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Discussion Starter #1
Unbeknownst to me, my Vortech BOV had spat out its O-ring, causing a boost loss (and the associated power loss I had last year that I could not identify). As I went to fix it, the adjustment knob broke off. I figured it was time to upgrade to A&A's latest offering, a new BOV made by Turbosmart. I also figured it would be a good time to use my new Sony HD camcorder :)

Here are the two blow off valves side by side:







And installed. You will notice I am using A&A's latest passenger side feed intercooler design: The BOV goes in the passenger side wheel well:

Vortech:


Turbosmart:


Now for the video:


You can tell that the TurboSmart sounds much deeper and more "hollow". I thing it sounds like Darth Vader breathing... Though the girl through it sounded like mud rubbing against the wheel inside the wheel well... To counterpoint, Chuck COW thought my car was dragging a plastic bag when he heard the Vortech BOV :LOL:... I guess it is an acquired taste for the N/A people;)
The Vortech definitely had more of a "sizzling" sound to it. Either one is essentially inaudible at low RPMs and can get very loud at high RPMs when the supercharger starts to move a lot of air and it all needs to be vented from a 1 inch hole, although the Turbosmart is definitely louder. I would say it starts to be audible inside the car right around 2500RPM -off throttle- of course (since a blow off valve's job is to close on throttle to allow boost to form). Both are also adjustable for preload.
I like it better than the Vortech but I have entertained plumbing its discharge back into the intake for a full recirculating system which would be essentially noiseless. Maybe that'll be a future project of mine.
 

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I like it better than the Vortech but I have entertained plumbing its discharge back into the intake for a full recirculating system which would be essentially noiseless. Maybe that'll be a future project of mine.
:thumbsup3: When I've driven in, or next to, high boost imports, the BOV noise just seems obnoxious.
 

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I have entertained plumbing its discharge back into the intake for a full recirculating system which would be essentially noiseless. Maybe that'll be a future project of mine.
Don't think you want to do that. The relief valve is in the inlet side now, would not reduce the over boost if fed back into the intake. Assuming no pressure drop to the inlet vs. the line you have it installed, you would end up with back pressure on the discharge side of the valve equal to the inlet. The valve would not open.
 

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Discussion Starter #7
Don't think you want to do that. The relief valve is in the inlet side now, would not reduce the over boost if fed back into the intake. Assuming no pressure drop to the inlet vs. the line you have it installed, you would end up with back pressure on the discharge side of the valve equal to the inlet. The valve would not open.
That is not how blow off valves work. There is a piston inside the valve that is actuated (sucked up) by engine manifold vaccum; you can clearly see the vacuum port on top of both blow off valves.

Every single factory boosted engine recirculates boost via the bypass valve, many do it because they have a MAF located before the turbo inlet, so venting air atmospherically would bleed off un-metered air, and for noise reasons. It works fine; you are feeding the blower inlet air that it is discharging; there is no net pressure generated anywhere and the BOV doesn't care either way because what it sees is the intake manifold vaccum.
 

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Discussion Starter #9 (Edited)
I thought we were talking about a supercharged system.
There is no difference in so far as the operation of the blow off valve is concerned; the throttle plate closes, the engine is still spinning, engine tries to pull air through a restriction, this causes a drop in pressure inside the intake manifold, the vacuum pulls the piston on the blow off valve up, the BOV opens. The only difference is that in a turbo car the turbocharger will spin down and you will stop hearing the air rushing out of the BOV, but it is still open as long as the throttle is mostly closed.
There isn't even a difference between supercharger bypass valves and turbo blow off valves. The Turbosmart I am using now is very commonly used on turbo cars. Here you can see it on a Subaru WRX: http://www.youtube.com/watch?v=oBVAPMvlFLs&feature=related

Conversely, here is a SuperCharged Corvette with a TiAl BOV, one of the most popular ones in the turbo world:


And here is a turbo car with a TiAl:


There is *NO DIFFERENCE*. If I plumb my blow off valve discharge back into the air inlet of the supercharger, all that will happen is the BOV discharge will become less audible.
Perhaps if you tell me why exactly you think there is a difference I can explain to you in more detail?
Also, if you want to learn more (and please, no offense whatsoever is meant by this!), I found the following books to be extremely informative, interesting, and easy to read. Here are my 3 favorites, in order:





That first one pretty much covers everything you need to know. A. Graham Bell is my favorite author for this stuff and his 4 stroke book doesn't go far into FI but does contain a wealth of info on heads, cams, exhaust, etc. The Corky Bell books have ALL of the math you need to size blowers and turbos, so that's pretty neat too. None of those books require any kind of in-depth knowledge in the topic, but, conversely, my college textbooks on internal combustion from when I was getting my Mechanical Engineering degree are all math :lol:
 

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Now I understand. Makes sense. I was thinking you were using the valve to prevent too much pressure build up from rpm of the compressor.

Guess I better get a suppercharger installed on my 08 LS3 and learn more about superchargers!
 

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my kit came with the turbosmart, i cruse in the left lane, mostly passing everyone.

lil ricers pull up next to me. (right where the bov is). a quick rev and the (darth vader) swisshhhhhh!!! and they disappear.
 

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Is that Jeremys car? MrBig?


my question is how hard to check the BOV in place? Taylor moved mine to in front of the fan. although i have the twin spal setup now


 

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Discussion Starter #14
Is that Jeremys car? MrBig?




my question is how hard to check the BOV in place? Taylor moved mine to in front of the fan. although i have the twin spal setup now


That could be Mr.Big's car, I'm not sure. I got the photo from Google.
Wow, that does look inacessible.
Just dyno the car; mine lost 20ish WHP when that O-ring went because it was leaking boost...

Hey how do you like the Spal setup? Is it very noisy?
 
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