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Compressor surge.


JamieP

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EDIT... I MEAN COMPRESSOR STALL, thanks Wez.

 

Only since watching a video of my car on track have i noticed im getting a lot of this with my T67 setup, i run a Tial 50mm bov turbo side down in the bumper.

 

Is it anything to worry about?

 

Will it damage my turbo?

 

Should i fit an extra BOV?

 

 

Regards Jamie:)

Edited by JamieP (see edit history)
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Compressor surge or stall?

 

Surge is during spool up, it basically means the turbo is producing more air than the engine can take.

 

Compressor stall is on lift off and sounds like a flutter, this is when the pressure generated has no where to go but back through the turbo the wrong way, hence stalling. Balancing a BOV spring to hold high boost and vent very little boost is a nightmare which is why you normally get stall on light driving lift off. If you are getting stall on high boost lift off then either the BOV is not man enough or the spring is too strong to open enough.

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Compressor surge or stall?

 

Surge is during spool up, it basically means the turbo is producing more air than the engine can take.

 

Compressor stall is on lift off and sounds like a flutter, this is when the pressure generated has no where to go but back through the turbo the wrong way, hence stalling. Balancing a BOV spring to hold high boost and vent very little boost is a nightmare which is why you normally get stall on light driving lift off. If you are getting stall on high boost lift off then either the BOV is not man enough or the spring is too strong to open enough.

 

 

 

LOL! he even had me at it, i was sure it was stall he was talking about, so i guess i didn't read it properly:innocent:

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Jamie, as mentioned on one of your youtube comments the sound is stall, not surge. It's nothing to worry about, it'll stall like a bugger under low boost lift off, but thats part and parcel of having a BOV that is set for high pressure.

 

If you are not seeing pressure drop at WOT and high load then you can reduce the BOV spring until it starts to affect the boost hold. It'll help reduce compressor stall to the minimum your system allows, but it's pretty pointless.

 

Edit- balls, Wez already explained it in a better way!

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I don't run any form of BOV on high power turbo engines, and have never found turbo life or spool compromised. Several major turbo experts agree that BOV's are for noise reduction rather than turbo life increase, or spool decrease. F1 turbo engines and Indy engines never used them, nor any Group C engines, as far as I know, and some Group C / IMSA units did 24 hour races, and all would welcome less spool time.

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Very interesting Chris. You are most probably right. It just contradicts the logical through and understanding of what is happening.

How does BOV reduce noise? I would think it genrates more noise with the well known PPffftt... I'm guessing that if i block off mine, it would just make the stall sound, right?

 

If there are no real function, why does to soop come with a by-pass type as stock?

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Porsche and Saab started it with the 944 turbo, and the 99 turbo, their customers were not the type to want a "funny noise" when lifting off under boost, so they relieved the back pressure by re circulating back to the intake, thus stopping the noise, too. Others followed. Most used the Bosch recirculating valve still in current use today.

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