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Do i really need a BOV???

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Old Feb 25, 2009 | 06:47 PM
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Default Do i really need a BOV???

I am building a rear mount system, I noticed that the STS kit does not include a BOV. I am installing the turbo on a 94' LT1 w/M6 trans. So do I need a BOV?
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Old Feb 25, 2009 | 07:01 PM
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M6 yes A4 not so much but i have one
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Old Feb 25, 2009 | 07:01 PM
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yes, you do!

you need some sort of bypass to release the pressure. when the throttle plate closes, the pressure has nowere to go. it will fight the air being pushed up and slam back into the compressor. my understanding is that it can/will cause damage to the turbo.
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Old Feb 25, 2009 | 07:03 PM
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For a stick 6 speed ,Yes! For an auto,, not really. But is a nice safty feature to stop over boosting in a bad waste gate situation, espespecially when you can change the springs settings for your max PSI level. If ever a waste gate goes bad or sticks ,the BOV will open thus protecting your engine ,head gaskets ETC and is better for the turbos when you slap off the throttle because your giving all that pressurized air somewhere to go other then slamming back into the turbo or turbo's Which is hard on them !!So,My new answer is YES LOL Now, that ive thought about it !!YES,YES,YES, LOL

It also makes a really cool sound when you let off the throttle too WOOSH!!!LOL LOL!!!!
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Old Feb 25, 2009 | 07:42 PM
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How the hell are you going to PSHHHHH S R T 4 drivers w/out a BOV? Isn't that the whole point of going FI?
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Old Oct 7, 2009 | 10:18 PM
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Originally Posted by barnat
For a stick 6 speed ,Yes! For an auto,, not really. But is a nice safty feature to stop over boosting in a bad waste gate situation, espespecially when you can change the springs settings for your max PSI level. If ever a waste gate goes bad or sticks ,the BOV will open thus protecting your engine ,head gaskets ETC and is better for the turbos when you slap off the throttle because your giving all that pressurized air somewhere to go other then slamming back into the turbo or turbo's Which is hard on them !!So,My new answer is YES LOL Now, that ive thought about it !!YES,YES,YES, LOL

It also makes a really cool sound when you let off the throttle too WOOSH!!!LOL LOL!!!!

This is an old thread but I hate to see bad infomation left out there. A bov does not protect the engine from overboost in any way. The bov needs vacuum to open, when you are boosting it will not open. The bov spring sizes are selected according to how much vacuum your car produces not how much boost you want to run.
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Old Oct 7, 2009 | 10:30 PM
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Originally Posted by unclebens
This is an old thread but I hate to see bad infomation left out there. A bov does not protect the engine from overboost in any way. The bov needs vacuum to open, when you are boosting it will not open. The bov spring sizes are selected according to how much vacuum your car produces not how much boost you want to run.

I am glad you brought this up unclebens. And you are absolutely right.
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Old Oct 7, 2009 | 10:39 PM
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Id like to add that i dont agree that you dont need a bov on an auto car. The point is to release boost pressure when the the throttle blade it slammed shut when you let out,right? So how is that any different on an auto then a m6?

Alex
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Old Oct 7, 2009 | 10:44 PM
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Originally Posted by SPRAYED 01
Id like to add that i dont agree that you dont need a bov on an auto car. The point is to release boost pressure when the the throttle blade it slammed shut when you let out,right? So how is that any different on an auto then a m6?

Alex


With an auto you are only slamming the throttle blade shut once during a run, whereas a manual transmission car it will be at every gear shift if you're not powershifting. I usually do a BOV on all of my turbo cars regardless of type of transmission.
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Old Oct 7, 2009 | 10:44 PM
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Originally Posted by SPRAYED 01
Id like to add that i dont agree that you dont need a bov on an auto car. The point is to release boost pressure when the the throttle blade it slammed shut when you let out,right? So how is that any different on an auto then a m6?

Alex
Its not simply other than you will be slamming it shut more on an M6 more than likely.... I have one on my A4.... dont know why anyone would leave it out. (If you can afford a Turbo build, you can at least afford "some kind" of BOV!)
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Old Oct 8, 2009 | 12:22 AM
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You will be killing turbos without a BOV on a gasoline engine. The transmission type has absolutely nothing to do with it so not sure why it was mentioned. Diesels don't really have one because they don't generally have a throttle body.
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Old Oct 8, 2009 | 12:28 AM
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Originally Posted by needaz28
yes, you do!

you need some sort of bypass to release the pressure. when the throttle plate closes, the pressure has nowere to go. it will fight the air being pushed up and slam back into the compressor. my understanding is that it can/will cause damage to the turbo.


yes sir.
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Old Oct 8, 2009 | 06:27 AM
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Its very boost dependant. But a BOV is not essential. It is preferred to have one when higher levels of boost are used, and on some more fragile turbo units.

But below say 10psi as a general guide, it is definately not essential.
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Old Oct 8, 2009 | 06:42 AM
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NO!!! a BOV is not needed with most of the turbos that are out today.....I ran a PT88, and a T101....a t max with no BOV, and everything is just fine.....
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Old Oct 8, 2009 | 07:57 AM
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otherwhitemeat,

That blows my mind. How long and how many runs have you had to bov.
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Old Oct 8, 2009 | 02:11 PM
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FYI I think Barnat has a BOV confused with a pop off valve.
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Old Oct 8, 2009 | 05:22 PM
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Originally Posted by SPRAYED 01
otherwhitemeat,

That blows my mind. How long and how many runs have you had to bov.
8 years without a BOV and hunderds of runs
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Old Oct 8, 2009 | 06:46 PM
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Grand nationals and Syclones/typhoons dont run a Bov.
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Old Oct 8, 2009 | 09:21 PM
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The purpose of a bov is to release pressure in the cold side so the air doesn't back up into the turbine resulting in compressor surge. Compressor surge causes the turbine to slam into a wall of air, think about the wheel spinning 100k rpm then down half of that then back to 100k rpm (not real numbers).

The turbo's lifespan will be shortened without the bov's relief. Another option is to run a bypass valve instead of a blow off valve. A bpv recirculates the release air back into the intake tract before the turbo to prevent the split second of running rich between shifts (basically its a much quieter bov).
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Old Oct 8, 2009 | 09:58 PM
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Originally Posted by imma_stocker
The purpose of a bov is to release pressure in the cold side so the air doesn't back up into the turbine resulting in compressor surge. Compressor surge causes the turbine to slam into a wall of air, think about the wheel spinning 100k rpm then down half of that then back to 100k rpm (not real numbers).

The turbo's lifespan will be shortened without the bov's relief. Another option is to run a bypass valve instead of a blow off valve. A bpv recirculates the release air back into the intake tract before the turbo to prevent the split second of running rich between shifts (basically its a much quieter bov).
True.... but now a days, all the turbos come with anti-surge covers. So again...there is not a need for a BOV, another then sound and a little spool recovery...and that's mainly for m6 cars.
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