Do I need a BOV?

[Al-sw20]

So why did Toyota put a OEM bov on it in the first place?

For emissions and to stop the turbo making fart noises between shifts .

The ST185 GT-Four has the same 3sgte as the SW20. No BPV/BOV. They don't have failing turbos.

[mr2magic]

I'll just leave this here:
http://www.themotorhood.com/themotorhoo ... he-experts

You don't need it, but it's cheaper than buying a new turbo if and when it lets go.

just my 0,02

[Al-sw20]

I'll just leave this here:
http://www.themotorhood.com/themotorhoo ... he-experts

You don't need it, but it's cheaper than buying a new turbo if and when it lets go.

just my 0,02

Do ST185 Celica GT-Fours turbos let go?

[mr2magic]

Oh i bet they do. .just like any other gt gtx efr sb pt ct..powered vehicle out there.

The simple truth is noone with a blown turbo will go to the lengths necessary to diagnose the exact cause...so neither of us knows exactly how many turbos fail due to surge caused by running without a bov.

Whether the gt4 has a bov or not and whether the turbo charger lasts or not is completely irrelevant for me. Compressor surge is a fact, that it causes enormous stress on the thrust bearings on journal bearing turbos is a fact, that it causes enormous stress on the shaft is a fact. If i use a bpv/bov i can reduce the stress to an absolute minimum which, no matter which way you look at it will prolong the life of the turbo.

As already noted....this is my view and i will continue to use a bov. Not using one gains nothing, using one loses close to nothing.

[Al-sw20]

Except it's not compressor surge. That happens under load.

[mr2nut123]

But there has to be an acknowledgement that it does put more stress on the turbo than running one....plenty of people have poped turbos very quickly without one (outside the Mr2 community).

sorry your not going to get that acknowledgement from me.
its a BS myth.

there is no evidence anywhere online to back up the theory it will blow your turbo.

I ran mine 400hp build with a 3071 for many years without a BOV. What he said. I'd rather have the noise from that backpressure and buy a few turbos anyway even IF it did

[mr2magic]

Except it's not compressor surge. That happens under load.

Who on earth told you that?

Here from Garrett:

Turbobygarrett Welcome to Turbobygarrett
Become a Gearhead
Where to buy | Product Catalog

About Us
Products
Turbo Tech

You are here
Home > What is compressor surge?
A. The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side. Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:

-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application
Turbo
Q. What is compressor surge?

[jimGTS]

Except it's not compressor surge. That happens under load.

Who on earth told you that?

Here from Garrett:

Turbobygarrett Welcome to Turbobygarrett
Become a Gearhead
Where to buy | Product Catalog

About Us
Products
Turbo Tech

You are here
Home > What is compressor surge?
A. The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side. Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:

you are quoting ON boost compressor surge!
NOT what we are talking about

[jimGTS]

I'll just leave this here:
http://www.themotorhood.com/themotorhoo ... he-experts

You don't need it, but it's cheaper than buying a new turbo if and when it lets go.

just my 0,02

i can almost guarantee half of those "experts" also sell BOVs!
so they are not going to talk bad about them

[jimGTS]

-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application
Turbo
Q. What is compressor surge?

you know half of those "reasons" didnt exist on garrets website UNTIL they are or were sponsored by those selling BOVs from what i hear.


the quote clearly explains ON BOOST comp surge, yet goes on to mention the reasons for failure are OFF boost surge/flutter.

[mr2magic]

1) Compressor surge is when there is a pressure delta between the compressor housing (lower pressure) and the region after the housing (higher pressure) which causes a pressure wave to impact with the spinning compressor. This is completely irrespective of the cause of the surge.

2) Surge can be induced in two ways:
a) The engine is not able to ingest the mass of air being produced by the turbo causing a pressure build up through the intake system from the valves back to the compressor housing
b) The throttle plate is closed suddenly during spool also causing a pressure build up in the intake system before the throttle plate back to the compressor housing.

Surge never can occur without boost or load, prior or during to it's accurance.

As to the remarks on who is sponsoring what and why - that's pure hearsay and not part of the discussion.

I'll repeat myself - you do not need a bov! Having one will definately and without a doubt reduce the stress on the thrust bearings and the turbine shaft.

[masterbateson]

whats an AFM?

[mr2magic]

AFM = Air Flow Meter

old school technology (replaced by MAF and MAP/AIT systems) for measuring the amount of air being ingested by an engine for a given load. It uses a spring loaded hinged flapper door with a defined cross section that is attached to a variable resisitor such that the resisitance changes according to how wide open the flapper door is. The door itself opens according to the amount of air flow.

Pre '93 mr2 used these whereby the infamous 'don't touch the screws' with regards to disconnecting the wiring was born

[Pauln]

AFM = Air Flow Meter

Pre '93 mr2 used these whereby the infamous 'don't touch the screws' with regards to disconnecting the wiring was born

I have a late '93 rev 2 with an AFM, so its probably safer to say rev 3 on rather than go by year.

[pbmr2]

I`m also in the "they are not needed" camp but would point out that the pressure build up can pop pipes off from time to time.

Ran without a BOV on 3 different cars and at some point each one of them popped off a vac pipe or intake pipe. Never had any turbo troubles.

On some forums it`s call the pigeon mod, due to the sound.

[masterbateson]

my cars def on a AFM and not MAF, to be honest up till now i thought they were both the same things and just different way of saying it.

My cars a 92 turbo so falls well into that period.

Never heard of a screamer pipe b4? = noisy exhaust?

[Al-sw20]

Screamer pipe is a short piece of pipe that vents to the atmosphere straight off an external wastegate rather than rerouting the exhaust gas back into the exhaust further along.

They scream when the car is under load/boost as the expelled exhaust gases just get dumped straight out. Generally sounds really shit on a road car.

[masterbateson]

just been reading about ditching the bov on another forum (driftworks)
sounds like its a bit pointless unless you are running massive boost?
Might take mine off and try it.

[masterbateson]

And after reading a bit more on a 200sx forum i think i wont bother removing my BO because from what I've read so far all it does is makes your car make a weird noise, and I havent heard anything yet about any type of performance gains?? only losses/car running cr&p.

If thats the case why would anyone do it?

[Al-sw20]

Quicker response between shifts. The turbocharger doesn't have to fill the entire outlet to throttle body piping again with compressed air.


An AFM equipped car might run rough because it measures the air pre turbocharger.