Bov's & Wastegates

[thrtytwo]

ok so yeh, i searched but couldnt find anything definative.

Basically i understand (or think i do) that a BOV will vent excess boost (pressure) when you let off the throttle (eg gear change) so that the turbine wheel isnt compressing air between itself and the closed throttle body. thus prolonging the life of your turbine.

SO

A wastegate releases excess boost when its too high and could cause damage to your turbo. is that even when your throttle is open ? does that mean a wastegate is working all the time (at high boost) ?

THEN

Does that mean u could get along with only a waste gate ?

Im a bit of a noob just trying to learn so any info would be awesome.

[GOT04]

i know that the PAC rotor drag cars dont have BOV's just wastegates

[202.3rwkw]

ok so yeh, i searched but couldnt find anything definative.

Basically i understand (or think i do) that a BOV will vent excess boost (pressure) when you let off the throttle (eg gear change) so that the turbine wheel isnt compressing air between itself and the closed throttle body. thus prolonging the life of your turbine.

SO

A wastegate releases excess boost when its too high and could cause damage to your turbo. is that even when your throttle is open ? does that mean a wastegate is working all the time (at high boost) ?

THEN

Does that mean u could get along with only a waste gate ?

Im a bit of a noob just trying to learn so any info would be awesome.

Okay, you are in the ball park on the bov answer.

a wastegate is used to control the set level of boost in the turbochager. it is either internally (inside the exhaust side of the turbo) or externally mounted on the exhaust manifold. they both do te same job. when the turbo is driven by the exhaust gas it speeds the exhaust wheel, also driving the compressor wheel, therefore creating boosted air. when the turbo reaches the desired set boost level - controlled by the actuator, the wastegate is opened, allowing air to bypass the exhaust wheel and therefore controlling the speed of the turbocharger.

not the worlds most clear explanation but ..........

[thrtytwo]

Okay, you are in the ball park on the bov answer.

a wastegate is used to control the set level of boost in the turbochager. it is either internally (inside the exhaust side of the turbo) or externally mounted on the exhaust manifold. they both do te same job. when the turbo is driven by the exhaust gas it speeds the exhaust wheel, also driving the compressor wheel, therefore creating boosted air. when the turbo reaches the desired set boost level - controlled by the actuator, the wastegate is opened, allowing air to bypass the exhaust wheel and therefore controlling the speed of the turbocharger.

not the worlds most clear explanation but ..........

that helps heaps mate cheers.

[TTT]

first part is right

second part is also right but you are thinking wrong.

Your turbo exhaust wheel spins from the exhaust gases that the engine produces.

Since it is connected to the compressor wheel at the front of the turbo, this sucks more air in.

The more gas you give it, the faster it spins, sucking in more air.

SO

There are 2 parts.

1 is the gas going out of the turbo and

2 is the air getting sucked in by the turbo.

Wastegate is used to CONTROL the amount of boost your engine sees.

At a set boost level (set by the pressure of the wastegate spring) the wastegate flap will start to open and vent some of the gases.

Then it will be open enough to vent x amount of gas so that your engine only sees X amount of boost.

If you had no wastegate, when you accelerate, the gas from the engine would go through the turbos exhaust wheel which in turn would spin faster and faster meaning the compressor wheel at the front will spin just as fast, sucking in more and more air and the engine would get more and more pressure in it (boost) until it goes bang.

Wastegate is basically just that.

A waste gate. It is a gate that opens and wastes some of the energy (heat/gas) that the engine has produced in to the exhaust system, preventing it from going through the turbine wheel.

By doing so, it controls the speed at which this wheel turns and therefore controlling the amount of boost your engine sees.

When you come off the gas to change gears, the wastegate slams shut as there is no boost there.

At the same time, your throttle body valve slams shut as it is directly connected to your accelerator pedal via cable.

At this instance, there is still air between the turbo compressor (front wheel) and the throttle body valve.

Since there is no boost, there is vacuum.

The job of the bov is to vent this out of that location.

Vacuum causes the bov piston to open and release the air.

Some bovs vent it out completely to atmosphere making psshh noise.. and some vent it back in to the inlet pipe between the air filter and turbo compressor wheel.

This prevents the flutter sound from happening on gear changes.

So a bov is used to vent air that is in between the turbo and engine

And

A wastegate is used to control the amount of boost your engine sees

[thrtytwo]

that was very clear thanks dude.

also now that i understand that, i know the diff between atmospheric and plumb back. so how come some BOVs are plumb back but say its a sequential BOV which is known for its flutter, would it not flutter if it was plumbed back ?

on that point, are atmospheric BOVs legal ? or is there a Db rating ?

[TTT]

that was very clear thanks dude.

also now that i understand that, i know the diff between atmospheric and plumb back. so how come some BOVs are plumb back but say its a sequential BOV which is known for its flutter, would it not flutter if it was plumbed back ?

on that point, are atmospheric BOVs legal ? or is there a Db rating ?

1.) Blow Off Valves “DO NOT” make any kind of fluttering noises.

Get that out of your head right now.

All they do is make a single release sound. Different bovs make different sounds but they are always a single release sound. Psshhh of some sort.

The HKS sequential and super sequential bovs also make a single release sound.

The older style HKS bovs called HKS SQV (SeQuential Valve) looks like this..

It makes a regular bov pssshhh type sound.

Notice the 2 vacuum nipples?

It needs this because it has 2 chambers in it.

It actually has 2 valves.

HKS use this to prevent leaks under massive boost pressure.

That is where the “sequential” term comes in.

The newer HKS bov called the SSQV (Super SeQuential Valve) looks like this..

This also has twin chambers and twin vacuum nipples.

This bov is known for it’s high pitched sound.

Instead of a regular psshhh sound, it lets out a high pitched “squeek” that is the best way I can describe it.

The spring tension on the valve that opens and closes can be adjusted. So if it’s too tight, when driving around, it will not vent and your car will make a fluttering sound.. it is “CAUSED” by the bov being too tight and not opening…. But the sound it not coming out of the bov.. the bov does not make a fluttering sound.. it does cause it though.. it causes it because it is not doing it’s job of opening so the air that would have escaped it, is not trying to escape from the air filter where it came in causing the fluttering sound as it pushes back through..

Kinda like the sound you get with old water pipes when you turn the tap on high then shut it quickly.. you get that tap tap tap sound from the pipes as it all backs up.

Apexi also make a twin chamber bov.. looks like this..

See the 2 nipples again.

The red thing with the holes can be twisted to get different pitch and loudness of sound on gear changes.

Greddy also make twin chamber bovs..

So wether it’s plumbed back or vent to atmosphere, it can still cause a fluttering sound depending on how tight the spring tension is.

Bovs and legalities change from state to state.

In nsw, atom venting bovs are illegal. Full stop.

People have even been defected for aftermarket plumb back ones… depends what mood the officer is in I guess.

[dead32]

so if i adjust the spring tension on my blitz bov to be flat with the locking nut, will it damage anything? would it help with stalling? venting less gas to atmosphere theoreticaly would cause less fluctuations hence not messing up the afm signal? does that make sense? lol

[TTT]

kind of a band aid solution.

see if you close it up so much that it flutters, that means tha air is going back through the afm and it measures it twice..

it doesn't only measure one way...

it just measures air going past it in any direction.

so still dumps more fuel.

so you MIGHT still have stalling issues.

I say stick with the stock bov to the point where you get flutter using stock plumback bov.

at that point, upgrade to Stock twin gtr bovs.

they seem to have no problems at about 650rwkw

if you have more than that.. well.. I have no answer.

[dead32]

hmm i see your point, the std spot for the factory bov is plated over, the blitz bov has its own pipe (presumably came when the bov was bought) the blitz item came with the car, i care not for the pshhhh sound i'd rather not have to heal toe it everywhere, can be a bitch.

[thrtytwo]

basically im wondering if its only sequential BOVs that flutter ?

i know some people say theyre normal BOVs flutter when they have pressure fluctuation or something ?

im not really sure :S....

thats why i made this thread any clarification would be awesome

edit: also im not sure, if your BOV is plumbed back do you still hear it ? and are atmospheric illegal in any way or form ??

(why was this thread moved ? its not vehicle specific, and IS relating to forced inducion performance ?? oh well...)

Edited August 17, 2006 by thrtytwo

[JUNR34]

Since your in Perth as well mate I can tell you that ALL atmo BOV are illegal here, so expect a canery if you get pulled over. I think Ill keep my stock BOV since they do the job don't really think its ness to change something thats not broken unless you have alot of power under your hood.

You know what mods I rekon be a good idea to make a stick for BOV. Therefore people wouldnt have to always create one very time which basically ask the same questions....just a thought haha.

[thrtytwo]

Since your in Perth as well mate I can tell you that ALL atmo BOV are illegal here, so expect a canery if you get pulled over. I think Ill keep my stock BOV since they do the job don't really think its ness to change something thats not broken unless you have alot of power under your hood.

You know what mods I rekon be a good idea to make a stick for BOV. Therefore people wouldnt have to always create one very time which basically ask the same questions....just a thought haha.

cheers mate, i might just have to get a twin trumpet and make sure not to go hard past any coppers

[TTT]

You’ve got to be kidding me..

http://www.skylinesaustralia.com/forums/in...howtopic=130349

I went to the effort of giving you shed loads of info with pics etc and you start a new thread on this.?

What an ungrateful sh*t.

Add you to the list of people I won’t bother replying to..

Pfft..

Someone make me a mod..

I got some banning to do..

[Mr. Oizo]

You’ve got to be kidding me..

http://www.skylinesaustralia.com/forums/in...howtopic=130349

I went to the effort of giving you shed loads of info with pics etc and you start a new thread on this.?

What an ungrateful sh*t.

Add you to the list of people I won’t bother replying to..

Pfft..

Someone make me a mod..

I got some banning to do..

I second this motion.

[thrtytwo]

dude, totallt sorry, i didnt see that, to be honest i thought i was asking a different question in that thread, which is why i started a new, more specific one. i didnt mean any disrespect as i handt seen your post yet.

[thrtytwo]

thanks for the very detailed post mate, cleared a lot of stuff up for me, sorry bout other thread, i hadnt seen this !

[R31Nismoid]

ive merged them.

no need for two threads on the same thing.

I doubt your memory is that bad