Hi All,

i’ve searched the threads and found some info but not everything I could use to get a complete direction. I’m seeing lots of feedback and videos of a constant hissing sound with blow off valves and superchargers. Am I right and I will need one if running 12 to 14 pounds? If so what is the absolute quietest alternative.

Thanks in advance,

Jonn

 

What type of BOV setup are you concerned about? Venting to atmosphere is a lot louder than recirculating.

 

Turbosmart Kompact in recirculated mode is silent. With top down you might over hear some whooshing but if you soundproof your intake cover/box or use thicker piping you might reduce the noise even more. Remember that it's probably coming from the air-filter/piping even if recirculated.

https://www.turbosmart.com/product-c...-valve/kompact

 

What Supercharger needs a BOV? I thought pressure is self limiting unlike Turbochargers which can produce excessive pressure at high turbine speeds.

-- Chuck

 

The SOS kit does.

 

All FI has to have a venting source either externally like a "BOV" or looped back into the intake called a recirculation valve, however they are the same exact valve, just has provisions for adapting back into intake pathway if you want and the other doesn't. Unlike a Turbo, the Supercharger is belt driven/tied to engine directly to make boost, so its always venting when under vacuum/cruise throttle, and the higher the motor/supercharger revs the more/loud the venting, and then once you are in boost and then take your foot off the gas it acts more like a turbo whoosh in that particular scenario, but otherwise with the SC its always making some noise, which can get annoying to some people when running open BOV at a high boost pulley. But to further elaborate, what makes them loud and annoying besides the inherent design difference on when they blow off compared to a turbo, is if you have them venting to atmosphere - which is arguably best for performance because all the spent hot supercharged air is not recirculated back into the intake charge. But for more traditional/OEM set ups that are supercharged or turbocharged, noise and "emissions" are the primary motive for recirculating the blow off back into the intake or exhaust depending on Turbo/Supercharged config.

 

Keep in mind at high boost you may want to reconsider the recirculating and vent to atmosphere.. as you'll be blowing hot air into the intake with a recirc setup.

With that being said.. my SOS Novi 1200 at 16psi with a Tial QRJ (supposedly quiet) is annoyingly very loud IMO and damn near ruins the car for me.

 

Does this hold true on an IC setup as well if the bpv is located post-ic? Rotrex does specifically state NOT to recirculate hot air into the blower inlet, and if you are recirculating, it needs to be done post-ic. I'm not sure on the layout of the SOS HX, I'm assuming the recirculated air is before it's going through the core from the heat exchanger, so it's hot air?

Sucks to hear. I have the QRJ with the diffuser cone, and I was specifically trying to avoid it being obnoxious although I had a feeling it would be no matter what if venting to atmosphere. I ended up changing my setup last second due to time constraints with my fabricator and not having the proper materials, so it's currently set up for VTA, but if it does prove annoying I'm going to go back to the original plan and recirculate it from the cold piping.

Dustin @RAIN H8R suggests using a hose discharge on the QRJ as it quiets it down significantly.

 

Ditch the diffuser, buy the aluminum hose attachment for the discharge. Attach a silicone or rubber hose that is 6 inches or longer to the adapter and clamp it on.

the noise you hear is air on metal. Air on a hose dampens the noise

 

I wondered about doing something like this. Wouldnt the hose adapter/long hose choke the evacuation and maybe cause compressor surge?