if u look at some FAST 1/4 mile race cars some dotn run BOV beacuse when u go thru gears the BOV opens causing a pressure drop in the piping. you turbo will ahve to work that much more and take time to pressurize that pipe again. all out racers dotn care about turbo life as much as anythign they can get in 1/4.

 

but not having a BOV DESPOOLS the turbo... IE you now have to RESPOOL which takes time too!

think about it, the pressure in the piping don't stay constant at 12PSI, the turbo keeps pumping pumping and with the throttle blades shut the turbo just fills the pipe... 20, 30, 40, 50PSI... all the while with the compressor working harder and harder and harder to keep it in there, which slows it WAY down.., which in turn makes the engine need to respool it to get boost...
and if you're REALLY unlucky, you'll kill your motor too!
where as a proper BOV vents into the exhaust side of the housing, helping the turbo stay spooled while there is no exhaust flow because the throttle is shut...
Maybe no bov would be ok if you could shift instantly and had a dog tranny, but I still wouldn't risk it..
not having a bov is retarded

 

drag racer dont always lift off teh throttle while changign gears


i also never said take out your BOV

 

I personally believe that the difference in 'respooling' when changing gears with/without a BOV would be negligable with a stock or a similarly sized turbo, have you ever taken your car close to redline at full boost then let off the throttle then got back on it again (after boost=0, ie, your bov has vented everything, turbo RPM=0)? no lag there getting the turbo to spin back up again instantly, why should it be different on a gear change? (again I'm talking a standardish size turbo here.. obvioulsy the bigger the turbo the more lag that would happen here)

not having a bov is retarded you say? there are some turbo cars that come without BOV from the factory, so obviously it can't be too detremental to anything important(ie, engine, turbo) if a factory car doesn't have one.

Or maybe i'm really stupid and have no idea what i'm talking about and you guys all right.....

Ps- i'm not trying to get all you guys to not run a BOV, I couldn't care less...

 

but alot of cars do come stock with a bov.

 

it doesn't matter what you believe, it's a fact that compressor surge caused by excess boost while changing gears is detrimental to the turbo and engine. it may not cause that much damage on cars without them because they are running very low boost levels, but once you start hitting the turbo with 15-20psi of boost, something's going to break. i would rather spend the extra $300 and be safe than lose a turbo.

 

0 boost doesnt necessarily mean turbo RPM = 0.

your boost gauge only reads manifold pressure at that point and time...not what the turbo is producing. when you let off the gas to shift, the turbo doesnt just STOP producing boost...it doesnt work like a switch. i dont think a BOV would really help respooling (given that all BOVs perform the same. a slower responding BOV may make a difference)...its just a preventative measure to prevent turbo damage.

but i think thats the past posts just said.

 

i'm more worried about the backpressure than the turbo respooling, although it is a noticeable difference.

 

I had a greddy type s and it wasn't loud enough so now I have the turbo xs rfl. It sound so sweet. If I rev the engine to 6k my boost builds 4psi. I thought this was odd but the bov opens and its loud as hell. I scare people all the time when I'm driving around. Has anyone had theres pop off? Mine did it again today. Scares the crap outta me cuz I thinks my cars F'ing up again but After it keeps stalling and I pull over and pop the hood its just lying in the engine bay hanging on by the vacuum hose need to get a flange made...

 

Those cars are running <5psi of boost. That really isnt enough pressure to over power the exhaust flow and cause backspin. Like terrh (I think?) said. The tb closes, and pressure builds up in the pipe. Eventually, it will go back out the turbo.

 

I have a great blow off valve story.
It was 2 years ago.... my TII was in its prime. I had finally saved up a little money for some mods.
1st mod I did was a brake upgrade. I got some generic slotted rotors, braided brake lines, and high performance brake pads.
2nd mod I got was a K2RD turbo inlet duct. Ted was nice enough to sell me one of the prototypes. It was just one straight pipe going from the turbo to the AFM, with nice blue silicone couplings.
I still had the stock blow off valve on the car, and obviously the car wouldn't Idle correctly unless the outlet was plugged into something....ie the stock TID.
Heres were it gets interesting(retarded).
I attatched a peice of hose to the end of the stock BOV, and clamped down a peice of threaded pipe to the end of the hose. What I did next.... was my crowning achievement.......... I threaded a sprinkler head to the pipe. The sprinkler head acted as a valve, holding vaccuum at idle, and releasing pressure when the throttle body closed under boost. It sound very odd..... if you can imagine. To my suprise it worked.... well.
The only drawback was that the sprinkler heads I was using would eventually fail due to the extreme head & pressure. So I switched to a more heavy duty sprinkler head, and it has lasted ever since. Im proud of my Sprinkler head mod.... it worked... it sounded cool..... and it was pretty god damn funny to see the looks on peoples faces when I popped the hood and showed them how it worked.
Maybe I'll do a write up on it. hahah

 

pssssssssssst

 

PHHHHFFFFFTTT T T T T T T T T T

 

vrrrooommmmm psstttttttt vrrooommmmmmm pstttt vrooooooomm screecchhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

 

Siezed bearing?

 

no

 

BOVs are more for turbo life than performance. Not having one in a street car is just plain dumb. I don't know how much performance you get out of one, but I'm guessing that it isn't much.

 

It all depends on the Application. Grand Nationals don't need them(along with many other turbo cars that are automatic..... Z31s dont need them... many other cars do fine without BOVs.

 

that's because they use the almighty "pop-off valves," or something like that. maybe it's pressure release valve, or air bypass valve, i'm so confused.

 

Geeze, no one knows anything in the 2nd gen section!

The turbo drag cars that don't have bov's dont have them because they flatshift. The throttle plates never close on a drag car going down the strip so there is no compressor surge therefore no need for a bov.

The performance gain is that when throttle plates are closed the compressor doesn't surge and doesn't lose speed keeping it at efficency.

 

extreme dragers don't use bov's because they never let off of the gas, therefore no need for one. Plus if they are running mad boost they have the money replace that big *** turbo. Also extreme dragers are sponsered and rebuild their engine and every other part every week so they could care less if their turbo gets a little back pressure.
Street cars on the other hand need bov's because of the constant shifting and spool up. And bov's do save your turbo and a street car needs to save money (via $$$turbo). I have witnessed this on my car.
Oh yeah, I have a greddy type s and hate it, it sounds girlly and I am trying to buy a SARD R2D2, sweet sounding and it sounds like its actually releasing my 20+ lbs. of psi.

 

Suds is right, absolutely right. NeilTII is partially right. Extreme drag racers don't let off the throttle because almost all extreme drag cars are automatic. Less chance for driver error. just smash the gas and since the tranny works like suds said... yeah, you get the picture.
Charles

 

There are so many misconceptions.

 

anyone got a sound file of a type s

 

are there any stock blow off valves on other cars worth using?? just curious