Turbo Questions - Help a turbo noob

[Toyo Truck]

Hey guys,

To those that own turbos, I have a few questions.
I am starting to get the hang of turbos, but there's a few simple things I'm still not 100%.
Can one of you turbo gurus help me out with some answers on some likely to be fairly
noob-action turbo questions?? I'd appreciate it fellas.
(I want to do some turbo mods, but wanna make sure I know what's going on down there!)

1) With BOV's most if not all I have seen have a nipple on the top of them
for vaccum line to the manifold. (at least on a 1G-GTE it does)
I presume that when the vaccum rises in the manifold, it opens the BOV yeah?
(IE the pressure of the air inside the intake, and the vaccum from the manifold
are greater than the spring in the BOV valve holding it shut so it opens momentarily)

2) If I disconnect the vaccum hose from the top of the BOV, it shouldn't open any more
right? IE the spring should hold the BOV valve shut yeah?

3) With no BOV connected/working, to vent excess boost, the turbo wastegate will
open?? I've only seen separate turbos, so with the 1G-GTE's and twin turbos,
do you have a wastegate for each turbo? or 1 wastegate for the two turbos?

4) With an external wastegate, how do these work? do you seal up the standard
wastegate and just run the external gate? What are the major benefits of one?

Thanks fellas,

Cheers,
Bart

[SillyCarS]

1g's dont have BOVs

that line from the plenum (read intake manifold) runs to a diaphram that opens the wastegate a the back of each turbo when the required boost is achived, this stop the turbo from continuing to produse more and more boost, a boost controller if added goes in between the two. also the pressure signal it is sending is boost no vac

dont disconnect it

[PlacentaJuan]

if you disconnect the vacuum line from the BOV, then it will most likey leak under boost. when boosted the 'vacuuim' line also supplies boost which helps to keep the BOV closed also.

the bov will not help the wastegate since it is not designed to open until you take your foor off the accelerator.

the only time a BOV will "regulate" boost is when your BOV is faulty or not designed for the high boost pressures you are runnign and it starts to leak.

[LeeRoy]

1) With BOV's most if not all I have seen have a nipple on the top of them
for vaccum line to the manifold. (at least on a 1G-GTE it does)
I presume that when the vaccum rises in the manifold, it opens the BOV yeah?
(IE the pressure of the air inside the intake, and the vaccum from the manifold
are greater than the spring in the BOV valve holding it shut so it opens momentarily)

On boost, boost fills the line and helps to hold the valve shut, when the butterfly closes and the manifold becomes a vacuum it pulls the valve open. Posititve pressure on the underside of the valve also pushes it open. Keep in mind that that vacuum line due to its size and length can also delay the vac/boost signal sent to the bov.

2) If I disconnect the vaccum hose from the top of the BOV, it shouldn't open any more
right? IE the spring should hold the BOV valve shut yeah?

Depending on the spring yes and no. In a low boost application if the valve is really tight then it shouldnt open, but if your running high boost then the pressure will probably make it creep open.

3) With no BOV connected/working, to vent excess boost, the turbo wastegate will
open?? I've only seen separate turbos, so with the 1G-GTE's and twin turbos,
do you have a wastegate for each turbo? or 1 wastegate for the two turbos?

Wastegates dont vent boost, they regulate it. Once desired manifold pressure is reached their vacuum lines open the gates and stop/slow the turbos therefore moderating how much air they flow. So by lessening the exhaust travelling through them you lower the air they produce, and also lower the boost theyre making. Once they stop making this set pressure the gates shut, turbos pump more air, and once desired psi is reached, the gates open again and regulate it.

On on and off (well the switching between) throttle, manifold pressure is still present, and without a bov or similar, this pressure makes its way back out through the turbo compressor.

4) With an external wastegate, how do these work? do you seal up the standard
wastegate and just run the external gate? What are the major benefits of one?

Basically yes. They work the same as an internal gate but have the benefits of being available in bigger sizes, etc. Can also be mounted where you want. Also, the majority of large turbos do not come with an internal gate.

[merc-blue]

Wastegate regulates boost.
When desired boost is obtained (enough to open the wastegate) exaust goes out the gate instead of throu8ght the turbo,. reducing the turbo speed and boost.

BOV stops compressor surge, and helps your A/F ratio
When you back off throttle the air is still being pushed by the turbo until it slows but its being forced against the throttle butterfly so it bounces back to the turbo which can slow it, even spin it backwards and is often a cause for damage to turbos.
The BOV takes the air that is forced against the butterfly and routes it to the intake before the turbo but after the AFM because the air has already gone though the AFM its been counted in the system and its nice to keep the same amount of air in there.
BOVs that vent to the atmo on street cars.... same with waste gates generally belong to people of lesser education ofter who have obtained a very cool haricut and a chubby slapper of a girlfriends

[Z2TT]

Hi,

Another thing I should add about the 2 types of Blow off Valves.

If you have a car with an Air Flow Meter and run a Atmospheric venting blow off valve, your engine will run rich for a short period of time after the blow off valve has vented, because air measured by the air flow meter is lost. This is not good. In this case you are better off to get a recirculating bypass valve that vents the air back into the intake, unless off course you love the sound of a atmo venting BOV.

If you have a car with a MAP sensor that is located in the manifold then you wont have this problem.

[Toyo Truck]

Hey Guys,

Thanks for all the awesome info. Thats bloody rad!
Exactly what I was after, and this is the reason I love Toymods so much.
Bloody best forum in the world...for cars.

You have answered all my queries above thanks guys +repskis,
but now I may have an issue!!
Turns out this thread may end up saving my turbos from what you guys say!
(I figured something was wrong, and read below you will see why)

When I bought the car,
Its a GZ20 Soarer, Factory Manual, 1G-GTE Gen 3, Turbosmart BOV, Turbosmart adj.
boost controller, Autometer Boost Guage.

Now when I got it, the rubber pipe from the intake (plenum chamber?) was connected to
the top of the Turbosmart BOV.
Problem with that is, old mate previous owner, took this rubber hose off a small metal
pipe running accross the engine and down over to near where the turbos are.

Photo of how I got the car (Rubber hose connected to top of BOV)


Photo of what I think should happen and what I run now (Rubber hose connected to pipe)


1) IS this pipe the vaccum line that actuates the wastegate as described above??
IE to vent excess boost from the turbos????????

2) IF it is, does that mean that the BOV has been doing the venting for my turbos
whenever I connect the rubber hose to the BOV??

3) How do I get the wastegate to work aswell as the BOV? do I just put a "T" piece in the
rubber hose and run another rubber hose to the top of the BOV? or will this not be enough
vaccumm to do both the BOV and the wastegate?

Cheers,
Bart

[MWP]

You are still not quite understanding the purpose of a BOV.

BOVs are used to stop compressor surge during closing of the throttle (ie, during gear changing).
Compressor surge is that turbo flutter noise that you hear from some turboed cars.
Its bad for two reasons, it shortens the life of the turbo, and slows the turbos speed which means it takes longer to come back on boost when needed (ie, after a gear change).

BOVs do not control how much boost a turbo makes *at all*... thats the job of the wastegate(s).

You must always have the wastegate(s) in working order.
Without it/them working, youll hit fuel cut or overboost and kill the engine and/or turbos.
A BOV not working correctly may reduce engine power output, but wont damage anything.

So, first... work out where that steel line over the engine goes to.
If it goes to the wastegates, then slap your mate quite hard and tell him he's a n00b.

Go buy a vac line T piece (get em from any car parts shop), and run that vac line from the inlet manifold to both the BOV and the steel line.

[Z2TT]

This is how it should be setup.

Each turbo should have a hose running from the turbocharger to the wastegate, in your application you have a Boost controller, So the 2 hoses coming from the turbing housings should be joined together with a T Piece then goto the boost controller, then a hose comes out of the boost controller and gets split into 2 hoses using a T piece, the 2 hoses goto your actuators.

As for the BOV, you should just have a Vacuum hose running from the Inlet manifold to the nipple on the BOV, like MWP said just get a T piece to split one of the hoses coming out of your inlet manifold and run it to the BOV.