[How to] Install a blow-off valve

Adydas

New member
dont know if i can raise a Q here but, i was under the impression the alltrac been AFM needed to plumback and couldnt vent to atmoshpehere.. Is this true?
 

SuperWhite92

New member
You're supposed to, since if you don't, you're blowing off air that has been measured, and so the car won't run correctly. It will rich out, and if it riches out too much the car can stall.
However, it's been discovered that a properly adjusted BOV vented to atmosphere won't stall the car, while providing all the "benefits" of a BOV.

Basically, we're supposed to recirculate it but we don't, because we're ricers 8)
 

db

Active member
^^ What he said. My BOV is vented to the atmos and the worst that happens for me is a puff of black smoke when I'm shifting with a good amount of boost built up.

I do get small amounts of backfire (little pops in the exhaust) sometimes but since I have no cats its hard to tell if the BOV is influencing it or not.

Oh, and I didn't recirc mine simply to keep the install simple.
 

88alltracohio

New member
Adydas":1qrsokxu said:
dont know if i can raise a Q here but, i was under the impression the alltrac been AFM needed to plumback and couldnt vent to atmoshpehere.. Is this true?

whats plumback, is that recirculation? and is there thing you can do to fix running to rich, besides recirculate/ bypass?
 

smog7

Moderator
has anyone know of someone that has succesfully recirculated an mr2 bpv using the stock intake system? also anyone have pics of where the vacuum line should be connected?
 

LegacyofDan

New member
from what i understand from what is said here, that there is disadvantages to have a BOV?...such as ur car will run richer?...are there other disadvantages?
 

Toxygene

Active member
LegacyofDan":2nvdul0a said:
from what i understand from what is said here, that there is disadvantages to have a BOV?...such as ur car will run richer?...are there other disadvantages?

Aside from scaring pedestrians and needing to be quite while shifting around cops?

You'll only have the disadvantages if you don't recirculate it.
 

BriinumsBo

New member
Hmm, i`m not sure, but maybe i got a bad construction bypass valve or smth. I have a bypass valve from nissan s14, but the problem is that it is open whenever there is a vacuum in the intake manifold. so its open also when idle. best available place for bov/bpv in our engine bay is right after the turbo BEFORE the IC, so whenever idling, the air would circulate through the turbo all the time and would get extremely hot.
the same applies when boosting and switching gears(or just releasing gas pedal) at that moment the air mass would circulate through the hot turbine without flowing through the IC to cool down - this is asking for detonation when you press the pedal again...
 

Gary

Moderator
BriinumsBo":sy1dpo31 said:
Hmm, i`m not sure, but maybe i got a bad construction bypass valve or smth. I have a bypass valve from nissan s14, but the problem is that it is open whenever there is a vacuum in the intake manifold. so its open also when idle. best available place for bov/bpv in our engine bay is right after the turbo BEFORE the IC, so whenever idling, the air would circulate through the turbo all the time and would get extremely hot.
the same applies when boosting and switching gears(or just releasing gas pedal) at that moment the air mass would circulate through the hot turbine without flowing through the IC to cool down - this is asking for detonation when you press the pedal again...
Come again?
Also, BPV should be closed when idling.
 

BriinumsBo

New member
i mean its not the best, but the easiest place to attach a bov - either putting a T-piece hose instead of the stock rubber between turbo and IC ur just weld it on the IC front piping.. the best option is after the IC, but the space is limited...

but still the problem persists if the BPV is put BEFORE the IC, so the air is getting hotter while circulating through the turbo (while changing gears), doesnt it?

i tried to vent to atmosphere but i didnt really enjoy the overfueling after gear change..
 

Gary

Moderator
BriinumsBo":35n5tbiq said:
but still the problem persists if the BPV is put BEFORE the IC, so the air is getting hotter while circulating through the turbo (while changing gears), doesnt it?
I don't think it is a big deal since Toyota also place the stock BPV right after
the compressor outlet.
The BPV doesn't recirculate air all the time, just a short burst after the boost changes to vacuum.
 

BriinumsBo

New member
Gary":gdwnq7x2 said:
BriinumsBo":gdwnq7x2 said:
but still the problem persists if the BPV is put BEFORE the IC, so the air is getting hotter while circulating through the turbo (while changing gears), doesnt it?
I don't think it is a big deal since Toyota also place the stock BPV right after
the compressor outlet.
The BPV doesn't recirculate air all the time, just a short burst after the boost changes to vacuum.

stock BPV? wtf is that? on a st205? :shock:
anyways, after a bit of googling i read that when idling the inlet has vacuum of 0.5 bar, but when changing gears, it dorps to 0.8bar vacuum.. is that right?
 

Gary

Moderator
Not only on ST205, MR2T also came with stock BPV.
That is what I have in my ST185.
I does vent to the atmosphere though.
Here is a clip.
You can also see the boost gauge when it vents.
http://www.youtube.com/watch?v=REoG0k_LVjs
BTW, stock idle is 18-21 in.Hg. or 0.6-0.7 bar (vacuum)


mr2bovgi0.jpg
 

BriinumsBo

New member
are you using AFM? do you run into stalling problems?
also how does your MR2 bpv differentiate between idle and gearchange? does it have to do with the fact that idling has a bit lower vacuum than gear change? so the spring is set at some 0.8bar or smth?
 

Gary

Moderator
I'm using an AFM.
It stalled only a few times during the past year.
The stock BPV is a pull type, 2 chambers with a diaphragm, no spring.
It only opens when there is a change in pressure in the manifold. (from pressure to vacuum).
At idle, it stays shut without any possibility of leak.
 

Gary

Moderator
I'm too lazy, I like the sound, it has never given me any problem, and I have a plan to upgrade intake, turbo, BOV and IC in the future.
 
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