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Discussion Starter #1 (Edited)
I posted a while back about a boost problem I was having. My truck will build boost and then flutter really bad. sometimes it will come out of the flutter and hold steady but most times it won't. I tried to get a video today but all i had was my cell. You can see when the boost gauge starts to jump back and forth but it's hard to hear through my phone. It is very audible though.

I've been through the wastegate twice, it is operating properly, i've been through the BOV and it is fine. No leaks on any of the vacuum lines and It does it with my exile et01 with and without c02 and also my hallman manual controller. I'm at a loss at this point. I'm thinking the issue may be compressor surge but i'm not totally sure and if that is the case why did it start doing it now? someone suggested a bad plug having something to do with it, but idk..

if it helps anybody in helping me, I did break two followers back at the end of january, the issue began at the beginning of march but i didn't drive it much in between so i don't know if the its related to the issue

video
http://www.youtube.com/watch?v=VVovVaQR6eQ&feature=youtu.be
 

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Sounds like its operating on the surge line to me and fact it amplifies on the shift would seem to back it up. Once the go in to surge they sometimes wont recover. You havnt changed air filter or ducting? If air flow through the engine has reduced (you mentioned valve train problem) could induce surge.
 

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Mine does the exact same thing! From what I can gather it has excessive back pressure and is causing this to happen. Jose mentioned it in a thread a few days ago. My car is a 421 with a 75mm compressor but with a 96mm turbine wheel. Back pressure on my combo is between 2.0-2.3 to 1. Mine will only go to 18psi but reads 34-38psi at the turbine housing.

What engine and what turbo do you have? What is the exhaust wheel size?

Could it be valve float also? I know I don't have a ton of spring pressure (200ish), what is yours?
 

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Discussion Starter #4
Sounds like its operating on the surge line to me and fact it amplifies on the shift would seem to back it up. Once the go in to surge they sometimes wont recover. You havnt changed air filter or ducting? If air flow through the engine has reduced (you mentioned valve train problem) could induce surge.
what exactly is the surge line? does that have something to do with the turbo map?

airfilter and ducting are all the same.. only thing that has occured is the followers breaking. Like i said i fixed it right after and didn't drive it much for a the month of february and then started noticing the issue at the beginning of march.
 

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Discussion Starter #5
Mine does the exact same thing! From what I can gather it has excessive back pressure and is causing this to happen. Jose mentioned it in a thread a few days ago. My car is a 421 with a 75mm compressor but with a 96mm turbine wheel. Back pressure on my combo is between 2.0-2.3 to 1. Mine will only go to 18psi but reads 34-38psi at the turbine housing.

What engine and what turbo do you have? What is the exhaust wheel size?

Could it be valve float also? I know I don't have a ton of spring pressure (200ish), what is yours?
turbo is a pt8847
http://www.precisionturbo.net/Stree...ils/Street-and-Race-Turbocharger---PT8847/287

5.4L bored .030 over. I don't think it's valve float just based on others running similar combo's with the same heads and springs.
 

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Discussion Starter #8
Is your fuel tank vent big enough?

Blessings........ron
I don't see why not, its ran the same way its been for years. What's your thought on the vent?
 

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Discussion Starter #9
Have you looked at the cap ,my cap was bad changed it and rotor problem went away.
Distributor cap? This is a COP setup
 

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Take the air filter off it and see what happens.
 

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What about spark plug gap ? Can it be blowing out the spark ?
 

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Discussion Starter #12
Plugs were gapped at .026 when I put them in. They had about 15 passes on them and 4-500 miles on the street when the issue started. I'll do a comp test and if all checks out I'll throw a new set of plugs in and see what happens
 

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Discussion Starter #15
I'll try it without the filter too.. I made a nice step up on the filter a while back.. the filter on the left is what I ran the first year I had the setup together the filter in the right has been on since last august.

 

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Discussion Starter #17
Yes and in the log you can see it wreaking havoc on the maf readings
 

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I'm still thowing out stupid suggestions, and never run into it personally, but I have heard of guys having to either move the MAF to get it out of some turbulent area that had been accidentally created....and one guy even went with some straightening vanes to clear up that kind of problem. Usually it comes from modding the tube, or relocating the MAF too near a bend.
 
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