so why do people install bov.. coz it sounds better.. or it serves a purpose in rotary engines? is it harmful for the turbo or good? does it increase performance?

 

The BOV on any turbo application is to increase turbo longevity by bleeding off the pressure when the throttle plates close, when this happens with no BOV it causes the turbo to spin in the reverse direction.

 

so is it good to install a bov on twin turbo fd3s making 300horses to the wheels?
coz my friend told me that when u release the gas pedal after reving the engine to higher rpm's .... it releases the air or som like that .. than something to do with ECU and it adds more fuel to the engine which is not required?
i might be totally wrong coz i am new with rx7 and have no clue wat soever of BOV?

 

A BOV is a good idea on any turbo application. It shouldn't really affect the fuel injection system at all because the ECU should sense the drop in manifold pressure and adjust the injector pulse width accordingly. That is if it is a stock ECU or if you're running an aftermarket setup and it's tuned properly.

 

You already have one.

People change/upgrade them. Unless you have a problem forget about it until you've read more about your car and decide what direction you want to take it.

 

Your friend is referring to a MAF based system. When you run a open BOV with a MAF, it runs rich every time the BOV opens unless its recirculated back in front of the MAF. This can also, be avoided by running a blow-through system and having the BOV placed before the MAF but most/all manufacturer's run draw-through systems, so it would have to be something custom.

HOWEVER, our cars run off a MAP system so the tune relies completely off manifold pressure after the throttle body. Therefore the computer knows when the pressure drops and adjusts fuel accordingly. Our cars already run BOVs (or our turbos would blow up in short time) but its vented into the airbox so it doesn't make noise. If you want to hear the psssh sound, you can disconnect it from the airbox and then you will hear it.

Buying an aftermarket BOV serves no purpose but to change the sound. The BOV exists to protect your turbo, it does nothing else. However, if your running a lot of boost on the twins, you might want to get another BOV to prolong the life of the twins or if your stock bov is failing would be another reason. To note, most people running stock twins, will not need to change their BOV unless its not working.

thewird

 

thanx to the wird
that made more sense
would you suggest any bov for stock twins and any1 reliable in toronto , scarborough, missisauga.brampton, markham or GTA .. who could install it professionally for a reasonable price

 

Eh, for something that simple you can do it yourself lol. But again, how much boost are you running? The stock BOV is adequate for OEM twins 99% of the time.

Picture of engine bay?

thewird

 

Show me a turbo that reverses its direction when you let off the throttle with no BOV. Not going to happen.

Com'on Kevin, I thought you were smarter than that.

 

Stock one sounds fine if you vent it to atmosphere....if it's the sound of a BOV your wanting to hear, don't waste your money on something you don't really need,especially if your running stock twins....

If you want to spend some money on your car look into reliability mods. first....

 

I remember reading an article somewhere that compared turbo life with a BOV and without one. It was years ago that I read this, so I don't remember where it was from or where to find it. The result was that there was no appreciable difference in turbo life whether or not the system used a BOV. It then went on to explain that in AFM/MAF equipped cars, BOVs were more of an emissions device because the BOV would dump air back into the system behind the AFM/MAF, thus avoiding the EFI system dumping mass amounts of fuel as all that air is backed up or released into the atmosphere. Another thing a BOV did was keep the turbo spooled up as it was now not surging, but pumping air through the BOV and back into the system.

So the long and short of it is that people who buy aftermarket BOVs are just in it for the noise, unless their OEM BOVs are leaking at higher boost or they didn't have an OEM BOV to begin. Not that the noise is a bad thing, of course...

 

Really? How do you think the compressor will stall?

http://www.turbobygarrett.com/tech_center/faqs.html#t9

Please see the Anti Surge Valve section.

http://en.wikipedia.org/wiki/Turboch...low_off_valves

 

Its like Boom boom pow! This is all....

 

Well where is the air going to go that just passed through the turbo and hits a shut throttle plate??? It has to go back, and this is through the compressor, and hitting the compressor wheel in the opposite direction, this will slow it down and can reverse it, that's how people have had the compressor wheel nuts back off even though they are a left hand thread.

 

LOL your actually serious about that aren't ya.

Nowhere in any of the links you provided did it say that the turbo spins backwards. It will definitely slow the compressor/turbine wheel down, but it will not change the direction of it.
Running high boost without a BOV can cause the compressor nut to spin off for sure, that still not changing the rotating direction of the shaft.

I'll keep arguing until you provide video evidence of a turbo spinning backwards due to compressor surge.

 

How would the nut come off if the wheel didnt spin the wrong way?

 

The compressor wheel gets hit with enough backpressure to slow it down while the turbine wheel and shaft continue spinning. The nut loosens and the compressor wheel spins freely on the shaft.

 

Due to a opposing force on the shaft. It's Simple Physics. How do you think the shaft slows down so fast?

 

Must be quantum physics. How else could it stall when its spinning at 180,000 RPM. It's like a missile getting ready to fire and then someone puts a banana in the hole. Don't ask me where I came up with that, I need to stop waking up at 1 am.

thewird

 

nismo im with you...its all about pressure. the turbine/compressor wheels can work both ways...


if the pressure on the compressor outlet side is greater than the pressure on the exhaust inlet side, it will absolutely spin the turbine in the OPPOSITE direction it was originally designed for. there is no doubt about it...physics alone.

 

This is fun.

mmmk, so here you are at the top of 3rd gear, 15psi of boost, no BOV. You stab the clutch and let off the throttle creating a buildup off boost pressure in the I/C system that slows the turbo spinning at 200,000rpm right down to 0rpm and then continues to spin the assembly in the reverse direction? All within a fraction of a second?? while you start full throttle back in 4th gear?

Even if you pulled 3rd gear at 15psi and completey let off the throttle and didn't shift into the next gear, the worst that happens is the turbo slows down to say 50,000rpm, the boost pressure builds up and has nowhere to go so it surges back out throught the intake of the turbo.
Check it out next time your under the hood of your car, disconnect the bov and giver a rev. You know that Chuff Chuff Chuff noise you hear, hold your hand in front of the intake of the turbo. Air will be blowing back out the intake. Just dont get your hand sucked in when reving lol.

Never will the turbo spin backwards.


Oh btw, drifting is a true test of drivers skill, stretched tires make your car perform better and streetracing is only for cool people.

 

so are bov's illegal in canada ontario toronto
will cops pull me over and give me a ticket for that PSHHHHHHT sound?

 

There's plenty of BOVs that aren't too obnoxious. But no, to my knowledge they aren't illegal.

 

^ Tial has pretty quite BOV's
thats what i have... but if you want quiet stay with stock

LOL... i think he ment it as an exaggeration...
but it will slow down in speed as you previously stated AKA turbo lag...

anees
The simple way i under stood it was:
its like blowing into a straw (aka turbo spools up), then you put your finger over the end of the straw (aka Letting off the throttle) .... Its going to cause a build up in pressure slowing down your turbo..
making it work harder to get air out and causing lag for the next time you apply the throttle ... A blow off valve is there to relieve that pressure while still keeping your turbos spinning with minimal resistance... hence if u had a blow of valve on that straw, you would still be able to blow out air as hard as you can....... with no resistance. or untill you run out of breath... but then thats a whole other explanation of a turbo's efficiency ..lol

 

Thats the funniest thing I ever heard lol. No its not illegal. The only thing thats illegal is nitrous. A loud exhaust can get you an unnecessary noise ticket but if you don't drive like an idiot, cops won't bother you.

thewird