To Blow Off Valve or not to Blow Off Valve??

[aimre]

Here, ill add to mre confusion.

http://www.youtube.com/watch?v=OtMmze0KM6Q

At about 20 sec in, youll hear the Audi drive past, and u can hear it dose. But then at 50 sec, when the lancia drives past, it sound like its got a BOV.

Although audi won both constructors and drivers championship

BTW, there a bad accident in that, which marked an end to Group B rallying.... its safe to watch the first 1.20 min

[aimre]

http://www.youtube.com/watch?v=quDX36WJM7k

some more dosing rally cars

5 min in and its all about the lancia... lots of BOV noises

http://www.youtube.com/watch?v=tdgkmirNPf8

O btw, these cars were 4 sec slower than f1 cars of the time, which were making over 1000hp from theit 1.5L engines

[Muzz]

Sorry for the slow reply to your post sting, i havnt had much time latly.

Garrett says it themselves, CAN cause damage when in CONTINUOUS or LONG PERIODS of time in the surge region.

No, what Garrett says is exactly this:

Continued operation within this region can lead to premature turbo failure due to heavy thrust loading.

Not "continuous operation in this region", but "continued operation in this region", there’s a big difference.

This could very easily mean - if the turbo continues to see surge conditions throughout its life, this may lead to early failure. NOWHERE in that statement does it imply that the surge needs to be continual for the effects to be damaging, so don’t try and pretend it does, ok.

Infact if you read on slightly, you’ll also come to this statement:

This situation is commonly addressed by using a Blow-Off Valves (BOV) or bypass valve.

^^If they were actually saying that damage may occur, only if the turbo was continually running in surge, they wouldn’t go stating that the problem is usually addressed by running a bov, now would they.

Generalized FAQ answers is not SOLID PROOF of anything.

Exactly what are you trying to say with this statement?

Are you trying to say Garrett doesn’t actually have proof that operating in surge conditions is bad for their turbos? Did they go and put false info into there FAQ and turbo tech sections yeah? There making misleading statements like the one below are they?

In cases of extreme surge, the thrust bearings of the turbo can be destroyed

Maybe your trying to say they’ve never really bothered to work out if surge conditions are detrimental??
Dude, do you seriously think that the engineers who have determined that operating in surge is bad for the turbos they are designing, have done so without any proof? Stop kidding yourself, ok.

Consider the forces involved between continuous operating in the surge region versus a little bit of chatter from your charge pipes filled with some boost.

Ok, I will.

Got negligible?

No, I get equal.

Consider a turbo experiencing a surge condition for half a second, consider the same turbo experiencing the same surge but for a period of 10-15 seconds.

There’s going to be NO differences in the forces involved, the only difference is the TIME that the forces are being applied....

A continuous period of surge compared to the same amount of surge in short bursts of time, would probably only cause more heat energy release, due to the extended periods of friction. Heat that probably won’t even effect the temp of the metal receiving the extra friction, much, as it would already be damn hot.

A little bit of chatter from your charge pipes.

Where did you learn that the chatter is actually coming from the piping?
Is this solid info you’re sharing here, or are you stating what you think?

Garrett seems to think it’s from the compressor.

This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor.

Maybe you’re just doing your best to make it seem like surge from suddenly blocking the airflow is somehow less damaging than surge for other reasons.
Is this something you actually know, or is it something you feel, or is it just a misleading statement to try and help convince people of your opinion?

[Muzz]

Also please get off your high horse about everyone's knowledge. You've done one fluid mechanics course and you think you know it all?

Hahahahhahahhaha you’re funny.
High horse? Wouldn’t that imply that I think I know more than you guys?

unless you’ve studied fluid dynamics to a very high level which none of us have.

Infact, id even go as far as to say that, im the one who understands how very extremely little I actually know.

none of us here can even BEGIN to understand

as I’ve stated, NONE of us have the knowledge

We don’t know how much surge will effect the turbo

I’m not saying my setup will be better than yours or anything at all like that

^^Yes clearly I’m under the impression I know more than everyone else, everything ive said screams it out hey.
BTW, I haven’t done a fluid dynamics course, never implied I did????

Please... Leave your comments on education at the door and concentrate on the discussion not those discussing it.

do you understand how the surging air effects the turbines mechanicals? Im guessing not, which really dosnt make what your saying any more than an uneducated opinion

I never said anything about Aimre's Education. I was stating that he dosnt know exactly how operating in surge is going to effect the parts of the turbo, like the rest of us, so cant really go saying its not going to effect the turbo, as he dosnt have that knowledge. And neither do i which i though was made clear by this statement:

unless you’ve studied fluid dynamics to a very high level which none of us have.

[Muzz]

Just read the 1st 6 pages of this thread. Quite a few people have stated that there is zero effect on turbo life from running in an unstable surge condition at every gear change for a split second, like its a fact.

I was just wondering if anyone who has stated this has any actual info to support their claims??
Turbo manurfactures all seem to state that the thrust loads on the shaft when the throttle is snapped shut, can cause accelerated wear of the thrust bearing. I havnt seen anything to prove or disprove this yet. Untill somone can show it dosn't, ill be listening to the people designing these products who say it does.

[aimre]

I never said anything about Aimre's Education.

Im guessing not, which really dosnt make what your saying any more than an uneducated opinion, the worst kind there is.

i'll reply further when i get back from uni

[DLO01]

I was just wondering if anyone who has stated this has any actual info to support their claims??
Turbo manurfactures all seem to state that the thrust loads on the shaft when the throttle is snapped shut, can cause accelerated wear of the thrust bearing. I havnt seen anything to prove or disprove this yet. Untill somone can show it dosn't, ill be listening to the people designing these products who say it does.

I asked a turbo manufaturer/repairs workshop some questions in regard to Bov's and thier effect on Turbos. Hope this clears up any misconceptions or myths that we may have. This is their response:

I asked **** here the same questions as you've asked me, and although he has seen no 100% positive sign of damage due to no BOV, he still recommends using one for over 10psi of boost pressure when using a Ball Bearing turbocharger.

As for the BOV helping keep the turbocharger spooling, I can definately say this works, as turbocharger reversion would definately cause the turbocharger to reduce spool speed quite rapidly. There may only be a small difference in response time, but there is definately a difference.

This is the best sort of answer your gonna get i think. They way I see it, your gonna have more load on the shaft with more boost you have, so therefore you will get more wear. Simple.

[string]

Quote: String
"A little bit of chatter from your charge pipes. "

Where did you learn that the chatter is actually coming from the piping?
Is this solid info you’re sharing here, or are you stating what you think?

Garrett seems to think it’s from the compressor.

Oh dear. I completely meant and said that the charge pipes cause "chatter". I can take partial quotes out of context too.

Garrett doesn’t actually have proof that operating in surge conditions is bad for their turbos.

You're shooting down my interpretation of garrett's FAQ only to try to bend it in your direction. Please...

[string]

When turbochargers operate in surge for long periods of time, bearing failures may occur

Please explain to me your interpretations of continuous and continued, and how they relate to Garrett's own words: "long periods of time" (which you so beautifully claimed they did not say).

[string]

10-15 seconds of surge = x ammount of boost pushing back for 10-15 seconds of mayhem.
Off throttle surge = x ammount of boost in a given volume leaking back through the compressor, obviously diminishing pressure quickly over time, thus also force. You thought you were being smart with your pedanticism over the term "force", you have failed.

Also, explain to my why metal which is already hot "probably" won't have it's temperature affected by friction. I thought you did mechanical engineering???

[Bludger]

just dose and replace when failure occurs

[Lukezen27]

just dose and replace when failure occurs

Yeah I've decided to dose and that's it

aimre makes a good point, the cost seems about that same in the end anyway...