BOV Operation?
05-04-2013, 02:40 PM
#1
BOV Operation? Finally got my turbo kit on and to the point of testing it out. One thing that's concerning me is how the BOV is functioning. It's an RPS 50mm unit that came with my kit. It has the heavy spring in there because with the light one it was always open at idle.
With the heavy spring it will only open a smidgen at full vacuum (~23 inHg), but not even enough to let out any air. But when I close the throttle at more than about 2-3 psi of boost the BOV will open. The turbo will also start fluttering before the BOV opens, and it's a noticeable gap between these two events, probably up to 1/2 second. Once the BOV opens the fluttering stops. If I close the throttle at less than 2-3 psi the BOV stays shut and the turbo just flutters.
Is this okay, or should I trim the BOV spring down so it opens sooner? I pulled it apart and inspected it, seems fine mechanically.
With the heavy spring it will only open a smidgen at full vacuum (~23 inHg), but not even enough to let out any air. But when I close the throttle at more than about 2-3 psi of boost the BOV will open. The turbo will also start fluttering before the BOV opens, and it's a noticeable gap between these two events, probably up to 1/2 second. Once the BOV opens the fluttering stops. If I close the throttle at less than 2-3 psi the BOV stays shut and the turbo just flutters.
Is this okay, or should I trim the BOV spring down so it opens sooner? I pulled it apart and inspected it, seems fine mechanically.
05-04-2013, 05:39 PM
#2
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I have noticed the exact same thing. I am interested to hear what people say or if there is an inbetween spring thats known to work. Im only going to run around 10psi and the heavy spring is just not responsive enough and rarely ever vents more than a little bit
05-04-2013, 05:57 PM
#3
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I was just wondering the same thing. Bc I noticed this same thing with my rps 50mm. I haven't driven my car yet but was wondering if it should be venting at idle or closed
05-04-2013, 06:00 PM
#4
From what I read it should not be open at idle or cruise. But I think its weird that it doesn't open at full vacuum. Also the gap in time between the turbo fluttering and the bov opening is concerning. All I know is fluttering isn't good.
05-04-2013, 10:14 PM
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Build boost and let out of it, it opens up to release the pressure then closes back up. This way the turbine does have to work so hard to spool back up. I found info on it from a few different websites
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05-05-2013, 06:53 PM
#8
I just did some digging on this and from what I get out of it. Its supposed to be closed at idle No...Open at idle and when NOT under boost and part throttle crusing. When you hammer on it and
Build boost and let out of it, it opens up to release the pressure then closes back up. Under boost or when manifold vacuum drops...spring pressure closes the valve.This way the turbine does have to work so hard to spool back up. I found info on it from a few different websites
Build boost and let out of it, it opens up to release the pressure then closes back up. Under boost or when manifold vacuum drops...spring pressure closes the valve.This way the turbine does have to work so hard to spool back up. I found info on it from a few different websites
You may wanna re-read the info, or check your sources for accuracy
05-05-2013, 07:08 PM
#9
You think it should be open at idle and cruise? I don't believe that is correct. Keep in mind some peoples turbos don't even spin at idle, so the engine will be sucking in air through the open BOV at idle. Mine spins at idle but not very quickly
05-05-2013, 07:27 PM
#10
Yes... Wide open at idle. You should have manifold vacuum to the BOV.
You don't want or need boost at idle.. And yes it will pull air in before throttle plate.
The purpose of the BOV is to limit the amount of surge back to the compressor when boost is built and the throttle is closed. Understand?
05-05-2013, 08:52 PM
#12
Yes... Wide open at idle. You should have manifold vacuum to the BOV.
You don't want or need boost at idle.. And yes it will pull air in before throttle plate.
The purpose of the BOV is to limit the amount of surge back to the compressor when boost is built and the throttle is closed. Understand?
You don't want or need boost at idle.. And yes it will pull air in before throttle plate.
The purpose of the BOV is to limit the amount of surge back to the compressor when boost is built and the throttle is closed. Understand?
05-05-2013, 09:12 PM
#13
I have always just shimmed lighter springs if the heavy one too much and the light one is opening at idle. When I contacted Tial years ago, this is what they recommended in order to keep it CLOSED at idle and cruise. I am sorry, but I don't want random unfiltered crap sucked in through my BOV and apparently Tial agrees as they said to shim it. On a MAF car if the BOV is post MAF this would also cause a big issue as it would be letting in unmetered air.
05-06-2013, 12:13 AM
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When my car was procharged it completely understood how it worked. I figured it would be the same way with the turbo. I got mixed up for some reason after reading a few things apparently. My bad on any miss info to anyone.
I just like the OP want to make sure everything is working correctly
I just like the OP want to make sure everything is working correctly
05-06-2013, 11:18 AM
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I have always just shimmed lighter springs if the heavy one too much and the light one is opening at idle. When I contacted Tial years ago, this is what they recommended in order to keep it CLOSED at idle and cruise. I am sorry, but I don't want random unfiltered crap sucked in through my BOV and apparently Tial agrees as they said to shim it. On a MAF car if the BOV is post MAF this would also cause a big issue as it would be letting in unmetered air.
Ive had to use washers to shim a bov before, its crude but works well.
Last edited by thor'svr4; 05-06-2013 at 11:24 AM.
05-14-2013, 10:25 AM
#17
wanted to update this for the guys working with RPS 50mm BOV's.
ran into the exact same issue when I fired the car ive been building. car idles around 14" of vacuum. Heavy spring wouldnt let it open (opened around 25" on a vacuum pump) light spring was wide open at idle (opened around 11" on a vacuum pump) and wouldnt shut on a free rev
tried shimming the light spring which got it shut but ran into a coil bind issue and wouldnt let it open all the way. Called RPS (guys are awesome btw) and they recommended either purchasing a TIAL spring or the less expensive option of cutting down the heavy spring.
Started cutting down the heavy spring and reshaping the end curve to sit correctly. Started with 2 coils from the end tip and then went a half coil at a time. Ended up with 4 total coils and its perfect now. Just comes off the seat at idle but still shut, shuts on a free rev, opens with the throttle is closed, back to close at idle. Again this is a car idling at 14"
FWIW
ran into the exact same issue when I fired the car ive been building. car idles around 14" of vacuum. Heavy spring wouldnt let it open (opened around 25" on a vacuum pump) light spring was wide open at idle (opened around 11" on a vacuum pump) and wouldnt shut on a free rev
tried shimming the light spring which got it shut but ran into a coil bind issue and wouldnt let it open all the way. Called RPS (guys are awesome btw) and they recommended either purchasing a TIAL spring or the less expensive option of cutting down the heavy spring.
Started cutting down the heavy spring and reshaping the end curve to sit correctly. Started with 2 coils from the end tip and then went a half coil at a time. Ended up with 4 total coils and its perfect now. Just comes off the seat at idle but still shut, shuts on a free rev, opens with the throttle is closed, back to close at idle. Again this is a car idling at 14"
FWIW
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Q8y_drifter (10-27-2023)
05-14-2013, 10:59 AM
#18
wanted to update this for the guys working with RPS 50mm BOV's.
ran into the exact same issue when I fired the car ive been building. car idles around 14" of vacuum. Heavy spring wouldnt let it open (opened around 25" on a vacuum pump) light spring was wide open at idle (opened around 11" on a vacuum pump) and wouldnt shut on a free rev
tried shimming the light spring which got it shut but ran into a coil bind issue and wouldnt let it open all the way. Called RPS (guys are awesome btw) and they recommended either purchasing a TIAL spring or the less expensive option of cutting down the heavy spring.
Started cutting down the heavy spring and reshaping the end curve to sit correctly. Started with 2 coils from the end tip and then went a half coil at a time. Ended up with 4 total coils and its perfect now. Just comes off the seat at idle but still shut, shuts on a free rev, opens with the throttle is closed, back to close at idle. Again this is a car idling at 14"
FWIW
ran into the exact same issue when I fired the car ive been building. car idles around 14" of vacuum. Heavy spring wouldnt let it open (opened around 25" on a vacuum pump) light spring was wide open at idle (opened around 11" on a vacuum pump) and wouldnt shut on a free rev
tried shimming the light spring which got it shut but ran into a coil bind issue and wouldnt let it open all the way. Called RPS (guys are awesome btw) and they recommended either purchasing a TIAL spring or the less expensive option of cutting down the heavy spring.
Started cutting down the heavy spring and reshaping the end curve to sit correctly. Started with 2 coils from the end tip and then went a half coil at a time. Ended up with 4 total coils and its perfect now. Just comes off the seat at idle but still shut, shuts on a free rev, opens with the throttle is closed, back to close at idle. Again this is a car idling at 14"
FWIW
