Venting the Stock BPV on an ST205 GT4, Bad or is it ok? Options

[Goonter]

Ive been reading all night about blow off valves and bypass valves. All i seem to read about is bad things (besides the sounds it makes) about blow off valves. Things like you run rich, lose power and crap like that. I wanted to know if this is the same way for 3SGTE ( i would assume so) Also does running rich every time you shift gear waste a noticeable amount of gas?

Also say i don't get a BOV. The BPV is designed to recirc the air back to the intake box. If i get an Apex'i intake filter to replace my box, Is there any way i can recirc the air back to the intake system? (btw I'm just getting the filter. The rubber intake piping will stay. I noticed the BPV is bolted onto the box so i see no way of getting it recirc'd to the intake system unless the piping was metal and a flange was welded onto it for the BPV to bolt onto.

This post has been edited by Goonter: Sep 24, 2011 - 6:08 PM

[bsamps4]

I wish I had a definitive answer for you, but let me try to answer your question with a question. "If blow off valves were so bad, then why do thousands of people use them?"

With certain blow off valves you could likely route them to recirculate with your intake if this was a big concern. Or you could use your stock diverter and make a custom intake to mount it to. I believe Apexi makes a pipe with connections for your diverter. Another thing that you should look out for in your research is whether the car owner's that are complaining about them are using MAP or MAF sensors. I understand that on a MAF sensor that re-circulation is necessary due to the placement of MAF sensors.

In short I think you'll be fine running a BOV. Have fun with it they sound awesome!

[Neon90424]

2nd gen BOV vent to atmosphere = bad metered air is lost causing rich mixtures recirculation = metered air is returned to system.
3rd gen BOV vent to atmosphere = cool Recirculation = 0.00001 second faster spool

This post has been edited by Neon90424: Sep 19, 2011 - 10:42 AM

[Sunny]

Hi,

the advantage of a BOV is very simple, it protects the turbo to began pumping which means high stress for it -> pumping = turbo spins but no air flow

if you use a sencond gen. 3S-GTE is the problem that the MAF calculated the air for the ECU but she doesn't enter the engine becouse she went to athmosphere -> the engine run to rich
to solve this just went the air back in front of the turbo after the map sensor

the 3rd gen. uses a MAP sensor to calculate the correct fuel which means the wented air is not calculated -> no rich mixture

greetz

This post has been edited by Sunny: Sep 19, 2011 - 1:33 PM

[Unicorn]

Hi,

the advantage of a BOV is very simple, it protects the turbo to began pumping which means high stress for it -> pumping = turbo spins but no air flow

if you use a sencond gen. 3S-GTE is the problem that the MAF calculated the air for the ECU but she doesn't enter the engine becouse she went to athmosphere -> the engine run to rich
to solve this just went the air back in front of the turbo after the map sensor

the 3rd gen. uses a MAP sensor to calculate the correct fuel which means the wented air is not calculated -> no rich mixture

greetz

Sunny's post has pretty much nailed it, I just want to re-word it a little to make it clearer - a blowoff valve protects the turbocharger from surge loading, which is explained at length all over the Internet. I have a couple of links to very detailed descriptions of the cause, nature and effect of turbo surging, if you'd like me to post them just let me know. So anyway, you know that the BOV protects the compressor from surging by venting the excess pressure to the atmosphere, rather than it being recirculated as it would if a CBV was used.

What Sunny said about the second gen engine is this - the problem with using a BOV on a 2nd gen 3S-GTE is that the use of a Mass Air Flow (MAF) sensor by the ECU to calculate the air needed by the engine for the correct AF mix means the AF mix is actually wrong because the BOV vents the excess pressure to the atmosphere - the ECU doesn't account for this. That air doesn't enter the engine because it's being vented to the atmosphere, the ECU doesn't know anything about it, and this causes the engine to run with a lack of air and the end result is that it runs rich.

Because the 3rd Gen 3S-GTE is a little more advanced and uses a Manifold Absolute Pressure (MAP) sensor, it can more accurately calculate the correct fuel to air mixture. In this engine, the vented air from the blowoff valve is not taken into the equation by the ECU, because the MAP sensor provides realtime manifold pressure data to the ECU, and therefore the AF mixture is normally correct and the engine does not run rich.

Sunny says that the solution with a second gen 3S-GTE engine is to recirculate the air back in front of the turbo in the system after the MAF sensor, that way the ECU doesn't take that air into consideration to affect the AF mixture, but it still makes it into the engine so the mixture doesn't end up being rich. This is done with a Compressor Bypass Valve (CBV) in place of a BOV.

I wrote that in kind of a hurry, so if I got any of it backwards please correct me and I'll edit accordingly!

Hope this helps.

This post has been edited by Unicorn: Sep 19, 2011 - 5:04 PM

[Smaay]

Unicorn is 100% correct!

[Goonter]

Awesome detailed explanation unicorn. Thanks alot that's what i've been looking for. I guess that kinda answers my question for the intake too since if theres no BPV no need to recirc the air back to the intake.

[Unicorn]

No problem at all, just glad I can help a little

By the way, in modern mechanics, MAP sensor theory often only covers it's use as an ignition timing sensor input for the ECU, but in this case it is used to read air mass data using the "Speed Density Method". This takes engine RPM and air temperature into account in calculating the approximate amount of air being ingested by the engine. This information is used by the ECU to calculate how much fuel should be injected, and also through the traditional use of the MAP sensor, it can be used to adjust ignition timing.

This is a very "heavy reading" article, but it's got all the info you could ever need on speed density method: http://support.moates.net/2010/02/11/theory-speed-density/

For the purpose of this thread though, the important piece of information from there is this:

The goal of Speed-Density is to accurately predict the amount of air ingested by an engine during the induction stroke. This information is then used to calculate how much fuel needs to be provided and may also be used for determining an appropriate amount of ignition advance.

This post has been edited by Unicorn: Sep 19, 2011 - 6:52 PM

[jlspec]

What has been said is correct, but I like to add some more.

The reason that the 3rd gen is ok using the BOV is because the map system measures the air as it enters the throttle/intake manifold. In other words the BOV is located before the sensor. The second gen measures the air at the intake which the BOV is located afterwards.

The best solution for the second gen or any system using a AFM is using a aftermarket system like the old HKS VPC. For example the HKS VPC system installs the sensor right before the throttle body and after the BOV.

In any case the BOV is still recommended when using a 1st or 2nd gen 3SGTE due to a lack of a BPV.

[Goonter]

Thanks for the informative replies guys. I appreciate it. Good to know i can put a BOV without sacrificing power or fuel. Thanks again

[Goonter]

Alright i know i got my answer for the topic and all that stuff. But i guess i'll change the title and hopefully get someone with knowledge to what i wanna do and see if it's bad or not.

Soooo i wanna vent my stock BPV and see what it sounds like. Is there any drawbacks with doing this or no? I heard that i just unplug the BPV where it meets the intake box and plug the hole where the BPV used to be. Is this the right way? If not what is? (if anyone has done it before)

And i already know about the car not running rich with a BOV since we have MAP sensors so im guessing if i do this it would be the samE?

[UndaGrwnD]

im sorry that i bring up a old topic.

but i wanted to know the same, how does the stock blow off valve sounds when venting to atmosphere?

i know that you can unplug the BPV, and plug something in the airbox hole were the BPV should be...but how does it sound...?

[Smaay]

What has been said is correct, but I like to add some more.

The reason that the 3rd gen is ok using the BOV is because the map system measures the air as it enters the throttle/intake manifold. In other words the BOV is located before the sensor. The second gen measures the air at the intake which the BOV is located afterwards.

The best solution for the second gen or any system using a AFM is using a aftermarket system like the old HKS VPC. For example the HKS VPC system installs the sensor right before the throttle body and after the BOV.

In any case the BOV is still recommended when using a 1st or 2nd gen 3SGTE due to a lack of a BPV.

this is all wrong! MAP means pressure, not air! a MAP systems is totally different from a MAF system.

[Stambo]

^^ i agree. But a speed density system measures vacuum.

[Smaay]

^^^ yes because thats pressure, not airflow.

when the throttle plate is closed, its reading vacuum, when its open its either reading 0 or boost. I have a boost gauge on my car still that is currently running NA. at idle is 18-20 inHg and at WOT its reading 0

[evo_lucian]

im sorry that i bring up a old topic.

but i wanted to know the same, how does the stock blow off valve sounds when venting to atmosphere?

i know that you can unplug the BPV, and plug something in the airbox hole were the BPV should be...but how does it sound...?

I have both a rfl and stock abv and often swap them when I am bored. The stock bov sounds like a softer rfl. Sounds better IMO , its only audible when you get on it as opposed to the rfl that's loud all the time. Sometimes I think the rfl blows off in vacuum too lol.