Is turbo whine technically good or bad?

[Scooby]

Ok you engineers out there, what causes turbo whine?? It seems like the products out there that are designed to increase the flow and smooth out the turbulence at the mouth leading into the turbo (thus improving efficiency) typically have the added effect of reducing turbo whine. So is turbo whine actually a byproduct of something inefficient such as turbulence?? And if so, shouldn't we strive to reduce it? I know it sounds good, but what is it exactly?

 

[DLeno]

the whine is a natural consequence of generating sound waves from the rotating wheels and all the complex periodic micro turbulances. The energy contained in those sound waves is, you are right, produced by the engine and as such are part of the "lost energy" so to speak. But those energy levels (contained in the sound waves themselves) are so small they are inconsequential. thus, direct efforts to reduce turbocharger whine itself are mis-applied as regards increasing the charger's efficiency.



In the stock intake tube, for example, there are some crafty characteristics designed to reduce sound emissions (they have to meet certain noise standards in order to sell the truck) but those devices don't necessarily improve turbocharger efficiency; they are designed to meet a federal noise requirement.



One observation I make is that the speed at which the essential mechanical events happen inside the turbo occur (for the higher power levels) are well above the highest frequency detected by (even young female) human hearing. So the audible components of those events must (I presume) occur from some complex sidebands or difference frequencies.



so in other words, (my opinion here) don't target the whine. embrace the whine



now then, there is an argument in favor of reducing turbulance, and such efforts, in my opinion, may be productive (even though none yet have been proven with statistical rigor to produce a repeatably measureable benefit). As a side effect, they may also reduce noise. So no, I would not strive to reduce it for its own sake. I would target turbulance and take the unintended consequence of sound reduction as a bonus.

 

[Scooby]

Thanks for input. I agree that I wouldn't target whine to reduce it for the sake of just reducing it. I intended to mean that we should be targeting the reduction of the inefficiency that is causing the noise (if in fact that inefficiency is the culprit).



I didn't realize the junk inside the torque tube was designed to reduce noise alone - I thought it might be there to reduce turbulence. I was just reading on another thread about the gutting the tube and getting more turbo whine... I didn't think it made sense to introduce more turbulence (inefficiency) just to get a nice sound... ... but then again... .

 

[DLeno]

well I didn't mean to imply that the junk in the stock intake tube had no turbulance benefit. It may. I'm only saying that its primary reason appears to be noise reduction, and its primary effect appears to be that and a reduction of air flow.



Consider the TAG device -- intended to reduce turbulance at the compressor inlet, improve spoolup, fuel economy, give warm feelings, and generally promote world peace. There are some good engineering reasons why it would straigten the air out (by the way it is constructed), essentially producing air moving in one direction instead of many (kind of like polarized light, such as what is filtered by a polarizer lens on a camera or sunglasses). And there are anectotal stories of perceived improvement. Yet we don't have any real scientifically valid evidence of a repeatably measureable benefit (power, spoolup). BTW, this device is known to reduce the noise of turbo whine. Theoretically, we think it may break up micro turbulances, cancel sound waves, whatever. Just no proof (as of yet anyway) that it actually benefits anyone for the reason one might feel compelled to buy it (improved turbocharger performance).