Damo wrote:I'm not realy fussed what people class as the 'best' flutter, as everyone (who likes the sound) has their own take on whats sounds good. Usualy, the bigger the turbo and the greater the volume of the I/C and piping between the turbo and T/B will give the longest, deepest sounding flutter, usualy on lowish boost and when partialy backing off rather than gear changing.
It also helps to have a filter right off the turbo with the shortest pipe practical.
As for AFM location, I don't think it makes a whole lot of difference where it is, but would probably give better sound with it between the turbo and T/B. Problem with this setup would be subjecting the AFM to boost, and if the log is still in place like the above pic (and plumbed correctly), you will be subjecting things to boost pressure which arn't supposed to 'see' it.
As for the BOV saving turbo's unless you are running a 40yo turbo or something designed for a diesel engine, IT IS A CROCK OF SHIT!
BTW, click my lower youtube address in my sig to hear/see my flutter. Best at 4 - 5 seconds.
Damo
agree 100%
both times had a bov connected but the longer video had the vacuum line plugged and was a quality bov so it didnt open under boost
with a t25 u still get flutter with afm in front of turbo just not as loud. also t2 flutter is the funniest thing i have heard in a long time ....
Low Slow and Sarcastic
Always Oscar Mike on the AO
haha yeh ash that was way back when i had the Turboshit type 2, then after that i got the Shitz I mean blitz leaky bov didnt have a decent bov till i got the GReddy now that actually worked had a valve instead of a piston
Low Slow and Sarcastic
Always Oscar Mike on the AO
Well, for mine, I dont give a shit if it flutters or it dont. To me, Flutter (and the pursuit of it) = wank! Thats me tho!
I use a bov, turbosmart Type 1 (old style) and its so quiet youve got a job to hear it! It just sighs, thats about it.
Ive got this other big adjustable thing which hisses like all getout if i wanted just a bov sound!
Bov theory is sound tho, (ignoring the reduction in lag claim...thats a crock) even if it actually does nothing to lengthen the life of a turbo!
Its hard to prove they do any good but its harder to DISprove tho.
IMHO of course!
L8tr
E
Forcd4 wrote:Oh fuk no dude it's you a again, the oracle.
Pretty simple actualy, find out wether Frod have engineered a slight delay in throtal closing on the XR6T(tronic throtal) to prevent a pressure build up stopping/rapidly slowing the turbine shaft. If not, it means that a bunch of part time N12 enthusiasts are smarter than the engineers at Ford and anyone else who has the same technology!! For their sake, I would hope not.
Damo
Do humanity a favor, use your brain and fight the forces of WOO WOO!
Panda_ET wrote:haha yeh ash that was way back when i had the Turboshit type 2, then after that i got the Shitz I mean blitz leaky bov didnt have a decent bov till i got the GReddy now that actually worked had a valve instead of a piston
yer actually i was thinking of my VL/T when i wrote that sorry P.
When you consider the shaft RPM versus the rotating mass of the wheels and shaft assembly, adding a few parts of a second delay in throttle closing would have little if any effect on the slowing time of the rotating assembly given you have immediately converted your turbo compressor wheelinto a simple fan. Its not compressing anything anymore when the throttle is shut.
See further below.
I have done countless subjective comparisons on my own cars, both with bovs and without and i was NEVER able to determine any change in spooling/lag times for a given setup.
NO-ONE else has been able to positively claim beyond reasonable doubt the reduction in lag with the use of a bov.
Oh yes they loudly claim it "can" reduce the incidence....blah blah blah but they NEVER directly claim it actually REDUCES lag,.
Perhaps it might but a simple dyno run and some very basic monitoring equipment could confirm or deny this.
Put simply, they (manufacturers/sellers/users) cant confirm or deny.
I seriously doubt anybody here could determine any reduction in spool times with a bov even it it was reduced.
What places incredible uneven loads on the front end of the turbo is compressor surging/stalling/cavitation.
Turbo compressors rely on maintaining very accurate and laminar airflow over the blades to actually do anything at all.
Disturbing the air entry angle (angle of attack) of the airflow to a very high speed aerofoil (cpmpressor wheel blade) can result in a catastrophic delamination of airflow
The sudden halt of mass airflow from the turbocharger upon throttle closing can just result in the airflow simply stopping and the air spinning around as a mass, paddled around harmlessly by the compressor wheel but can causes the compressor to cavitate, surge, whatever you like to call it under extreme conditions.
It places massive loads unevenly over the compressor area which is quite large compared to its supporting bearing and shaft area.
Reconsider the kinds of RPMs where this issue rears its head then. 100,000 plus perhaps!
Multiply the out of balance weight factors by the wheel rpm and its weight and you have some mighty heavy high frequency vibrations, shock and impact loadings and shit going on in there in both axial and radial directions.
Easily enough to compromise the integrity of the wheel, shaft and bearings, and can be enough to cause considerable damage over time, fatigue and even eventual failure of the components.
If this kind of out of balance does not worry you, then you wouldnt see any need to balance a turbo rotating assembly after a turbo rebuild would you?
But ill bet if you have yours rebuilt, or assemble a turbo out of a box of shitters you either have it meticulously balanced at the turbo shop or are simply just waiting for it to fail eh?
Admit it, you know all too well what even tiny weight imbalances can do in time to a billion rpm turbocharger. If this does not worry you, then stop reading here and go and fuck yourself because thats how stupid you are.
Moving along:
When i was an aircraft engineer, we'd do engine changes on 747's and older 707's.
To waste time, wed often stay in the aircraft just moleing about in 1st class for a couple of hours or so!
The plane was towed over to the engine run area and given a right good rogering on the ground before the plane was let loose in the sky. A dyno run if you will!
The planes were carefully placed to face into the prevailing breezes and the blast fence was towed around the back of the plane on its tracks.
On the odd occasion, on a full power run the aircraft would begin to violently vibrate and shake and the engine would "burp". The engineers doing the run immediately shut the engine down.
747's weigh quite a bit and require heavy loads to make them shake their arses out.
What had happened was the incoming airflow to the compressor was disturbed by, say as little as a minor windshift, just enough to cause the airflow in the compressor to delaminate from the compressor blades resulting in the dreaded (and feared) cavitation/surge or stall.
Speaking of stalls, planes fall out of the sky when they stall! Fortunately, turbos and turbine engines just "burp"!
If the jet engine was surged, it was pulled straight off the plane, torn down in the engine shop and rebuilt regardless of whether it was just fitted brand new.
The uneven loads and forces generated by a compressor stall/surge exerted on the rotating assemblies of a fucking great big jet engine are sufficient to consider the brand spanking new engine fucked.
Biiiig money ladies I can assure you. Many arses in slings!
Have any of you ever been in an outboard powered boat and experienced prop cavitation (read stall/surge) *hands up*?
I suspect a lot.
Its quite a violent occurrence with heavy vibrations from very low to very high frequency transmitted into the boat hull.
It can shake the crap out of the boat and the entire event is transmitted to the boat hull from the prop shaft bearings alone!
It almost demands the throttle be shut off such is the racket and vibration.
And, have any of you seen the results of prolonged and repeated cavitation just on the outboard propellor?
Sufficient loads to actually REMOVE metal from various areas of the prop blades!
All this happening at very low blade tip speeds as well. Perhaps a couple of thousand RPM.
Well, altho the effects of cavitation in air on metal turbo wheels is pretty minor in the scheme of things, the uneven loadings and vibrations around the wheel are transmitted in exactly the same fashion as the outboard shaft bearings but at tremendously high frequencies and magnitudes!!!
Guess where they eventually go?
Interestingly, if you run a turbocharger in a suck thru setup, the sudden closing of the throttle simply causes a fairly decent vacuum in front of the wheel and the turbo will happily wizz away at a zillion RPM running in a partial vacuum.
No air in there...nothing to stall or surge, nothing to compress and create shaft loading so suck thru applications dont require any attention such as bovs and shit.
I dont subscribe to the amusing urban myths of pressure reversions alone spinning the wheels off backwards and shearing the shafts and so-on. Nice bedtime stories for the mechanically minded kids in my personal view.
I suspect they are the stuff of seriously stalled or surged turbos with laughably thin shafts of days gone by= catastrophic failures.
But I definitely support the theory of eventual fatigue damage occurring from repeated compressor stalling which happens possibly every time the throttle is snapped shut at high shaft speeds!!!!
I suspect Ford know this all too well and simply approach the issue in a different and very funky manner.
Its doesnt really matter what side of the throttle body you let air out, just so long as you maintain even and laminar airflow over the entire compressor wheel surfaces.
A bov is a pretty agricultural method of reducing the incidence of compressor stalling but whatever actually works.
Just a spring loaded piston or poppet valve. Requires a certain amount of spike to actually crack the spring.
The Ford example neatly overcomes the initial spring drama. Just hold the outlet valve open a bit....very cool when you think about it!
Armed with the above FACT's fitting a bov, ANY bov at all, can only be an advantage, It certainly cannot do any harm apart from piss off the law!
I like the notion that I am doing SOMETHING positive towards preventing, or at least reducing the incidence of compressor stall.
There is little argument against the incidence and results of surging/stalling of a high speed compressor wheel due to suddenly halted OUTPUT airflow.
/rant
L8tr
E
Forcd4 wrote:Oh fuk no dude it's you a again, the oracle.
hey E, why not just write a book? i agree with what your saying though. having something to stop compressor reversion can only be a good thing. it can't hurt.
tassuperkart wrote:Apology in advance, begin rant!
When you consider the shaft RPM versus the rotating mass of the wheels and shaft assembly, adding a few parts of a second delay in throttle closing would have little if any effect on the slowing time of the rotating assembly given you have immediately converted your turbo compressor wheelinto a simple fan. Its not compressing anything anymore when the throttle is shut.
See further below.
I have done countless subjective comparisons on my own cars, both with bovs and without and i was NEVER able to determine any change in spooling/lag times for a given setup.
NO-ONE else has been able to positively claim beyond reasonable doubt the reduction in lag with the use of a bov.
Oh yes they loudly claim it "can" reduce the incidence....blah blah blah but they NEVER directly claim it actually REDUCES lag,.
Perhaps it might but a simple dyno run and some very basic monitoring equipment could confirm or deny this.
Put simply, they (manufacturers/sellers/users) cant confirm or deny.
I seriously doubt anybody here could determine any reduction in spool times with a bov even it it was reduced.
What places incredible uneven loads on the front end of the turbo is compressor surging/stalling/cavitation.
Turbo compressors rely on maintaining very accurate and laminar airflow over the blades to actually do anything at all.
Disturbing the air entry angle (angle of attack) of the airflow to a very high speed aerofoil (cpmpressor wheel blade) can result in a catastrophic delamination of airflow
The sudden halt of mass airflow from the turbocharger upon throttle closing can just result in the airflow simply stopping and the air spinning around as a mass, paddled around harmlessly by the compressor wheel but can causes the compressor to cavitate, surge, whatever you like to call it under extreme conditions.
It places massive loads unevenly over the compressor area which is quite large compared to its supporting bearing and shaft area.
Reconsider the kinds of RPMs where this issue rears its head then. 100,000 plus perhaps!
Multiply the out of balance weight factors by the wheel rpm and its weight and you have some mighty heavy high frequency vibrations, shock and impact loadings and shit going on in there in both axial and radial directions.
Easily enough to compromise the integrity of the wheel, shaft and bearings, and can be enough to cause considerable damage over time, fatigue and even eventual failure of the components.
If this kind of out of balance does not worry you, then you wouldnt see any need to balance a turbo rotating assembly after a turbo rebuild would you?
But ill bet if you have yours rebuilt, or assemble a turbo out of a box of shitters you either have it meticulously balanced at the turbo shop or are simply just waiting for it to fail eh?
Admit it, you know all too well what even tiny weight imbalances can do in time to a billion rpm turbocharger. If this does not worry you, then stop reading here and go and fuck yourself because thats how stupid you are.
Moving along:
When i was an aircraft engineer, we'd do engine changes on 747's and older 707's.
To waste time, wed often stay in the aircraft just moleing about in 1st class for a couple of hours or so!
The plane was towed over to the engine run area and given a right good rogering on the ground before the plane was let loose in the sky. A dyno run if you will!
The planes were carefully placed to face into the prevailing breezes and the blast fence was towed around the back of the plane on its tracks.
On the odd occasion, on a full power run the aircraft would begin to violently vibrate and shake and the engine would "burp". The engineers doing the run immediately shut the engine down.
747's weigh quite a bit and require heavy loads to make them shake their arses out.
What had happened was the incoming airflow to the compressor was disturbed by, say as little as a minor windshift, just enough to cause the airflow in the compressor to delaminate from the compressor blades resulting in the dreaded (and feared) cavitation/surge or stall.
Speaking of stalls, planes fall out of the sky when they stall! Fortunately, turbos and turbine engines just "burp"!
If the jet engine was surged, it was pulled straight off the plane, torn down in the engine shop and rebuilt regardless of whether it was just fitted brand new.
The uneven loads and forces generated by a compressor stall/surge exerted on the rotating assemblies of a fucking great big jet engine are sufficient to consider the brand spanking new engine fucked.
Biiiig money ladies I can assure you. Many arses in slings!
Have any of you ever been in an outboard powered boat and experienced prop cavitation (read stall/surge) *hands up*?
I suspect a lot.
Its quite a violent occurrence with heavy vibrations from very low to very high frequency transmitted into the boat hull.
It can shake the crap out of the boat and the entire event is transmitted to the boat hull from the prop shaft bearings alone!
It almost demands the throttle be shut off such is the racket and vibration.
And, have any of you seen the results of prolonged and repeated cavitation just on the outboard propellor?
Sufficient loads to actually REMOVE metal from various areas of the prop blades!
All this happening at very low blade tip speeds as well. Perhaps a couple of thousand RPM.
Well, altho the effects of cavitation in air on metal turbo wheels is pretty minor in the scheme of things, the uneven loadings and vibrations around the wheel are transmitted in exactly the same fashion as the outboard shaft bearings but at tremendously high frequencies and magnitudes!!!
Guess where they eventually go?
Interestingly, if you run a turbocharger in a suck thru setup, the sudden closing of the throttle simply causes a fairly decent vacuum in front of the wheel and the turbo will happily wizz away at a zillion RPM running in a partial vacuum.
No air in there...nothing to stall or surge, nothing to compress and create shaft loading so suck thru applications dont require any attention such as bovs and shit.
I dont subscribe to the amusing urban myths of pressure reversions alone spinning the wheels off backwards and shearing the shafts and so-on. Nice bedtime stories for the mechanically minded kids in my personal view.
I suspect they are the stuff of seriously stalled or surged turbos with laughably thin shafts of days gone by= catastrophic failures.
But I definitely support the theory of eventual fatigue damage occurring from repeated compressor stalling which happens possibly every time the throttle is snapped shut at high shaft speeds!!!!
I suspect Ford know this all too well and simply approach the issue in a different and very funky manner.
Its doesnt really matter what side of the throttle body you let air out, just so long as you maintain even and laminar airflow over the entire compressor wheel surfaces.
A bov is a pretty agricultural method of reducing the incidence of compressor stalling but whatever actually works.
Just a spring loaded piston or poppet valve. Requires a certain amount of spike to actually crack the spring.
The Ford example neatly overcomes the initial spring drama. Just hold the outlet valve open a bit....very cool when you think about it!
Armed with the above FACT's fitting a bov, ANY bov at all, can only be an advantage, It certainly cannot do any harm apart from piss off the law!
I like the notion that I am doing SOMETHING positive towards preventing, or at least reducing the incidence of compressor stall.
There is little argument against the incidence and results of surging/stalling of a high speed compressor wheel due to suddenly halted OUTPUT airflow.
/rant
L8tr
E
herein lies E's biggest rant ever, at 1329 words it goes beyond rant and towards doctoral thesis...
[sorry didn't actually read it , but I'm with Damo on this one.]
just not as loud. also t2 flutter is the funniest thing i have heard in a long time ....
, but I'm with Damo on this one.]