No Bov, And Turbo Life-span

[Kaido_RR]

thanks for the input paul and bogcock

im starting to understand why people see it as a bad thing... i think for the time being i will reconnect my atmo bov and look at investing in a set of stock gtr bovs. would it be best to run both or will it be fine with just one?

[paulr33]

how many vlt's you think have suffered compressor failure as a the result of running stupid amounts of boost and not using a BOV and having the loudest flutter known to man

[33SOM]

how many vlt's you think have suffered compressor failure as a the result of running stupid amounts of boost and not using a BOV and having the loudest flutter known to man

None. Turbos are made to spin

[Kaido_RR]

None. Turbos are made to spin

but direction of spin is what is in question...

yes a turbo is ment to spin in x direction and z speed but if u have a force in y direction at u speed/force it will cause an unbalance in the turbo itself resulting on possible damage....

well thats what i grather from what paul was saying

[33SOM]

' date='10 Jun 2006, 12:03 AM' post='2244222']

but direction of spin is what is in question...

yes a turbo is ment to spin in x direction and z speed but if u have a force in y direction at u speed/force it will cause an unbalance in the turbo itself resulting on possible damage....

well thats what i grather from what paul was saying

i dont think bearings care what way there spining. Dont turbos make pressure?

Friends of mine have had no bovs for years with no problems...

[Kaido_RR]

i dont think bearings care what way there spining. Dont turbos make pressure?

Friends of mine have had no bovs for years with no problems...

miss the point

if a shaft is set to move/spin in X direction, and there is a force actting on it in Y direction. there will be stress put onto the shaft as it trys to overcome the force in Y direction. as the shaft will always want to move in the X direction

ps if im not right jump right in paul

[R31Nismoid]

i dont think bearings care what way there spining. Dont turbos make pressure?

Friends of mine have had no bovs for years with no problems...

ok, basic principle for you.

Grab a straw.

Twist both ends in the same way equally.

Now, twist one side one way... and the other end opposite.

You can see that the forces are fighting one another and the stress on the straw then causes it to buckle and deform.

Obvsiouly this is a gross exaggeration to the highest extent, but its the most simple thing i can think of at the moment

Personally, ive had a turbo fail. Now it was the bearings in the cartridge that let go.

I was running no BOV at the time, i also had other issues relating to piston rings kinda "missing" and below average oil pressure, but it was ball bearing and restricted etc

I wont say no BOV caused it, i doubt that it did. But you will never know, its one of those things... i dont even know if it contributed... its a very grey area unfortunately.

MAF/AFM based cars and stalling is primarily associated with driving style.

I had issues, but i adjusted my driving style to compensate and i never stalled again until i went GTR BOV's

Hope that adds something

[33SOM]

ah makes sense now

[Busky2k]

Theres no way the turbo would spin backwards with no BOV.

Also are you claiming that the factory BOVs were not for emmissions paulr33? Thats a very flawed statement if you say so.

[paulr33]

i paulr33 clearly state:

the factory BOV or recircluation valve was not fitted for emissions and has nothing whatsoever to do with emissions

[archie01]

how many vlt's you think have suffered compressor failure as a the result of running stupid amounts of boost and not using a BOV and having the loudest flutter known to man

I know of one that failed because of this.

The turbo had been rebuilt by Kyp from ATP a year before it failed.

The turbo failed because the owner was constantly coming on and off the throttle (doing burnouts) on a particular occassion.

It was running 16psi of boost when it let go.

Kyp rebuilt the turbo again and put it down to the constant on / off throttle application (doing burnouts) and the amount of boost it ran that caused it to fail.

Had it been running 7psi it would not of happened. This is because the turbo is spinning a lot less at this boost level and is therefore 'de-spooling' a lot less when the throttle is shut and putting a lot less stress on the shaft and bearings than it would have running 16psi and above.

Given the above, I also conclude that BOV or recirculating valves were put there MAINLY and INITIALLY for emission reasons and NOT for turbo longevity reasons.

When Nissan introduced the BOV in its vehicles they weren't running high amounts of boost pressure. Turbo longevity was not much of an issue for them. What was an issue was meeting and passing emissions. I agree with Simon's rationale on the first page. Then as Nissan began running more boost through their turbochargers in later years a nice by product of the inclusion of the BOV was that it was also helping the turbo survive longer from those people who would drive them hard/abuse them (ie come on and off the throttle constantly) in an effort to reduce any warranty claims.

As an aside, in one of the HPI dvd's, I remember one the owners of a large japanese tuning workshop saying with regards to their GTR drag car that they experience turbo failure often because they run a high amount of boost pressure and no BOV's.....food for thought.

[paulr33]

so how does fitting a BOV from factory provide any changes to the car's setup from an emissions point of view

a) no bov factory

when the throttle body closes the air reverbs back, chops on the compressor wheel and does a mid air collision. with a larger intercooler core and a pod filter or open mounthed air intake you can hear the LOUD and AUDIBLE compressor chop. with the oem are intake and standard air filter you won't hear the compressor chopping / flutter. the results would be jerky gearchanges, excess stress (or more stress than 0) and the loud flutter / compressor chop if you had a pod filter or open air intake. the car will still drive correctly, have the same exhaust and intake emissions, and run correctly. its only when a misconfigured ATMO bov is used that stalling is induced in the problem so this is ruled out from factory as no factory nissan bov is atmo

b) bov on factory

when the throttle body closes the air reverbs, hits the valve on the BOV and recircs to the front of the turbo compressor inlet. the air is reused and the system continues to run as normal. there is no excess pressure/foce placed on the compressor from the flutter/chopping

i dont believe nissan cared about running "more boost" on factory applications, i dont believe this was a concern nor did the worry about it. why would they ?

[paulr33]

straight off turbobygarrett:

Blow-Off Valves

50mm Compressor Blow-Off Valves Assemblies:

The TiAl Blow-Off Valves design is the result of extensive development and testing. The 50mm compressor bypass valve is a vital component of any turbocharged blow-through induction system. This custom TiAl manufactured Blow-Off Valves will improve throttle (time to boost) response as well as help relieve the damaging effects of compressor "surge loading". The CNC machined housings are available in several high luster anodized colors.

Note: Blow-Off Valves Assemblies include fitting and V-band clamp.

[paulr33]

i still to this day believe

the factory BOV was included to prevent excessive compressor wear and tear and causing premature failure. i believe it has nothing whatsoever to do with emissions and was never designed for an emissions solution/fix

[paulr33]

from turbobygarrett again::

What is the difference between a BOV and a Bypass Valve? How do they work, and are they necessary?

A Blow Off Valve (BOV) is a valve that is mounted on the intake pipe after the turbo but before the throttle body. A BOV's purpose is to prevent compressor surge. When the throttle valve is closed, the vacuum generated in the intake manifold acts on the actuator to open the valve, venting boost pressure in order to keep the compressor out of surge.

Bypass valves are also referred to as compressor bypass valves, anti-surge valves, or recirculating valves. The bypass valve serves the same function as a BOV, but recirculates the vented air back to the compressor inlet, rather than to the atmosphere as with a BOV.

[R31Nismoid]

on a MAF equipped car the BOV was used for emissions.

it avoids over-fuelling in a MAF based application

end of story

[paulr33]

so on the rb30et factory on the vl turbo that has no bov how does it pass emissions then ? how does it avoid the over fueling? the overfueling is only an issue when its amto vent as the measure air is thrown out the window. in a no bov mode the air still used.

i thought ?

[R31Nismoid]

It was under the 1980's rules, they are somewhat more strict than backthen

Emission laws are far more stringent than 20 years ago

i didnt have a BOV for a while, it stalled and carried on cause it was using MAF

[paulr33]

so did yours behave like that from the factory? the stalling and overfueling ?

nevermind just re-read it. but i stll dont get why it would fall under emissions

the vlt's from factory didnt stall

[archie01]

so how does fitting a BOV from factory provide any changes to the car's setup from an emissions point of view

a) no bov factory

....... the car will still drive correctly, have the same exhaust and intake emissions, and run correctly. .....

Did you read Simons quote from the article or did you just disagree with him without reading it?

i could tear all those comments to shreads, each of them is full of flawed of comments (the ones from the so called expert)

your point a) was answered like this:

As you close the throttle, the build up of pressure and the larger volume inside the intake has to go somewhere; it can't go into the engine because the throttle is shut. Instead, it has to do a U-turn and it comes screaming out the airflow meter. That creates the 'gobble-goggle' sound.

"The gobble-gobble sound is something the public has grown to love.

"The airflow meter is not all that smart and does not realise the air is going in the wrong direction; it therefore measures the air twice (once going into the engine and again going out in the wrong direction). The computer now tips in twice as much fuel as what's required, making it run rich - making it not pass emissions.

You clearly state that with no BOV there will be "the same exhaust and intake emissions" and Simon clearly believes the emissions will change.

In his quote, Simon offers the reason why he believes emissions will change.

You do not offer a valid / logical reason why you believe emissions won't change.

Simon has been a leader in the aftermarket vehicle modification industry (specialising in turbocharged cars) for as long as I can remember but more importantly he has backed up his view with an example of what he believes is happening, which by the way makes sense to me.

This could be discussed till the cows come home but until you provide me with a logical reason why Simons theory is flawed I have to agree with him.