This is my understanding of how it works.

-Turbo Builds Pressure
-Pressure Moves to Engine and you start movin... lol
-Butterfly doors shut when you let off throttle.
-That excess pressure has to go somewhere... so it starts heading back towards the turbo (only way it can go)
-Since BOV is installed, that excess pressure vents out... keeping the turbo from surging.

My understanding is that if you did not have a BOV.. that excess pressure would head back towards the turbo and cause it to surge.

Is this incorrect?

I had some guy tell me he ran 19psi on his WRX and said that my BOV was restrictive. He said he runs without one..

I wanted to call him an idiot, but I didn't want to get into it with him until I fully understood. I told him I would never run without a BOV...

What do you guys think?

 

I am breaking my 7 in right now with no BOV and it doesn't surge, but then again I am not boosting it what-so-ever.

 

the big boys don't run them...set-up a flat switch thru your clutch and you shouldn't need one. You will have some surge putting around town, but a big boy turbo shouldn't be affected.

hopefully RICE RACING will chime in here.

 

flat switch... explain please.

 

so that's basically how it fixes your problem.

hope that helps.

 

I haven't wired one before, but basically a switch (clutch would work) that retards timing ~15*ATDC above a certain rpm, which would allow for rpms to drop while you remain WOT and slam it into the next gear, release switch and ignition "returns" and you go screamin' forward.

WOT between shifts and no BOV = quicker shifts.

 

ahh very nice. Makes sense.

But, how is a larger turbo less likely to surge vs a smaller turbo?

If I ran a GT35 on a setup, and a GT42 on another.. both without BOV's... what would happen? You said I'd get some surging putt-putting around town...?

 

larger turbo = beefy parts, as in larger wheel that can take the beating. I think turbochargers the size of the twins can't handle surging, but a decent size single turbo can. I'm guessing most that are rotary friendly.

putting around town, as in getting 1-3psi on hill climbs or something...small amount of surge but not creating a problem, then when you run 20+ flat shifting no need for a BOV. Probably not the best idea for the street. A drag track, probably not a bad thing. I want to say Rally cars don't use them either, IIRC

 

larger turbos have more trouble slowing down and are more likely to surge. go for it if you don't like your turbo.

 

Yes, the WRX guy is an idiot.

Garrett GT-series BB centers have angular contact bearing which minimize damage from compressor surge.

Compressor surge will eventually kill the turbo.
Compressor surge causes the RA to slide axially (mostly) which kills bearings.

Those that argue against having a BOV on a street vehicle are idiots.


-Ted

 

I figured as much.

Thanks guys

 

FYI Buick GNs/ T Types do not have BOVs...little different with an auto though as they are not constantly lifting for shifts.