Whats the point of having a BOV?
Whats the point of having a BOV?
09-11-04, 10:32 PM
#3
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A turbo spools air and creates pressure, it uses this pressure to force more air into your intake manifold. When you press the gas, the turbo is spooling and sending this pressurized air to the intake manifold and your throttle plate is open, so it goes into your engine. When you release the gas and the throttle plate closes, this pressurized air has nowhere to go except where it came from. The blow off valve is mounted near the throttle body usually, and it releases this pressurized air. without a bov air slams back into your turbo, and causes damage.
09-11-04, 11:34 PM
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Basically, if you don't have a bov, you would get backspin on the turbo and that would kill the bearings of the turbo, and the turbo itself, it's just venting the extra air. It doesn't matter where the bov is mounted as long as it is mounting between the turbo and throttle body, mine is near the turbo, others have them near the throttle body, they both work the same. BOV's can be vented back into the intake(past the throttle body, or the atmosphere, honda boys like the atmospheric types, but so do I, it's a nice sound....
09-12-04, 12:12 AM
#7
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Not having a BOV will not magically kill the bearings at all.
Quite a few turbocharged cars have come out with no BOV's from the factory.
They're primarily there for emmissions and noise reduction (yes, reduction).
Also having a BOV will decrease your power on gearshits. This has been proven many times by racers..
Keeping the turbo spooled up means sweet F A if you have to then refill all the intake piping/intercooler/manifold with pressurised air once the BOV shuts again.
IMHO at least...
Quite a few turbocharged cars have come out with no BOV's from the factory.
They're primarily there for emmissions and noise reduction (yes, reduction).
Also having a BOV will decrease your power on gearshits. This has been proven many times by racers..
Keeping the turbo spooled up means sweet F A if you have to then refill all the intake piping/intercooler/manifold with pressurised air once the BOV shuts again.
IMHO at least...
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09-12-04, 02:22 AM
#8
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having a bov ... you dont NEED one.. if youre losing alot of power between shifts, you need to reset your bov. the idea is simply to reduce pressure between shifts. think about it.. how much boost do you make at 7k? how much boost do you make at 4k? when you shift from 7k-4k, you have alot of extra pressure built up that your ecu has to compensate to handle. its a preventative measure, like a turbo timer.
09-12-04, 11:16 AM
#11
Just remember- a BOV is as stated by Projectfdfc-It's to ensure turbo longevity by relieving boost pressure to the atmosphere when throttle lifted. A POP OFF Valve will release pressure above a set amout to ensure engine life. A POV however should not be installed/used as a boost limiter. If used continuously shortened turbo life will be encountered as it will cause the turbo to actually spin at higher speeds.
09-12-04, 02:30 PM
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lol So many different things in here.
A blow off vlave vents excess pressure that builds up when your throttle plates are CLOSED. If you dont have one, the hig pressure charge has nowhere to go and will run back into the compressor wheel. This is not good for the turbo and can lead to bearing failure.
A pop off valve releases excess pressure caused from a boost spike or faulty wastegate. Its a last ditch safety device and SHOULD NOT be used to control boost. When a pop off valve is released, and you stay on the gas, you may continue to see the same boost, but your turbo is overspinning to outrageous numbers. This will also lead to bearing failure and/or turbine/compressor wheel damage. If you are using a POV, and it gets triggered, LET OFF THE GAS and find out what caused the boost spike.
A blow off vlave vents excess pressure that builds up when your throttle plates are CLOSED. If you dont have one, the hig pressure charge has nowhere to go and will run back into the compressor wheel. This is not good for the turbo and can lead to bearing failure.
A pop off valve releases excess pressure caused from a boost spike or faulty wastegate. Its a last ditch safety device and SHOULD NOT be used to control boost. When a pop off valve is released, and you stay on the gas, you may continue to see the same boost, but your turbo is overspinning to outrageous numbers. This will also lead to bearing failure and/or turbine/compressor wheel damage. If you are using a POV, and it gets triggered, LET OFF THE GAS and find out what caused the boost spike.
09-12-04, 05:47 PM
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Better go tell all those fella's in their group A touring cars back in the 80's the used to race here in Australia (no doubt other places too..) that they had it all wrong....
The sierra cossies' used to push about 40psi around the track. Now if anyone here can tell to me, with a straight face, that 40psi around a race track is less abuse than any street car... you've got to be kidding yourself.
If there were an advantage to running a BOV i'm sure they, and most other forms of racing with turbocharged cars, would put one on. Especialy in a racing environment where finishing a race is very important...
Not too mention those companies like Nissan, Holden, mitsubishi and i'm sure many others, that have released cars without BOV's (funnily enough, before most of the current emmissions rules were brought in...). They must not have thought about turbo longetivity either.. Silly big companies..
For the risk of repeating myself...
They're an emmission control measure..
For nosie, also to stop the MAF getting fooled into thinking there is air flowing into the engine when, in fact, it could be flowing the opposite way (out the meter, from the air being pushed back out the turbo inducer).
These are real problems for companies..
But hey, you guys keep running BOV's and keep those companies in business.
No skin off my nose.
The sierra cossies' used to push about 40psi around the track. Now if anyone here can tell to me, with a straight face, that 40psi around a race track is less abuse than any street car... you've got to be kidding yourself.
If there were an advantage to running a BOV i'm sure they, and most other forms of racing with turbocharged cars, would put one on. Especialy in a racing environment where finishing a race is very important...
Not too mention those companies like Nissan, Holden, mitsubishi and i'm sure many others, that have released cars without BOV's (funnily enough, before most of the current emmissions rules were brought in...). They must not have thought about turbo longetivity either.. Silly big companies..
For the risk of repeating myself...
They're an emmission control measure..
For nosie, also to stop the MAF getting fooled into thinking there is air flowing into the engine when, in fact, it could be flowing the opposite way (out the meter, from the air being pushed back out the turbo inducer).
These are real problems for companies..
But hey, you guys keep running BOV's and keep those companies in business.
No skin off my nose.
09-12-04, 08:15 PM
#14
Originally Posted by White_FC
Better go tell all those fella's in their group A touring cars back in the 80's the used to race here in Australia (no doubt other places too..) that they had it all wrong....
The sierra cossies' used to push about 40psi around the track. Now if anyone here can tell to me, with a straight face, that 40psi around a race track is less abuse than any street car... you've got to be kidding yourself.
If there were an advantage to running a BOV i'm sure they, and most other forms of racing with turbocharged cars, would put one on. Especialy in a racing environment where finishing a race is very important...
Not too mention those companies like Nissan, Holden, mitsubishi and i'm sure many others, that have released cars without BOV's (funnily enough, before most of the current emmissions rules were brought in...). They must not have thought about turbo longetivity either.. Silly big companies..
Let me say this-I do agree that on race engines BOV are not used. A fellow that races Toyota-2TC engine-1588 cc 2 valves-After mods 358HP @ 15 lbs. Engine life is about 6 hours. 12 psi 310HP @ 15 hours of engine life. So I must say, if rebuilding the turbo, etc is your bag, don't use a BOV, but if longevity is a consideration, keep the bOV in there.
For the risk of repeating myself...
They're an emmission control measure..
For nosie, also to stop the MAF getting fooled into thinking there is air flowing into the engine when, in fact, it could be flowing the opposite way (out the meter, from the air being pushed back out the turbo inducer).
These are real problems for companies..
But hey, you guys keep running BOV's and keep those companies in business.
No skin off my nose.
The sierra cossies' used to push about 40psi around the track. Now if anyone here can tell to me, with a straight face, that 40psi around a race track is less abuse than any street car... you've got to be kidding yourself.
If there were an advantage to running a BOV i'm sure they, and most other forms of racing with turbocharged cars, would put one on. Especialy in a racing environment where finishing a race is very important...
Not too mention those companies like Nissan, Holden, mitsubishi and i'm sure many others, that have released cars without BOV's (funnily enough, before most of the current emmissions rules were brought in...). They must not have thought about turbo longetivity either.. Silly big companies..
Let me say this-I do agree that on race engines BOV are not used. A fellow that races Toyota-2TC engine-1588 cc 2 valves-After mods 358HP @ 15 lbs. Engine life is about 6 hours. 12 psi 310HP @ 15 hours of engine life. So I must say, if rebuilding the turbo, etc is your bag, don't use a BOV, but if longevity is a consideration, keep the bOV in there.
For the risk of repeating myself...
They're an emmission control measure..
For nosie, also to stop the MAF getting fooled into thinking there is air flowing into the engine when, in fact, it could be flowing the opposite way (out the meter, from the air being pushed back out the turbo inducer).
These are real problems for companies..
But hey, you guys keep running BOV's and keep those companies in business.
No skin off my nose.
09-12-04, 09:38 PM
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Dude, a racing team would not on purpose kill a $1000 turbo if adding a <$50 part would fix it.
Not having a BOV will not kill your bearings....
Doesn't matter what sort of volume of air we're talking about lets face it, the pressures, lets call it < 40 PSI, seen in an engine is not going to hurt the metal wheel of the turbo or put any much side loading onto the bearing at all... The side load created by the exhaust pulses on the exhaust wheel would be MUCH more than the side loading from air rushing back out.
Further to that, the compressor wheel generally will keep moving in the normal direction when you let off even without a BOV, it wont stall on a normal shift. It just cavitates, this means basically it has a 'bubble' of air around the wheel protecting it from the pressure of the air being exerted against it.
There is much to be learnt from people who race cars.. They're generally right in what they do in terms of trying too keep an engine and it associated parts together.
Not having a BOV will not kill your bearings....
Doesn't matter what sort of volume of air we're talking about lets face it, the pressures, lets call it < 40 PSI, seen in an engine is not going to hurt the metal wheel of the turbo or put any much side loading onto the bearing at all... The side load created by the exhaust pulses on the exhaust wheel would be MUCH more than the side loading from air rushing back out.
Further to that, the compressor wheel generally will keep moving in the normal direction when you let off even without a BOV, it wont stall on a normal shift. It just cavitates, this means basically it has a 'bubble' of air around the wheel protecting it from the pressure of the air being exerted against it.
There is much to be learnt from people who race cars.. They're generally right in what they do in terms of trying too keep an engine and it associated parts together.
09-12-04, 11:39 PM
#17
ACBron Motorsport
i havent run a BOV on my turbo for over 6 months now, it runs fine and there has been now notcible wear in that time. and i dont have to put up with that crappy "look at me" "pssch" sound 
Fact is exhaust gasses spool up your turbo and if you get off the throttle, the exhaust gasses slow and so does you turbo, BOV or not! every one seems to forget about the hot side of the turbo when talking about BOV's for some reason.
Fact is exhaust gasses spool up your turbo and if you get off the throttle, the exhaust gasses slow and so does you turbo, BOV or not! every one seems to forget about the hot side of the turbo when talking about BOV's for some reason.
09-13-04, 12:40 AM
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Originally Posted by RotaryWeaponSE7EN
Well lets say someone on this forum has a 405rwhp AE. That is also his daily driver. On that car he has bov. I take it its for the best. Just my .02 cents.
In other late breaking news theres someone on this forum who has turned his air pump into a supercharger to give his n/a engine 100kw more. I take it this was also for the best. Just my 0.02+10% cents.
09-13-04, 01:00 AM
#19
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I haven't used a BOV in about 12 months. That includes a few trips to the race track for track days. The turbo is still as good as ever.
Someone mentioned it already, but factory cars have BOVs to reduce the noise. It says as much in the factory service manuals for both FCs and FDs. That should settle that!
Your turbo will not spin backwards when you close your throttle, and you won't cause any more wear than just normal turbo usage will do. It's purely personal preference as to whether you want to run one or not. I choose not too, because they sound like ****, and do nothing.
Someone mentioned it already, but factory cars have BOVs to reduce the noise. It says as much in the factory service manuals for both FCs and FDs. That should settle that!
Your turbo will not spin backwards when you close your throttle, and you won't cause any more wear than just normal turbo usage will do. It's purely personal preference as to whether you want to run one or not. I choose not too, because they sound like ****, and do nothing.
09-13-04, 06:35 AM
#20
have yall ever seen a intake pip explode under the hood? ( well not explode, just shoot the couplers off ).
the point of a bov is to prevent it from presureizing too quickly. and yes it does destroy your turbo, but it takes a painfully long time. im talking years.
the pones who dont use bovs dont use them because their stupid.
its just like saying a wastegate has no purpose.
everything oyu put into a car has a purpose and does something to help the engine. PERIOD. poopies guys you know this.
the point of a bov is to prevent it from presureizing too quickly. and yes it does destroy your turbo, but it takes a painfully long time. im talking years.
the pones who dont use bovs dont use them because their stupid.
its just like saying a wastegate has no purpose.
everything oyu put into a car has a purpose and does something to help the engine. PERIOD. poopies guys you know this.
09-13-04, 09:39 AM
#21
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Originally Posted by SirCygnus
have yall ever seen a intake pip explode under the hood? ( well not explode, just shoot the couplers off ).
the point of a bov is to prevent it from presureizing too quickly. and yes it does destroy your turbo, but it takes a painfully long time. im talking years.
the pones who dont use bovs dont use them because their stupid.
its just like saying a wastegate has no purpose.
everything oyu put into a car has a purpose and does something to help the engine. PERIOD. poopies guys you know this.
the point of a bov is to prevent it from presureizing too quickly. and yes it does destroy your turbo, but it takes a painfully long time. im talking years.
the pones who dont use bovs dont use them because their stupid.
its just like saying a wastegate has no purpose.
everything oyu put into a car has a purpose and does something to help the engine. PERIOD. poopies guys you know this.
Yeah I have seen an intercooler hose blow off before... In my engine bay.. No big deal, tighened the thing back on and never had a problem again.
and the point of a BOV has nothing to do with protecting intake piping from pressure spikes. and either way, the pressure has to go somewhere? Stock it is fed through a rather small diameter hose, that coincidently people never seem to have problems with 'exploding'.
and no, it doesn't destroy your turbo.
and I have no idea what the f*ck a 'pone' is... but let me assure you that you are calling some very smart people with alot of time and money invested in their cars stupid. Which is, in itself, stupid.
and no this has nothing to do with calling a wastegate stupid. It is there to control how much exhaust you let through the turbine wheel? I really don't see how that has any relevance here...
and at last i agree with you on something. BOV's do have a purpose, a big one at that, it also has a fair bit to do with the engine. It's called emissions, wether it be noise or pollution.
09-13-04, 09:54 AM
#22
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The lack of a proper BOV causes compressor surge which can kill a turbo in a very short time depending on the turbo itself as well as the amount of boost being run. I know someone w/ an Eclipse turbo convertible automatic who insisted on NOT running a BOV when he made hard IC piping. His reasoning was that it was an automatic and you have constant load on the motor during shifts since you don't lift off. After blowing 2 brand new 16G's in a matter of months running 20 psi, he finally put an HKS SS BOV in and that turbo hasn't been removed in 2 years.
09-13-04, 10:11 AM
#23
I find this topic very interesting in that we have established two completely opposite points of view. Needless to say I believe all responses should be in a polite and proper manner.
Having said that, I would like to know why the factory places a blow off valve on their cars if it's not needed. It's certainly not there to make noise, and I cannot see how emisions are controlled by this valve as throttle plates are closed so no pressurized air enters the system to cause a disruption in mixture.
Just curious for an explanation, and always eager to learn.
Having said that, I would like to know why the factory places a blow off valve on their cars if it's not needed. It's certainly not there to make noise, and I cannot see how emisions are controlled by this valve as throttle plates are closed so no pressurized air enters the system to cause a disruption in mixture.
Just curious for an explanation, and always eager to learn.
09-13-04, 02:07 PM
#24
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yea holy ****.. i started a shitstorm. But yea I after all the reading, I would say that the BOV is only necessary on very large turbos to reduce large pressures on the turbo itself. I think its pretty much useless for anything thats stock.