Now we've all obviously heard that turbo flutter is horrendous for your turbo yada yada. However I'm now getting a new one- this guy is attempting to tell me that turbo flutter has NO effect on turbo rpm whatsoever and is therefore not damaging to the turbo in any way, however, this goes against literally EVERYTHING I have ever been told about the subject. He cited some half-baked video, and it got me wondering whether this had ever been tested? Has anyone here with a turbo rpm gauge (or monitoring software) ever tested whether turbo flutter actually slowed the turbine down more than with a BOV, and if not whether anybody would be willing to test it? I've tried searching high and low, and can't find ANYTHING on the topic with actual testing.

 

Turbo flutter is just the blow off valve being to small and thus making the fluttering sound. I don’t see how that has anything to do with turbo rpm or turbo damage.

 

It's caused by a sudden decrease in air flow causing a pressure spike, and the pressurized air to back up into the compressor. I'm sure someone who knows more will chime in, but it's gonna slow the wheel.

 

"Turbo Flutter" is compressor surge and is potentially fatal to the turbo. Closing a downstream butterfly with no BOV to release the pressure sends the compressor flow to near zero ie to the left of the surge line on the map. To the left of the line, the lines of constant compressor speed fall to the left.
#ad


Note that to the right of the surge line, the speed lines fall to the right. This is stable - if you restrict the outlet, the flow reduces, the operating point moves to the left along the speed line and output pressure increases - which counteracts the declining flow. Eventually you reach a point where flow and pressure balance unlike the surge region where - as flow reduces -> pressure output reduces -> flow reduces further -> pressure output reduces further . . . you get the picture. All this happens in an instant - the flow eventually hits zero then reverses, the pressure output reaches zero, then flow starts again. The result is rapid, violent pressure fluctuations that will destroy the compressor wheel if sustained.

 

been saying for 20 years

https://forums.nasioc.com/forums/sh...9e60133a96de3d3913d4&p=46809692&postcount=829
https://forums.nicoclub.com/bov-placement-hot-or-cold-t448569.html#p5053814
https://www.evolutionm.net/forums/e...-recirculating-bov-question.html#post11883983
https://www.customtacos.com/threads/do-i-need-a-bov-now.185881/post-2090553?nested_view=0
https://zilvia.net/f/showpost.php?p=5524317&postcount=22