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No Boost After Shifting?

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Old Oct 17, 2007 | 04:44 PM
  #1  
Rixio_Scon's Avatar
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400Rwhp Seq Twins Baby!!
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From: "Sunny" ol England
No Boost After Shifting?

Im usually quite good at troubleshooting but this one has me stumped...

The car was mapped last week and this problem wasnt there when it was mapped or being mapped. It happened afterwards...possibly on the way home.
I noticed when i got home that the Charge Control Actuator (Y pipe one) wasnt connected to the plenum & there was a split in my elbow. Both have been rectified, but now have another problem.

If i drive nice and steady. I.E 1/4 throttle...when the car gets to 2-3k it starts burbling/sqealing up to 5k...not like its a mapping issue, more like a turbo/vacuum issue...if i floor it it seems to disappear

If i shift through the gears...I.E 2nd to 3rd. I lose boost and have nothing until i lift off and re-apply throttle...at which point i have positive boost

BUT if i leave it in 2nd from e.g 2k and floor it, it goes all the way to redline without incident...

Its difficult to explain...

This sounds similair...

"Chris Davis Adds
After reassembling everything on the car I was getting full boost in both turbos including a nice transition from the primary to the secondary. The problem was between 2000 rpm and 4500 rpm I kept getting a loud squeal coming from under the intake plenum. I narrowed down the noise to the air control valve (ACV). I removed the intake plenum again but could not find anything wrong with the ACV. I finally received advice from Dave at Blackstone Performance. I told him my problem and he told me to open the ACV and check to see if the metal disc had slipped down a little while I was reinstalling the valve. I loosened the three nuts on the valve and sure enough the disc was not flush with the intake manifold (I could tell because it left an imprint in the black carbon build-up). I tried to pull the metal disc up with a screw driver but the disc kept falling back down. In order to make the disc stay in place, I had to remove the solenoid rack (again) and pull the valve completely off. Next, I put a little rubber cement around the disc (from the advice of Dave) to give the piece a little tackiness so it wouldn't fall off again. After reassembling everything, another sore back, and much frustration the car runs perfect with no annoying chirps.
I also learned in the process (from Dave) that the ACV is only active between 2000 and 4500 rpm which is what clued him in to the problem. I can also remove the intake plenum in about 15 minutes but I hope to never have to remove it again. Anyway, I just thought you might want to mention something about the ACV disc to save someone else the headache of having to remove the solenoid rack twice. Once, as you know, is plenty.
Chris Davis"

^^^^^That means nothing to me and really dont have a clue what hes talking about but the problem sounds similair...^^^^^^^^ (Or is that just me being thick)

All the Check valves were checked with Mityvac and are all fine...All the Solenoids are fine and were checked before mapping.

Car is running BNR S3 Twins at 1.15bar / 16 psi

Oh ye great FD guru's...please helpeth me in my hour of need...
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Old Oct 17, 2007 | 05:11 PM
  #2  
Mahjik's Avatar
Mr. Links
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From: Kansas City, MO
I would recommend checking this thread:

https://www.rx7club.com/3rd-gen-archives-73/weird-boost-issue-685269/
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Old Oct 17, 2007 | 05:46 PM
  #3  
Rixio_Scon's Avatar
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400Rwhp Seq Twins Baby!!
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From: "Sunny" ol England
Will have a read
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Old Oct 17, 2007 | 11:45 PM
  #4  
zack4173's Avatar
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From: Bonney lake Washington
That sounds similiar to a problem I had a while back except for the noise issue not sure what that is. I was loosing boost if I anytime I shifted or any time i was WOT then let off for a second then went back on my boost would be gone. My problem was that my throttle control solenoid was shot. I would check that out first. It could also be one of the vacuum lines to the solenoid.
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