Need New Turbo

[Ralph Wiggum]

Definatly foreign object damage. Something quite soft though as it didn't chip the blades..

Perhaps part of the air filter or part of a plastic intake hose..?

[RAP1D]

Yeah, plastic of some kind maybe... there's lots of cheaply fabricated plastic between the filter and the compressor wheel, something came off

[deon]

This is not strictly correct...

Cavitation by definition can only occur in a liquid, and refers to the phenomenon where localised pressures drops below the vapour pressure of the liquid. This creates small bubbles that collapse upon pressure recovery. The collapse of the bubbles generates very high energy, high velocity movement of the liquid in very localised sense - if this occurs near to a solid surface such as a pump casing or impeller, then these can be damaged.

Cavitation is not posible in a turbo charger as it flows a gas, not a liquid.

If you read Simons post via the link Marcus provided this would be explained... For those that have not read Simon's most excellent post, there are two salient points relavent to this discussion:

1) there are a number of reasons why a BOV might be installed, on the Falcon Simon's guess was that it was installed to make the car quieter, and AVOID the flutter NOISE.

2) BOV's were invented for a reason - Simon has indicated this primarily relates to emissions. Some turbo cars use an air flow meter to gauge the amount of fuel required - flow back through this meter is measured twice resulting in too much fuel and poor emissions, stop the flow going back through the air flow meter and the air flow measurement is correct meaning better emissions...

Also think about this logically, which of the following do you think is more likely to happen - The pressure on the induction side of the motor is so great it a) bends the super high strength fins on the compressor wheel of turbo, or b) you blow off a hose clamp?

Cheers,

Ben.

Cavitation occurs in FLUIDS, yes fluid and liquids are two different things and air is indeed a fluid. BOV's are not used in rally cars and other high performance cars because there is a possibility of leakage and since long term reliability is not an issue in a race car they dont use BOV's. Also BOV's do provide better performance for on/off throttle applications I.e. street driving, racing on the other hand is usually at full throttle constantly, in applications like drifting where there is continuous throttle modulation BOV's are very useful. For the street in a car that isnt to heavily modified BOV's are good especially in a manual. In saying that most people remove the BOV to get that flutter sound and it doesnt really cause major damage unless your running a very high boost level.

Edited 02/05/07 09:13 AM by deon

[Cubes]

Cavitation occurs in FLUIDS, yes fluid and liquids are two different things and air is indeed a fluid. BOV's are not used in rally cars and other high performance cars because there is a possibility of leakage and since long term reliability is not an issue in a race car they dont use BOV's.

Wrong... No bov = improved throttle response, has nothing to do with 'because they might leak'. In the past I've known a few mildly modified VL turbo's pushing over 200,000km's on their stock 'journal' bearing turbos with no bov.

Also BOV's do provide better performance for on/off throttle applications I.e. street driving, racing on the other hand is usually at full throttle constantly, in applications like drifting where there is continuous throttle modulation BOV's are very useful. For the street in a car that isnt to heavily modified BOV's are good especially in a manual. In saying that most people remove the BOV to get that flutter sound and it doesnt really cause major damage unless your running a very high boost level.

Come on deon. You are clearly speculating.

You clearly have not compared no bov to bov.

No bov provides the greatest benefit at light throttle to moderate acceleration.

Accelerate from a from standing start with part throttle, short shift in to second and get back on the throttle. OMFG... instant power the delay to fill the ic and piping is now near nonexistent.

No bov in this situation most definitely improves response or less lag what ever you wish to call it.

Drive it around at WOT and its not as much of a noticable difference.

Believe the marketing hype from bov manufacturers. lmao.

Edited 05/05/07 02:39 PM by Cubes

[deon]

Wrong... No bov = improved throttle response, has nothing to do with 'because they might leak'. In the past I've known a few mildly modified VL turbo's pushing over 200,000km's on their stock 'journal' bearing turbos with no bov.

Come on deon. You are clearly speculating.

You clearly have not compared no bov to bov.

No bov provides the greatest benefit at light throttle to moderate acceleration.

Accelerate from a from standing start with part throttle, short shift in to second and get back on the throttle. OMFG... instant power the delay to fill the ic and piping is now near nonexistent.

No bov in this situation most definitely improves response or less lag what ever you wish to call it.

Drive it around at WOT and its not as much of a noticable difference.

Believe the marketing hype from bov manufacturers. lmao.

I have driven a car with no bov and then fitted with one..and there IS less lag...why? well heres why when your car flutters yoru turbo is SLOWING DOWN because the pressure build up is huge and air is beign forced to escape through the fins..hence why it slows down, only difference with a BOV is the excess pressure is released and the turbo, as a result spins faster.. You say I you short shift into another gear you get instant power..NO difference witha BOV because if you "short sh*tft" as you say it shouldnt have time to open. Beleive the marketing hype? maybe you just choose not to believe anything that's marketed, not EVERYTHING is bad. and answer this question. what race cars have BOV's and what dont. You may notice that rally cars, alot of race cars and many other cars that run no bov have another similarity..sequential gearboxes, ie clutchless shifts, BOVS not needed there.. You may like to think they are pointless and stupid "Show off valves" only boy racers and hoons buy them, but there is a good reason for them and most often then not theyre better than no bov..in saying that I prefer the flutter so id rather not run a BOV the difference in performance in my opinion doesnt justify the money however in saying that there IS a noticable difference and it IS better running say a standard bov on light-medium boost levels than taking it off..just not by much

[Cubes]

Deon buddy.. Please use the return key your posts are a pain in the arse to read.

Your results are CONSIDERABLY different to what I have experienced both on the dyno, street and track.

I don't believe your speculation. Yes the turbo will slow but with a bov the turbo has to refill the IC and its piping when you run a bov... Many go to great lengths to shorten their IC pipe work. You sound like your quoting from the turbo smart website. :D

Regardless of the 'theory' crap in practice its what I have and many others have experienced... hey Even Simon from Nispro thinks along the same lines as I.

Go grab a turbo'd car if you don't already own one and test it for your self. The results will surprise you.

Have a little read of what Simon thinks.

http://autospeed.drive.com.au/cms/A_1457/article.html

Maybe you will believe some one who is well known in the industry rather than some mug on the internet who has done some extensive testing on various cars with and without a bov.

Edited 06/05/07 01:30 PM by Cubes

[deon]

Deon buddy.. Please use the return key your posts are a pain in the arse to read.

Your results are CONSIDERABLY different to what I have experienced both on the dyno, street and track.

I don't believe your speculation. Yes the turbo will slow but with a bov the turbo has to refill the IC and its piping when you run a bov... Many go to great lengths to shorten their IC pipe work. You sound like your quoting from the turbo smart website. :D

Regardless of the 'theory' crap in practice its what I have and many others have experienced... hey Even Simon from Nispro thinks along the same lines as I.

Go grab a turbo'd car if you don't already own one and test it for your self. The results will surprise you.

Have a little read of what Simon thinks.

http://autospeed.drive.com.au/cms/A_1457/article.html

Maybe you will believe some one who is well known in the industry rather than some mug on the internet who has done some extensive testing on various cars with and without a bov.

why would many manufacturers put a BOV in their car if it were pointless and/or worse than not having one?

[Cubes]

why would many manufacturers put a BOV in their car if it were pointless and/or worse than not having one?

It improves drivability/smoothness and emissions.

[deon]

hmm good read..good points, but he still says that the spiking in the piping causes the turbo to run out of its efficiency range which is bad..as for the rest of the stuff written there I think there needs to be more information.

[Cubes]

hmm good read..good points, but he still says that the spiking in the piping causes the turbo to run out of its efficiency range which is bad..as for the rest of the stuff written there I think there needs to be more information.

He doesn't actually say it runs out of its effieciency range at all.

"If you change gears at quite a good speed, you can actually get a boost spike on changes; if you're trying to hold a constant 30 pounds, when you do a racing change you'll get 32-33 pounds when you crack the throttle open again. If everything's working well, you've got a full head of stream waiting to go into the throttle as soon as it's opened.

If its not tuned correctly it may cause detonation. Pushing a turbo out of its effiency island in to choke when changing up gear is impossible; if that were the case then at the top end of that gear it would be well and truley in to choke anyhow so its a moot point.

On the note of boost spike... The only issue I'd be concerned about is using silicon hose with worm drive clamps. Start pushing 20+psi and you may very well begin to blow ic piping off during gear changes. Regardless, its generally recommended to run tbolt clamps over 20psi anyway.

Edited 07/05/07 07:37 AM by Cubes