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Low boost with non-sequential mod

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Old Feb 17, 2012 | 04:53 PM
  #1  
vanvai777's Avatar
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Low boost with non-sequential mod

Let me start with my car: 1,950 miles into my first rebuilt motor, mild port, downpipe, and a lightweight flywheel are the only relevant mods. I also redid all of the vacuum lines with silicone.
Ever since the rebuild I have noticed boost problems as I was raising the boost with the break in. There were a few torn vacuum hoses going to the actuators that got torn installing the motor and I didn't know about the restrictor pills at first... But after looking over everything many times and fixing all seen problems, I was stuck at a 11-4-8 boost pattern with a serious drop in power at the transition. Only got power back at the 7-8k range.
Next I did the poor mans non sequential mod just to see the difference and now the boost is as follows:

WOT at 2,500
2,500 - 4,500 builds to 6.5 lbs
4,500 - 5,000 drops to 4-5 lbs
5,000 to redline holds at 4 lbs

Although it has less boost as non sequential, it's still feels much better without the huge drop in power at 4,500 RPM. I'm at a bit of a loss to why I'm seeing such low boost...

Any ideas to get the boost to normal levels?
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Old Feb 17, 2012 | 08:07 PM
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DaleClark's Avatar
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You have a boost leak, plain and simple. Non-sequential with no boost controller should be minimum 7 psi. That's also probably why you didn't have boost in sequential mode.

Dale
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Old Feb 20, 2012 | 06:46 PM
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It's a boost leak alright. I've narrowed it down to having the boost leak tester attached to the intake elbow and it sounds like the leak is somewhere under the UIM. Only problem is, I've removed the UIM and looked over every line I could see and nothing seems out of place... It won't even get over 1psi before pressure escapes. Not sure where to go from here....
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