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Boost dropping off on the top end.

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Old 03-25-2010, 10:24 AM
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^^Thats a good question. You want a wastegate spring that is at the least, half the max target boost or not holding boost can occur. I forgot all about this.
Old 03-25-2010, 10:26 AM
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Originally Posted by Soul Coughing,Mar 25 2010, 10:27 AM
you can't adjust duty cycle over RPM. It's only adjustable as a percentage for the entire pull. If you're dropping boost at higher RPM, you're either running out of compressor or have an inefficiency in your exhaust system that is causing exhaust back pressure. If you set it up via the EMS, you can control boost more efficiently, but lose the ability to change boost pressure as easily on the fly. I have the same issue with my current setup as i have a Tru-boost, but run an EMS. Especially when you're running the turbo setup as a Daily driver.
He has a sidewinder tubular manifold so I wouldnt think he would have back pressure or its a very piss poor design. Also, that 6262 turbo he is running definitely isnt even breathing at that power and boost level so i wouldnt think it would be that either.
Old 03-25-2010, 12:40 PM
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Originally Posted by Spoolin,Mar 25 2010, 01:26 PM
He has a sidewinder tubular manifold so I wouldnt think he would have back pressure or its a very piss poor design. Also, that 6262 turbo he is running definitely isnt even breathing at that power and boost level so i wouldnt think it would be that either.
I've seen less believable things happen. He said he's running a 15 pound wastegate spring, so he shouldn't have an issue with the actual spring. Usually when boost drops up top, and additional wastegate duty cycle is needed, emap is starting to exceed map.

Considering the actual car isn't here, conjecture can only be made, but if the parts of the system are found to be working correctly, then its usually the efficiency of the system that can be found to be at fault.
Old 03-25-2010, 12:45 PM
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Originally Posted by Soul Coughing,Mar 25 2010, 03:40 PM
I've seen less believable things happen. He said he's running a 15 pound wastegate spring, so he shouldn't have an issue with the actual spring. Usually when boost drops up top, and additional wastegate duty cycle is needed, emap is starting to exceed map.

Considering the actual car isn't here, conjecture can only be made, but if the parts of the system are found to be working correctly, then its usually the efficiency of the system that can be found to be at fault.
You are correct and thats why I asked him to see where his wastegate duty cycle was and to try raising it to about 80-90% but he has the True Boost. He may need to just get rid of it and use the AEM EMS to control the boost so he can up that duty cycle percentage.
Old 03-25-2010, 12:59 PM
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Boost leak? Check all your vacuum lines and clamps/couplers. Also make sure your BOV is functioning properly. It can leak there too.

Exhaust leak pre turbo? Check your manifold and turbo bolts.
Old 03-25-2010, 01:11 PM
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You know whats funny Carey? When I first went to start my car the other night when I was done, I had a ziplock bag over the charge pipe over by the turbo that I forgot to remove. I had it there to cover the hole until I get a new charge pipe made coming off the turbo. Anyway, the car started and made a huge pop that scared the crap out of me and the exhaust was smoking bad. I shut it off immediately and was like WTF was that. There was smoke billowing out of the exhaust and I thought for sure I didnt get the cams in correctly and f**ked something up. After looking all over for a sign of what went wrong, I see the ziplock bag still over the charge pipe but with a hole in it. I started laughing hard and was like.......Thank God thats all it was. I removed the bag, started her up and it was all good. LOL I guess the injectors were pumping fuel in at a huge rate and the engine wasnt getting enough air and caused the excessive smoke out of the exhaust. After restarting it without the ziplock bad on there, the smoke was gone and it was running great. What a major scare that was. LOL
Old 03-25-2010, 01:35 PM
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Haha, you must have had that ziplock on there pretty good.
Old 03-25-2010, 03:14 PM
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Originally Posted by boostedf22c,Mar 25 2010, 12:59 PM
Boost leak? Check all your vacuum lines and clamps/couplers. Also make sure your BOV is functioning properly. It can leak there too.

Exhaust leak pre turbo? Check your manifold and turbo bolts.
No boost leak and no pre turbo exhaust leak. I just got the whole downpipe redone and went from 2.5" intercooler piping to 3". I am pulling 20 on vac and everything seems to be in order. The only thing I havent changed is my turbo mani. I dont think It would be that but you never no. My comp. test reads 180-185 all the way across. I am getting tired of throwing money at this little grimlen My tuner Is very competent, The guy that tunes @ inlinepro referred me to him.
Old 03-25-2010, 03:26 PM
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These types of problems are really annoying, and almost always end up being something simple.
Old 03-25-2010, 04:05 PM
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I cant wait to find the problem so I can post It. I have seen a few threads with people not making the power that they should. We should start a thread with the end result problems so others would have a better shot spotting the problem before they throw a bunch of cash at it.


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