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Old 06-30-2009, 06:24 PM   #1
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Default intake prrs like a cat?!

So about a week ago I installed a freshly rebuild td04-19t. I took the car out for a ride and everytime I went into full boost and I would let the gas pedal off the bov would go off and the intake made a weird sound. It kinda sounds like the air is not fully coming out of the bov. I adjusted the spring on it and it's still the same. I have a Greddy type rs bov, 3" intake elbow to behind the headlight with a k&n filter. My guess is that the bov is not letting the pressure out of the IC causing the air to hit the turbo? What do you guys think?
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Old 06-30-2009, 06:34 PM   #2
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Oh and forgot to ad that my old 15g didn't do this
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Old 06-30-2009, 06:56 PM   #3
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Your car is trying to tell you that you're a ***** and that there's no reason to let off while in boost.




Yes, I have nothing useful to add to this thread.
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Old 06-30-2009, 07:22 PM   #4
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Sounds like compressor surge. Go look on youtube for compressor surge vids and see if its the same sound.
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Old 06-30-2009, 07:38 PM   #5
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Yes, it sounds similar... But why would I get compression surge with a bov?
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Old 06-30-2009, 07:44 PM   #6
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bov could be bad, or needs cleaning, or one of the many other things that cause compressor surge.
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Old 06-30-2009, 07:47 PM   #7
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The last autox I was at had an EVO that would randomly and inconsistantly experience compressor surge. Could be that you're just exceding the capacity of your BOV to blow off.
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Old 06-30-2009, 07:56 PM   #8
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Just my .02 but a 19t compressor wheel upgrade doesn't flow THAT much more that a bov can't keep up with it.
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Old 06-30-2009, 08:08 PM   #9
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Did you hook up the vacuum line when you installed your new turbo? Did you have the BOV off and perhaps hooked it up backwards?
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Old 06-30-2009, 09:53 PM   #10
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Quote:
Originally Posted by wayne_curr View Post
Did you hook up the vacuum line when you installed your new turbo? Did you have the BOV off and perhaps hooked it up backwards?
no i didn't take it out. I just replaced the turbo....and how could i hook it up backwards? at low and high boost it seems to be good, its mostly at middle boost....i dont know if its surge tho cause it kinda sounds like the bov but a deeper noise
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Old 06-30-2009, 10:20 PM   #11
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http://www.youtube.com/watch?v=kfw_mTEVFuM
it sounds just like this clip....its a greddy type rs too....i wonder if its a problem with these bov or if its supposed to sound like that. only thing is my car never sounded like this before the new turbo
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Old 07-01-2009, 12:00 AM   #12
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Quote:
Originally Posted by miataspeed2005 View Post
no i didn't take it out. I just replaced the turbo....and how could i hook it up backwards? at low and high boost it seems to be good, its mostly at middle boost....i dont know if its surge tho cause it kinda sounds like the bov but a deeper noise
If you didn't hook the boost reference for the BOV after the throttle body, it wouldn't work properly. Would still function in a way, but would get compressor surge for sure.
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Old 07-01-2009, 08:27 AM   #13
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Quote:
Originally Posted by dustinb View Post
If you didn't hook the boost reference for the BOV after the throttle body, it wouldn't work properly. Would still function in a way, but would get compressor surge for sure.
I'm 99.9% sure it's in right, but I will take a picture when I get home from work and I'll post it up.
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Old 07-01-2009, 10:06 AM   #14
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I've heard plenty of other cars with part throttle lift compressor surge just like the one in the video.

I'm going to speculate that the BOV mechanism is not moving freely enough to be operated by the supplied vacuum. If that is so, clean/lubricate the valve assembly, reduce spring tension more if possible, and/or attempt to determine if your plenum vacuum is leaking somewhere. This part is guesswork for me.

What I do know is that your larger compressor wheel has a different map and your surge line has stepped to the right on the chart. This means at part throttle you might have surge as a frequent dinner guest now. And fiddling with the BOV may garner zero gain.

I will defer to those with more edjumuckayshun in the subject to support or supplant my theories.
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