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please weigh in.... comressor surge

3K views 9 replies 7 participants last post by  REXronald 
#1 ·
Someone please educate me...

What exactly is 'compressor surge'

why is it bad for your turbo's life

what causes it?

how can it be avoided?

how would i know if it was happening to my car (i read that the sound of compressor surge can be heard while its happening... what does it sound like?)


thanks
 
#2 ·
sorry to answer my own q

but i got it... web search is nice option...

"- Blow Off Valve (BOV) - Ahhh the ol' noise maker. Ever run a turbo car and hear the loud purge noise created when he/she shifted? Thats due to the BOV. The BOV is similar to the wastegate in operation. It has a vacuum line running to just after the throttle body to sense vacuum. What it does is when it senses strong vacuum (ex. when you close the throttle body in a shift) the valve opens and purges the boost withen the piping. This prevents compressor surging which will damage the turbo very quickly. Compressor surge happens because the turbo is still spinning when the throttle body slams shut. This causes the system to suddenly pressurize itself even more (if the BOV was non-existant or not working) and this surges the turbo causing it to slow down which exerts alot of force on the turbo shaft and other components. To prevent the valve from opening prematurely the spring tension is adjustable via a screw or bolt on top of the BOV. "


Anyone care to speculate if the stock BOV going to 20 psi (which the spring weight can obviously hold) is going to create an excessive amt of compressor surge due to not being able to vent that much pressure fast enough... and should i therefore upgrade BOV not because of inability to hold boost, but inability to blow off boost fast enough... ?????
 
#5 ·
REXronald said:
Someone please educate me...

What exactly is 'compressor surge'

why is it bad for your turbo's life

what causes it?

how can it be avoided?

how would i know if it was happening to my car (i read that the sound of compressor surge can be heard while its happening... what does it sound like?)


thanks

Compressor surge accurs when you let off throttle and BOV doens't open or doesn't open enough in time. It cna range from sounding like a turkey call to air surges that flutter.

Wastegate flutter accurs during boost gain (mainly when peak boost is reached) under throttle and is a quick sound (similar to a pressure cooker in some cases).

Not one is on throttle, and one is not.

Compressor surge isn't DEADLY to the turbo but can reduce life by MANY 10,000's .

If you are getting comp surge, loosen the spring (or cut it if you can't adjust a screw).


-kobi
 
#9 ·
I have the GFB Stealth BOV. It has a fully adjustable noise level from full recirc to full atmosphere and anywhere in between. And the spring can be adjusted by simply turning the head of the valve. Works great now that I have it set up right,and sounds pretty good at 50/50!
 
#10 ·
well...

after having used the RFL bov for a little while now... i have it set similarly to the tension the stock bov... (i can tell its close in tension just by how much pressure its takes on 1 or 2 fingers to depress and open the valve....

With 4 washers in the TXS RFL, the valve is either causing surge or its just partially opening and closing when blowing off small amounts of boost at low psi levels.. or when slowly backing of the throttle (only partially needed to blow off boost).... so i can't tell if the sound is compressor surge or just the valve slightly opening/closing quickly to vent off bits of boost... my argument is this....

the only way to stop this sound is the loosen the living crap out of the spring (no washers and set with very little tension)... but this causes the car to come near its stalling point (just enough tension to keep it closed at idle) and it is WAY WAY less tension than the stock BOV. My is that i've never heard the stock bov make this same flutter sound and it had quite a bit of tension... so i assume its just the valve opening/closing slightly and the reason i hear it is because now its the RFL and its loud vs the stock BOV which can hardly be heard...

make sense? I'm pretty sure this isn't surge, its just fluttering sound of partial boost release through the valve.
 
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