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

[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