Fluttering noise after installing new turbo - Subaru WRX Forum
 
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post #1 of 9 Old 06-21-2004, 11:13 AM Thread Starter
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Fluttering noise after installing new turbo

I just put in my vf34, STI injectors, and Walbro fuel pump and everything went well. What's happening is that between 15 and 18-19 lbs of boost, I hear a fluttering noise from the turbo and my boost gauge jumps up and down with the fluttering fluctuating about 1-2 lbs. I didn't make any adjustments to my ABC, but I think I had it way to open when I was running stage 2. Any guesses as to what to adjust or check? I thought it might have been my BOV (APS adjustable) so I tightened it down a bit in case it was opening to early, but that didn't seem to have much of an effect (except making the BOV noise a little more crisp). Any suggestions would be appreciated.
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post #2 of 9 Old 06-21-2004, 03:57 PM Thread Starter
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For more background:
I had bought my turbo from another guy here in WA and I asked if he had any problems with flutter on his car. I'm going to look at the ABC and hopefully it will help or take care of it all together.
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post #3 of 9 Old 06-21-2004, 07:39 PM
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Can you describe it a little more,

as for what I see now, it could be Wastegate Flutter (sound like a pressure cooker in your turbo?) with a bad map (or EBC) for the boost control, also not helped by the flutter.

-kobi
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post #4 of 9 Old 06-22-2004, 12:09 PM Thread Starter
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The noise that I can hear inside the car, sounds like the flow of air is disrupted (very quickly) and then freed up (very quickly) creating the flutter. I think it's definately something with the wastegate/ABC system.

I've got UTEC, and I did adjust the ABC last night, seemed to help a bit. When I first installed the UTEC with my other Stage 2 components I cranked the ABC pretty far open, so I cranked it closed about 3 more turns. Any suggestions for how many cranks it would need to be open the ABC from all the way closed for Stage 4? I was worried that since it was a used Turbo, there was something wrong with it. I'm running the generic TurboXS Stage 4 map, waiting for my Dyno tune appointment on the 17th of July. The thing that scares me the most is watching the Boost Guage fluctuating so much at the high boost. It seems to happen more at >60% Throttle. I'm hoping it's just a map problem that will get fixed when it gets tuned.

Too bad, I can't just teleport to my Grandma's house, she lives in Greensboro and have you take a look.

256 WHP on Mustang dyno that measures Stockers at 167.
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post #5 of 9 Old 06-22-2004, 01:24 PM
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That is compressor surge. It is caused by the compressed air (boost) backing up and slowing down the compressor wheel in the turbo. That is why you hear it more at low throttle positions. At high throttle positions the blow-off/bypass valve opens and lets that compressed air out before compressor surge happens. It is nothing to worry about.
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post #6 of 9 Old 06-22-2004, 01:47 PM Thread Starter
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It happens when my foot is heavier on the gas (not exactly sure I was getting throttle positions right). If it is compressor surge, I've got the APS adjustable BOV, should I "loosen it" thus making it easier to open?

Will a good dyno tune be able to take care of this?

256 WHP on Mustang dyno that measures Stockers at 167.
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post #7 of 9 Old 06-27-2004, 10:43 PM
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Quote:
Originally posted by Cosmo
It is nothing to worry about.
If it was comp surge it would be something the worry about, it seriously alters the lifespan of the turbo, and should be corrected, but... its not Comp Surge (if its over 60% unless you were just 100% dropping to 60% fast). It could be wastegate flutter (if it happens right before you reach peak boost), test it that way. See if you can recreate it under lower boost than spiking towards peak; flutter should only happen during the spool on the way to peak, and will last from 1/2 second to 2 seconds depending on the turbos. It pretty much acceptable throughout and won't damage the turbo, just some Downpipes are shaped to cause a noise during wastegate venting (not purposely of course)

hope this helps

-kobi
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post #8 of 9 Old 06-28-2004, 05:16 PM Thread Starter
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Thanks for responding Kobi, I thought no one was going to answer. I'm pretty confident it's wastegate flutter. It does only happen on the way to peak boost, and does eventually steady out. It just freaked me out when I saw the needle on the boost gauge bouncing around all crazy like.

I've got the TurboXS 4" downpipe, if I got something like the Perrin with a divorced wastegate pipe, would that help?

256 WHP on Mustang dyno that measures Stockers at 167.
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post #9 of 9 Old 07-01-2004, 08:38 PM
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nah both are known to make a bit of noise, just some more than others. no harm though.

-kobi
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