Junia

100-120 thousand miles is nothing. My old silvia with the CA had atleast 100,000 miles and they don't come with a BOV or a recirculation valve from the factory.

Rotortuner

Ill bet it had a BOV or recircualtion valve, to find a car that doesnt have one from the factory is nearly imposible. Beetles, DSM, eclipse, 323 gt, gtx, sr20 etc.

CJG

CarlRx7

bov opens because of the vac. increased behind the throttle plates. the pop off valve sees the boost and pops off saving your motor is your wategate sticks closed.

carl.

Junia

Nope the the silvia/180sx with the CA18DET never came with one from the factory. Also if I remember correctly the EP71 Starlet Turbo doesn't come with one either(but I'm not completely sure on that one).

seanrot

iTrader: (2)

lol i said that already

FB II

this is a good read too.

http://www.autospeed.com/cms/A_1457/article.html

bov's suck

1sgen

iTrader: (1)

you people opposing the bov must be crazy, beside all the good things everybody said about the bov there is one major factor to it that is when you shut the throttle the turbo is still trying to pump air in and that air has nowhere to go and we all know what happenes to compressed air , so if you where to get back on it you will use the hot air in the pipes and will cause you lag, how much lag it depends on your turbo.
the bov gets that hot air out and lets the turbo build fresh cold air again , now which sounds better.
also it does save your turbo :-)

FB II

yes, i am crazy then. A) people have already mentioned the supposed air destroying the shaft and compressor. not true. tons of people are currently NOT using a bov, there are people on this very forum not using them for years with no problems, go to either one of the posted links and read. a few guys hitting over 500rwhp. B) there is nothing WRONG with bov's. except for alot leak, which is just lame. it's just UN NECCESSARY (sp? ahahaha) C) look back at the lemans series when they were allowed turbos.... none used BOV's!!!!!!! (wait, 1 guy did i think at the end of the era) those things went thru more and more stress than any of our engines will see. blah blah about the fact that they don't care because they were funded new turbos and motors. that bs too, if a bov actually served a useful purpose in gaining either MORE power or TURBO longevity, why would they not be all over that? they existed...... it's because it's not of any good use. the only thing they kept replacing were motors. AND those turbos were the same style as the ones most of us have. the stock setup on a turbo FC. back then they didnt have the dual ballbearing crap and all that. wurd peaceula.

CarlRx7

i see where both of the sides is coming from.

when the throttle plates close, the boost builds up right? well not exactly, you have to remember that with the throllte plates closed your not letting air in, which in turn doesn't let air out. so infact the exhaust blades slow down making less boost, so the damage is not as bad as some might think.

me im using a bov just for the fact that i like the PSSSSHHHHT sound. but for performance a bov is not required, now a pop off valve would be perfect, as to only let the boost out that is over your set limit, keeping the turbo at max most of the time. when a bov opens every time the engine is under vac. so when you slam on the gas. your creating a slight vac between the engine and the turbo, so then the bov opens a little, venting little boost your trying to make..

sorry if i seem like a 1st grade teacher, but its 4 am down in fl and im watching the hurricane charley go over me. BORED!

Carl.

comradegiant

I understand the difference between a wastegate and a BOV, and they are simply different means to the same end. When you cut throttle, in a properly working system, the wastegate will dump all the air running the turbine, ceasing boost. Putting something on the intake side to release boost pressure is unnecessary because it should be dealt with using the air driving the turbine.

Junia

I think having a bov is more of a personal preference thing. I threw a hks super sqv on mine before and it annoyed the **** out of me so I got rid of it.

Rotortuner

No, your still not understanding the difference. You understand what a bov does but not what the waste gate does. Here I will explain the line of events. You floor the car and you watch the boost guage, it starts to build boost very fast climbing to where you have the boost set at. then once the boost reaches the set value the positive boost pressure in the intake is used to open an exhaust waste gate that vents exhaust, this vented exhaust doesnt go throught the exhaust blades, there for it stops making boost. the waste gate just controls boost and keeps the turbo from making too much. so the waste gate only opens when you floor it and you hit your max boost then the waste gate opens, as soon as you lift your foot the waste gate slams shut because there is no more positive pressure in the intake to pushe the actuator selenoid. Once you lift your foot the pressure after the throttle plates flashes to vacume and pulls through a vac line connected to your BOV, the vac pulls back on a piston which releases the unsused pressurized air from your intake. BOV's are supposed to be located a close to the turbo as possible, this allows air to be vented back and hardly any pressurized air slams into the compressor.

I still dissaggree with whats been said on here.


here is a prety credible site, that explains what exactly happens, and isnt a bunch of bumbling idiots on other forums that cant aggress either:

http://www.syclone.freeserve.co.uk/blow.htm

Washington University in St. Louis Formula SAE Racing:

http://www.newton.dep.anl.gov/askasc...9/eng99202.htm

Go ahead dont use a BOV, it just takes long too spool your turbo again. I had a BOV that wasnt working on a t2 that I was racing and it took noticiably longer to spool and then the engine blew up.


CJG

Aaron Cake

iTrader: (1)

No, you don't. They are two completely different devices for completely different purposes.

No, it won't. The wastegate position will be unchanged for a short while of time as the turbo still produes the same amount of boost. As it begins to spin down, the wastegate will CLOSE to try and bypass less exhaust and keep the boost level at the point set by it's spring (and/or boost controller).

Wastegates have NOTHING to do with BOVs, and vice versa.

You really need to read up on basic turbocharger information. Check out this article:

http://auto.howstuffworks.com/turbo.htm

REVHED

Assuming BOV's are necessary, the most logical place for it to be located would be close as possible to the point of reversion which is the throttle body.

Rotortuner

I understand what your thinking, but every one always puts them close to the turbo because if you put them by the throttle body you will still have a large volume of high pressure air between the turbo and the BOV that the turbo "sees". So they put them close to the turbo, so that the BOV can bleed the 8-12 inches of pipe between the turbo and BOV and all pulses/pressurized air forward is blead backwards. Im not sure i explained that very well. But look at nearly all set ups and they will be on the turbo side of the IC.

CJG

RotaryRevn

REVHED

I disagree. The general consensus has always been to place the BOV close to the throttle body. By placing it close to the throttle body you are catching the biggest mass of pressurised air before it even hits the point of reversion.

web777

BOV's aren't necessary to make big power but it does help venting the unused boosted air. Sure, many older cars don't have one - maybe because it wasn't invented yet?? The flutter sound when not using the BOV is air escaping through the air filter - which can't be that healthy for the turbo. I'm sure you can run with or w/o with the same reliability, but I think it's cheap insurance having one.