwhp @ 16psi), but then again it comes down to the car setup, driving style etc as every car is difference.

i understand what your saying about the turbine blade spinning but i was under the impression that even when idle or during gear change the turbine blades are still spinning at very high rpm. Also the reason why i stated the forumlas so show that torque was also affect by angular acceleration not just mass, and one would assume the angular acceleration to be a large number due to the rpm that the turbine blades are traveling at.

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cmerr0411 Rookie

cmerr0411

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sorry i cant quote, internet too slow.

but Micheal said where does the air go? if its not vented it stay in the pipe.

You're right where does it go? it pushes back to the turbo thats the only way it can go. if you got 12 psi in an enclosed area it going to go back the way it came. its just not going to stop and sit there and wait for the butterfly to open back up. the turbo is going to loose rpm then its going to have to spool again.

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cmerr0411 Rookie

cmerr0411

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sorry i cant quote, internet too slow.

but Micheal said where does the air go? if its not vented it stay in the pipe.

You're right where does it go? it pushes back to the turbo thats the only way it can go. if you got 12 psi in an enclosed area it going to go back the way it came. its just not going to stop and sit there and wait for the butterfly to open back up. the turbo is going to loose rpm then its going to have to spool again.

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Kaido_RR Grand Master

Kaido_RR

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Posted (edited)
sorry i cant quote, internet too slow.

but Micheal said where does the air go? if its not vented it stay in the pipe.

You're right where does it go? it pushes back to the turbo thats the only way it can go. if you got 12 psi in an enclosed area it going to go back the way it came. its just not going to stop and sit there and wait for the butterfly to open back up. the turbo is going to loose rpm then its going to have to spool again.

correct :P the air will go back towards the turbo but how much of the air will hit the turbo. depending on what car you have and your intercooler piping setup will determine the length of pipe and how far the air will have to travel to reach the turbine of course some of the air will come into contact with the turbine blades, and theoretically impacting on the turbine rpm. the time between the throttle body closing and opening is maybe a second, depending on the speed the air is traveling, the amount of air in the pipe and the total distance between throttle body and turbine blades will determine how much air is transfer through the blades and how much air remains in the pipe.

also depending if the air flow is laminar or turbulent, will have an affect on things too.

Edited by [Michael]
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