Blow off valve nipple???????

[Elanlover]

By the way, I'm hearing two things with this BOV. After getting it set up properly I now here the "whoosh" that's supposed to be present when I let off the gas after full throttle as the BOV opens to let pressure off the turbo. I only hear that when the turbo's been engaged. But, I also hear a second sound that was always present (sadly, leaving me to believe that the thing was installed properly to begin with).

Whenever I take my foot off the gas, doesn't matter if I'm changing gears of if the turbo's been engaged, I hear a stuttering sound that has to be air escaping from somewhere. Is that normal? I hear it every time i let off the gas with some mild acceleration or more. Making me wonder if I've got a leak in the intake piping or connectors somewhere.

Anyone with this (or another) BOV hear this as well???

Thanks!

[Monty]

That stuttering/fluttering is normal, it`s the turbo stalling and u can hear it more if u`ve got an open air filter. But the dump valve should stop this, maybe u`ve got the spring set to strong and so it doesn`t open early enough

and another thing is u shouldn`t be getting the woosh sound from the BOV on exceleration only on lift off. Unless the sound is off the turbo spooling up.

[Elanlover]

Thanks Monty. Just to be clear though, I do seem to be hearing 2 different sounds.

The first is what I'd expect (and what was missing before I installed the BOV properly). Its a "pssst" sound that comes when I've had it floored and the turbo engaged then release the throttle to change gears. This has to be the vacuum hose being attached to the nipple on the BOV because it only started when I hooked that up and its accompanied by the turbo boost gauge not dropping to 0 as quickly as it used to.

The "other" sound was there from the day I installed the new intake pipe with K&N filter and the pipe from the throttle body to the intercooler which has the BOV mounted in the middle. This sound is almost like a stutter and lasts a bit longer than the "pssst" sound. Its present whenever I have been accelerating (even lightly with no turbo engaged) and take my foot off the gas. Since the turbo's not engaged it can't be the BOV releasing due to the vacuum connection.

Its this sound that I'm trying to understand if its normal or due to another issue. Will probably open the hood tonight and have a look. I can get the car to make this sound by reving the engine while in neutral.

[F1 LOTUS]

If you're running a lot of pre-load on the BOV then what you're hearing is probably flow reversal through the compressor as pressure builds-up against the closed throttle plate. With less valve pre-load, the vacuum created on the engine side of the throttle can more easily release this pressure preventing it from back-flowing? BTW, the Turbo is always 'engaged' no matter what speed the engine is turning, just not fast enough to generate any significant pressure to register on our boost gauges.
I don't think the noise is anything to be concerned about; The stock intake system (soft rubber hoses, air box etc) serves as an effective muffler for the stuttering sounds, in my experience just changing the stock paper air filter for a drop-in K&N made the sound more audible!
Something that may be worth checking is the vacuum hose, if this is too soft it could be collapsing and effectively sealing itself and preventing the BOV opening enough to relieve the pressure?

[Elanlover]

Thanks Brian, I think the hose I installed is ok. Its relatively hard but I've no idea how hard it needs to be. I do seem to be getting the sound I need to hear when I let the foot off the gas indicating the nipple is getting enough vacuum to trigger the BOV. Good point about the turbo. Bad choice of words on my part. Should have said when the turbo is delivering measurable boost.

I spoke with the folks at Turbo XS and they say the noise is nothing to be concerned about. Doesn't happen on every car but its common. I could get a recirculating BOV and plumb it back into the intake which would eliminate the noise (or at least reduce it significantly). That's another $200 with a left over BOV in the garage

Would have to find a way to plumb it back to the intake as well. The nice pipes that Top End made would need to be cut into and a flange welded in, plus getting it powder coated all over again. Seems like a lot of work and expense. Was thinking that I could punch a hole into the top of the K&N filter though (think its metal or hard plastic) and connect a hose up there..............

[Doug]

Was thinking that I could punch a hole into the top of the K&N filter though (think its metal or hard plastic) and connect a hose up there..............

that could be done--it is plastic.

a few people made "silencers" for them a few years back--not sure if it is still in the forum or not? maybe those people are around or could be found?

[jabrown39]

I really didn't like the loud dump noise on my BOV and tried to make a silencer. I got a pneumatic silencer from www.2linc.com and hooked it up with a rubber end piece. I wrote it all up on www.brownlab.info/Elan/BOV/index.htm. It really only takes the gross edge off the noise. What is interesting is hearing the faint "duck" call noise when the pressure is reversed and dirty air is sucked in the wrong way. I am going to go the fully plumbing route with a second air box I got off of Ebay.

I am interested in knowing what everyone else came up with.

Cheers,
Jim

[Elanlover]

I'm going to try adding 2 more washers to the BOV to make the spring tighter. Turbo XS recommends a maximum of 8 washers. It ships with 6 but they are standard washers found in any hardware store. If that doesn't help I'm going to get a recirculating BOV and plumb it back into the air intake through the top of the K&N filter. I've been told that silencers "help" but not that much which seems to match your experience jabrown39.

[Nobby]

I’m toying with the fitting of a recirculating BOV and plumbing it back into the air intake through the side to help/stop the noise.

Before I start what want to know is how effective this is in reducing the noise

Can anyone who's completed this method of plumbing tell me how successful this is?

Cheers,
Nobby

[Doug]

should work pretty darn well -- for emissions reasons all new turbo cars incorporate recirc methods (unless they are low pressure and just skip the bypass completely)

FWIW, my Mitsu Evo runs 21lbs boost and you can not hear it at shifting unless you really do all you can to TRY to hear it!

[mailman221]

I would also be interested in who has tried a recirculating BOV and which brand-model? I currently have the Top End setup with the TurboXS BOV-H, H type and would like to change but would prefer one that would bolt right on to my existing plumbing. Turbo XS makes a unit #RBV - H34 which is rated for high boost application, 10 - 25 lbs. Will it open properly if I am not using full boost? Any additional opinions on this subject would be appreciated.

[Doug]

a high boost set-up may mean it will not open unless your boost is at that level when you chop the throttle--thus you may not want that one!

Many people have plumbed the bypass hose from the bypass valve and have drilled a hole in the side of the stock trashcan (air filter can) to plumb the hose into--this will muffle the noise very well IMHO and per what they have said -- though I have never heard it in that set-up I believe it would work well. If you plumb into an open air filter set-up then you will likely only partially change the sound because you will still have sound energy coming easily out of the open set-up . . .

[Elanlover]

I would also be interested in who has tried a recirculating BOV and which brand-model? I currently have the Top End setup with the TurboXS BOV-H, H type and would like to change but would prefer one that would bolt right on to my existing plumbing. Turbo XS makes a unit #RBV - H34 which is rated for high boost application, 10 - 25 lbs. Will it open properly if I am not using full boost? Any additional opinions on this subject would be appreciated.

I've talked to the folks at Turbo XS about this. They recommend the Racing Bypass Valve Type H34 (RBV-H34) whihc should fit the Top End piping exactly. I plan on cutting a hole into the top of the K&N filter (carefully as to ensure no little bits get succked into the intake when re-attached), going to Home Depot for some standard plumbing fittings then improvising a connection between that and the BOV.

I wouldn't worry about the valve not opening. That's what the washers are for. The Racing Bypass Valve Type H34 (RBV-H34) should operate almost the same ast the BOV-H you (and I) have currently installed. And, that's why they supply you with all those washers - to increase or decrease the pressure required for the valve to actuate.

I won't be doing this until spring however as I have new brakes and a rollbar to install between now and then.

[mailman221]

Not sure I understand the function of the washers, but when I installed mine the instructions stated that to add washers if the car does not idle smooth and add one at a time until it does. My car idled smoothly upon initial installation of the BOV, thus I have no washers installed. It functions very properly, releasing under any level of boost when shifting. The amount of release is proprtionate with the amount of boost and how aggresively I am driving.

Do the washers also control at what pressure the BOV releases?

[F1 LOTUS]

No firsthand experience here but, I thought the washers dictated how much vacuum was required to crack the valve open This is a vacuum operated valve not a pressure relief valve isn't it?

[Elanlover]

Brian and mailman, my experience with the BOV was that without some washers the car wasn't hitting max boost. I now have all 6 washers in the BOV althohgh 4 or 5 would probably do the trick. From the Turbo XS website under their "Installation" section:

5. If the vehicle does not run smoothly or if a reduction in maximum boost pressure occurs , add additional packer washers as per steps 1 through 4 above

I was experiencing a reduciton in boost. Now Brian, while you claim no firsthand experience with this I can assure you that you likely have moew knowledge than I on this issue and intake/throttle body related stuff. So, if this doesn't make sense please chime in.............

I assumed the BOV going off was due to the air in the intake plenum forcing the BOV open from the "other" end if you will. The BOV can be opened by 2 events. The first, and normal operation, is when there is sufficient vacuum in the attached "nipple hose". This should be when you take your foot off the gas after full throttle and turbo pressure. The second method (and not normal) would be if the spring tension isn't high enough and you have intake pressure that is strong enough to push the BOV open from the intake side of the valve usually when the turbo is raising the air pressure in the intake. This is what I had. Installing the washers made this go away.

Thus my comment about the washers eliminating the concern about excess air pressure from the turbo opening the valve. Just add more washers. Now, that does make the amount of vacuum required to open the valve from the "right" end higher. But, I don't see that as problem. better to have the BOV opening only snall amounts (still relieves some pressure at least) than you not getting full boost.

As I said, I've got all 6 washrs in there now and its working great for me. Full boost and opens to relieve pressure when i take the foot of the gas as per normal operation. In fact, I am considering stuffing 2 more washers in there to see the effect. Turbo XS states that 8 is the max they recommend.

Mailman, if you have NO washers in there I think you need to add at least 4. Run the car out on the road under full throttle, in all gears, and see if you're hitting full boost. You probably aren't (with the exception of any other mods you've added like a manual boost controller). I think you'll find that at least 4 washers are required to give the proper performance. Even if you have a MBC, which would mask this issue, you're probably leaking aur from the BOV if it hasn't got any washers installed.

[Monty]

BOV will not really effect the car at idle, IMO the washer is a form off adjustment, so when adding the washers u`r shortening the spring which makes it more stiff then the piston comes more harder to open so doesn`t release the pressure to early.

[Elanlover]

BOV will not really effect the car at idle, IMO the washer is a form off adjustment, so when adding the washers u'r shortening the spring which makes it more stiff then the piston comes more harder to open so doesn't release the pressure to early.

I'd find it hard to believe that you'd get the BOV activating at idle causing roughness. You'd have to have a lot of pressure in the intake to do that. I certainly didn't have that at all. With boost on though you can get the valve releasing if the spring isn't tight enough causing you to have a reduction in max boost as air leaks through the BOV.

[mailman221]

Actually, when I installed the BOV I ran it for about three weeks without the MBC, (with no washers installed) and I had exactly the same boost, that the car had before. The only difference was that the engine had much quicker boost between shifts and spooled up faster. The car did seem to have slightly more power as a result of installing the K & N air filter and being able to breath better.

I then installed the MBC and was able to adjust the boost past 1 bar where the car began to cut out and backed it off to between 8 - 9 bar. The car has very noticeably more more power and the BOV still reacts exactly as it should.

My understanding of the purpose of the BOV is to release the pressurized air to protect the Turbo Charger and increase effficieny. I think it's purpose is to evacuate the air mass when the throttle is closed, and feed it into the atmosphere or back into the turbo inlet hose, thereby protecting the turbo from the air hitting it in reverse when spooled up doing potential damage.
It also keeps the turbo spooled up between shifts reducing lag.

If this the case, and please correct me if I'm wrong, would adding washers not increase the spring pressure and allow the BOV to open at only higher air pressures depending on how many washers are added, thus limiting it's orginal purpose - to protect the Turbo?

That actually goes back to my orginal question as the recirculating Racing TurboXS is rated at 10 - 25 lbs and does it offer the same protection? If it does not open until 10 lbs., it may not protect the turbo as intended.

Again any help, comments and suggestions are appreciated. Some of us would be in deep muck without this forum.

[mailman221]

One additional comment on this tread and my reply. The reason I did not add any additional springs was that the BOV was reacting prefectly the engine was idling perfectly and had full original boost indicating to me that the BOV was operating as intended. It seems like a lot of washers to have to add. I wonder if Elanlover got a defective unit or one with a bad spring. Did TurboXS question the number of washers you were having to put in?

My philosophy is: If it ain't broke, don't fix it!