To much boost
- Thread starter swich
- Start date
Most bov's are rated for certain psi before they start to leak. which im not exactly sure what that is but i think its around 30psi. So if you plan on running 30 pounds of boost or more then maybe it would work but i would never recommend it to anyone.
for positive displacement supercharged applications, some kind of boost bypass is necessary because the supercharger will continue pumping air even if the throttle plate is closed, causing the air to find the easiest way out, normally by pushing the throttle plate into the plenum. OEM supercharger applications normally use either a vacuum operated butterfly valve (basically a turbocharger wastegate) internally between the inlet and outlet of the supercharger or an externally routed electronically controlled vacuum-switching-bypass-valve to elimate boost spikes and engine damage
centrifugal superchargers technically need no such bypass as they are basically the compressor side of a turbocharger. you'll just get some mad off-throttle surge noise, and ALOT more engine braking. in high-abuse applications this can possibly be damaging as most gear sets aren't built to take the kind of axial load applied by high boost compressor surge. this normally isn't a problem, though, as almost all centrifugal superchargers are aftermarket, provided in kit form, and come with some kind of bypassing feature.
a "dump valve" is, anymore, a different term for a BOV. a BOV vents excess boost to atmosphere, a BPV vents that boost into the inlet of the supercharger. this is both quieter and easier on engine management systems than a BOV tends to be.
a proper supercharger setup uses pulley sizing to dictate boost levels. using a BOV or BPV to do so can be easier and more flexible but tends to be loud, creates a weak point in the system, and causes problems. most problems stem from the use of a BOV and the nature with which it operates off and on boost. the simplest remedy for this is to use valving designed for supercharged applications or spend good money for a well made kit (most of the better kits use positive displacement superchargers with built in bypassing).
centrifugal superchargers technically need no such bypass as they are basically the compressor side of a turbocharger. you'll just get some mad off-throttle surge noise, and ALOT more engine braking. in high-abuse applications this can possibly be damaging as most gear sets aren't built to take the kind of axial load applied by high boost compressor surge. this normally isn't a problem, though, as almost all centrifugal superchargers are aftermarket, provided in kit form, and come with some kind of bypassing feature.
a "dump valve" is, anymore, a different term for a BOV. a BOV vents excess boost to atmosphere, a BPV vents that boost into the inlet of the supercharger. this is both quieter and easier on engine management systems than a BOV tends to be.
a proper supercharger setup uses pulley sizing to dictate boost levels. using a BOV or BPV to do so can be easier and more flexible but tends to be loud, creates a weak point in the system, and causes problems. most problems stem from the use of a BOV and the nature with which it operates off and on boost. the simplest remedy for this is to use valving designed for supercharged applications or spend good money for a well made kit (most of the better kits use positive displacement superchargers with built in bypassing).
Thanks killer that is very helpful
I have seen guys putting the 4gze charger on the D motors. they use BPV on there setups.
I dont really understand how these devices work. I know what they are for but dont know how they work.
Is there a way to get them to open/bypass as soon as you tap off the throtle?
i understand that they get rid of unwanted boost. but does a waste gate not do they same thing?
If you where to limit they amount of boost going to the engine to say 7psi then when you tap off or close the throtle the boost spick would get let out by the waste gate?
or have i got this all wrong?
I have seen guys putting the 4gze charger on the D motors. they use BPV on there setups.
I dont really understand how these devices work. I know what they are for but dont know how they work.
Is there a way to get them to open/bypass as soon as you tap off the throtle?
i understand that they get rid of unwanted boost. but does a waste gate not do they same thing?
If you where to limit they amount of boost going to the engine to say 7psi then when you tap off or close the throtle the boost spick would get let out by the waste gate?
or have i got this all wrong?
the 4a-gze charger is an Ogura SC12 roots supercharger that uses an electronically controlled vacuum-switching-bypass-valve (VSV in toyota speak) to divert boost during on-boost closed-throttle situations. i'm sure it's not hard to replace it with a vacuum controlled bypass valve.
a BOV or BPV contain a chamber that is hooked up via a vacuum line to the intake manifold. this chamber acts upon a piston that closes the valve and is spring assisted. when you close the throttle this chamber sees vacuum and the pressure on the piston causes the valve to open. when you open the throttle the chamber should be equalized to the pressure on the piston and the spring then closes the valve. too easy, right?
a BOV or BPV contain a chamber that is hooked up via a vacuum line to the intake manifold. this chamber acts upon a piston that closes the valve and is spring assisted. when you close the throttle this chamber sees vacuum and the pressure on the piston causes the valve to open. when you open the throttle the chamber should be equalized to the pressure on the piston and the spring then closes the valve. too easy, right?
when you reach your set PSI of boost your wastegate opens ... so you do not gain anymore boost - it just keeps pushing ... lets say 8 psi ... when you let off the throttle ... the air that is left over and not able to go into the engine because your throttle body is closed ... will go backwards down the charge pipe and back into your turbo - to prevent this from happening a blow off valve is installed so that when the air comes backwards the blow off valve opens to release the excess air that is traveling backwards to atmosphere ... thats the way I understand it all ...
thank killer
So then its just the matter of setting up a BPV from the boost site to the intake side of the SC and then up to the throtle/intake manifold of the engine?
Seems simple when put like that. Do you have or know any where i can get i diagram to show me how to do this?
Now what is better a blow of valve or bypass valve?
But as far as i know SC are already limited to a certain amout of boost so i wont need a waste gate will i?
So then its just the matter of setting up a BPV from the boost site to the intake side of the SC and then up to the throtle/intake manifold of the engine?
Seems simple when put like that. Do you have or know any where i can get i diagram to show me how to do this?
Now what is better a blow of valve or bypass valve?
But as far as i know SC are already limited to a certain amout of boost so i wont need a waste gate will i?
right, your psi is based on what pullies you run