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.

 

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

 

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

 

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.

 

I put the lighter spring in mine. It stays open at idle and cruise. With the heavier spring it wouldn't open. I don't have any issues with it.

 

I just did some digging on this and from what I get out of it. Its supposed to be closed at idle 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. 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 could shim the lighter spring

 

You may wanna re-read the info, or check your sources for accuracy

 

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

 

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?

 

i would try this.

 

Yes I know how it works, but if it's open at idle then air could be getting sucked in through the BOV, bypassing the air filter. This would only be an issue if the turbo isn't moving much air at idle.

 

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.

 

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

 

Mine is open at idle.

 

This is exactly how my BOV functions. It's closed 100% of the time unless i just let off the throttle after being in boost, then it opens and vents the air pressure between the throttle body and turbo.

Ive had to use washers to shim a bov before, its crude but works well.

 

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

 

Thanks for the update! I should have updated this also. I had the same issue shimming the light spring, I shimmed it about 1/4" and it was coil binding and still open at idle. So I cut down the heavy spring, 1.5 coils I believe, and it's good now. Closed at idle (15-16 inHg), but opens at vacuum greater than idle. So it's a little more responsive now. I also greased up the center pin to help it move smoothly. At idle mine would suck in air through the BOV, so I wanted it to be firmly closed at idle.

 

Thanks for that info Tally, deff going to try cutting down the spring

 

http://www.theturboforums.com/thread...ut-extra-surge

^^ That should let you keep the light spring but keep it closed at idle.