BOV question
11-25-2009, 02:03 AM
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11-25-2009, 02:06 AM
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the spring is not for how much boost it can hold. TiAL is known for holding big boost. the spring is based off of your engine vacuum. my LSJ car idles around 16-18 inches of vacuum so i need a 8psi spring
11-26-2009, 09:48 PM
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11-27-2009, 12:15 PM
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theres no downfall to performance. you can hold more boost with an atmospheric bov. personally tial is the best and is know for being on almost every single fast turbo car. the flow rate over others is just awesome. i run the tial q but its off the car for winter time(i like keep my parts salt free) but i vent to the atmosphere instead of recirculating. the tial is quieter then most bov's.
01-20-2010, 01:59 AM
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and as far as BOV vs Recirc....if you want quicker turbo response and a lowered possibility of running rich, then go recirculated as your MAF has already measured the air that is coming in and if you vent atmospheric, then the air isn't there and the car can run rich, this is decreased with recirculated....
taken from WRX forums
STOCK BPV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the stock spring is not very strong, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
ATMOSPHERIC BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the since the spring is heavier in aftermarket applications, the excess air creates a back-pressure by having nowhere to go other than back where it came from... The turbo's compressor wheel receives resistance and can stall. This is referred to as Compressor Surge. This can seriously damage your turbo over time. The second ill effect is that your ECU has demanded fuel, but that air is not routed back to the intake, thus causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust in cat-less application).
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose the opening and vents that excess boost off to the atmosphere. This creates a very rich moment during the shift, because your ECU has demanded fuel, but that air is not routed back to the intake, again causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust).
**Additional Notes** - If the valve is adjusted to a lighter spring tension, you will effectively prevent the stalling, but it will also allow the piston to push too easily creating boost leak, before you even reach your target boost pressures. Now you may think you have a "perfectly tuned" the valve.. But this is VERY unlikely, because boost pressures vary. Your valve's spring will ALWAYS be too strong or too tight. Causing boost leak, or compressor Surge, and always leading to that rich mixture between shifts.
HYBRID or 50/50 BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, the piston is only pushed far enough to reveal the first opening which routes the excess boost to flow back to the intake. (Just like stock)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose both openings: theoretically this satisfies the plumb back to the intake, and then vents off any additional boost off to the atmosphere.
**Additional Notes** - The idea behind a Hybrid valve is simple and effective. It's got two openings. One to plumb back to the intake, and one to vent to atmosphere. The Vent opening is further back than the Intake opening, so that under light load and light boost levels, the valve functions EXACTLY like a by pass valve. But once you're shifting under full boost, there is so much pressure that the piston is pushed even further back revealing BOTH openings. Theres only so much boost that first opening can plumb back in that moment, so the rest is vented off to the atmosphere.
---------
The Mechanics of it all: The movement of the piston isn't entirely dependent on Spring Tension alone. One of the largest contributing factors to the function of the BPV is pressure differential between the intake tract and intake manifold. This applies to all the valves mentioned above. Basically, when the vehicle is under boost with your foot to the floor, the pressure in the intake tract and the intake manifold are the same keeping the piston in place. Once you let off the throttle and the plate closes off, the turbo is still pulling air through the intake tract continuing to build pressure, but the intake manifold goes into vacuum. In this case, one side of the piston loses pressure and the piston moves, opening the BOV/BPV.
---------
"Rabble! Rabble! Don't put BOVs on MAF metered engines!!!" - Many people will also mention MAF readings being a reason why you shouldn't put a BOV on the car. And while some people may just regurgitate the information without knowing what's going on, I know there are those who are interested in knowing. Basically, if you refer to the diagram below, you will see air entering the ram scoop, through the air box and past the MAF sensor. The MAF sensor reads the amount of air passing through and sends the information to the ECU. Your ECU will demand the proper amount of fuel to counteract it in order to maintain proper Air/Fuel ratios. Look at where the BPV is placed. It's after the turbocharger and before the intake manifold. If you Blow Off the excess air, recall that the same air was initially metered and accounted for by your MAF sensor on it's way in through the intake. So while your ECU is counting on that air to be re-routed back to the intake tract(specifically into the turbo inlet hose), blowing that air off will result in a rich mixture of A/F and you will burn VERY rich during the shift. While some after market companies may refer to it as a 'cooling effect', it does have some negative effects over time and can seriously cause damage to your engine and/or turbocharger.
Hope this helps!!
01-21-2010, 12:58 PM
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True and False....if the BOV is a push type where the boost is pushing opposite the spring...then a stiffer spring is needed....if the BOV is a pull type (SSQV) then that's fine. The spring pressure is vac vs. boost pressure....if you have the push type with a 8 psi spring and you are trying to push 12psi...won't work too well
and as far as BOV vs Recirc....if you want quicker turbo response and a lowered possibility of running rich, then go recirculated as your MAF has already measured the air that is coming in and if you vent atmospheric, then the air isn't there and the car can run rich, this is decreased with recirculated....
taken from WRX forums
STOCK BPV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the stock spring is not very strong, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
ATMOSPHERIC BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the since the spring is heavier in aftermarket applications, the excess air creates a back-pressure by having nowhere to go other than back where it came from... The turbo's compressor wheel receives resistance and can stall. This is referred to as Compressor Surge. This can seriously damage your turbo over time. The second ill effect is that your ECU has demanded fuel, but that air is not routed back to the intake, thus causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust in cat-less application).
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose the opening and vents that excess boost off to the atmosphere. This creates a very rich moment during the shift, because your ECU has demanded fuel, but that air is not routed back to the intake, again causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust).
**Additional Notes** - If the valve is adjusted to a lighter spring tension, you will effectively prevent the stalling, but it will also allow the piston to push too easily creating boost leak, before you even reach your target boost pressures. Now you may think you have a "perfectly tuned" the valve.. But this is VERY unlikely, because boost pressures vary. Your valve's spring will ALWAYS be too strong or too tight. Causing boost leak, or compressor Surge, and always leading to that rich mixture between shifts.
HYBRID or 50/50 BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, the piston is only pushed far enough to reveal the first opening which routes the excess boost to flow back to the intake. (Just like stock)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose both openings: theoretically this satisfies the plumb back to the intake, and then vents off any additional boost off to the atmosphere.
**Additional Notes** - The idea behind a Hybrid valve is simple and effective. It's got two openings. One to plumb back to the intake, and one to vent to atmosphere. The Vent opening is further back than the Intake opening, so that under light load and light boost levels, the valve functions EXACTLY like a by pass valve. But once you're shifting under full boost, there is so much pressure that the piston is pushed even further back revealing BOTH openings. Theres only so much boost that first opening can plumb back in that moment, so the rest is vented off to the atmosphere.
---------
The Mechanics of it all: The movement of the piston isn't entirely dependent on Spring Tension alone. One of the largest contributing factors to the function of the BPV is pressure differential between the intake tract and intake manifold. This applies to all the valves mentioned above. Basically, when the vehicle is under boost with your foot to the floor, the pressure in the intake tract and the intake manifold are the same keeping the piston in place. Once you let off the throttle and the plate closes off, the turbo is still pulling air through the intake tract continuing to build pressure, but the intake manifold goes into vacuum. In this case, one side of the piston loses pressure and the piston moves, opening the BOV/BPV.
---------
"Rabble! Rabble! Don't put BOVs on MAF metered engines!!!" - Many people will also mention MAF readings being a reason why you shouldn't put a BOV on the car. And while some people may just regurgitate the information without knowing what's going on, I know there are those who are interested in knowing. Basically, if you refer to the diagram below, you will see air entering the ram scoop, through the air box and past the MAF sensor. The MAF sensor reads the amount of air passing through and sends the information to the ECU. Your ECU will demand the proper amount of fuel to counteract it in order to maintain proper Air/Fuel ratios. Look at where the BPV is placed. It's after the turbocharger and before the intake manifold. If you Blow Off the excess air, recall that the same air was initially metered and accounted for by your MAF sensor on it's way in through the intake. So while your ECU is counting on that air to be re-routed back to the intake tract(specifically into the turbo inlet hose), blowing that air off will result in a rich mixture of A/F and you will burn VERY rich during the shift. While some after market companies may refer to it as a 'cooling effect', it does have some negative effects over time and can seriously cause damage to your engine and/or turbocharger.
Hope this helps!!
and as far as BOV vs Recirc....if you want quicker turbo response and a lowered possibility of running rich, then go recirculated as your MAF has already measured the air that is coming in and if you vent atmospheric, then the air isn't there and the car can run rich, this is decreased with recirculated....
taken from WRX forums
STOCK BPV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the stock spring is not very strong, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, so that excess air is effectively routed back to the intake tract. (The MAF sensor expects this excess air to be plumbed back to the intake, so the ECU demands more fuel to balance the A/F ratio.)
ATMOSPHERIC BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, and the since the spring is heavier in aftermarket applications, the excess air creates a back-pressure by having nowhere to go other than back where it came from... The turbo's compressor wheel receives resistance and can stall. This is referred to as Compressor Surge. This can seriously damage your turbo over time. The second ill effect is that your ECU has demanded fuel, but that air is not routed back to the intake, thus causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust in cat-less application).
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose the opening and vents that excess boost off to the atmosphere. This creates a very rich moment during the shift, because your ECU has demanded fuel, but that air is not routed back to the intake, again causing an extremely rich moment between the shift (Often resulting in a fire ball out the exhaust).
**Additional Notes** - If the valve is adjusted to a lighter spring tension, you will effectively prevent the stalling, but it will also allow the piston to push too easily creating boost leak, before you even reach your target boost pressures. Now you may think you have a "perfectly tuned" the valve.. But this is VERY unlikely, because boost pressures vary. Your valve's spring will ALWAYS be too strong or too tight. Causing boost leak, or compressor Surge, and always leading to that rich mixture between shifts.
HYBRID or 50/50 BOV:
* When the throttle is open - The piston is not under pressure, so the compressed air from the turbo flows right through.
* When the throttle is closed at low boost levels (Example: Shifting around 2200 RPM) - The piston is under light pressure, the piston is only pushed far enough to reveal the first opening which routes the excess boost to flow back to the intake. (Just like stock)
* When the throttle is closed at high boost levels (Example: Shifting around 4500 RPM) - The piston is under heavy pressure, and the piston moves far enough to expose both openings: theoretically this satisfies the plumb back to the intake, and then vents off any additional boost off to the atmosphere.
**Additional Notes** - The idea behind a Hybrid valve is simple and effective. It's got two openings. One to plumb back to the intake, and one to vent to atmosphere. The Vent opening is further back than the Intake opening, so that under light load and light boost levels, the valve functions EXACTLY like a by pass valve. But once you're shifting under full boost, there is so much pressure that the piston is pushed even further back revealing BOTH openings. Theres only so much boost that first opening can plumb back in that moment, so the rest is vented off to the atmosphere.
---------
The Mechanics of it all: The movement of the piston isn't entirely dependent on Spring Tension alone. One of the largest contributing factors to the function of the BPV is pressure differential between the intake tract and intake manifold. This applies to all the valves mentioned above. Basically, when the vehicle is under boost with your foot to the floor, the pressure in the intake tract and the intake manifold are the same keeping the piston in place. Once you let off the throttle and the plate closes off, the turbo is still pulling air through the intake tract continuing to build pressure, but the intake manifold goes into vacuum. In this case, one side of the piston loses pressure and the piston moves, opening the BOV/BPV.
---------
"Rabble! Rabble! Don't put BOVs on MAF metered engines!!!" - Many people will also mention MAF readings being a reason why you shouldn't put a BOV on the car. And while some people may just regurgitate the information without knowing what's going on, I know there are those who are interested in knowing. Basically, if you refer to the diagram below, you will see air entering the ram scoop, through the air box and past the MAF sensor. The MAF sensor reads the amount of air passing through and sends the information to the ECU. Your ECU will demand the proper amount of fuel to counteract it in order to maintain proper Air/Fuel ratios. Look at where the BPV is placed. It's after the turbocharger and before the intake manifold. If you Blow Off the excess air, recall that the same air was initially metered and accounted for by your MAF sensor on it's way in through the intake. So while your ECU is counting on that air to be re-routed back to the intake tract(specifically into the turbo inlet hose), blowing that air off will result in a rich mixture of A/F and you will burn VERY rich during the shift. While some after market companies may refer to it as a 'cooling effect', it does have some negative effects over time and can seriously cause damage to your engine and/or turbocharger.
Hope this helps!!
01-21-2010, 01:23 PM
#11
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I know right.....very educational.....however I DO have a MAF metered car with NO CAT and a BOV....and i run just fine....though it is occasionally rich in between shifts and if i am getting to the gone when i shift at night...you can see a small flash of fire ball behind me....
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