This guy I work with tells me that SC bypass vavles do make sounds, is that true?

 

No noise with my 10# system.

 

im pretty shuer blow off valves make the hissing sound and bypass valves are quiet

 

My original Bosch bypass valve made a farting noise at -3 psi.
I replaced it with a newer one (newer design) and it's hissing a little at the same vacuum.
In the Saab forums they call it hoot valve... all clear!

 

I have a stock Bosch venting to ATM and you can hear it a bit when you throttle down. For example, take the motor to 3K rpm and let off to shift. I get a 'slight' SHHhhhh. Nothing like the BOVs you hear. But I notice it.

If you route the BPV back into the intake system (as per manufacturer instruction) you will NOT hear anything.


-Scott

 

When I had my procharger system with the bypass routed back into the system, it was silent except for when I was shifting hard going under overpasses with out any other cars on the road. I have a B&B tri flo exhaust which isnt too loud so I could barely hear the valve when it was operating. Blow off valves are loud but arent installed on MOST mass air cars due to fuel issues ( pisses of the MAF sensor). Although it can be done with tuning. BOV work best with speed density systems using a MAP sensor like Accel or FAST.

 

wow, this question again huh? is everyone calling it a bypass when its routed back into the intake and a BOV when it vents to the atmosphere? nobody has ever been able to tell me the difference between a bypass valve and a BOV

bypass/blowoff valves are routed back into the intake so that air that doesnt get into the motor isnt measured by the maf. all the air going through the maf must get into the motor. if its metered, then some is blown out through the valve, there's problems.

if you want to blow the air off without routing it back into the intake, then the maf must be located after the valve(pressure side).

as previously mentioned, the valve will make very little to no noise if routed back into the system.

im sure that the tial, hks and vortech race valves sound different than the plastic bosch valves.

heres a little about vortech's
http://www.vortechsuperchargers.com/...s/aircomp.html

 

Given that I have BOTH on my car, a surge / bypass valve IS different in operation to a BOV. Although there continues to be a general sense of confusion as may people use the terms interchangably. however as I understand it:

Surge valve : When the car is at idle and the manifold is in vacuum the surge valve is OPEN. 'Extra' boost from the blower spinning - but with the TB closed - is therefore diverted (either back into the intake side of the blower OR to atmosphere). As the vaccuum declines and ultimately reaches a boost status, the valve slowly closes until it is fully closed at zero vacuum allowing 100% of the air to go to the TB). When you lift your foot and go to vacuum, the surge valve snaps open and once again the boost from the spinning blower is redirected through the intake.

BOV : At idle this valve is CLOSED. NO air is released from this valve in a vacuum condition. This valve remains closed as the vacuum declines on exceleration and remains closed into a boost condition. When you lift your foot, the 'new' vacuum causes the BOV to snap open to release the boost until it returns to a 'normal' vaccum level. This is where you get the wheezing / huffing sound. You have to go into a boost condition to get the sound.

Impressions: The good part about this system is a "belt and suspenders" insurance policy. You have TWO ways to vent boost. (note: make sure you also use two different vacuum sources though. Ask me how I know). I currently have an HKS BOV and a stock ATI surge valve venting to atmosphere. I hate both of them for sound and will be changing. Venting the ATI valve to atmosphere IS noisy and NOT in a good way. I will be plumbing it back into the intake tube at some point. The HKS is "OK" and I will probably keep it, but I'm not keen on the sound. It may appeal to me more once I have the surge valve redone and JUST have the 'wheeze' of the BOV on its own.

I should point out that on a lower boost setup this is not such a big deal. Up to about 6 - 8 lbs the blower can almost run without a valve. At 15#'s it becomes more important

NOTE: If you vent ANY air to atmosphere either through the BOV or the surge valave, you have to relocate the MAF UP to the TB area. As mentioned, ALL air that has been measured by the MAF has to find its way to the intake
hope that helps.

 

Anyone that wears both a belt and suspenders at the same time needs a fashion consultant.

My bypass. It's a little loud.
Procharger bypass

Close up

 

Video clip with sound

You'll have to lighten up the video a little bit to see it better.

 

First time my car was started and rolled out, the 2" bypass/bov is dumped out the driver's side fender:

http://media.putfile.com/rollout1

A race against a bolt on trans am lt1, I'm on and off the throttle, looking for traction off of the start and you can hear the bypass/bov going off (video is from the trans am) :

http://media.putfile.com/NathanVsRandy66

I'm running a 2" hks bov that's been slightly modified to act as a bypass.

 

97TA-WS6-Con I'm glad somebody finally explained that I have been tempted many times I also run both a bov and a bypass valve on my TA. You said to ask why you need a seperate vacumm source ok I'm asking?

Jeff
96 SS BLOWN
96 TA 396 D1

 

Well, as much as it is a good idea to have both systems as an insurance policy, if BOTH parts are T'ed to the same vacuum source and if that vacuum source is lost for some reason (say it becomes detached somehow) and, say at 13.4# (or thereabouts) at 5500 rpms, (roughly) and you choose to shift, it appears there is a very real risk that all the surge / by-pass / BOV's in the world will not help if they have the same vacuum source.

You might find this results in soiling your underwear at the sound of horrendous mechanical death.

You THEN get to find out what it costs to totally rebuild a D1SC ($1299 approximately of ocurse. Just an estimate) Then you get to praise the lord that your brand new (third time rebuilt) motor did not ingest any parts.

Of course this is entirely speculation on my part.

BUT, I would still recommend that IF you have two valves, then plumb them to seperate vaccuum sources on the manifold. Just a thought.

PS: Although it remains uncertain as to what happened - and bearing failure remains a possibilty- and though it did not appear that my vacuum line HAD become detached from the manifold nipple, it remains a wise idea to have two sources.

 

Dude OK I understand but I think the better solution is to keep your foot on the floor during shifts so that doesn't happen Besides I'm all out of vacumm sources but I do tie all of them up with wire ties to keep them from blowing off. I learned that all vacumm lines need tied the hard way when I blew my brake booster line off the manifold on a pass and didn't figure that out untill I hit the brakes no brakes! talk about soiled drawers! I did get it stopped before I went of the end of the track but it was a scary ride.

Jeff
96 SS BLOWN
96 TA 396 D1

 

A small zip tie on either end of the bypass vacuum line is cheap insurance.